CA1287428C - Composition of heat-sensitive electrosensitive substances and a panel heater made therefrom - Google Patents
Composition of heat-sensitive electrosensitive substances and a panel heater made therefromInfo
- Publication number
- CA1287428C CA1287428C CA000475974A CA475974A CA1287428C CA 1287428 C CA1287428 C CA 1287428C CA 000475974 A CA000475974 A CA 000475974A CA 475974 A CA475974 A CA 475974A CA 1287428 C CA1287428 C CA 1287428C
- Authority
- CA
- Canada
- Prior art keywords
- sensitive
- heat
- electroresistive
- composite
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Landscapes
- Surface Heating Bodies (AREA)
- Resistance Heating (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A heat-sensitive electroresistive composite and a thermostatic heating unit made from the composite. The heat-sensitive electroresistive composites have the property of showing an abrupt variation in electric resistance depending on temperature, and they include organic compounds containing a plural number of alkylene oxides as the unit structure in their molecules and fine pieces of carbon in the form of powder, fiber, whiskers, etc. The above-mentioned organic compounds may be normal chain polyalkylene oxide and its derivatives or cyclic ether compounds. The mixing ratio of organic compounds to the fine pieces of carbon is, for example, 100 to 10-80, but the mixing ratio is not necessarily limited to the range for the other types of organic compounds and fine pieces of carbons. The thermostatic heating units are formed by sealing the neat-sensitive electroresistive composites together with electrodes within insulators. These thermostatic heating units may be a sheet form panel heater using a plastic sheet as the insulator.
A heat-sensitive electroresistive composite and a thermostatic heating unit made from the composite. The heat-sensitive electroresistive composites have the property of showing an abrupt variation in electric resistance depending on temperature, and they include organic compounds containing a plural number of alkylene oxides as the unit structure in their molecules and fine pieces of carbon in the form of powder, fiber, whiskers, etc. The above-mentioned organic compounds may be normal chain polyalkylene oxide and its derivatives or cyclic ether compounds. The mixing ratio of organic compounds to the fine pieces of carbon is, for example, 100 to 10-80, but the mixing ratio is not necessarily limited to the range for the other types of organic compounds and fine pieces of carbons. The thermostatic heating units are formed by sealing the neat-sensitive electroresistive composites together with electrodes within insulators. These thermostatic heating units may be a sheet form panel heater using a plastic sheet as the insulator.
Description
1287428 lOA 827 COI`~OSITION OF HEAT-SEN~ITIVE ~LECTROSENSITIVE
SUBSTANCES AND A PANEL HEATER I`~DE THEREFROM
sACXGROUN~ OF THE INVENTIO~
1. Field of the Invention This invention relates to a composition of heat-sensitive electroresistive substances and a panel heater made therefrom, and more particuiarly to a composition of h-at-sensitive electroresistive substances whose electric resistance varies abruptly with a positive characteristic at a certain temperature level, and also to a thermostatic panel heater using the foregoing composition.
SUBSTANCES AND A PANEL HEATER I`~DE THEREFROM
sACXGROUN~ OF THE INVENTIO~
1. Field of the Invention This invention relates to a composition of heat-sensitive electroresistive substances and a panel heater made therefrom, and more particuiarly to a composition of h-at-sensitive electroresistive substances whose electric resistance varies abruptly with a positive characteristic at a certain temperature level, and also to a thermostatic panel heater using the foregoing composition.
2. Description of tne Prior Art Barium titanate ceramics doped with a rare earth element, Y, ~i, or Sb are known as heat-sensitive resistors.
Although barium titanate in its neat state is an insulator, it turn to be a semiconductor as a result of doping.
Generally, resistivities of semiconductors show negative temperature characteristics, namely, the resistivity decreases with increasing the temperature of the semiconductor.
In the case of doped barium titanate ceramics the resistivity show ne~ative temperature coefficients in the lower temperature resion, but positive temperature coefficients appear at a temp-erature which is sligntly lower than the Curie tempera,ure.
Over the temperature range between the temperature described above and the temperature wnich is nigher than the Curie temp-arture by ~150~C, the positive tem~erat~re characteristics are 1.
I
~Z87~2~
observed. Because of this positive temperature eoefficient characteristies, doped barium titanate ceramics give a steady-state constant temperature when electric power is supplied.
Therefore, doped barium titanate eeramies are ealled as PTCR
(positive temperature coefficient resistor). Electrical resis-tivity for the heat sensitive s~bstances of this invention exhibits positive temperature characteristics which is much stronger than that of doped barium titanate. Although the mechanism of the electrical conductivity in the heat sensitive substances of this invention could probably be different from that in doped barium titanate, the term "positive temperature charactertistic" of "PTC (positive temperature coefficient) effect" used hereafter in the same sense at that for doped barium titanate because both give the same electrical eharaeteristics, namely, constant temperature under the supply of electricity.
Besides doped barium titanate ceramics as inor-ganic substances the system of carbon-paraffin-polyethylene has been known as an organic substance which has a strong posi-tive temperature characteristics.
On the ~ther hand, as an organie material having suffieiently strong positive eharaeteristies, the ternary sys-tem of earbon-paraffin-polyethylene has been known. However, this composition is poor in eompatibility with earbon, and has a problem in the mixing method as well as in change in characteristics with the passage of time.
When a heat-sensitive electroresistive composite having a positive characteristic is raised in temperature from ~28~8 low range, the value of resistance increases precipitously when the temperature reaches a certain point. Also, in the contrary, when the temperature of the composite is lowered from the higher temperature range above the aforesaid certain point, the value of resistance decreases sharply at the certain point mentioned above. Now, when the composite provided by this invention is heated by supplying electricity, while the amperage of the electric current is high during the initial period, after a while, upon reaching a certain temperature the current becomes weak because the value of resistance increases suddenly.
Thereafter, when the temperature of the composite is lowered by cooling it the resistance value decreases. As thè resul~, the electric current becomes high in amperage again, and the tempera-ture returns to the certain level. By utilizing the property described above, this composite can be used as a temperature sensor, temperature fuse, and thermostatic heating element.
Organic compounds witl~ melting point around room temperature + 50C, with the desirable propertiesl such as high thermal s.ability, low toxicity, and also are a good insulator of electricity, are found in large number. Such organic com-pounds ar~, for e~ample, paraffins, polyalkylene ~lycols, higher alkyl ethers, higher alkyl esters, higher fatty acids, and hi~h~r al~ohols.
Also, these organic compounds are melted when heated from outside up to the degree above the melting point, and the lleat is s.ored as latent heat of fusion, in those compounds.
Accordincly, they are known as a regenerative media. By using ~Z874~8 systems without requiring additional installation of a tempera-ture sensor and a thermal fuse separately inside of the heating unit.
In other words, the heat-sensitive electroresistive composite provided by this invention has the property that its temperature does not go up beyond a certain level as an in-herent property of a resistor.
Consequently, the heating element using the foregoing composite is completely free of malfunction, and it is also extremely dependable and safe. Furthermore, in view of the energy consumption, since its temperature does not e~ceed a specified point, it suffers no energy loss. Thus, in addition to the above, it has an outstanding merit in terms of economy.
The present invention is intended, therefore, to provide a heat-sensitive electroresistive composite having desirable thermostatic properties including a positive characteristic.
Furthermore, the inventor of this invention has designed a way to make heating elements, particularly sheet form (panel) heating type units, by sealing the composites together with electrodes in insulators. In this manner, the inventor has developed heating units which are quite suitable as the base materials for floor heating systems of buildin~s, heating carpets, heating mats for agricultural and stock farming applications, such as brooder, breeder, seedling culture, as well as for other uses.
This invention was achieved based on the following findings. That is, the inventor found that, among organic compounds, polyethylene glycol is remarkably high in compatibility ~ ~1~37~28 as a regenerative medium, and the heat genèrated by the electric heater receivin~ the electricity from a generator using an irregular natural energy source, such as wind power (aerogenerator), tidal power (tidal power plant), and solar energy (solar power plate), can be stored. However, the regenerative medium itself is a good insulator of electricity and it is impossible to energize it with electricity directly for heating. Therefore, it is necessary to heat it by using an electric heater, and also a thermostat or a thermoprotector must be provided for temperature control. This inevitably increases the cost for equipment.
SUI~ll`lARY OF THE INVENTION
To solve the problems of the prior art, a heat-sensitive electroresistive composite having a positive characteristics was used as a thermostatic heating element as men~ioned above~ The heat-sensitive electroresistive composite also functio~s as a temperature sensor and as a thermal fuse. Hence, it can be used for obtaining safe and economical accumulator and room-heating systems without requiring additional installation of a tempera-ture sensor and a thermal ~use separately inside the heating unit.
In other words, the heat-sensitive electxoresistive composite provided by this invention has the property that its tem~erature does not ~o up beyond a certain level as an in-herent property of a resistor.
Consequently, the heating element using the foregoing composite is completely free of malfunction, and it is also J
~287g~
extremely dependable and safe. Furthermore, in view of the energy consumption, since its te~perature does not exceed a specified point, it suffers no energy loss. Thus, in addition to the above, it has an outstanding merit in terms of economy.
The present invention is intended, therefore, to provide a heat-sensitive electroresistive composite having desirable thermostatic properties incluaing a positive characteristic.
Furthermore, the inventor of this invention has designed a way to ma~e heating elements, particularly sheet form ~panel) heating type units, by sealing the composites together with electrodes in insulators. In this manner, the inventor has developed heating units which are quite suitable as the base materials for floor heating systems of buildings, heating carpets, heating mats for agricultural and stock arming applications, such as brooder, breeder, seedling culture; as well as for other uses~
This invention was achieved based on the following findings. That is, the inventor ~ound that, among orsanic compounds, polyethylene glycol is remarkably hi~h in compatibilit~-with carbon powder, he further conducted a strenuous study in order to find out the reason for the above. As a result, the inventor obtained confirmation that the organic compounds containing a plural number of al~yl oxides as the unit structures in their molecules show a far better miscibility with carbon powder than the other organic compounds, and that due to the above, they show positive characteristics in stable manner.
6.
--` 128~4 ~8 In accordance with one aspect of this invention, there is provided a heat-sensitive electroresistive composi-te which exhibits an abrupt change in electric resistance with increasing temperature, which comprises organic compounds containing a plural number of alkylene oxides as the unit structure in their molecules; and fine pieces of carbon in the form of a member chosen from powder, fiber, and whiskers.
6A.
12~37~ !3 BRIEF DESCRIPTION OF THE DRAWINGS
The abovementioned features and objects will become more apparent from the following description wherein like reference numerals denote like elemen.s and in which:
FIGURE 1 is a side view of an electrical resistance measuring device;
FIGURE 2(a) is a perspective view;
FIGURE 2(b) is a sectional ~riew taken along the line A-A in ~igure 2(a);
FIGURE 3(a) is a plan view;
FIG~RE 3(b) is an enlarged sectional view ta~en along the line B-B in Figure 3(a);
FIGURE 4 is a graph showing the relation bet~een the temperature and the electric resistance o~ cyclic polyethers in Embodiments 1-5;
FIGURE 5 is a graph showing the relation between the duration of electric current feeaing the temperature for various compositional ratios of graphi~e to polyeth~rlene glycol in Embodiment 6;
FIGURE 6 is a graph showing the relationship ~etween the electrocurrent feeding time, the temperature and the electro-current, for the same composite;
~ IGURE 7 is a ~raph showins the relation between the temperature and the electric resistance of straight chain poly-ethers in Embodiments 7-11;
FIGURE 8 is a plan view showing a sheet form heating element;
28~
FIGURES 9, 10, 11 and 12 are graphs showinc3 the rela-tions between current feeding time and temperature as well as the current feeding time and current (or power consumption), for sheet form (panel) heatinc~ elements as embodiments of this invelltion; and FIGURE 13 is a graph showing the Resistance-temperature curve of the neat-sensitive element.
DETAILED DESCRIPTION OF THE INVENTION
The composites provided by this invention have strongly positive characteristics, and they are characterized as follows.
That is, carbon contained in them are quite readily dispersed in the organic compounds which are specified by this invention.
The organic compound llas a plural number oE alkylene oxides as tl~e Ullit structure in their moleculès, and thus a remarka~ly conspicuous positive characteristics can be shown in stable manner by these components. The organic compounds which contain the plural number of alkylene oxides as the unit structure in their molecules show excellent positive characteristics, regard-less of whether tlley are straight chain compounds or cyclic com-pounds. The actual examples of such organic compounds are listed below.
~ s the strai~Jht chain compounds, there ~re polyoxy-alkylcnes; or exalllple, polyethylene ~lycol and its hic3h mole-cular (weight) polyethylene oxide, block copolymers of polyoxyethylene and polyoxypropylene (so called Pluronic* or ethylene glycol-propylene glycol copolymer (EG-PG copolymer) and ~ ;, * Trade mark 8.
. .
~21~7~28 Tetronic* or EG, PG block copolymer), polyoxyethylene alkyl ester, polyoxyethylene alkyl-allyl ether, polyoxye-thylene alkyl ester, polyoxyethylene alkyl-amine, polyoxyethylene sorhitan fatty (a~id) ester.
~ s the cyclic compounds, in addi~ion to trioxane, there are many and various types of crown ethers, such as dibenzo-14-crown-4, 15-crown-5, benzo-15-crown-5, 18-crown-6, dibenzo-18-crown-6, dicyclohexyl-18-crown-6, dibenzo-21-crown-7, dibenzo-24~
crown-8, dicyclohe~yl-24-crown-8, tetrabenzo-24-crown-8, dibenzo-60-crown-20.
A concrete description of the positive characteristics of the heat-sensitive electroresistive composite using those compounds will be given later.
Carbons to be mixed with the or~anic com~ounds listed above as examples, which contain the plural number oE alkylene o~ide as the unit structure in their molecules, ar~ fine Era~-ments of carbon, such as graphite, active carbon, amorphous carbon, etc., in tl~e form of powder, fiber, whiskers, composed of sin~le crystals, etc. These carbons must be miscible with the foregoing normal chain or cyclic polyethers.
~ he most characteristic points of the mixtures of the aforesaid two components are that they are mixed homoc~eneously with high stability no matter what their composition ratio is, and that phase separation is not caused to them. ~lso, there is a ran~3e where the positive characteristlcs are shown at a certain mixing ratio oE the micro-Eragments oE car~ons. This mixing ratio is usually 10-80 parts by weight compared with 100 parts by weight in organic compounds. When the mixing ratio oE the fine pieces of carbon * Trade mark 9.
1:~87~
is below 10, the electricity is not transmitted due to the high resistance. On the contrary, when the composition ratio of the fine pieces of carbon becomes above 80, the electric conductivity gets too high and positive characteristics do not appear even the temperature range investigated (-20 ~ 130C).
However, the abovementioned range of mixing ratio where the positive characteristics are shown differs largely depending on the type of organic compounds as well as the type of fine pieces of carbon. Therefore, such a range is not limited to that mentioned above.
For the organic compounds, alkylene oxide group present in plural number in their molecules plays an important role in the dispersion of the fine pieces of carbon. Accordingly, this alkylene oxide is assumed to be a factor for bringing about the markedly stable and strongly positive characteristics shown by the composites obtained from the foregoing organic compounds and micro-fragments of carbons.
The following was proved by actual examples of the embo~iments of this invention which will be mentioned later.
That is, the positive characteristics are shown when plural number of alkylene oxide groups, regardless of their form, whether normal c,lain or cyclic, are presènt in molecules. The above is established even for trioxane containing only 3 sets of alkylene oxide ~roups, or even when chemical bond between alkylene oxides themselves is severed by the benzene nucleus in crown esters or by the six-membered ring of cyclohexane.
Polyethylene glycol shows the most desirable properties in the process of development up to now. Also, it has been 10 .
-` ~2874~51 confirmed that it shows the positive c}larac-teristics even when ethylene groups in polyethylene glycol molecules are partially replaced by propylene groups, or when its terminal group is changed from hydroxyl group, by substituting an alkoxy group, s-lch as methoxy group, or by alkyl es~er or alkylamine.
As has been mentioned above, tne reason that the mix-tures of organic compounds containin~ a plural number of alky-lene oxide as the unit structure in tneir molecules and -the fine pieces of carbons show the conspicuously positive chara-cteristic is not fully clarified yet, but the following is con-ceivable. That is, the fact that these compounds have a pro-perty highly s-trongly facilitating the homogeneous dispersion of carbon powder, e-tc. contributes to the abovementioned tend-ency of snowing a high degree of positive characteristics.
The reasons for the assumption mentioned above are given below. First, it is a well known fact that protons and metallic ions are coordinated with lone pairs of electrons on oxygen atoms in alkylene o~ide groups. On the other hand, the following are also wi.dely ~nown facts. That is, the fine piece oE carbon have the graphite structure,and the ~ electrons can move within the conjuga-ted system, thus providing electric conductivlty. It is assumed that the ~ electrons of graphite are localized in some local part of craphite crystal which causes the other portion iJl the crystal to be positively char~ed. :[f it is assumed -that this Dositive portion is coordinated with -the lone pair oE electrons on oxygen atoms in all~ylene oxide, the excellent dispersibili-ty of fine pieces of carbon can be explained.
11 .
As to the conduction mechanism of the mixture system of the organic compound and fine fragments of carbon, in the region where the carbon particles are in the state of complete mutual contact the Ohmic conduction mechanism provides the explanation. On the other hand, as to the region where there exist extremely small spaces between the particles, the tunnel effect can be applied to explain the conduction mechanism.
As will be explained with reference to the embodiments shown later, in the positive characteristics, the sharp increase in electric resistance value is observed during the feeding of electricity at the temperature below the melting point of the organic compound medium. The data for the above is shown in Table 1. Also, the relations between the temperature and the value of electric resistance of respective composites are shown in Figure 4 and Figure 7.
~2~7428 Amount of Temperature fine pieces where the Melting of carbon resistance value Point mi~ed (parts shows the sharp Organic Compound tC) by weight) rise (C) Trioxane 64 25 40 18-crown-6 39-40 28 38 senzo-15-crown-5 79-79.5 28 62 Dicyclohexyl-18-crown-6 38-54 28 24 Dibenzo-24-crown-8 113-114 28 102 Polyethylene glycol #6000 56-61 Polyethylene glycol #2000 49-53 28 42-46 Pluronic F68, F88 50 28 46 Pluronic F88 50 28 46 The heat sensitive electroresistive composites as listed above are formed into heat-sensitive electroresistive composite sheets by using them as they are or by using them after letting the non-conductive sheets, such as thin woven fabric, non-woven fabric and sponge sheet, be impregnated with them so that the non-conductive sheets carry the foregoing composites in them.
Then, each of the heat-sensitive electroresistive composite sheets thus obtained is sealed in two non-conductive cover sheets applied to front and back sides of the former. At the same time, inside of the assembly prepared as mentioned above, conductors (lead wires) are buried at specified intervals.
As a whole, all of those components are made into a thin sheet form. In this way, a sheet form (panel) heating unit with the 13.
\
12~374:28 desirable property is obtained. Needless to say, even without being formed into thin sheet, tlle assembly of the components is sufficiently effective as a heating unit. However, when they are processed to take the sheet form, material required can be cut down in quantity r and also a heating panel ideal for floor heating, wall heating, etc. can be obtained. Besides, as the heating unit itself has the positive characteristics, it functions also as thermostat as well as thermoprotector, thereby making it feasible to simplify the structure, to com-pletely free itself from possible failure in performance, and in addition, to lower the production cost substantially.
In the end of this section, the heat sensitive substances of this inv~ntion are compared with doped barium titanates ceramics.
It is obvious that barium titanates ceramics have characteristics as general ceramics, namely, mechanically strong and stable at high temperature. The heat sensitive substances of this inven-tion have various useful characteristics whicll are not seen for doped barium titanate ceramics. Those àre described below:
l. PTC characteristics of this invention is much stronger than that of doped barium titanate ceraMics. In order to evaluate PTC characteristics, the values of the temperature gradience in ~esistance-Temperature ~urve deviated by Rf (see Figure 13) is takell for the heat sensitive substance of this invention and doped barium titanate ceramics and compared with each other. The value for the heat sensitive substance of this invention is taken from the data of Embodiment 2 and that for the doped barium titanate from J. Am. Ceram. Soc., 47, 484tl964). The values are 59.6/C
for this invention and 11.8 for the barium titanate ceramics.
14.
~2B7~2~
This means that in order to get the same increase in the relative resistance of the substance in Embodiment ~ when the temperature is increased by 1C, it is necessary to increase the temperature of the barium titanate ceramics by ~5C.
2. In the case of doped barium titanate ceramics it is possible to lower the Curie temperature by the increase in the dopant concentration. However, there is a higher limit for ceramics to be a semiconductor. Too high concentration of a dopant makes the ceramics to be insulators. Therefore, the lower limit of steady state constant temperature of doped barium titanate heater is w 70C. On the other hand, heaters from the heat sensitive substances of this invention could give a steady state constant temperature as low as ~ 20C (see Embodiment 4).
Actually the panel heater of Emboaiment 13 gives the constant temperature 50C (see Figure 9). Heaters of a lower constant temperature save energy consumption when they are properly used.
Although barium titanate in its neat state is an insulator, it turn to be a semiconductor as a result of doping.
Generally, resistivities of semiconductors show negative temperature characteristics, namely, the resistivity decreases with increasing the temperature of the semiconductor.
In the case of doped barium titanate ceramics the resistivity show ne~ative temperature coefficients in the lower temperature resion, but positive temperature coefficients appear at a temp-erature which is sligntly lower than the Curie tempera,ure.
Over the temperature range between the temperature described above and the temperature wnich is nigher than the Curie temp-arture by ~150~C, the positive tem~erat~re characteristics are 1.
I
~Z87~2~
observed. Because of this positive temperature eoefficient characteristies, doped barium titanate ceramics give a steady-state constant temperature when electric power is supplied.
Therefore, doped barium titanate eeramies are ealled as PTCR
(positive temperature coefficient resistor). Electrical resis-tivity for the heat sensitive s~bstances of this invention exhibits positive temperature characteristics which is much stronger than that of doped barium titanate. Although the mechanism of the electrical conductivity in the heat sensitive substances of this invention could probably be different from that in doped barium titanate, the term "positive temperature charactertistic" of "PTC (positive temperature coefficient) effect" used hereafter in the same sense at that for doped barium titanate because both give the same electrical eharaeteristics, namely, constant temperature under the supply of electricity.
Besides doped barium titanate ceramics as inor-ganic substances the system of carbon-paraffin-polyethylene has been known as an organic substance which has a strong posi-tive temperature characteristics.
On the ~ther hand, as an organie material having suffieiently strong positive eharaeteristies, the ternary sys-tem of earbon-paraffin-polyethylene has been known. However, this composition is poor in eompatibility with earbon, and has a problem in the mixing method as well as in change in characteristics with the passage of time.
When a heat-sensitive electroresistive composite having a positive characteristic is raised in temperature from ~28~8 low range, the value of resistance increases precipitously when the temperature reaches a certain point. Also, in the contrary, when the temperature of the composite is lowered from the higher temperature range above the aforesaid certain point, the value of resistance decreases sharply at the certain point mentioned above. Now, when the composite provided by this invention is heated by supplying electricity, while the amperage of the electric current is high during the initial period, after a while, upon reaching a certain temperature the current becomes weak because the value of resistance increases suddenly.
Thereafter, when the temperature of the composite is lowered by cooling it the resistance value decreases. As thè resul~, the electric current becomes high in amperage again, and the tempera-ture returns to the certain level. By utilizing the property described above, this composite can be used as a temperature sensor, temperature fuse, and thermostatic heating element.
Organic compounds witl~ melting point around room temperature + 50C, with the desirable propertiesl such as high thermal s.ability, low toxicity, and also are a good insulator of electricity, are found in large number. Such organic com-pounds ar~, for e~ample, paraffins, polyalkylene ~lycols, higher alkyl ethers, higher alkyl esters, higher fatty acids, and hi~h~r al~ohols.
Also, these organic compounds are melted when heated from outside up to the degree above the melting point, and the lleat is s.ored as latent heat of fusion, in those compounds.
Accordincly, they are known as a regenerative media. By using ~Z874~8 systems without requiring additional installation of a tempera-ture sensor and a thermal fuse separately inside of the heating unit.
In other words, the heat-sensitive electroresistive composite provided by this invention has the property that its temperature does not go up beyond a certain level as an in-herent property of a resistor.
Consequently, the heating element using the foregoing composite is completely free of malfunction, and it is also extremely dependable and safe. Furthermore, in view of the energy consumption, since its temperature does not e~ceed a specified point, it suffers no energy loss. Thus, in addition to the above, it has an outstanding merit in terms of economy.
The present invention is intended, therefore, to provide a heat-sensitive electroresistive composite having desirable thermostatic properties including a positive characteristic.
Furthermore, the inventor of this invention has designed a way to make heating elements, particularly sheet form (panel) heating type units, by sealing the composites together with electrodes in insulators. In this manner, the inventor has developed heating units which are quite suitable as the base materials for floor heating systems of buildin~s, heating carpets, heating mats for agricultural and stock farming applications, such as brooder, breeder, seedling culture, as well as for other uses.
This invention was achieved based on the following findings. That is, the inventor found that, among organic compounds, polyethylene glycol is remarkably high in compatibility ~ ~1~37~28 as a regenerative medium, and the heat genèrated by the electric heater receivin~ the electricity from a generator using an irregular natural energy source, such as wind power (aerogenerator), tidal power (tidal power plant), and solar energy (solar power plate), can be stored. However, the regenerative medium itself is a good insulator of electricity and it is impossible to energize it with electricity directly for heating. Therefore, it is necessary to heat it by using an electric heater, and also a thermostat or a thermoprotector must be provided for temperature control. This inevitably increases the cost for equipment.
SUI~ll`lARY OF THE INVENTION
To solve the problems of the prior art, a heat-sensitive electroresistive composite having a positive characteristics was used as a thermostatic heating element as men~ioned above~ The heat-sensitive electroresistive composite also functio~s as a temperature sensor and as a thermal fuse. Hence, it can be used for obtaining safe and economical accumulator and room-heating systems without requiring additional installation of a tempera-ture sensor and a thermal ~use separately inside the heating unit.
In other words, the heat-sensitive electxoresistive composite provided by this invention has the property that its tem~erature does not ~o up beyond a certain level as an in-herent property of a resistor.
Consequently, the heating element using the foregoing composite is completely free of malfunction, and it is also J
~287g~
extremely dependable and safe. Furthermore, in view of the energy consumption, since its te~perature does not exceed a specified point, it suffers no energy loss. Thus, in addition to the above, it has an outstanding merit in terms of economy.
The present invention is intended, therefore, to provide a heat-sensitive electroresistive composite having desirable thermostatic properties incluaing a positive characteristic.
Furthermore, the inventor of this invention has designed a way to ma~e heating elements, particularly sheet form ~panel) heating type units, by sealing the composites together with electrodes in insulators. In this manner, the inventor has developed heating units which are quite suitable as the base materials for floor heating systems of buildings, heating carpets, heating mats for agricultural and stock arming applications, such as brooder, breeder, seedling culture; as well as for other uses~
This invention was achieved based on the following findings. That is, the inventor ~ound that, among orsanic compounds, polyethylene glycol is remarkably hi~h in compatibilit~-with carbon powder, he further conducted a strenuous study in order to find out the reason for the above. As a result, the inventor obtained confirmation that the organic compounds containing a plural number of al~yl oxides as the unit structures in their molecules show a far better miscibility with carbon powder than the other organic compounds, and that due to the above, they show positive characteristics in stable manner.
6.
--` 128~4 ~8 In accordance with one aspect of this invention, there is provided a heat-sensitive electroresistive composi-te which exhibits an abrupt change in electric resistance with increasing temperature, which comprises organic compounds containing a plural number of alkylene oxides as the unit structure in their molecules; and fine pieces of carbon in the form of a member chosen from powder, fiber, and whiskers.
6A.
12~37~ !3 BRIEF DESCRIPTION OF THE DRAWINGS
The abovementioned features and objects will become more apparent from the following description wherein like reference numerals denote like elemen.s and in which:
FIGURE 1 is a side view of an electrical resistance measuring device;
FIGURE 2(a) is a perspective view;
FIGURE 2(b) is a sectional ~riew taken along the line A-A in ~igure 2(a);
FIGURE 3(a) is a plan view;
FIG~RE 3(b) is an enlarged sectional view ta~en along the line B-B in Figure 3(a);
FIGURE 4 is a graph showing the relation bet~een the temperature and the electric resistance o~ cyclic polyethers in Embodiments 1-5;
FIGURE 5 is a graph showing the relation between the duration of electric current feeaing the temperature for various compositional ratios of graphi~e to polyeth~rlene glycol in Embodiment 6;
FIGURE 6 is a graph showing the relationship ~etween the electrocurrent feeding time, the temperature and the electro-current, for the same composite;
~ IGURE 7 is a ~raph showins the relation between the temperature and the electric resistance of straight chain poly-ethers in Embodiments 7-11;
FIGURE 8 is a plan view showing a sheet form heating element;
28~
FIGURES 9, 10, 11 and 12 are graphs showinc3 the rela-tions between current feeding time and temperature as well as the current feeding time and current (or power consumption), for sheet form (panel) heatinc~ elements as embodiments of this invelltion; and FIGURE 13 is a graph showing the Resistance-temperature curve of the neat-sensitive element.
DETAILED DESCRIPTION OF THE INVENTION
The composites provided by this invention have strongly positive characteristics, and they are characterized as follows.
That is, carbon contained in them are quite readily dispersed in the organic compounds which are specified by this invention.
The organic compound llas a plural number oE alkylene oxides as tl~e Ullit structure in their moleculès, and thus a remarka~ly conspicuous positive characteristics can be shown in stable manner by these components. The organic compounds which contain the plural number of alkylene oxides as the unit structure in their molecules show excellent positive characteristics, regard-less of whether tlley are straight chain compounds or cyclic com-pounds. The actual examples of such organic compounds are listed below.
~ s the strai~Jht chain compounds, there ~re polyoxy-alkylcnes; or exalllple, polyethylene ~lycol and its hic3h mole-cular (weight) polyethylene oxide, block copolymers of polyoxyethylene and polyoxypropylene (so called Pluronic* or ethylene glycol-propylene glycol copolymer (EG-PG copolymer) and ~ ;, * Trade mark 8.
. .
~21~7~28 Tetronic* or EG, PG block copolymer), polyoxyethylene alkyl ester, polyoxyethylene alkyl-allyl ether, polyoxye-thylene alkyl ester, polyoxyethylene alkyl-amine, polyoxyethylene sorhitan fatty (a~id) ester.
~ s the cyclic compounds, in addi~ion to trioxane, there are many and various types of crown ethers, such as dibenzo-14-crown-4, 15-crown-5, benzo-15-crown-5, 18-crown-6, dibenzo-18-crown-6, dicyclohexyl-18-crown-6, dibenzo-21-crown-7, dibenzo-24~
crown-8, dicyclohe~yl-24-crown-8, tetrabenzo-24-crown-8, dibenzo-60-crown-20.
A concrete description of the positive characteristics of the heat-sensitive electroresistive composite using those compounds will be given later.
Carbons to be mixed with the or~anic com~ounds listed above as examples, which contain the plural number oE alkylene o~ide as the unit structure in their molecules, ar~ fine Era~-ments of carbon, such as graphite, active carbon, amorphous carbon, etc., in tl~e form of powder, fiber, whiskers, composed of sin~le crystals, etc. These carbons must be miscible with the foregoing normal chain or cyclic polyethers.
~ he most characteristic points of the mixtures of the aforesaid two components are that they are mixed homoc~eneously with high stability no matter what their composition ratio is, and that phase separation is not caused to them. ~lso, there is a ran~3e where the positive characteristlcs are shown at a certain mixing ratio oE the micro-Eragments oE car~ons. This mixing ratio is usually 10-80 parts by weight compared with 100 parts by weight in organic compounds. When the mixing ratio oE the fine pieces of carbon * Trade mark 9.
1:~87~
is below 10, the electricity is not transmitted due to the high resistance. On the contrary, when the composition ratio of the fine pieces of carbon becomes above 80, the electric conductivity gets too high and positive characteristics do not appear even the temperature range investigated (-20 ~ 130C).
However, the abovementioned range of mixing ratio where the positive characteristics are shown differs largely depending on the type of organic compounds as well as the type of fine pieces of carbon. Therefore, such a range is not limited to that mentioned above.
For the organic compounds, alkylene oxide group present in plural number in their molecules plays an important role in the dispersion of the fine pieces of carbon. Accordingly, this alkylene oxide is assumed to be a factor for bringing about the markedly stable and strongly positive characteristics shown by the composites obtained from the foregoing organic compounds and micro-fragments of carbons.
The following was proved by actual examples of the embo~iments of this invention which will be mentioned later.
That is, the positive characteristics are shown when plural number of alkylene oxide groups, regardless of their form, whether normal c,lain or cyclic, are presènt in molecules. The above is established even for trioxane containing only 3 sets of alkylene oxide ~roups, or even when chemical bond between alkylene oxides themselves is severed by the benzene nucleus in crown esters or by the six-membered ring of cyclohexane.
Polyethylene glycol shows the most desirable properties in the process of development up to now. Also, it has been 10 .
-` ~2874~51 confirmed that it shows the positive c}larac-teristics even when ethylene groups in polyethylene glycol molecules are partially replaced by propylene groups, or when its terminal group is changed from hydroxyl group, by substituting an alkoxy group, s-lch as methoxy group, or by alkyl es~er or alkylamine.
As has been mentioned above, tne reason that the mix-tures of organic compounds containin~ a plural number of alky-lene oxide as the unit structure in tneir molecules and -the fine pieces of carbons show the conspicuously positive chara-cteristic is not fully clarified yet, but the following is con-ceivable. That is, the fact that these compounds have a pro-perty highly s-trongly facilitating the homogeneous dispersion of carbon powder, e-tc. contributes to the abovementioned tend-ency of snowing a high degree of positive characteristics.
The reasons for the assumption mentioned above are given below. First, it is a well known fact that protons and metallic ions are coordinated with lone pairs of electrons on oxygen atoms in alkylene o~ide groups. On the other hand, the following are also wi.dely ~nown facts. That is, the fine piece oE carbon have the graphite structure,and the ~ electrons can move within the conjuga-ted system, thus providing electric conductivlty. It is assumed that the ~ electrons of graphite are localized in some local part of craphite crystal which causes the other portion iJl the crystal to be positively char~ed. :[f it is assumed -that this Dositive portion is coordinated with -the lone pair oE electrons on oxygen atoms in all~ylene oxide, the excellent dispersibili-ty of fine pieces of carbon can be explained.
11 .
As to the conduction mechanism of the mixture system of the organic compound and fine fragments of carbon, in the region where the carbon particles are in the state of complete mutual contact the Ohmic conduction mechanism provides the explanation. On the other hand, as to the region where there exist extremely small spaces between the particles, the tunnel effect can be applied to explain the conduction mechanism.
As will be explained with reference to the embodiments shown later, in the positive characteristics, the sharp increase in electric resistance value is observed during the feeding of electricity at the temperature below the melting point of the organic compound medium. The data for the above is shown in Table 1. Also, the relations between the temperature and the value of electric resistance of respective composites are shown in Figure 4 and Figure 7.
~2~7428 Amount of Temperature fine pieces where the Melting of carbon resistance value Point mi~ed (parts shows the sharp Organic Compound tC) by weight) rise (C) Trioxane 64 25 40 18-crown-6 39-40 28 38 senzo-15-crown-5 79-79.5 28 62 Dicyclohexyl-18-crown-6 38-54 28 24 Dibenzo-24-crown-8 113-114 28 102 Polyethylene glycol #6000 56-61 Polyethylene glycol #2000 49-53 28 42-46 Pluronic F68, F88 50 28 46 Pluronic F88 50 28 46 The heat sensitive electroresistive composites as listed above are formed into heat-sensitive electroresistive composite sheets by using them as they are or by using them after letting the non-conductive sheets, such as thin woven fabric, non-woven fabric and sponge sheet, be impregnated with them so that the non-conductive sheets carry the foregoing composites in them.
Then, each of the heat-sensitive electroresistive composite sheets thus obtained is sealed in two non-conductive cover sheets applied to front and back sides of the former. At the same time, inside of the assembly prepared as mentioned above, conductors (lead wires) are buried at specified intervals.
As a whole, all of those components are made into a thin sheet form. In this way, a sheet form (panel) heating unit with the 13.
\
12~374:28 desirable property is obtained. Needless to say, even without being formed into thin sheet, tlle assembly of the components is sufficiently effective as a heating unit. However, when they are processed to take the sheet form, material required can be cut down in quantity r and also a heating panel ideal for floor heating, wall heating, etc. can be obtained. Besides, as the heating unit itself has the positive characteristics, it functions also as thermostat as well as thermoprotector, thereby making it feasible to simplify the structure, to com-pletely free itself from possible failure in performance, and in addition, to lower the production cost substantially.
In the end of this section, the heat sensitive substances of this inv~ntion are compared with doped barium titanates ceramics.
It is obvious that barium titanates ceramics have characteristics as general ceramics, namely, mechanically strong and stable at high temperature. The heat sensitive substances of this inven-tion have various useful characteristics whicll are not seen for doped barium titanate ceramics. Those àre described below:
l. PTC characteristics of this invention is much stronger than that of doped barium titanate ceraMics. In order to evaluate PTC characteristics, the values of the temperature gradience in ~esistance-Temperature ~urve deviated by Rf (see Figure 13) is takell for the heat sensitive substance of this invention and doped barium titanate ceramics and compared with each other. The value for the heat sensitive substance of this invention is taken from the data of Embodiment 2 and that for the doped barium titanate from J. Am. Ceram. Soc., 47, 484tl964). The values are 59.6/C
for this invention and 11.8 for the barium titanate ceramics.
14.
~2B7~2~
This means that in order to get the same increase in the relative resistance of the substance in Embodiment ~ when the temperature is increased by 1C, it is necessary to increase the temperature of the barium titanate ceramics by ~5C.
2. In the case of doped barium titanate ceramics it is possible to lower the Curie temperature by the increase in the dopant concentration. However, there is a higher limit for ceramics to be a semiconductor. Too high concentration of a dopant makes the ceramics to be insulators. Therefore, the lower limit of steady state constant temperature of doped barium titanate heater is w 70C. On the other hand, heaters from the heat sensitive substances of this invention could give a steady state constant temperature as low as ~ 20C (see Embodiment 4).
Actually the panel heater of Emboaiment 13 gives the constant temperature 50C (see Figure 9). Heaters of a lower constant temperature save energy consumption when they are properly used.
3. In the case of barium titanate ceramics, it is difficult to produce heaters with wide surfaces. However, it is quite easy to produce a sheet form panel heater with surfaces as wide as necessary.
4. It is also possible to produce thin flexible sheet form heaters ~rom the heat sellsitive substances (see Embodiment 6).
As is described above, the strong PCT characteristics, a proper constant temperature (probably 30~50C), wide surface and the flexibility are essential for room heating panel.
~ ereunder, a concrete description on the effects of the heat-sensitive electroresistive composites according to :~287~Z~
this invention as well as on the characteristics of the heating units using the former will ~e given with reference to the embodiments of this invention.
E~lsODII~NT 1 Ten grams of heat-sensitive electroresistive composite 1 obtained by mixing 25 wt. % of graphite carbon (produced by Yoneyama Ya~uhin Kogyo Co., Ltd. Japan) and 75 wt. ~ of trioxane (extra pure reagent from Nakarai Kagaku Yakuhin, Co., Ltd. Japan) was placed in a test tube 2 of 10 mm in outside diameter as shown in Figure 1. Then, the composite was melted by heating and stirred quickly. Thereafter, the mouth of the test tube was sealed with a silicone rubber stopper 5 fitted with stainless steel electrodes 3 and temperature sensor 4 (covered with Teflon* or triEluoroethylene polymer ilm). While raisin~ t~le temperature gradually (about 2 C/min) rom around 12 C in an air thermostatic oven, the temperature and the value o resistance were measured by using a Ta~ara ~ogyo Digital Multi D611 and Takeda-Riken Digital Multimeter TR6841.
The results of the measurements are shown by -the curve ~ in Figure 4. As is seen in Figure 4, when the -temp-erature of the heat-sensitive electroresistive composite 1 exceeded 40C, the variation in resistance value be~an to be conspicuous, and whell the temperature passed the line o 50C, tlle resistance value increased sharply witll the positive charac-teristics shown distinctly. The inflection point of the resis-tance value was about 47C which is lower than the melting point oE 64C o~ trioxane.
* Trade mark 16.
~Z8~
EI~BODI~ENT 2 A mixture of 28 wt. ~ of graphite carbon used in Embodiment 1 and 72 wt. ~ of 18-crown-6 (from Merk Co. of West ~ermany) was melted and stirred in the same manner as used in Embodiment 1. Then, as shown in Figure 1, the temperature sensor 4, the stainless steel electrodes 3, and the silicone rubber stopper 5 were fitted. Thereafter, the temperature-resistance curve was plotted. The result is shown by the curve ~ in Figure 4. At 39C, the resistance value showed a rapid increase and the clear-cut positive characteristics were observed.
In the same manner as employed in Embodiment 1, a mixture of 28 wt. % of graphite carbon and 72 wt~ % of ben20-15-crown-5 (from Nakarai Kagaku Co., Ltd.) was melted and stirred. Thereafter, as shown in Figure 1, the temperature sensor 4, the stainless steel electrodes 3, and the silicone rubber stopper 5 were installed, and the resistance value at each temperature was measured. The result is represented by the curve ~ of Figure 4. In this case, when the temperature rose beyond 60C, the resistance value increased rapidly, with the ~ccompanyin~J positive characteristics appearing clearly.
Twenty-eight wt. % of graphite carbon and 72 wt. %
of dicyclohexyl-18-crown-6 (produced by Nakarai Kagaku Co., Ltd.) were melted and mixed. Then, as shown in Figures 2(a) and 2(b), the mixture was spread over a copper foil 7 on a glass board 6. F~rthermore, on top of it, another copper foil 7 was bonded. The temperature sensor 4 was also provided, and the resistallce value at each temperature was measured. The results of the measurement are shown by the graph 4 in Figure 4. When tne temperature exceeàed 24C, the abrupt increase in resistance value was observed, and 'he highly positive characteristic was exhibited.
El;~O~I~N
Graphite carbon in an amount of 28 wt. % and 72 wt.
of dibenzo-24-crown-8 ( rom Na~iarai Kagaku Yakuhin Co., Ltd.
Japan) were heated and melted in the test tube the same as in Embodiment 1, and the resistance value at respective temperatures were measured. The results are indicated by the curve ~ in Figure 5. When the temperature reached a level over 102-103C, the resistance value started to increase with a quick pace, and the strongly positive characteristics was obtained in the high temperature range.
E~ODI~ENT 6 Composites obtained by mixing polyethylene ~lycol (herein after will be called PEG ~6000 Erom Dai-ichi ~ogyo Seiyaliu Co., Ltd. Japan) with 20, 40, 60, and 80 wt. Q of ~raphite carboll, respectively, were placed in glass petri dishes (each petri dish is 12 cm in diameter and 2.5 cm in depth), respectively. Then, two copper plates with 0.4 mm thic~ness and 25 mm x 60 mm area were immersed and disposed as electrodes, with a distance of 9 cm ~rovided between them. The foregoing 18.
~2B~
nlicture ~as cooled -to room temperature and solidified, then, it was connected to a 100 V a.c. power source to start feeding the electrici-ty. The dura-tion of power supply, the varia-tion in temperature, the variation in electric current, and the resis-tance value during -the initial period and the terminal period of power supply were measured. The relation between the time (duration) and the temperature during 5 minutes in the initial period of power supply is shown in Figure 5, and the relation between the temperature and -the amperage of current for the same period is shown in Figure 6.
As shown in Figure 5, with 20 wt. % of carbon, the rise in temperature after the power feeding was not observed. With 80 wt. % of carbon, the temperature showed a sharp climb after the supply of power. At 30-60 wt. % in concentration of carbon, the temperature rose after the supply of power, and thereafter, the temperature was maintained constant at a certain le~el. It is evident also from Figure 6 that the foregoing phenomena is due to the positive characteristic o heat-sensitive electro-resis-tive composite 1. During the rise of temperature, the resistance value increases abruptly when the temperature exceeds a certain point. As the result, the amperage becomes low. When the temperature becomes constant, the amperage also becomes very low as shown in Figure 6. Figure 6 shows the result for the case of 30 wt. ~ in carbon concentration out of those snown in ~igure 5.
EMBODIMEL~T 7 ~, A mix-ture of PEG #~00~, ?EG ~2000 (from the 19 .
~28~7~2~
same company) and graphite carbon with a ratio by weight of 5:5;4 was melted by heating and stirred. Then, as shown in Figures 3(a) and 3(b), the mixture was poured into the space between two non-conductive sheets 9 (300 x 80 x 0.16 mm) made of polyester sheet lined with a fiber layer 8. On both sides, copper foil ta~e electrodes 10 were installed. The total thickness was 0.25 mm. Onto the surface thereof a temperature sensor 4 was mounted, and the resistance value at each tempera-ture was measured. The result obtained is shown by the curve (7) in Figure 7. At 40C, the flection point of the gradient was observed, and the positive characteristic was shown distinctly.
E~ODI~NT 8 Graphite carbon in amount of 28 wt. ~ was mixed with Pluronic wherein straight chains of poly (oxyethylene) are bonded to both ends of the normal chain molecules of poly (oxy-propylene) (F 68 from Asahi Denka Kogyo K.K. Japan, 8000 in average molecular weight). Then, after being melted by heating, the mixture was formed into a sheet as shown in Fi~ure 3 by the same process as taken in Embodiment 7. The resistance value at each temperature was measured, and the result indicated by the curve ~ in Figure 7 was obtained. ~t a temperature beyond ~6~C, the resistance value increased sharply, and a clear cut positive characteristic was shown.
E~ODI~NT 9 Into Pluronic F88 (11800 in average molecular weight), 20.
12a~7~28 which is the same as that in Embodiment 8 but somewhat greater in average molecular ~eight, 28 wt. % of graphite carbon was mixed. Thereafter, the measurement was carriea out in the same manner as in E~bodiment 8. The results are represented by the curve (9) in Figure 7. Same as in Embodiment 8, a highly positive characteriatic was confirmed.
~ODIMENT 10 Graphite carbon in amount of 28 wt. % was mixed into PEG ~5000 wherein the terminal are etherified with methoxy group (~ai-ichi Kogyo Seiya~u Co., Ltd. Japan), and the same as shown in Figure 3. Then, the resistance values at respective tempera-tures were measured. The curve ~ in Figure 7 represents the results of measurement. At around 45C, the resistance value started to increase rapidly, with the highly positive charac-teristic appearing at the same time.
E~ODIMENT 11 Into a mixture of PEG ~6000 and PEG X2000 with a ratio by weight of 1:1, 40 wt. % of fine splinters of carbon ~iber (l~i-201s from Kureha Cnemical Industry Co., Ltd. Japan, 15~in diameter, 130~ in length) was mixed. Then, as in Embodiment 7, the mixture thus prepared was formed into a sheet as shown in ~igure 3. The resistance value at each temperature was measured, and the result shown by the curve (11) in Figure 7 was obtained.
From about 44C, a high rate rise in resistance value was shown, and the positive characteristic was demonstrated clearly.
:~2~3742~
~lsoDI~NT 12 Figure 3(a) is a plan view showing the basic embodiment of the panel (sheet form) heating element, and Figure 3(b) is an enlarged sectional view taken along the line B-B thereof. In this en~odiment, for sealing the heat-sensitlve electroresistive composite l having the characteristics shown in Figure 6 and described in the Embodiment 6 in the space between two rectangular non-conductive cover sheets 9 and 9 used as insulators, a fiber layer 8 made of cotton gauze was impregnated with the heat-sensitive electroresistive composite 1. Also, tne copper foil tape electrodes 10 and 10 provided at the edge portions on both sides along the longitudinal direction of the sheet were used as conductors. The non-conductive cover sheets 9 and 9 are the laminated film formed of polyester film and an ethylene-vinyl acetate copolymer filmr and their edges were fused together by heat. The sheet form heating unit is 30~ mm in length and 100 mm in ~idth. I-t is a very thin sheet with a thickness of less than 2 mm at ma~imum. The charac~eristics of such sneet with various types of heat-sensitive electroresistive composite l sealed in them, respectively, are described in the embodiments starting from 14.
E~IBODII~lENT 13 The embodiment shown in Figure 8 is a large size shee-t orm h@atin~ unit. This she~t Eorm he~tin~ unit of 500 mm in vertical length, 850 mm in width and about 4 mm in thickness was made by using 2 non-conductive sheets 9 and 9 made of polycarbonate plates of l mm in thickness. The inside of this sheet form heating unit is divided into fifths alons the longi-12~ 2~3 tudinal direction into narrow sections by using but~l tape of5 mm in width and 2 mm in thickness. In this way, _ine compart-ments of thin space that is about 75 mm in width and about 830 mm in length were formed. Then, on both sides of the respective partition tapes 11 made of the butyl tape, conductors 12 and 12 with a capacity of ten am?s were disposed. Each of the thin spaces was filled, without any special treatment with 120 g of the heat-sensiti~;e electroresistive composite 1. Tre compo-sition ratio of the heat-sensitive`electroresistive com~osite 1 was 600 g of PEG (~6000) to 295 g of graphite powder.
Table 2 shows the relationship between the duration (time) of the connection of the abovementioned sheet form heating unit to a lOO ~ a.c. power source and the surface temperatures at A-E positions in Figure 8.
As is seen clearly from Table 2, right after the start of current feeding, as much as 7 A of current floweà; ~ut after one minute, it became 2 A; and after 5-10 minutes, it became nearly an equilibrium value of 0.6 A. Also, the temperature reached 34C from 21C, and it became a heating element that functions as a thermostat without letting the temperature go up to a range beyond 37C. Then, when the temperature went down, the amperac3e was increased because the resistance value decreased.
Thus, the temperature returnea again to a certain level. There-fore, it is most suitable as a thermal mat. For this embodiment, a sneet of thick cloth was placed over the surface of the sheet form heating unit, and the surface temperature was measured from tne outside of this covering cloth.
lZ~7~Z8 Current Surface Temperature (C) Time (A) A B C D E
-Right After Start of Power Supply 7 21 21 21 21 21 0.5 3.8 22 22 23.4 23 23 1 1.89 23 23 23.9 24 23 1.5 1.30 25 25 26 25 24 2 1.0 27 27 28 28 27 3 0.89 29 29 30.4 29 28 0.74 32 32 33.4 33 31 0.64 3~ 34` 35.3 35 34 0.61 35 35 36.4 37 35 0.59 37 37 36.6 37 36 `
300 0.62 37 37 36~2 37 36 Hereunder, a further detailed description will be given with reference to the Embodiments having the structure shown in Figures 3(a) and 3(b) referred to in Embodiment 12, but using other heat-sensitive electroresistive composites.
E~IBODIMEL~T 14 A coMposite containing PEG ~2000, PEG ~6000 and gra-pnite carbon with a ratio by weight of 5:5:4 was stirred after becoming molten by heating. Then, the composite was inserted between two polyester sheets lined with a fiber layer (thickness of the polyester sheet with fiber layer of 100~) as seen in Figure 3(a), and the entire assembly was formed into a sheet (300 mm in length, 80 mm in width) with a thickness of 250~.
24.
3~Z~7~Z~
The electrode used ~-as the zigzag copper tape as shown in the figure which was adhered in advance to inside of a polyester sheet (each electrode on both sides). An electric current of 100 V a.c. was fed to this sheet form heating unit, and the temperature and power consumption at respective times after the start of the sup?ly of power were measured. The results are shown in Figure 9. ~fter the current feeding, the tempera-ture rose gradually a?~roaching the saturation value. In the meantime, the power consumption reduced rapidly with the passage of time, and reached a certain constant level.
E~ODIMENT 15 A composite containing poly(oxyprop~lene) glycol etheylene oxide ~herea ter, will be cal`led Pluronic) (8000 in average molecular weight, Pluronic F 68 from Asashi Kagaku Kogyo ~.X.) and graphite carbon with the ratio weight of 10:4 and a composite containing Pluronic F 88 (11800 in average molecular weight) and graphite carbon with a ratio by weight of 10:4 were melted, respectively. Then, they were formed into sheet form heating elements the same ty~e as in Embodiment 12. Thereafter, the power of 100 V a.c. and ~00 V a~c. were fed to the heating elements containing F68 and F88, respectively and the temperature and the amperage were measured. The results are shown in Figure 10. Also with Pluronic F68 and Pluronic 88 having the structure wherein PEG is bonded to both ends of the polypropylene glycol chain, the temperature rose after the supply of power, and then, after a while, became a certain constant level, while, corres-ponding to the above, the amperage decreased and reached a 12~7~
constant value after a sh~rt time. Therefore, also in the case, it is possible to obtain sheet form heating units.
El~ODIMENT 16 A mixture of 10 parts (parts by weight) of P~G ~5000 wherein the ends are methoxidized and 4 parts of graphite carbon were melted by heating and stirring. Then, the same as in Embodiment 12, it was for~ed into a sheet form heating element, and the temperature and tne resistance value at each time after the feeding of electricity 100 V a.c. were measured. The results are shown in Figure 11. Also in t~is case, the temper-ature rose after the current feeding, and became a constant temperature after a while. In parallel with the above, the current decreased, then became constant in value after a short time.
E~ODI~NT 17 A composite of PEG ~2000, PEG ~6000 and the above-mentioned fine pieces of carbon fiber (~1-201 S from ~ureha Chemical Industry ~o.`, Ltd. Japan) with a ratio by weight of 3:3:4 was stirred after melted by heating, and formed into a sheet form heating unit as in Embodiment 12. Then, the tempera-ture and the resistance value at each time after feeding the current of 100 V a.c. were measured. The results are shown in Figure 12. Same as in the foregoing Embodiments 14 through 16, the temperature went up after the supply of power and then be-came a constant temperature. Meanwhile, the wattage also reached an equilibrium after being reduced to a certain point. Thus, it was proved that it can be applied as a safe and stable heating unit to various types of uses.
26.
As is described above, the strong PCT characteristics, a proper constant temperature (probably 30~50C), wide surface and the flexibility are essential for room heating panel.
~ ereunder, a concrete description on the effects of the heat-sensitive electroresistive composites according to :~287~Z~
this invention as well as on the characteristics of the heating units using the former will ~e given with reference to the embodiments of this invention.
E~lsODII~NT 1 Ten grams of heat-sensitive electroresistive composite 1 obtained by mixing 25 wt. % of graphite carbon (produced by Yoneyama Ya~uhin Kogyo Co., Ltd. Japan) and 75 wt. ~ of trioxane (extra pure reagent from Nakarai Kagaku Yakuhin, Co., Ltd. Japan) was placed in a test tube 2 of 10 mm in outside diameter as shown in Figure 1. Then, the composite was melted by heating and stirred quickly. Thereafter, the mouth of the test tube was sealed with a silicone rubber stopper 5 fitted with stainless steel electrodes 3 and temperature sensor 4 (covered with Teflon* or triEluoroethylene polymer ilm). While raisin~ t~le temperature gradually (about 2 C/min) rom around 12 C in an air thermostatic oven, the temperature and the value o resistance were measured by using a Ta~ara ~ogyo Digital Multi D611 and Takeda-Riken Digital Multimeter TR6841.
The results of the measurements are shown by -the curve ~ in Figure 4. As is seen in Figure 4, when the -temp-erature of the heat-sensitive electroresistive composite 1 exceeded 40C, the variation in resistance value be~an to be conspicuous, and whell the temperature passed the line o 50C, tlle resistance value increased sharply witll the positive charac-teristics shown distinctly. The inflection point of the resis-tance value was about 47C which is lower than the melting point oE 64C o~ trioxane.
* Trade mark 16.
~Z8~
EI~BODI~ENT 2 A mixture of 28 wt. ~ of graphite carbon used in Embodiment 1 and 72 wt. ~ of 18-crown-6 (from Merk Co. of West ~ermany) was melted and stirred in the same manner as used in Embodiment 1. Then, as shown in Figure 1, the temperature sensor 4, the stainless steel electrodes 3, and the silicone rubber stopper 5 were fitted. Thereafter, the temperature-resistance curve was plotted. The result is shown by the curve ~ in Figure 4. At 39C, the resistance value showed a rapid increase and the clear-cut positive characteristics were observed.
In the same manner as employed in Embodiment 1, a mixture of 28 wt. % of graphite carbon and 72 wt~ % of ben20-15-crown-5 (from Nakarai Kagaku Co., Ltd.) was melted and stirred. Thereafter, as shown in Figure 1, the temperature sensor 4, the stainless steel electrodes 3, and the silicone rubber stopper 5 were installed, and the resistance value at each temperature was measured. The result is represented by the curve ~ of Figure 4. In this case, when the temperature rose beyond 60C, the resistance value increased rapidly, with the ~ccompanyin~J positive characteristics appearing clearly.
Twenty-eight wt. % of graphite carbon and 72 wt. %
of dicyclohexyl-18-crown-6 (produced by Nakarai Kagaku Co., Ltd.) were melted and mixed. Then, as shown in Figures 2(a) and 2(b), the mixture was spread over a copper foil 7 on a glass board 6. F~rthermore, on top of it, another copper foil 7 was bonded. The temperature sensor 4 was also provided, and the resistallce value at each temperature was measured. The results of the measurement are shown by the graph 4 in Figure 4. When tne temperature exceeàed 24C, the abrupt increase in resistance value was observed, and 'he highly positive characteristic was exhibited.
El;~O~I~N
Graphite carbon in an amount of 28 wt. % and 72 wt.
of dibenzo-24-crown-8 ( rom Na~iarai Kagaku Yakuhin Co., Ltd.
Japan) were heated and melted in the test tube the same as in Embodiment 1, and the resistance value at respective temperatures were measured. The results are indicated by the curve ~ in Figure 5. When the temperature reached a level over 102-103C, the resistance value started to increase with a quick pace, and the strongly positive characteristics was obtained in the high temperature range.
E~ODI~ENT 6 Composites obtained by mixing polyethylene ~lycol (herein after will be called PEG ~6000 Erom Dai-ichi ~ogyo Seiyaliu Co., Ltd. Japan) with 20, 40, 60, and 80 wt. Q of ~raphite carboll, respectively, were placed in glass petri dishes (each petri dish is 12 cm in diameter and 2.5 cm in depth), respectively. Then, two copper plates with 0.4 mm thic~ness and 25 mm x 60 mm area were immersed and disposed as electrodes, with a distance of 9 cm ~rovided between them. The foregoing 18.
~2B~
nlicture ~as cooled -to room temperature and solidified, then, it was connected to a 100 V a.c. power source to start feeding the electrici-ty. The dura-tion of power supply, the varia-tion in temperature, the variation in electric current, and the resis-tance value during -the initial period and the terminal period of power supply were measured. The relation between the time (duration) and the temperature during 5 minutes in the initial period of power supply is shown in Figure 5, and the relation between the temperature and -the amperage of current for the same period is shown in Figure 6.
As shown in Figure 5, with 20 wt. % of carbon, the rise in temperature after the power feeding was not observed. With 80 wt. % of carbon, the temperature showed a sharp climb after the supply of power. At 30-60 wt. % in concentration of carbon, the temperature rose after the supply of power, and thereafter, the temperature was maintained constant at a certain le~el. It is evident also from Figure 6 that the foregoing phenomena is due to the positive characteristic o heat-sensitive electro-resis-tive composite 1. During the rise of temperature, the resistance value increases abruptly when the temperature exceeds a certain point. As the result, the amperage becomes low. When the temperature becomes constant, the amperage also becomes very low as shown in Figure 6. Figure 6 shows the result for the case of 30 wt. ~ in carbon concentration out of those snown in ~igure 5.
EMBODIMEL~T 7 ~, A mix-ture of PEG #~00~, ?EG ~2000 (from the 19 .
~28~7~2~
same company) and graphite carbon with a ratio by weight of 5:5;4 was melted by heating and stirred. Then, as shown in Figures 3(a) and 3(b), the mixture was poured into the space between two non-conductive sheets 9 (300 x 80 x 0.16 mm) made of polyester sheet lined with a fiber layer 8. On both sides, copper foil ta~e electrodes 10 were installed. The total thickness was 0.25 mm. Onto the surface thereof a temperature sensor 4 was mounted, and the resistance value at each tempera-ture was measured. The result obtained is shown by the curve (7) in Figure 7. At 40C, the flection point of the gradient was observed, and the positive characteristic was shown distinctly.
E~ODI~NT 8 Graphite carbon in amount of 28 wt. ~ was mixed with Pluronic wherein straight chains of poly (oxyethylene) are bonded to both ends of the normal chain molecules of poly (oxy-propylene) (F 68 from Asahi Denka Kogyo K.K. Japan, 8000 in average molecular weight). Then, after being melted by heating, the mixture was formed into a sheet as shown in Fi~ure 3 by the same process as taken in Embodiment 7. The resistance value at each temperature was measured, and the result indicated by the curve ~ in Figure 7 was obtained. ~t a temperature beyond ~6~C, the resistance value increased sharply, and a clear cut positive characteristic was shown.
E~ODI~NT 9 Into Pluronic F88 (11800 in average molecular weight), 20.
12a~7~28 which is the same as that in Embodiment 8 but somewhat greater in average molecular ~eight, 28 wt. % of graphite carbon was mixed. Thereafter, the measurement was carriea out in the same manner as in E~bodiment 8. The results are represented by the curve (9) in Figure 7. Same as in Embodiment 8, a highly positive characteriatic was confirmed.
~ODIMENT 10 Graphite carbon in amount of 28 wt. % was mixed into PEG ~5000 wherein the terminal are etherified with methoxy group (~ai-ichi Kogyo Seiya~u Co., Ltd. Japan), and the same as shown in Figure 3. Then, the resistance values at respective tempera-tures were measured. The curve ~ in Figure 7 represents the results of measurement. At around 45C, the resistance value started to increase rapidly, with the highly positive charac-teristic appearing at the same time.
E~ODIMENT 11 Into a mixture of PEG ~6000 and PEG X2000 with a ratio by weight of 1:1, 40 wt. % of fine splinters of carbon ~iber (l~i-201s from Kureha Cnemical Industry Co., Ltd. Japan, 15~in diameter, 130~ in length) was mixed. Then, as in Embodiment 7, the mixture thus prepared was formed into a sheet as shown in ~igure 3. The resistance value at each temperature was measured, and the result shown by the curve (11) in Figure 7 was obtained.
From about 44C, a high rate rise in resistance value was shown, and the positive characteristic was demonstrated clearly.
:~2~3742~
~lsoDI~NT 12 Figure 3(a) is a plan view showing the basic embodiment of the panel (sheet form) heating element, and Figure 3(b) is an enlarged sectional view taken along the line B-B thereof. In this en~odiment, for sealing the heat-sensitlve electroresistive composite l having the characteristics shown in Figure 6 and described in the Embodiment 6 in the space between two rectangular non-conductive cover sheets 9 and 9 used as insulators, a fiber layer 8 made of cotton gauze was impregnated with the heat-sensitive electroresistive composite 1. Also, tne copper foil tape electrodes 10 and 10 provided at the edge portions on both sides along the longitudinal direction of the sheet were used as conductors. The non-conductive cover sheets 9 and 9 are the laminated film formed of polyester film and an ethylene-vinyl acetate copolymer filmr and their edges were fused together by heat. The sheet form heating unit is 30~ mm in length and 100 mm in ~idth. I-t is a very thin sheet with a thickness of less than 2 mm at ma~imum. The charac~eristics of such sneet with various types of heat-sensitive electroresistive composite l sealed in them, respectively, are described in the embodiments starting from 14.
E~IBODII~lENT 13 The embodiment shown in Figure 8 is a large size shee-t orm h@atin~ unit. This she~t Eorm he~tin~ unit of 500 mm in vertical length, 850 mm in width and about 4 mm in thickness was made by using 2 non-conductive sheets 9 and 9 made of polycarbonate plates of l mm in thickness. The inside of this sheet form heating unit is divided into fifths alons the longi-12~ 2~3 tudinal direction into narrow sections by using but~l tape of5 mm in width and 2 mm in thickness. In this way, _ine compart-ments of thin space that is about 75 mm in width and about 830 mm in length were formed. Then, on both sides of the respective partition tapes 11 made of the butyl tape, conductors 12 and 12 with a capacity of ten am?s were disposed. Each of the thin spaces was filled, without any special treatment with 120 g of the heat-sensiti~;e electroresistive composite 1. Tre compo-sition ratio of the heat-sensitive`electroresistive com~osite 1 was 600 g of PEG (~6000) to 295 g of graphite powder.
Table 2 shows the relationship between the duration (time) of the connection of the abovementioned sheet form heating unit to a lOO ~ a.c. power source and the surface temperatures at A-E positions in Figure 8.
As is seen clearly from Table 2, right after the start of current feeding, as much as 7 A of current floweà; ~ut after one minute, it became 2 A; and after 5-10 minutes, it became nearly an equilibrium value of 0.6 A. Also, the temperature reached 34C from 21C, and it became a heating element that functions as a thermostat without letting the temperature go up to a range beyond 37C. Then, when the temperature went down, the amperac3e was increased because the resistance value decreased.
Thus, the temperature returnea again to a certain level. There-fore, it is most suitable as a thermal mat. For this embodiment, a sneet of thick cloth was placed over the surface of the sheet form heating unit, and the surface temperature was measured from tne outside of this covering cloth.
lZ~7~Z8 Current Surface Temperature (C) Time (A) A B C D E
-Right After Start of Power Supply 7 21 21 21 21 21 0.5 3.8 22 22 23.4 23 23 1 1.89 23 23 23.9 24 23 1.5 1.30 25 25 26 25 24 2 1.0 27 27 28 28 27 3 0.89 29 29 30.4 29 28 0.74 32 32 33.4 33 31 0.64 3~ 34` 35.3 35 34 0.61 35 35 36.4 37 35 0.59 37 37 36.6 37 36 `
300 0.62 37 37 36~2 37 36 Hereunder, a further detailed description will be given with reference to the Embodiments having the structure shown in Figures 3(a) and 3(b) referred to in Embodiment 12, but using other heat-sensitive electroresistive composites.
E~IBODIMEL~T 14 A coMposite containing PEG ~2000, PEG ~6000 and gra-pnite carbon with a ratio by weight of 5:5:4 was stirred after becoming molten by heating. Then, the composite was inserted between two polyester sheets lined with a fiber layer (thickness of the polyester sheet with fiber layer of 100~) as seen in Figure 3(a), and the entire assembly was formed into a sheet (300 mm in length, 80 mm in width) with a thickness of 250~.
24.
3~Z~7~Z~
The electrode used ~-as the zigzag copper tape as shown in the figure which was adhered in advance to inside of a polyester sheet (each electrode on both sides). An electric current of 100 V a.c. was fed to this sheet form heating unit, and the temperature and power consumption at respective times after the start of the sup?ly of power were measured. The results are shown in Figure 9. ~fter the current feeding, the tempera-ture rose gradually a?~roaching the saturation value. In the meantime, the power consumption reduced rapidly with the passage of time, and reached a certain constant level.
E~ODIMENT 15 A composite containing poly(oxyprop~lene) glycol etheylene oxide ~herea ter, will be cal`led Pluronic) (8000 in average molecular weight, Pluronic F 68 from Asashi Kagaku Kogyo ~.X.) and graphite carbon with the ratio weight of 10:4 and a composite containing Pluronic F 88 (11800 in average molecular weight) and graphite carbon with a ratio by weight of 10:4 were melted, respectively. Then, they were formed into sheet form heating elements the same ty~e as in Embodiment 12. Thereafter, the power of 100 V a.c. and ~00 V a~c. were fed to the heating elements containing F68 and F88, respectively and the temperature and the amperage were measured. The results are shown in Figure 10. Also with Pluronic F68 and Pluronic 88 having the structure wherein PEG is bonded to both ends of the polypropylene glycol chain, the temperature rose after the supply of power, and then, after a while, became a certain constant level, while, corres-ponding to the above, the amperage decreased and reached a 12~7~
constant value after a sh~rt time. Therefore, also in the case, it is possible to obtain sheet form heating units.
El~ODIMENT 16 A mixture of 10 parts (parts by weight) of P~G ~5000 wherein the ends are methoxidized and 4 parts of graphite carbon were melted by heating and stirring. Then, the same as in Embodiment 12, it was for~ed into a sheet form heating element, and the temperature and tne resistance value at each time after the feeding of electricity 100 V a.c. were measured. The results are shown in Figure 11. Also in t~is case, the temper-ature rose after the current feeding, and became a constant temperature after a while. In parallel with the above, the current decreased, then became constant in value after a short time.
E~ODI~NT 17 A composite of PEG ~2000, PEG ~6000 and the above-mentioned fine pieces of carbon fiber (~1-201 S from ~ureha Chemical Industry ~o.`, Ltd. Japan) with a ratio by weight of 3:3:4 was stirred after melted by heating, and formed into a sheet form heating unit as in Embodiment 12. Then, the tempera-ture and the resistance value at each time after feeding the current of 100 V a.c. were measured. The results are shown in Figure 12. Same as in the foregoing Embodiments 14 through 16, the temperature went up after the supply of power and then be-came a constant temperature. Meanwhile, the wattage also reached an equilibrium after being reduced to a certain point. Thus, it was proved that it can be applied as a safe and stable heating unit to various types of uses.
26.
Claims (8)
1. A heat-sensitive electroresistive composite which exhibits an abrupt change in electric resistance with increasing temperature, which comprises:
organic compounds containing a plural number of alkylene oxides as the unit structure in their molecules; and fine pieces of carbon in the form of a member chosen from powder, fiber, and whiskers.
organic compounds containing a plural number of alkylene oxides as the unit structure in their molecules; and fine pieces of carbon in the form of a member chosen from powder, fiber, and whiskers.
2. A heat-sensitive electroresistive composite as set forth in Claim 1, wherein said organic compounds containing said plural number of alkylene oxides as the unit structure in their molecules are straight chain polyalkylene oxide and its derivatives.
3. A heat-sensitive electroresistive composite as set forth in Claim 1, wherein said organic compounds containing said plural number of alkylene oxides as the unit structure in their molecules are cyclic ether compounds.
4. A heat-sensitive electroresistive composite as set forth in Claim 1, wherein said organic compound comprises polyethylene glycol and said fine pieces of carbon comprise graphite powder with a mixing ratio of 100 parts by weight of polyethylene glycol to 10 to 80 parts by weight of graphite powder.
27.
27.
5. A thermostatic heating element comprising:
a heat-sensitive electroresistive composite which exhibits an abrupt change in electric resistance with increasing temperature electrodes which are sealed together with said heat-sensitive electroresistive composite by means of insulators; and wherein said heat-sensitive electroresistive composite is in turn comprised of:
an organic compound containing a plural number of alkylene oxides as the unit structure in its molecules; and fine pieces of carbon in the form of a member chosen from powder, fiber, and whiskers.
a heat-sensitive electroresistive composite which exhibits an abrupt change in electric resistance with increasing temperature electrodes which are sealed together with said heat-sensitive electroresistive composite by means of insulators; and wherein said heat-sensitive electroresistive composite is in turn comprised of:
an organic compound containing a plural number of alkylene oxides as the unit structure in its molecules; and fine pieces of carbon in the form of a member chosen from powder, fiber, and whiskers.
6. A thermostatic heating element as set forth in Claim 5, wherein said heating element is a sheet form heating unit using plastic sheet as said insulator.
7. A heat-sensitive electroresistive composite as set forth in Claim 1, wherein said alkylene oxides are selected from the group consisting of straight chain polyalkylene oxide and its derivatives or cyclic ether compounds.
8. A heat-sensitive electroresistive composite as set forth in Claim 4, wherein said alkylene oxides are selected from the group consisting of straight chain polyalkylene oxide and its derivatives or cyclic ether compounds.
28.
28.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000475974A CA1287428C (en) | 1984-09-11 | 1985-03-07 | Composition of heat-sensitive electrosensitive substances and a panel heater made therefrom |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/649,535 US4629584A (en) | 1984-09-11 | 1984-09-11 | Composition of heat-sensitive electrosensitive substances and a panel heater made therefrom |
| CA000475974A CA1287428C (en) | 1984-09-11 | 1985-03-07 | Composition of heat-sensitive electrosensitive substances and a panel heater made therefrom |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1287428C true CA1287428C (en) | 1991-08-06 |
Family
ID=25670606
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000475974A Expired - Lifetime CA1287428C (en) | 1984-09-11 | 1985-03-07 | Composition of heat-sensitive electrosensitive substances and a panel heater made therefrom |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1287428C (en) |
-
1985
- 1985-03-07 CA CA000475974A patent/CA1287428C/en not_active Expired - Lifetime
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0376195A1 (en) | Method of producing a self-temperature control flexible plane heater | |
| FI65522C (en) | SKIKTAT SJAELVREGLERANDE UPPVAERMNINGSFOEREMAOL | |
| RU2344574C2 (en) | Carbon flexible heating structure | |
| FI80820B (en) | Self-regulating electrical heating device | |
| US4629584A (en) | Composition of heat-sensitive electrosensitive substances and a panel heater made therefrom | |
| EP0219678B1 (en) | Method for controlling steady state exothermic temperature in the use of heat sensitive-electrically resistant composites | |
| WO2008048176A1 (en) | Heating element | |
| CA1287428C (en) | Composition of heat-sensitive electrosensitive substances and a panel heater made therefrom | |
| CA2561750A1 (en) | Conductive composition for producing carbon flexible heating structure, carbon flexible heating structure using the same, and manufacturing method thereof | |
| KR920003017B1 (en) | Conductive heat storage medium | |
| JPH0374473B2 (en) | ||
| JP3317895B2 (en) | Temperature self-control function heater | |
| Hu et al. | TiO—epoxy composite thermistors | |
| CA1133085A (en) | Temperature sensitive electrical device | |
| JPH0429197B2 (en) | ||
| JP3957580B2 (en) | Self-temperature control type surface heater | |
| JPH0374472B2 (en) | ||
| KR960022851A (en) | Composition of Polymer PTC (Constant Temperature Coefficient) | |
| JPS59110101A (en) | Heat sensitive electric resistance composition | |
| JPS5966093A (en) | Conductive heat storage medium | |
| JPH0748396B2 (en) | Sheet heating element | |
| US3703478A (en) | Thermistors | |
| JPS60124388A (en) | Electrode for panel heater | |
| JP2000091060A (en) | Heat sensitive electric resistance heater and manufacture thereof | |
| JPH10223406A (en) | Ptc composition and ptc element employing it |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed | ||
| MKLA | Lapsed |
Effective date: 20040806 |