Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/14—Conductive material dispersed in non-conductive inorganic material
  • H01B1/18—Conductive material dispersed in non-conductive inorganic material the conductive material comprising carbon-silicon compounds, carbon or silicon
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon

Definitions

• the present invention relates to a conductive composition in which the weight ratio between liquid silicon rubber and conductive carbon black is 100:1-15, a carbon flexible heating structure which is obtained by molding the conductive composition in a particular shape or by coating the conductive composition on a mold having a particular shape, and a method of manufacturing the carbon flexible heating structure.
• polymer materials have been regarded as highly insulating materials. Although the polymer materials work well as electrically insulating materials due to a low conductivity, they function as electrical conductors when a filler such as carbon black, carbon fiber, or metal powder is added.
• the added filler forms an electrical path in the polymer material which works as a passage of electrons so that the polymer material becomes an electrical conductor.
• Carbon black and carbon fiber are mainly used as the conductive filler added to provide a positive temperature coefficient (PTC) function to the polymer.
• Crystalline polymer such as polyethylene is mainly used as the polymer material.
• the resistance of the polymer material is suddenly increased greatly, which is referred to as a static characteristic temperature coefficient or a PTC phenomenon. That is, while resistance is relatively low at a low temperature, when the temperature reaches a predetermined degree, the resistance increases suddenly so that current is difficult to flow.
• the temperature at which the above sudden change occurs is referred to as a switching temperature or Curie temperature.
• the switching temperature is defined as a temperature corresponding to double the minimum resistance value or a resistance value at a reference temperature (25°C) and is a major parameter in the property of the material.
• the material can be used for a temperature sensor or overheat protection using a resistance-temperature property, a heater using a current-voltage property, or a delay circuit or a demagnetic circuit using a current at ⁇ tenuation property.
• the PTC using polymer can greatly perform both protection functions with respect to overheat and overload.
• the polymer PTC material can be used as a superior PTC material by compensating for drawbacks of a conventional ceramic PTC such as a low conductivity, high process costs, and a fixed shape.
• a conventional ceramic PTC such as a low conductivity, high process costs, and a fixed shape.
• the polymer PTC material has already been widely used in designing small devices and the use thereof is fast increasing.
• the temperature of the polymer PTC decreases after heat or current is cut off. Also, the PTC material has a function of automatically restoring without being replaced when the over-current is removed.
• NTC NTC
• the NTC phenomenon occurs when the conductive particles are moved by cross- linking in a melting state so that a new structure is formed.
• the cross-linking forms a network to allow the conductive particles to strongly attract to each other and restrict motion of the conductive particles so that a structural stability can be obtained.
• the polymer PTC material is used to prevent damage to electronic products or electronic circuits and has already been used in designing small devices because the manufacturing shape thereof is free. However, since a cross-linker is added to restrict the NTC phenomenon and then the polymer PTC material is cured so that it has a hard plastic structure, the polymer PTC material has a limit in the process and purpose thereof when being used for a general heating body.
• the present invention provides a carbon flexible heating structure having superior physical and chemical properties such as heat resistance, winter-hardiness, ozone resistance, electricity insulation, and flexibility, a conductive composition used therefor, and a method of manufacturing the carbon flexible heating structure.
• the present invention provides a method of manufacturing the carbon flexible heating structure which can reduce manufacturing costs by simplifying a manu ⁇ facturing process.
• the present invention provides a carbon flexible heating structure in which a phenomenon of peeling off of the structure does not occur even when a periodic change between thermal expansion and thermal contraction repeats, by mixing and agitating only a diluent and liquid silicon rubber that is the same material as the conductive composition and coating the mixture on a surface of the carbon flexible heating structure, as necessary, for insulation.
• the present invention provides a carbon flexible heating structure which can be used in a variety of fields by making a frame mold into a variety of shapes such as a mesh shape, a plate shape, a rod shape, a ring shape, or a bar shape during the manu ⁇ facturing of the carbon flexible heating structure.
• a conductive composition formed of a mixture of liquid silicon rubber and conductive carbon black or liquid silicon rubber and graphite powder wherein weight ratios between the liquid silicon rubber and the conductive carbon black and the liquid silicon rubber and the graphite powder are 100:1-15 and 100:10-150, respectively.
• the thermal expansion coefficient of the liquid silicon rubber is 200x10 -K-I through 300x lO ⁇ -K "1 .
• the size of a particle of the conductive carbon black is 20 through 40 nm and the amount of absorption of dibutyl phthalate (DBP) is 300 through 50 ml/100g.
• the size of a particle of the graphite powder is 1 through 10 mm and electrical resistance is
• a method of manufacturing a carbon flexible heating structure comprises mixing a conductive composition formed of liquid silicon rubber and a filler, agitating a mixture of the liquid silicon rubber and conductive carbon black by adding a diluent at a rate of
• the carbon flexible heating structure according to the present invention and a conductive composition for manufacturing the same have superior phisical and chemical properties such as heat resistance, winter-hardiness, ozone resistance, and electricity insulation, and have a self-control resistance heating function and superior flexibility, so that the number of application fields of the carbon flexible heating structure according to the present invention are drastically increased.
• the carbon flexible heating structure according to the present invention can provide an economic manufacturing method by simplifying the manufacturing steps to lower the manufacturing costs.
• a phenomenon of peeling off of the structure does not occur even when a periodic change between thermal expansion and thermal contraction repeats, by mixing and agitating only a diluent and liquid silicon rubber that is the same materal as the conductive composition and coating the mixture on a surface of the carbon flexible heating structure, as necessary, for insulation.
• the carbon flexbile heating structure may be used in a variety of fields by molding the structure into a variety of shapes in the step of molding or by making a frame mold into a variety of shapes such as a mesh shape, a plate shape, a rod shape, a ring shape, or a bar shape.
• FIG. 1 is a flow chart for explaining a manufacturing process of a carbon flexible heating structure according to an embodiment of the present invention
• FIG. 2 is a plan view illustrating a structure of a carbon flexible heating mesh according to an embodiment of the present invention
• FIG. 3 is a cross-sectional view illustrating a fine structure of carbon flexible heating mesh of FIG. 2;
• FIG. 4 is a view illustrating a fine structure of a conductive composition according to an embodiment of the present invention.
• FIG. 5 is a view illustrating a fine structure of the conductive composition shown in
• FIG. 4 in a state in which the temperature is higher than room temperature
• FIG. 6 is a graph showing a temperature-resistance property of a conventional PTC device.
• FIG. 7 is a graph showing a temperature-resistance property of the carbon flexible heating structure of FIG. 1. Best Mode for Carrying Out the Invention
• FIG. 1 is a flow chart for explaining a manufacturing process of a carbon flexible heating structure according to an embodiment of the present invention.
• the manufacturing process includes mixing liquid silicon rubber and conductive carbon black (Operation 110), agitating by adding a diluent to a mixture of liquid silicon rubber and conductive carbon black (Operation 120), and molding and curing by pasting or coating the mixture on a structure having a particular shape (Operation 130).
• liquid silicon rubber and conductive carbon black are mixed at a mixture ratio of about 100:1-15 based on a weight ratio thereof.
• a diluent is added to the mixture of liquid silicon rubber and conductive carbon black and the mixture is agitated.
• Toluene or xylene is mainly used as the diluent.
• the diluent added to the mixture in the agitating operation 120 is preferably within a range of about 0-100% with respect to the weight ratio of the liquid silicon rubber.
• the agitating operation 120 when the content of carbon black is small, flexibility of the conductive composition is obtained without adding the diluent.
• the flexibility of the conductive composition is improved by adding the diluent and agitating the mixture.
• the conductive composition underwent the mixing operation 110 and the agitating operation 120 undergoes the molding and curing operation 130 so that a carbon flexible heating structure befitting a desired use is obtained.
• the conductive composition that is the agitated mixture is molded into a particular shape and then cured, or pasted or coated on a mold having a particular shape and then cured.
• a structure having a variety of shapes such as a mesh shape, a plate shape, a rod shape, a ring shape, or a bar shape may be used as the particular shape or the mold having a particular shape.
• Table 1 shows curing time after the conductive composition is coated on the mold having a particular shape.
• Table 2 below shows a thermal property of polyethylene and liquid silicon rubber according to the present invention.
• Table 3 below shows the life span of use of the silicon rubber according to a temperature.
• the liquid silicon rubber is used for the conductive composition because it exhibits superior heat resistance, winter-hardiness, ozone resistance, electricity insulation, and flexibility. As shown in Table 2, since the thermal expansion coefficient of the liquid silicon rubber that is 270x10 -K is higher, by about two times, than that of polyethylene that is 150 xlO -K , the carbon flexible heating structure has a self- control resistance heating function.
• the carbon flexible heating structure according to the present invention uses the liquid silicon rubber, it exhibits a superior flexibility so that the application fields of the carbon flexible heating mesh according to the present invention drastically increase. Also, silicon rubber can be used over 20 years or semi-permanently according to a range of temperature in which the silicon rubber is used.
• Table 4 shows typical properties of the conductive carbon black according to the present invention. [50] Table 4
• the conductive carbon black It is the typical properties of the conductive carbon black that the size of a particle is 40 nanometers, a porosity is 60%, and the number of particles is 38x10 per gram. This means that the conductive carbon black has a high conductive structure in which the absorption amount of dibutyl phthalate (DBP) is between 300-500 ml/100g.
• DBP dibutyl phthalate
• FIG. 2 illustrates a structure of a mesh type of a carbon flexible heating structure according to an embodiment of the present invention (hereinafter, referred to as the "carbon flexible heating mesh").
• FIG. 3 is a cross-sectional view the carbon flexible heating mesh of FIG. 2.
• a carbon flexible heating mesh 200 is a fabric made of a woof 230 and a warp 220. Port portions 210a and 210b are formed longer than the woof 230 and the warp 220 of the fabric as ports to supply electric power to both end portions of the woof 230 or the warp 220.
• the port portions 210a and 210b are formed of a conductive metal wire exhibiting superior conductivity and a tin-plated copper wire or a silver wire exhibiting superior conductivity are used as the conductive metal wire.
• a conductive composition 250 is preferably coated or pasted on a frame structure 240 to a thickness of 0.05 through 0.15 mm.
• a mixture obtained by mixing liquid silicon rubber and a diluent only and agitating the same can be coated on a surface of the carbon flexible heating mesh 200, as necessary, for insulation. Since an insulation coating 260 is formed of the liquid silicon rubber that is the same material as the conductive composition 250, even when there is a periodic change between thermal expansion and thermal contraction that repeatedly occur, a peeling-off phenomenon of the mesh 200 does not occur.
• FIG. 4 is a view illustrating a fine structure of a conductive composition according to an embodiment of the present invention at room temperature.
• FIG. 5 is a view il ⁇ lustrating a fine structure of the conductive composition shown in FIG. 4 in a state in which the temperature is higher than the room temperature.
• FIGS. 4 and 5 show a degree of orientation of a conductive carbon black 310 in a liquid silicon rubber 320.
• Particles of the conductive carbon black 310 are distributed with a narrow gap which is filled with the liquid silicon rubber 320.
• the narrow gap works as a potential barrier and electrons are tunneled though the narrow gap by thermal fluctuation so that electrical conductivity is exerted.
• the self-control resistance heating function according to the present invention uses tunneling current as described above.
• the tunneling current flows through the narrow gap when the narrow gap made of the silicon rubber 320 is maintained to be 1 nm or less and is very sensitive to a distance so that it changes in inverse proportion and ex ⁇ ponentially with respect to a change in the distance.
• FIG. 6 is a graph showing a temperature-resistance property of a conventional PTC device.
• FIG. 7 is a graph showing a temperature-resistance property of the carbon flexible heating structure according to an embodiment of the present invention.
• FIG. 7 shows a temperature-resistance characteristic curve of a general polymer PTC device as a comparative example.
• the temperature-resistance characteristic curve of the conventional PTC device shows that the heat temperature of the PTC device is determined by a crystalline melting temperature Tm of each polymer material and that the resistance rate no longer increases at a particular temperature after passing the switching temperature.
• the carbon flexible heating mesh according to the present invention unlike the conventional PTC device, exhibits a self-control resistance heating property, that is, the resistance rate gradually increases as the temperature increases.
• graphite powder can be used instead of the conductive carbon black.
• the graphite powder can be easily mixed with the liquid silicon rubber.
• the weight ratio between the liquid silicon rubber and the graphite powder is 100:10-150 in a conductive composition made of a mixture of the liquid silicon rubber and the graphite powder.
• the average particle size of graphite powder is 1-10 mm and electrical resistance is 0.0005-0.08 ⁇ -cm.
• a short staple can be used as a reinforcing material for the conductive composition obtained by mixing the liquid silicon rubber and the conductive carbon black or graphite powder as the filler.
• the short staple may be glass fiber, carbon fiber, or graphite fiber having a diameter of 1 through 50 mm.
• the conductive composition and the carbon flexible heating structure according to the present invention can be applied to the fields of a temperature sensor, a temperature compensation device, protection against overheat, a heater, and an electric circuit for protection of over-current and are not limited to the above-described embodiments.

Landscapes

• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Resistance Heating (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Surface Heating Bodies (AREA)
• Conductive Materials (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=35783058

Family Applications (1)

Country Status (4)

Cited By (1)

Families Citing this family (7)

Citations (4)

Family Cites Families (18)

• 2005
  • 2005-03-29 EP EP05789643A patent/EP1733401A4/de not_active Withdrawn
  • 2005-03-29 JP JP2007504893A patent/JP2007531217A/ja active Pending
  • 2005-03-29 WO PCT/KR2005/000914 patent/WO2006004282A1/en active Application Filing
  • 2005-03-29 CA CA002561750A patent/CA2561750A1/en not_active Abandoned

Patent Citations (4)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events