KR20070095125A - Polyester nanocomposite - Google Patents

Abstract

A polyester nanocomposite is provided to allow carbon nanotubes and metal nanoparticles as fillers having excellent heat conductivity characteristics to be effectively dispersed on a polyester matrix, to obtain a higher molecular weight, and to improve thermal, mechanical and electrical properties of the resin itself. A polyester nanocomposite is obtained by dispersing composite fillers comprising carbon nanotubes and metal nanoparticles in polyester, wherein 0.1-5 wt% of carbon nanotubes and 0.1-5 wt% of metal nanoparticles are dispersed in the balance amount of polyester. The carbon nanotube includes a single wall nanotube, the metal nanoparticle is a colloidal filler of gold, silver, copper, nickel or platinum, and the polyester is a cyclic oligomer depolymerized from polyethylene terephthalate and polybutylene terephthalate.

Description

Polyester nanocomposite {POLYESTER NANOCOMPOSITE}

1 is a manufacturing process of the polyester nanocomposite according to an embodiment of the present invention

The present invention relates to a polyester nanocomposite, and more particularly, carbon nanotubes and metal nanoparticles, which are fillers having excellent thermal conductivity properties, can be effectively dispersed on a polyester matrix, and high molecular weight can be expected. The present invention relates to a polyester nanocomposite capable of improving its thermal, mechanical, and electrical properties, electromagnetic shielding rate, and thermal conductivity.

In general, since the introduction of high molecular materials into the industrial field and daily life, many efforts have been made in terms of performance improvement to expand the use of the high molecular materials. The performance of polymer materials continues to improve due to the synthesis of new polymers, polymer blending, and the complexation of polymers with inorganic materials. Among these, the polymer nanocomposite material is a method of obtaining a composite material by dispersing nanoscale-sized fine materials in a matrix polymer in a nano-sized size, whereas by simply blending a composite material so far, the nano-sized material is uniformly distributed in the matrix polymer. Dispersed composites have new and improved properties than existing similar materials, and thus are being developed into functional polymer materials for various applications.

Nanoscale nanomaterials such as carbon nanotubes and fullerenes exhibit new properties and functions not found in bulk materials. For this reason, the manufacturing technology of new nanoscale materials is an important foundation technology supporting nanotechnology, and great attention is paid to the development thereof.

The development of advanced materials and new materials is very important as a foundation to support science and technology and industries in a wide range of fields such as electronics and biotechnology. In particular, the micro-machining technology at the nano level, which is the manufacturing and evaluation technology of new nano-sized materials, must be the most important as a major technical task of nano technology.

It has long been known that the smaller the material, the smaller the nanoscale-sized microparticles will exhibit. For example, when gold is nano-sized and ultrafine, it is dispersed in glass to give pale or red color. Fine gold colloids have long been used as colorants in craft glass.

Recently, a number of new nanoscale materials, such as fullerenes and carbon tubes, have been discovered and found to show unusual structures and excellent properties. For example, graphite material (bulk) composed of carbon atoms is a conductor, but when nanotubes are formed, new properties of metals or semiconductors appear depending on the size and structure of the tubes. In addition, when an electric field is applied to the tip of the nanotube, electrons easily come out of the tip of the tube. In addition, hydrogen can be stored in the tube. Carbon nanotubes having such excellent characteristics are currently being applied to flat panel display panels, hydrogen storage devices, etc. as materials of electron sources.

Such nanoscale materials have various shapes and structures. Here is an example of carbon. Bulk carbon is known as graphite and diamond, which form hexagonal meshes with carbon atoms arranged in layers. Diamonds, on the other hand, are strongly bound to form tetrahedral carbon atoms. For this reason, diamonds are the hardest of all materials and are precious as precious stones. Carbon nanotubes have a structure very similar to that of fullerene, but are crystals of needles extending in one direction rather than spherical. Needle-shaped crystals are hollow and are called nanotubes. Nanotubes range in diameter from about 1 nm to several nm and on the order of a few microns in length.

As such, the composite material in which the nano-sized material is evenly dispersed in the matrix polymer may have new and improved properties than the existing similar material, thereby manufacturing functional polymer materials for various uses.

The present invention has been made to meet the above requirements, and an object of the present invention is to effectively disperse carbon nanotubes and metal nanoparticles, which are excellent fillers on a polyester matrix, and to expect high molecular weight. To provide a polyester nanocomposite.

Another object of the present invention is to provide a polyester nanocomposite that can improve the thermal, mechanical, electrical properties, electromagnetic shielding rate and thermal conductivity of the resin itself by adding carbon nanotubes, metal nanoparticles.

The above and other objects and advantages of the present invention will become more apparent from the following description of the preferred embodiments with reference to the accompanying drawings.

Polyester nanocomposite according to the present invention for achieving the above object is a polyester nano composite in which the composite filler of carbon nanotubes and metal nanoparticles is dispersed in polyester, 0.1 ~ 5% by weight of carbon nanotubes and 0.1 ~ It is characterized in that 5% by weight of the metal nanoparticles are dispersed in the remaining amount of polyester.

Preferably, the carbon nanotubes are single wall nanotubes, and the metal nanoparticles are colloidal fillers of gold, silver, copper, nickel or platinum, and the polyester is polyethylene terephthalate or polybutyl. It is a cyclic oligomer depolymerized in renterphthalate.

More preferably, the degree of polymerization of the cyclic ester oligomer is 2 to 10, and the ring-opening polymerization temperature of the cyclic ester oligomer is 290 to 310 ° C.

More preferably, the cyclic ester oligomer is characterized in that the ring-opening polymerization time is 5 to 20 minutes.

Also preferably, the polyester has a molecular weight of at least 20,000 (number average), and the carbon nanotubes have a size and length of 100 nm to 100 μm, and a diameter of 0.5 nm to 50 nm. The metal nanoparticles are characterized in that the size of 2nm ~ 10nm.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. These examples are only presented by way of example only to more specifically describe the present invention, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples. .

The present invention provides a polyester nanocomposite in which carbon nanotubes and metal nanoparticles, which are nano-sized fillers having excellent thermal conductivity, are uniformly dispersed in a polyester resin.

In general, heat dissipation is an important problem because the lifespan of a semiconductor device is reduced by half when the temperature rises by 10 ° C. If the filler with high thermal conductivity is dispersed in the polymer matrix, it can be applied as a heat dissipating material. Among the fillers, the thermal conductivity of the carbon nanotubes has a high value of 2500 ~ 2980W / mK, and has a significantly higher value than the other fillers as shown in Table 1. This can be easily explained through the harmonic oscillator mode, which describes the phonon mode of heat transfer.

Heat transfer of diamond is mainly done by the consonant mode. That is, the carbon atoms are mainly dependent on the way the thermal energy is transferred by thermal vibration, which is the single atom because the same mass of the oscillator can transfer heat most efficiently in terms of the harmonic oscillator model. Diamonds consisting only of phosphorus carbon are very advantageous for heat transfer. However, since a diamond substrate is a cost problem to be practically used as a heat sink, it is currently used in very expensive devices or special devices. In addition, since the diamond thin film has a property of transmitting most electromagnetic waves to electromagnetic waves, it is not suitable for absorbing electromagnetic shielding.

TABLE 1

Filler Thermal Conductivity k (W / mK) Stainless steel 14 silver 428 Copper 401 aluminum 235 Aluminum nitride (AlN) 200 Alumina (Al ₂ O ₃ ) 39 Magnesium oxide 38 Diamond thin film 1000-1500 Carbon nanotubes 2500-2980

When heat is transferred through the phonon, this is achieved by the vibration transfer of atoms. In other words, heat is fundamentally a vibration of matter. In this case, if the mass difference of the heat transfer atoms is large, the heat conduction is not properly performed, and if the mass between the two heat transferrs is the same, the heat transfer is most efficient because of the highest vibration frequency.

In addition, when the spring constant between the two heat transferr is large, the most efficient heat transfer is achieved because the diamond heat transfer characteristics are excellent, and carbon nanotubes also show very good heat transfer properties for this reason.

Moreover, in the case of carbon nanotubes, the bonding force is stronger than that of diamond sp ³ hybrid bonds, and sp ² bonds having a large force constant value show better heat transfer characteristics than diamond.

Mixing carbon nanotubes may have the following advantages in manufacturing polyester / carbon nanotubes.

Even with a very small amount of addition, percolation of the thermal conductivity is achieved so that the interconnection of carbon nanotubes is possible, so that the cost is not large. And the desired physical properties can be envisioned by adjusting the mixing ratio of the filler to be mixed, that is, carbon nanotubes.

And silver shows the highest conductivity as shown in Table 1 of the metal filler. The nanoparticles of silver have conductivity through electrical conduction mechanisms such as charge transfer or electron transfer, and are characterized by controlling the conductivity of the material by adjusting the packing density according to its size.

By adding carbon nanotubes and silver nanoparticles, which are nano-sized fillers having excellent thermal conductivity, to a polyester matrix, a polyester nanocomposite having excellent thermal conductivity can be prepared.

The present invention is to provide a method for producing a polyester nanocomposite which can effectively disperse carbon nanotubes and metal nanoparticles on a polyester matrix and expect high molecular weight.

When preparing a polyester nanocomposite containing a composite filler of carbon nanotubes and metal nanoparticles, a method of preparing a polyester resin corresponding to a matrix can be broadly divided into two methods.

The first method is a method of condensation polymerization of monomers of polyester, that is, polyethylene terephthalate, terephthalic acid (TPA) or dimethyl terephthalate (DMT) and ethylene glycol (EG).

The second method is a ring-opening polymerization of the cyclic ester oligomer.

In the first polymerization method of the polyester nanocomposite manufacturing method, the stoichiometric ratio of the monomers must be accurately matched to obtain a high polymerization degree in a state where carbon nanotubes and silver nanoparticles are mixed, and are produced during condensation polymerization. In order to completely remove the by-products, a high vacuum of 1 torr or less is required, and the reaction time takes too long to reach a high molecular weight.

However, in the second polymerization method, due to the structure of the cyclic ester oligomer without end groups, it is possible to obtain the polymerization product in a short time without the formation of by-products and to disperse the nanoscale filler with the low viscosity of the cyclic ester oligomer. There is an advantage.

Accordingly, an object of the present invention is to more effectively disperse the composite filler in the state that the carbon nanotubes and the metal nanoparticles are added by ring-opening polymerization of the cyclic ester oligomer to polymerize the polyester nanocomposite in a short time without generating by-products. It is to provide a method of manufacturing.

Nanocomposites in which these carbon nanotubes are dispersed on a polymer matrix may be somewhat different depending on the type of polymer matrix, but a conductive network is formed even when only a volume ratio of 0.04% or more is dispersed to obtain a low volume resistance close to a semiconductor. Using these properties, the polyester nanocomposite can be applied to a heat dissipating material in the form of fibers, nonwoven fabrics, films, and various molded articles.

Carbon nanotube is recognized as the most excellent material among the existing materials, it is also a very suitable filler for improving the mechanical performance of the polymer material. In addition, carbon nanotubes are representative nano-materials of carbon materials that have a number of applications due to the change in physical properties depending on the structure and structure of the tube. Due to these excellent properties and structures, applications are expected in the fields of electronic information communication, environment, energy and medicine. Just as carbon black or carbon fiber is used as a conductive medium in polymer supports, development of composites applied to the optoelectronic field using the high conductivity of carbon nanotubes is underway, as well as mechanical, thermal and electrical properties. The realization of the production and application of excellent multifunctional nanocomposites is becoming visible. In particular, researchers are very interested in using carbon nanotubes as reinforcers of fiber or polymer composite materials in terms of development of structural materials utilizing the excellent strength of carbon nanotubes. To date, these efforts have been made by forming composites by melt kneading nanotubes with certain single component polymers or by polymerizing monomers in solution.

Carbon nanotubes used in the present invention are materials having high mechanical strength, high Young's modulus, and high aspect ratio. Carbon nanotubes are also materials with high electrical conductivity and high thermal stability. In the case of the nanocomposite in which the carbon nanotubes having various excellent properties are effectively dispersed in the polymer matrix, the polymer / carbon nanotube composite having improved mechanical, thermal and electrical properties may be manufactured.

The method of synthesizing carbon nanotubes is arc-discharge, pyrolysis, laser vapor deposition, plasma enhanced chemical vapor deposition, and thermal chemical vapor deposition. ), Electrolysis method, flame synthesis method, etc., the carbon nanotubes used in the present invention is synthesized by using a thermochemical vapor deposition method that can synthesize a large amount of carbon nanotubes.

In order to improve the dispersibility of the carbon nanotubes by physical pretreatment, the ball mill is pulverized so as to separate or entangle each single strand through a ball mill. Through this process, the ease of mass production, workability, economical efficiency, ease of production, characteristics of the composite material, etc. have a length of 100 nm to 100 μm and a diameter of 0.5 nm to 50 nm. In the chemical pretreatment method, the carbon nanotubes are sonicated in a mixed solution of sulfuric acid and nitric acid in a volume portion of 3: 1, and then filtered to remove the catalyst and impurities in the synthesis of carbon nanotubes. Use After adding carbon nanotubes in a state where the cyclic ester oligomer and catalyst are dissolved in dichloromethane in a container capable of vacuuming and stirring, dispersing with ultrasonic waves, and maintaining the vacuum state 290 ~ 310 If it is kept for 5 to 20 minutes in the cyclic ester oligomer is polymerized through the ring-opening polymerization to effectively disperse the carbon nanotubes, polyester / carbon nanotube nanocomposite is prepared.

The content of the carbon nanotubes of the polyester nanocomposite according to the present invention should be filled in at least 0.1% by weight, which is the minimum amount of percolation, preferably applying 0.5 to 5% by weight of carbon nanotubes. Preferably, the metal nanoparticles should be filled with at least 0.1% by weight or more in combination with the carbon nanotubes, and preferably, the metal nanoparticles in the range of 0.5-5% by weight may be applied together with the carbon nanotubes. When the mixing ratio of the carbon nanotubes and the metal nanoparticles is more than 5% by weight, the impact strength of the obtained composite material is lowered.

The polyethylene terephthalate is not particularly limited as long as it has a molecular weight that can be used for films and fibers, but it is particularly preferable to have at least 20,000 (number average) or more. When the molecular weight of polyethylene terephthalate is 26,000 or more, it is easy to be used in a product requiring gas barrier property, and when it is 45,000 or more, it is preferable to be used in blow molding or various storage containers. And 80,000 or more is preferable to be used for injection molding (injection molding).

The process of forming the nanocomposite is preferably carried out in the absence of air, for example in the presence of an inert gas such as argon, neon or nitrogen or in a vacuum.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Preparation Example: Preparation of Cyclic Ester Oligomer by Depolymerization]

3 mol% of a tin catalyst such as dibutyl tin oxide (nC ₄ H ₉ ) ₂ SnO was used as a catalyst, and polyethylene terephthalate was added to dichlorobenzene at 180 ° C. The reaction proceeded through refluxing at temperature for 48 hours. After filtration of the linear oligomer, the cyclic ester oligomer dissolved in dichlorobenzene was distilled under reduced pressure to remove the solvent, and the yield was about 80%. The composition of the cyclic ester oligomer thus prepared showed a distribution of 2 to 10 repeating units of the monomer.

Depending on the type of cyclic ester oligomer, melting points such as dimer 227.5 ° C, trimer 318.2 ° C, tetramer 324.1 ° C, and pentamer 252.2 ° C are different. The polymerization temperature is determined according to the composition ratio of the cyclic ester oligomer, but the composition ratio can be controlled according to the amount of the catalyst in the depolymerization as described above. In other words, the composition ratio of the cyclic ester oligomer through depolymerization under the condition that the amount of the catalyst is fixed can be prepared without significant change, thereby facilitating polymerization temperature control. This can be confirmed by gel chromatography (Gel Permeation chromatography), the dimer 53.2%, trimer 28.1%, tetramer 7.9%, pentamer 6%, other cyclic ester oligomers after hexamer showed a composition ratio of 4.8%.

Example 1

In order to improve the dispersibility of the carbon nanotubes synthesized by the thermochemical vapor deposition method, a physical pretreatment method is pulverized to reduce the degree of separation or entanglement by single strands through a ball mill. As a chemical pretreatment method, carbon nanotubes are sonicated for 48 hours in a mixed solution of sulfuric acid and nitric acid, and then used by filtration. In a vacuum and stirred container, 99% by weight of the cyclic ester oligomer obtained by the method described in the preparation example, 0.5% by weight of Single Wall Nanotube (ILJIN Nanotech, Korea) and silver nanoparticle colloidal solution ( NANOVER ^TM , Nanopoly Co., Korea) 0.5% by weight of the colloidal solution is mixed, then the antimony catalyst dissolved in dichloromethane (for example, antimony trioxide) 0.5 mol% is mixed After dispersing with ultrasonic waves and removing ethanol and dichloromethane, the mixture was polymerized at 310 ° C. for 20 minutes while maintaining vacuum and stirring, and then cooled with ice water to obtain a polyester nanocomposite. This manufacturing process is shown in FIG.

Example 2

A polyester nanocomposite was obtained in the same manner as in Example 1, except that 98.5 wt% of the cyclic ester oligomer, 1 wt% of carbon nanotubes, and 0.5 wt% of silver nanoparticles were mixed.

Example 3

A polyester nanocomposite was obtained in the same manner as in Example 1, except that 96.5 wt% of the cyclic ester oligomer, 3 wt% of carbon nanotubes, and 0.5 wt% of silver nanoparticles were mixed.

Example 4

A polyester nanocomposite was obtained in the same manner as in Example 1, except that 94.5 wt% of the cyclic ester oligomer, 5 wt% of the carbon nanotubes, and 0.5 wt% of the silver nanoparticles were mixed.

Example 5

A polyester nanocomposite was obtained in the same manner as in Example 1, except that 94 wt% of the cyclic ester oligomer, 5 wt% of the carbon nanotubes, and 1 wt% of the silver nanoparticles were mixed.

Example 6

A polyester nanocomposite was obtained in the same manner as in Example 1, except that 92% by weight of the cyclic ester oligomer, 5% by weight of carbon nanotubes, and 3% by weight of silver nanoparticles were mixed.

Example 7

A polyester nanocomposite was obtained in the same manner as in Example 1, except that 90 wt% of the cyclic ester oligomer, 5 wt% of the carbon nanotubes, and 5 wt% of the silver nanoparticles were mixed.

Comparative Example 1

A polyester nanocomposite was obtained in the same manner as in Example 1, except that only 95 wt% of the cyclic ester oligomer and 5 wt% of the carbon nanotubes were mixed.

Comparative Example 2

A polyester nanocomposite was obtained in the same manner as in Example 1, except that only 95 wt% of the cyclic ester oligomer and 5 wt% of the silver nanoparticles were mixed.

Experimental Example 1

In order to confirm the thermal conductivity characteristics of the polyester nanocomposite according to the examples and comparative examples, after making a film form using a hot press (TC), TC Probe (Perkin Elmer, USA) as a thermal conductivity measurement equipment Was used to measure the thermal conductivity of the film, the results are shown in Table 2.

TABLE 2

   division  Ingredient   Thermal Conductivity (W / mK)  polyester  Carbon nanotubes  Silver nanoparticles  Example 1  99  0.5  0.5  2.5  Example 2  98.5  One  0.5  2.7  Example 3  96.5  3  0.5  2.9  Example 4  94.5  5  0.5  3.5  Example 5  94  5  One  3.7  Example 6  92  5  3  4.6  Example 7  90  5  5  4.7  Comparative Example 1  95  5  0  1.7  Comparative Example 2  95  0  5  1.2

As can be seen in Table 2, it can be seen that the polyester nanocomposite of the comparative example in which a single filler is added to form the thermal conductivity is lower than the embodiment using the composite filler. Therefore, the polyester nanocomposite according to the present invention has excellent thermal conductivity when carbon nanotubes and metal nanoparticles, which are fillers constituting thermal conductivity, are added with silver nanoparticles in combination. Will have.

Experimental Example 2

The molecular weight of the polyester nanocomposite to which the carbon nanotube and the silver nanoparticles composite filler was added was dissolved in a solvent in which phenol and tetrachloroethane were mixed at a weight% of 3: 2 by 25. Viscosity average molecular weight (Mv) was measured by MHS (Mark-Houwink-Sakaruda) formula with a capillary viscometer in a thermostat at ℃.

As a result, the results are shown in Table 3, and the average molecular weight of the viscosity was at least 20,000, which can be used for fibers, nonwoven fabrics and films, and high molecular weights of 45,000 or more. It could be confirmed that it is available.

TABLE 3

   division  Ingredient Molecular Weight (Mv / 10 ³ )  polyester  Carbon nanotubes  Silver nanoparticles  Example 1  99  0.5  0.5  45  Example 2  98.5  One  0.5  43  Example 3  96.5  3  0.5  37  Example 4  94.5  5  0.5  35  Example 5  94  5  One  33  Example 6  92  5  3  29  Example 7  90  5  5  26  Comparative Example 1  95  5  0  35  Comparative Example 2  95  0  5  41

According to the present invention, it is possible to effectively disperse carbon nanotubes and metal nanoparticles, which are fillers having excellent thermal conductivity properties, on a polyester matrix, and to expect high molecular weight, through which the thermal, mechanical, electrical properties, and electromagnetic waves of the resin itself can be expected. Shielding rate and thermal conductivity can be improved, and the like.

In addition, the polyester nanocomposite prepared according to the present invention has the effect of being applied as a heat radiation material, an electromagnetic wave shielding material, etc. having excellent thermal conductivity as a fiber, a nonwoven fabric, a film, and various molded articles.

Claims (7)

In the polyester nano composite material in which a composite filler of carbon nanotubes and metal nanoparticles is dispersed in a polyester, A polyester nanocomposite, characterized in that 0.1 to 5% by weight of carbon nanotubes and 0.1 to 5% by weight of metal nanoparticles are dispersed in a residual amount of polyester. The method of claim 1, The carbon nanotubes are single wall nanotubes, and the metal nanoparticles are colloidal fillers of gold, silver, copper, nickel or platinum, and the polyester is polyethylene terephthalate or polybutylene terephthalate. Polyester nanocomposite, characterized in that the depolymerized cyclic oligomer in. The method of claim 2, The degree of polymerization of the cyclic ester oligomer is 2 to 10, characterized in that the ring-opening polymerization temperature is 290 ~ 310 ℃, polyester / carbon nanotube nanocomposite. The method of claim 3, The cyclic ester oligomer is a ring-opening polymerization time, characterized in that 5 to 20 minutes, polyester nanocomposite. The method according to any one of claims 1 to 4, The polyester nanocomposite, characterized in that the molecular weight of the polyester is at least 20,000 (number average). The method according to any one of claims 1 to 4, The carbon nanotubes are 100 nm to 100 μm in size and length, and the diameter is 0.5 nm to 50 nm, polyester nanocomposite. The method according to any one of claims 1 to 4, The metal nanoparticles are characterized in that the size of 2nm ~ 10nm, polyester nanocomposite.

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