WITH HIGH THERMAL CONDUCTIVITY TECHNICAL FIELD OF THE INVENTION

The present invention relates to a polymer-based composite material with high thermal conductivity.

STATE OF THE ART Thermal conductivity value is a concept which represents the ability of movement of the heat energy in a material.

The improvements in electronic devices, power generation, thermal coatings, developments in industries such as aeronautics, etc., have made thermal conductivity properties of engineering materials even more important. The heat generated during the actuation of electronic devices is generally dissipated through thermal conduction. Among the various methods utilized for dissipating heat, engineering materials with high thermal conductivity and low thermal expansion coefficient in the devices are used.

Polymers are widely used in many industries thanks to their cost- effective production and integration properties. However, since polymers have a relatively low heat conductivity coefficient, their uses in applications in which the heat is high, and dimensional stability is important, are limited. Therefore, the use of polymer materials is not preferred in fields such as energy, material, nanotechnology, electric & electronics. BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a polymer-based composite material which overcomes the aforementioned drawbacks and brings novel advantages to the related art. An object of the present invention is to provide a polymer-based composite material with increased thermal conductivity values.

Another object of the present invention is to provide a polymer- based composite material which is capable of exhibiting high thermal conductivity values in thickness and planar direction. The present invention relates to a polymer-based composite material comprising at least a matrix component and at least a reinforcement component for increasing thermal conductivity in order to realize all of the aforementioned objects which will become evident with the following detailed description. Accordingly, it comprises at least one polymer chemical compound as the matrix component, and at least one of the thermally conductive filler, additive or reinforcements selected from a carbon nanotube, carbon fiber, graphene, graphite, carbon black, aluminum nitride, boron nitride, or mixtures in certain weight percentages thereof as reinforcement component.

In a possible embodiment of the present invention, said matrix component comprises at least one of the thermoplastic-based polymers such as polyketone (POK), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polybutylene terephthalate (PBT), polyamide, polyketone, polyvinylchloride (PVC), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), or mixtures in certain weight percentages thereof.

In a possible embodiment of the present invention, the matrix component is preferably polyketone. In a possible embodiment of the present invention, the matrix component is in a range between 30% and 90% by weight within the composite material.

In a possible embodiment of the present invention, said reinforcement component preferably comprises chemical compounds such as carbon nanotube, boron nitride, and graphite as paired or ternary in a single or hybrid form.

In a possible embodiment of the present invention, carbon nanotube compounds in the composite material are not greater than 10% by weight.

In a possible embodiment of the present invention, boron nitride in the composite material is not greater than 20% by weight.

In a possible embodiment of the present invention, synthetic graphite in the composite material is not greater than 70% by weight.

A possible embodiment of the present invention comprises polyketone as a matrix component, and 30% synthetic graphite by weight, and 3% carbon nanotube by weight as a reinforcement component .

A possible embodiment of the present invention comprises polyketone as a matrix component, and 30% synthetic graphite by weight, and 3% boron nitride by weight as a reinforcement component .

A possible embodiment of the present invention comprises polyketone as a matrix component, and 30% synthetic graphite by weight, 1.5% carbon nanotube by weight, and 1.5% boron nitride by weight as reinforcement component. DETAILED DESCRIPTION OF THE INVENTION

In the detailed description provided herein to ensure a better understanding of the present invention, the present invention relates to obtaining a polymer-based composite material with high thermal conductivity and suitable for injection molding and is disclosed in examples that do not constitute any limiting effects on the scope of the invention.

The present invention discloses a composite material with increased thermal conductivity values in both planar and thickness directions. The composite material according to the invention comprises polyketone as a matrix component. Polyketone (POK) is a polymer with good mechanical properties, low friction coefficient, high wear resistance and chemical strength, good dimensional stability, high-temperature resistance, high elasticity, and gas barrier property. It is used in engine and fuel parts in the automotive industry and the electric- electronic industry. Further, matrix components may be used as selected from thermoplastic-based polymers such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polybutylene terephthalate (PBT), polyamide, polyketone, polyvinylchloride (PVC), acrylonitrile butadiene styrene (ABS), polycarbonate (PC). The matrix component is in a range between 30% and 90% by weight within the composite material.

In order to ensure that polymer products are used in the related industries, generally, it is necessary to support it with reinforcement components. In order to provide the production of the material with high thermal conductivity according to the invention, it is possible to add reinforcement components.

The composite material comprises at least one of the thermally conductive filler, additive or reinforcements such as carbon nanotube, carbon fiber, graphene, graphite, carbon black, aluminum nitride, boron nitride with certain weight percentages, or mixtures in certain weight percentages thereof as reinforcement component. Said reinforcement components in the preferred application consist of at least one of the chemical components such as carbon nanotube, boron nitride, and graphite, or mixtures in certain weight percentages thereof.

Another novelty of the present invention is that it is obtained a polymer-based composite material in which the synergy effect is created on its thermal conductivity values through using reinforcement components; namely graphite, carbon nanotube, boron nitride as planar, cylindrical, and cubic, respectively.

Said synthetic graphite is in a range between 0% and 70% by weight within the composite material.

Said carbon nanotube is in a range between 0% and 10% by weight within the composite material.

Said cubic boron nitride is in a range between 0% and 20% by weight within the composite material.

According to the aforementioned percentages of reinforcement components, in addition to the matrix component, only one reinforcement component, two different reinforcement components, or three different reinforcement components selected from synthetic graphite, carbon nanotube, and cubic boron nitride may be used.

Thermal conductivity values of the additives to be used in composite material as a reinforcement component are as follows. Thermal conductivity value of the graphite; 600 W/mK, the thermal conductivity value of the carbon nanotube 2000 W/mK, and the thermal conductivity value of the boron nitride 450 W/mK. In a preferred embodiment of the invention, these three additives are used in combination and thermal conductivity values of the resulting composite material are increased in both planar and thickness direction. Production of the aforementioned composite material is realized as follows.

Polymer, i.e. matrix component and additive materials such as wax and compatibilizer are fed to the main feeder of an extruder passing through gravimetrical feeders. Reinforcement compounds that provide thermal conductivity are fed to the side feeders of the extruder. Reinforcement components with different weight percentages are mixed by means of the twin-screw extruders with the melted polymer. Subsequently, by means of the pasta type pellet production machine, composite granulates are obtained. Then, composite material is produced with injection molding.

The uniform dissipation of the reinforcement components within the matrix component and continuous and even formation of pasta type pellets without breaking depends on process conditions such as extrusion regional temperatures, extrusion screw rotation, gravimetric feeder speeds, side feeder speeds. Process conditions vary with the weight percentages of reinforcement components .

TESTS

According to the teachings of the present invention, a polymer- based composite material with high thermal conductivity is obtained. Polyketone is used as the matrix component. Firstly, reference samples are obtained through subjecting polyketone polymer material to the tests without adding any reinforcement component therein. After that, other samples are subjected to the tests by producing 10 wt.% synthetic graphite + POK, 20 wt.% synthetic graphite + POK, 30 wt.% synthetic graphite + POK, 40 wt.% synthetic graphite + POK composite materials.

Other test samples are POK, 30 wt.% synthetic graphite, and composite materials comprising carbon nanotube with different weight percentages (1%, 2%, 3%). Other test samples are POK, 30 wt.% synthetic graphite, and composite materials comprising boron nitride with different weight percentages (1%, 2%, 3%).

Another test sample is subjected to the tests which are believed to be optimum weight percentages, and which comprises all reinforcement components, POK + 30 wt.% synthetic graphite + 1.5 wt.% boron nitride and 1.5 wt.% carbon nanotubes.

After obtaining the samples, each of them is tested for thermal conductivity .

THERMAL CONDUCTIVITY TESTS

Thermal conductivity tests are conducted according to the ASTM E1461 standard. Obtained thermal conductivity values of the synthetic graphite, carbon nanotube, and boron nitride doped POK based composite samples in planar and thickness direction are shown in Table 1. Table 1. Thermal conductivity values of the samples in planar and thickness direction.

When obtained thermal conductivity values are evaluated, it is observed that the more the amount of the synthetic graphite is, the more the thermal conductivity value of the POK based composite samples. The addition of the synthetic graphite to the samples is especially effective on the planar thermal conductivity value.

The use of carbon nanotube and boron nitride additives with synthetic graphite as a hybrid is reinforced the thermal conductivity net established, thus caused an increase in thermal conductivity values. As compared to boron nitride hybrid doped composites, the planar thermal conductivity value of the synthetic graphite and carbon nanotube doped POK composites are obtained in higher values.

The addition of the synthetic graphite does not make a great difference in the thermal conductivity in the thickness direction, whereas the addition of the boron nitride hybrid is effective on the thermal conductivity increase in the thickness direction. The highest thermal conductivity value in the planar direction obtained from POK based composites is 15.76 W/mK, and it is realized in the sample obtained by the addition of 30% synthetic graphite and 3% carbon nanotube as paired. The thermal conductivity value in the thickness direction reached its highest value of 3.02 W/mK in 30% synthetic graphite and 3% carbon nanotube doped POK based composites.

The composite materials with high thermal conductivity obtained by the invention are used in thermal management applications in the automotive, aeronautics, electronic industries thanks to their cost efficiency, energy conservation, and design flexibility. For example, composite material is used in the production of the pumps and coating of the electronic parts in the automotive and aeronautics industries. The protection scope of the invention is specified in the following claims and shall not be construed as limiting for the detailed description provided above, which only aims to be illustrative. Therefore, it is evident that the person skilled in the art may deliver similar embodiments in the light of the present invention without parting from the main subject of the invention.