Research On Thermal Conductive Plastics For LED

Thermal conductive plastic as the shell of LED, have many advantages, such as light weight, long service life, easy processing, low cost and so on. In order to improve the thermal and mechanical properties of the composites, to meet the requirements of the LED light’s shell. In this paper, using PBT as the substrate, MgO and BN as thermal conductive filler, using a Double screw extruder to prepare conductive composite materials.Studies the type, content and particle size of thermal conductive filler to composites thermal properties, mechanical properties, electrical properties、heat distortion temperature and processing performance of the influence of various performance. And by the addition of EVA and glass fiber to reinforced its performance.For different types of inorganic fillers, with the increase of the added amount of the inorganic filler, the thermal conductivity of the composite were gradually increased. The addition amount of the inorganic filler is the same, the larger particle size high-purity boron nitride filled the composite material have the highest thermal conductivity of the composite material. The more inorganic fillers add volume, the worse the mechanical properties of the composites, the thermal deformation temperature and density is gradually increasing. When the content of the filler is same, the mechanical properties of the composites filled with the high purity boron nitride sheet largest decrease, the mechanical properties of the composites filled with spherical magnesium reduce to a minimum. When the content is same,the heat distortion of the composites filled with the high purity boron nitride reached 111.9℃. From the view of density, the density of the composites filled with magnesium increase greater than the composites filled with the boron nitride. Although the cause of the inorganic filler is added to reduce the resistivity of the composite material, but remains at a high level, in line with the requirements of the insulation. Processing properties of the composites increased with the inorganic filler becomes worse.In order to improve the mechanical properties of composite materials, with different content of EVA and glass fiber reinforced and toughened on it. The more content of EVA,the higher the impact strength of composites,the worse the bending strength and tensile strength, thermal conductivity is essentially the same. By contrast, the content of EVA is 4%, the comprehensive properties of the composites is relatively excellent. The magnesia filled PBT matrix composite with glass fiber, the mechanical properties of the composites were improved to some extent. After adding glass fiber, surface resistivity and volume resistivity of the composites are decreased an order of magnitude, but remain at a high level. Generally speaking, adding EVA and glass fiber, the mechanical properties of the composites is significantly improved.