| Polymer composites with high thermal conductivity, due to its good thermal andinsulation properties, can be used in electronic packaging and aerospace fields, and has broadprospects for development. Especially with the contemporary requirements of environmentalprotection, the plastic used for LED lighting will replace traditional aluminum radiator shell.But polymer materials have poor thermal conductivity. Generally the thermal conductivity at25℃is lower than0.5W/(m·K), for example, thermal conductivity of epoxy resin is only0.20W/(m·K). In order to meet the need in LED and other industry, study on highperformance thermal composites receive much attention currently.At present, research on thethermal conductivity of the polymer material has just started. Because of the lower level ofproduction technology and high production costs, the application of thermal materials on theLED lighting is limited. In order to promote the development of thermally conductivecomposite materials, effective thermal conductive polymer is needed urgently. In this study,the way to improve the performance of epoxy resin is focused on the selective addition ofhigh thermal conductive fillers, such as magnesium oxide (MgO), carbon fiber.Firstly, tetraethylenepentamine is used as curing agent. Then the effect of MgO contenton curing kinetics (including curing temperature, activation energy and reaction order) isanalyzed by DSC，and curing process temperature of EP/MgO composite is discussed. It’sfound that with the increase of the amount of MgO, the activation energy increases, EP/MgOcomposites curing reaction order is basically not changed for about1.00.The approximationcuring temperature of the resin system has increased slightly for about2℃.Ultimately throughtheoretical analysis and the experimental verification, The best curing process is at35℃for24h and after cured at70℃for2h.Secondly, the coupling agent KH-560, KH-550and butyl titanate were used to treatMgO. It is found that thermal conductivity of using5.0wt%KH-560on MgO particle is thehighest. Compared with50μm MgO,10μm MgO is more effective to improve the thermalconductivity of composites. So10μm MgO particles were used after surface treated by5.0wt%KH-560. It was found that with the increase amount of MgO, thermal conductivity of EP/MgO composite material increased. When the amount is50vol%, the thermal conductivity ofthe composite is up to2.26W/(m· K), which is11.30times of the epoxy resin. MgOimprove the thermal stability and flame-retardant property of EP/MgO composite, but theinsulation and mechanical property of the composite material are decreased. When the dosage of MgO reaches40vol%, the volume resistivity is1.2×1015·cm, it decreases81.94%compared with epoxy resin，but still can meet the insulation requirements. Oxygen index is36.0%-36.5%.The composite system can pass UL94V-0level. The impact strength is only46.5%of the epoxy matrix, the bending strength is63.5%, and the tensile strength is49.6%.Finally, in order to improve the mechanical properties of composite materials, we usecarbon fiber and glass fiber instead of MgO, form the filler mixed system of5vol%fiber/35vol%MgO.The carbon fiber system shows excellent performance, compared with thesame dosage (40vol%) MgO filler system, the impact strength, bending strength and tensilestrength of5vol%fiber/35vol%MgO system increased165%,114%, and92.6%. The impactstrength, bending strength increased23.0%and46.1%compared with pure epoxy resin, Theresults also showed that the composite system has excellent flame-retardant and insulationproperty. |
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