Preparation Of Thermally Conductive And Flame Retardant Epoxy Resin Composites

Nowadays, the integration level, working frequency and power of electronic products increase progressively in the application field of electronic packaging. To meet such demand, it has become urgent to develop polymeric composite material with excellent overall performances, including thermal conductivity, flame retardancy, mechanical properties, processability, etc. Epoxy resin(EP) presents outstanding overall performances, such as heat resistance, electrical insulation, mechanical properties, thus can be widely applied as encapsulating material. In this paper, we introduced additive-type flame retardant and thermal conducting fillers into EP system to endow it with excellent thermal conductivity and flame retardancy.In this paper, boron nitride(BN) were modified by KH560 to fabricate BN-KH560 and multiwalled carbon nanotube(MWNTs) were employed by concentrated HNO3 to produce MWNTs-COOH. When using BN-KH560 as the major thermal conducting filler, by the incorporation of small amount of MWNTs-COOH, the composite exhibited outstanding thermal conductivity and compensated the deterioration of its mechanical performances by the reason of modification. When utilizing 1wt% MWNTs-COOH and 29wt% BN-KH560 as the fillers, the composite achieved outstanding overall performances; the thermal conductivity, tensile strength, unnotched impact strength, bending strength were 1.08W/m·K, 50.6MPa, 13.2 kJ/m2, 87.8MPa, respectively. Moreover, the glass-transition temperature(Tg) raised from 194.2℃ to 211.5℃, which proved prominent thermal synergistic effect.A halogen-free efficient flame retardant HCCP-DOPO with a structure of phosphonitrile and phosphaphenanthrene was synthesized by phosphonitrilic chloride trimer(HCCP), phydroxy benzaldehyde and DOPO. Owing to the intramolecular synergy flame retardant effect, when the loading of the filler was 9.3wt%(1.2% P content), the composite achieved UL94 V-0 rating and the corresponding LOI value was 33.1%. The cone calorimetry result showed that PHRR value of flame-retarded composite was 499kJ/m2, dropping 55% compared with that of the pure one. Meanwhile, the thermal conductivity reached 0.28 W/m·K. It is worth noting that the mechanical and thermal properties of the modified composite maintained at the high level despite of the flame retardation and thermal conductivating.When MWNTs-COOH and BN-KH560 were used as thermal conductivating agents, and HCCP-DOPO as the flame retardant, the modified epoxy exhibited excellent thermal conductivity and synergistic flame retardant effect simultaneously. When the loading of BNKH560, MWNTs-COOH and HCCP-DOPO was 29wt%, 1wt% and 7.7wt%, respectively, the composite achieved UL-94 V-0 rating and the corresponding LOI value was 42.5%. Moreover, the thermal conductivity reached 1.19W/m·K, the glass transition temperature was 210.5℃, tensile strength was 51.3MPa, unnotched impact strength was 12.5kJ/m2, indicating that the excellent mechanical and thermal properties of EP was maintained.