Modification Of Thermal Conductivity And Halogen-Free Flame Retardancy For Liquid Silicone Glue

Thermal conductive and halogen-free flame retardant silicone glue was prepared generally by filling in more thermal conductive fillers and flame retardants, which was harmful to the mechanical properties and fluidity. Therefore, the difficulty in current study was how to achieve a balance both high thermal conductivity, good halogen-free flame retardancy and excellent mechanical properties, fluidity. In this paper, high thermal conductive, good halogen-free flame retardant silicone glue was prepared by use of modified alumina as thermal conductive fillers, modified flame retardant NPS and zinc borate(ZB) as flame retardant fillers. The main research contents included three following parts.1、Hexadecyl trimethoxysilane was used to modify surfaces of alumina particles, the oil-absorbed value of the modified alumina and viscosity (vinyl silicone oil:alumina=1:4) of the corresponding silicone glue reduced56.8%、32.5%、35%and74.3%、48.6%、45.4%respectively, compared to the unmodified alumina and modified alumina by γ-aminopropyl triethoxysilane and vinyl-tris(β-methoxyethoxy)silane, showing the best surface modification. The properties of silicone glue were studied under different dosage the modified alumina. The results showed that, when the loading modified alumina900phr (for100phr vinyl silicone oil), the thermal conductivity of addition cured silicone glue was up to2.47W/(m·K), the viscosity of the resultant silicone glue was11800mPa·s, the tensile strength1.6MPa, the elongation at break35%.2、Halogen-free flame retarded technology was used to modify flame retardancy of silicone glue, the formula design on flame retardancy included following two systems, both of them showing good flame retardancy and mechanical properties.(1)ZB was used as a synergistic agent to enhance the flame retardant efficiency of modified NPS for silicone glue. When the ratio of NPS to ZB was29:1, the addition amount60phr (for100phr glue), the limiting oxygen index of silicone gule was28%, the tensile strength2.15MPa, the elongation at break105%.(2)Aluminium hydroxide (ATH) and mica powder was used as synergistic agents to enhance the flame retardant efficiency of Melamine Cyanurate Acid (MCA) for silicone gule. When the ratio of MCA, ATH to mica powder was71:8:1, the addition amount 80phr (for100phr gule), the limiting oxygen index of silicone gule was35%, the tensile strength2.6MPa, the elongation at break150%.3n Based on synergy of ZB to modified NPS for silicone, loading thermal conductive fillers modified alumina, the functionalized approaches of flame retarded and thermal conductivity not only showed obvious synergistic flame retarded effect of alumina to NPS/ZB, reducing amount of flame retardants, but also the balance would be realized between high thermal conductivity, good halogen-free flame retardancy and excellent fluidity, mechanical properties. The properties of silicone filled NPS/ZB was studied under different dosage modified alumina, When the addition of the alumina was600phr (for100phr vinyl silicone oil), NPS/ZB60phr, the vertical flame test rating of silicone was FV-0, the limiting oxygen index46%, the thermal conductivity1.67W/(mK), the viscosity8500mPa·s, the tensile strength1.72MPa, the elongation at break62%.