高导热高阻燃聚氨酯灌封胶的制备与性能研究

Study on preparation and performance of polyurethane potting sealant with high thermal conductivity and high flame retardancy

以正己基三甲氧基硅烷(HTTS)为表面活化剂制备了改性氧化铝和改性聚磷酸铵,以提高氧化铝和聚磷酸铵在聚合物基质中的分散性。在此基础上,以聚丙二醇、蓖麻油为羟基组分,改性氧化铝为导热填料,改性聚磷酸铵为阻燃剂,多亚甲基多苯基异氰酸酯为固化剂,再加上催化剂、消泡剂和分子筛,制备得到了双组分聚氨酯灌封胶。研究了HTTS、R值、导热填料和阻燃剂的添加量对聚氨酯灌封胶性能的影响规律。研究结果表明:当HTTS的添加量分别为2.0%和2.5%时,改性氧化铝和改性聚磷酸铵的活化效果较好;当R值1.15时,聚氨酯灌封胶的拉伸强度为2.76 MPa,断裂伸长率为254%;当改性氧化铝和改性聚磷酸铵的添加量分别为70%和8%时,聚氨酯灌封胶的导热系数为2.11 W/(m·K),阻燃级别达到UL-94 V0级,极限氧指数为28.5%。此外,所制备的聚氨酯灌封胶具有优异的稳定性,在50℃下储存30 d,A组分和B组分的旋转黏度分别在18~26 Pa·s和400~700 mPa·s的合理范围内波动。最后,所制备的聚氨酯灌封胶的体积电阻率为5.1×10^(13)Ω·cm,吸水率为0.21%,凝胶时间为49 min,邵D硬度为52,固化后胶体表面平整,无气泡,说明该灌封胶的性能可以满足电子灌封领域的要求。

The modified alumina and modified ammonium polyphosphate were prepared by using nhexyltrimethoxysilane(HTTS)as surface activator,which improved the dispersion of alumina and ammonium polyphosphate in polymer matrix.On this basis,the two-component polyurethane potting sealant was prepared by using polypropylene glycol and castor oil as hydroxyl components,modified alumina as thermal conductive filler,modified ammonium polyphosphate as flame retardant,polymethylene polyphenyl isocyanate as curing agent,as well as adding catalyst,defoamer,and molecular sieve.The effects of HTTS,R value,the addition of thermal conductive filler and flame retardant on the performance of polyurethane potting sealant were studied.The research results showed that when the addition amount of HTTS was 2.0%and 2.5%,respectively,the activation effect of alumina and ammonium polyphosphate was relatively excellent.When the R value was 1.15,the tensile strength of polyurethane potting sealant was 2.76 MPa,and the elongation at break was 254%.When the addition amounts of modified alumina and modified ammonium polyphosphate were 70%and 8%,respectively,the thermal conductivity of the polyurethane potting sealant was 2.11 W/(m·K),the flame retardant level reached UL-94 V0 grade,and the limiting oxygen index was 28.5%.In addition,the prepared polyurethane potting sealant had excellent stability.When stored at 50℃for 30 d,the rotational viscosity of component A and component B fluctuated within a reasonable range of 18-26 Pa·s and 400-700 mPa·s,respectively.Finally,the volume resistivity of the prepared polyurethane potting sealant was 5.1×10^(13)Ω·cm,the water absorption was 0.21%,the gel time was 49 min,and the Shore D hardness was 52.After curing,the adhesive surface was flat without bubbles,indicating that the performance of the potting sealant could meet the requirements in the field of electronic potting.