Study on preparation and performance of polyurethane potting sealant with high thermal conductivity and high flame retardancy
The modified alumina and modified ammonium polyphosphate were prepared by using n-hexyltrimethoxysilane(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 5.1×1013 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.
万方数据
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