Study On Polysiloxane Modified Epoxy Resin

In this paper, A hydroxyl terminated polydimethylsiloxane(PDMS) were used tomodify diglycidyl ether of bisphenol A(DGEBA).A PDMS-block-DGEBA copolymerthat acted as a compatibilizer was synthesized by DGEBA, γ-aminopropyltriethoxysilane(KH-550) and PDMS in the presence of a catalyst. Thereaction mechanisms and compatibilizing effects of the block copolymer were studiedby means of Fourier transform infrared (FTIR) spectrum analysis and observationunder scanning electron microscopy (SEM) , curing reaction kinetics by thedifferential scanning calorimetry(DSC). The difference of the content of PDMS, thedifference of polydimethylsiloxane (PDMS) with different molecular weight wereused to modify epoxy resin, influence of adding enhancer, influence of adding filler,and influence of adding multifunctional epoxy resin were studied. The mechanicproperties(including impact strength, flexural strength, elongation, and tensilestrength), electric properties(including volume electric resistivity, surface electricresistivity, dielectric constant, dielectric loss), thermal properties(thermal weight loss,thermal weight loss of ten hours at 250℃ and thermal weight loss of twenty hours at250℃)were tested.In this paper, isocyanate terminated polydimethylsiloxane was synthesized byhydroxyl terminated polydimethylsiloxane and toluene-2,4-diisocyanate. In two waysthe prepolymer of the isocyanate terminated polydimethylsiloxane and epoxy resinwas synthesized, and the isocyanate terminated polydimethylsiloxane contained thestructure of oxazolidinone and epoxy resin was synthesized. They were compatibilizer tomodified epoxy resin system. The reaction mechanisms and compatibilizing effects ofthe block copolymer were studied by means of FTIR spectrum analysis andobservated under SEM,curing reaction kinetics by DSC and the mechanic properties,thermal properties and electric properties were tested as well.From the test we can came to the decision that the polydimethylsioxane with the ilow molecular weight was more better to modify epoxy resin than the high molecular.The impact strength increased 70.2% and the elongation increased 109% when thePDMS% was 10% and all kinds of properties were the best. The accelerant2-ethyl-4-methyl imidazole was better than 2,4,6-tri[(dimethylamino)methyl]phenol.The strength decreased, while shrinkage and water absorption became well whenadding filler; the mechanic properties decreased when adding the multifunctionalepoxy resin. The mechanic properties and thermal weight loss of the isocyanateterminated polydimethylsiloxane and the isocyanate terminated polydimethylsiloxanecontained the structure of oxazolidinone modified epoxy resin were both better thancure epoxy resin. The electric properties of all modified epoxy resin became betterthan cure epoxy resin.