Preparation And Properties Of Silicone Modified Epoxy Resins

In this paper,based on bisphenol A epoxy resin and amine curing agent,a series of silicone-containing branched amide,a trifunctional silicone-epoxy and two kinds of Double-Decker Silsequioxanes were designed and prepared.The siloxane segments were successfully introduced into the network of epoxy resins in molecular level.The curing kinetics,mechanical properties,thermal stability and surface properties of epoxy resins were studied.The structure-properties relationship of silicone modified epoxy resin were discussed.The main results in this paper are as follows:The silicone-containing amines(PSPA and PSPTA)were designed and prepared from ethylenediamine,diethylenetriamine,phenyltrimethoxysilane and chloromethyldimethylchlorosilane.FTIR,NMR,Titration were used to determine the molecular structure.PSPA and PSPTA was used to cure bisphenol A epoxy resin(DGEBA).It was found that the glass transition temperature(Tg)of the cured resin decreased,but the branched molecular structure keep its Tg in a acceptable level.Results show that PSPA and PSPTA can effectively improve the toughness,impact resistance,adhesive strength and heat and water resistance of epoxy resin.The curing behavior of silicone modified epoxy resin was studied by DSC method.The reaction mechanism of the curing process was analyzed by non-modeling method.It was found that the reactivity of the silicone-modified curing agent slightly decreased after modification,but still maintains high reactivity and was suitable for room temperature curing epoxy system.Same results were found in the effective reaction energy study with non-modeling method.In addition,the non-isothermal curing kinetics were established by using the Malek method to determine the SB(m,n)model parameters.The isothermal curing kinetics were simulated by Kamal model with diffusion coefficient.The silicone-epoxy(SITEUP)was synthesized with eugenol,phenyltriethoxysilane and dimethylchlorosilane.The molecular structure was characterized by NMR and MALDI-TOF-MS.SITEUP was used as toughening agent for bisphenol A epoxy/isophorone diamine(DGEBA/IPDA).The addition of SITEUP significantly improved the impact toughness of bisphenol A epoxy resin,but the flexural modulus and glass transition temperature of the cured product were affected.Results show that 10%addition of SITEUP can change the fracture surface of DGEBA/IPDA from brittle to tough.5%addition of SITEUP can change the surface of cured resin from hydrophilicity to hydrophobicity.Two kinds of Double decker silsesquioxane(DDSQ)were synthesized with phenyltriethoxysilane,dimethylchlorosilane.NMR and MALDI-TOF-MS,GPC were used to determine the molecular structure.The DDSQs were incorperated into DGEBA/DDS curing system.It was found that a small amount of DDSQ addition has little effect on the curing kinetics of epoxy resin.Mechanical properties and SEM results showed that both DDSQs had toughening effect on epoxy resin.By comparing the effects of two different DDSQs,it was found that poly DDSQ has better performance because it can improve the crosslinking density of epoxy resin.The nano SiO2 was modified by a silane coupling agent EUPCP.The modification on the surface of SiO2 was determined by FTIR,XPS and TG.The effects of nano SiO2 before and after modification on epoxy resin were compared,which show that the modified SiO2 does better.When the amount of SiO2 raised 4%,the impact strength of curing resin increased by 17%,glass transition temperature increased by 10? and heat resistance was also improved.SEM graphs showed better dispersion of SiO2 modified with EUPCP,and toughed epoxy more.In summary,through molecur design,silicone can not only improve the toughness of epoxy resin,but also maintain mechanical properties of heat and water resistance in a high level.Silicone segments can effectively protect the organic segments from degradation,thence improve the heat stability of cured epoxy resin.The addition of silicone segments can significantly reduce the surface free energy of the epoxy resin,changing the cured epoxy resin from hydrophilicity to hydrophobicity,thereby improve the water resistance of cured resin.The work of this paper focused on the synthesis and performance of silicone modified epoxy resin,and can further used in high-performance epoxy adhesives and composite materials.