The Preparation And Properties Of Epoxy Resin Modifying Silicone/Montmorillonite Nanocomposites By Solution Intercalative

Silicone has many excellent properties of high temperature resistance,electrical insulation,hydrophobic property,weatherability and corrosion resistance for most hydrous chemical regents,such as dilute mineral acids.However,the shortages of silicone,such as curing condition,bonding ability,compatibility,production cost and mechanical properties,limit its more application.To improve the mechanical properties,flame retardance and barrier properties for water,in the study,silicone was modified to intercalate organic montmorillonite by solution intercalative polymerization.Cetyltrimethylammonium bromide(CTBA) was intercalated into layers of Na-MMT by cation exchange to prepare organo-montmorillonite(OMMT).Using Bragg's law,the d-placing of MMT and OMMT layers was calculated according to X-ray diffraction(XRD) analyses.The results show that CTBA was intercalated into MMT layers since the d-placing of MMT layers increased after CTBA intercalating.E-50 epoxy resin was used to modify silicone resin to improve the mechanical properties of silicone.Silicone/epoxy resin composites were prepared with different epoxy resin content.The hardness,impact strength,tensile strength and compressive strength were measured.The results show that epoxy resin can markedly improve the mechanical properties of silicone resin.The optimized mechanical properties (hardness is 131.4,tensile-strength is 1.988MPa,impact strength is 1.7739 kJ/m~2 and compressive strength is 12MPa) can be obtained when the weight percent of epoxy resin is 30%.The solution intercalative polymerization was used to prepare nanocomposite emulsion of silicone resin which modified by different content of epoxy resin and intercalated into organo-MMT.The curing conditions were also studied.When single triethanolamine or polyamide was used as curing agent,the curing cycle is up to three weeks at room temperature.However,the combined curing agent of 706(titanate three tertiary alcohol ester) and Triethanolamine only takes four hours for the curing nanocomposite emulsion.The foam is prone to be generated due to the curing reaction of polycondensation polymeriazation at 75℃,so it is better to cure nanocomposite emulsion in vacuum oven.Measurements of hardness,impact strength,tensile strength,compressive strength and thermal properties(DSC) were conducted.The d-spacings of organo-MMT nanocomposites with different OMMT content were obtained by XRD analyses.The epoxy-modifying silicone resin molecules have intercalated into the OMMT layers basing on the change MMT d-spacing.According to SEM spectrum of impact fracture surface,the fracture of PLS nanocomposite is ductile fracture.The effects of content of OMMT,epoxy resin and silicone on the properties of nanocomposite were investigated.The optimized weight ratio of epoxy:silicone equals to 6:30:70.In the study,the barrier property and flame retardance of nanocomposites were determined.The results show that both of the barrier property for water and flame retardance increase with the content of OMMT.However,flame retardance and thermal properties decrease due the addition of epoxy resin,although it can improve the mechanical properties of nanocomposites.The internal microstructure of specimen was analyzed by transmission electron microscopy.The result indicates that silicone modified by epoxy resin intercalated into the layers of OMMT and formed an alternating bright and dark stripes spectrum. It is not entirely orderly intercalative structure in the whole region,but basically orderly and partially exfoliated morphology.Most of organo-MMT exists in nanocomposite with bending status,which illuminates that montmorillonite expresses somewhat flexible under external force and can bear some deformation.