The Thermal Aging Stability And Adhesion Performance Of Addition-curable Liquid Silicone Rubber

Addition-curable liquid silicone rubber(LSR,denoted as liquid silicone rubber)is widely used in electronic appliances,medical and health,aerospace and other fields attributed to its advantages of simple process,no by-products,minimal volume shrinkage,and deep vulcanization.However,due to the fact that most of the side chains of silicone rubber are non-poLSR groups,the silicone rubber has a very low surface free energy and weak intermolecuLSR interaction,resulting in poor mechanical properties and adhesive properties of the silicone rubber,which limits its application range.Therefore,it is of great practical significance to reinforce the properties of silicone rubber.In this thesis,Dow Corning Sylgard 184 was chosen as the matrix of silicone rubber,a novel of silicone rubber composites with high mechanical strength and strong adhesive properties have been prepared by adding functionalized graphene oxide or adhesion promoter into the LSR matrix.First of all,graphene oxide(GO)was grafted by using maleimide siloxane(PTESMI)synthesized in this work to produce GO-PTESMI.Subsequently,the resulting GO-PTESMI was modified by addition reaction using Si-H terminated polydimethylsiloxane(PDMS)as a modifier,which fabricating a functionalizated graphene oxide(GO-PTESMI-PDMS).Graphene oxide/liquid silicone rubber(GO/LSR)and functionalized graphene oxide/liquid silicone rubber composites(GO-PTESMI-PDMS/LSR)were prepared by adding GO and GO-PTESMI-PDMS to Sylgard 184 followed by vulcanization,respectively.The composition,microstructure,thermal stability and dispersity of filler in the silicon rubber matrix were investigated by FT-IR,XPS,XRD,TGA,SEM and TEM.The thermal and mechanical properties of these composites were also e.xplored.The results showed that the GO filler was reunited in GO/LSR matrix.When the amount of GO was 0.20 wt%,the mechanical properties of GO/LSR were slightly higher than those of LSR,but the heat resistance was reduced.However,GO-PTESMI-PDMS is evenly distributed in LSR matrix.When the amount of GO-PTESMI-PDMS was 0.25 wt%,the mechanical properties of composite were the best in all GO-PTESMI-PDMS/LSR composites.The tensile strength and tear strength of GO-PTESMI-PDMS/LSR composite increased by 34.5%and 23.7%compared with LSR,respectively,and the heat resistance was also improved.It was indicated that the reinforcing effect of GO-PTESMI-PDMS on silicone rubber was better than that of GO.Secondly,the adhesion promoter A was synthesized by addition reaction from Tetramethylcyclosiloxane with glycidyl allyl ether and vinyltrimethoxysilane.The adhesion promoter B was prepared by condensation reaction of vinyl hydroxyl siloxane and trimethoxy glycidyl ether.Two kinds of self-adhesive liquid silicon rubbers,A/LSR and B/LSR,were fabricated by adding A and B to Daw Corning Sylgard 184 followed by heat-curing,respectively.A,B,A/LSR and B/LSR were characterized by FT-IR,1H NMR and TGA measurements.The adhesive,mechanical and thermal properties of the self-adhesive silicone rubber were also investigated.For the self-adhesive A/LSR,the results showed that the shear strength of A/LSR to the stainless steel substrate was 514%higher than that of LSR and the mechanical properties of A/LSR were the best when the mass fraction of A was 2.0 wt%.For the self-adhesive B/LSR,when the mass fraction of B was 2.5 wt%,the shear strength of B/LSR to the PA and PET substrates was increased by 421 and 300%,respectively,and the mechanical properties of B/LSR were the best in all B/LSR with different B concentrations.It was confirmed that the addition of A and B could improve not only the adhesion strength but also thermal and mechanical properties.