Preparation And Properties Of New Type Of Silicone Rubber

Silicone polymer had unique Si-O-Si main chain structure,so that silicone rubber had some excelent properties than organic rubber,such as:low glass transition temperature,low surface free energy,hydrophobicity,high gas permeability,excelent oxidative stability and biocompatibility,and so on.It was found many commercial applications in automotive and construction industries,microelectronics,specialty textiles,medical devices and implants.However,due to the weak molecular interaction between polysiloxane backbones,the preparation of silicone rubber must be reinforced and cured.However,the application fields and properties of silicone rubber products were affected by the agglomeration of reinforcing fillers,the weak bonding force between organic/inorganic two-phase interface,deactivation and residue of catalyst.Therefore,in order to improve the intermolecular forces between polysiloxane backbones and the interfacial bonding strength between organic and inorganic phases,this paper proposed the preparation of two new types of silicone rubber,which laid a theoretical foundation for the further development of silicone rubber.1.Preparation of self-reinforced and hydrogen bond cross-linked silicone rubber?SR?based on silicone-polyurea block copolymer?Si-PU?.Firstly,?,?-aminopropyl terminated polydimethylsiloxane?A-PDMS?was synthesized by an anionic ring-opening polymerization method using octamethylcyclotetrasiloxane?D₄?and 1,3-bis?3-aminopropyl?tetramethyldisiloxane?NH₂MMNH₂?.Secondly,Si-PU with different polyurea segment was synthesized by A-PDMS,?4-isocyanatocyclohexyl?-methane?HMDI?and ethylenediamine?EDA?in tetrahydrofuran?THF?/isopropyl alcohol?IPA?mixed solvent.Finally,SR was obtained at room or high temperature.The shift of-NH in FTIR and the multiple peak of-C=O proved the existence of hydrogen bond in SR.Swelling experiments showd that the hard segment content increased,and the hydrogen bond crosslink density of SR increased;SEM,XRD and DMA proved the microphase separation structure in SR;the higher the hard segment content,the rougher the cross section.The hardness and tensile strength of SR increased,and the elongation at break decreased,which proved the reinforcing effect of microphase separation structure on SR.The TGA results showed that the thermal decomposition of SR mainly occurred at 200°C and was completely decomposed at about 600°C,the thermal stability decreased with the increase of hard segment content.The hydrophobic properties of SR increased with the increase of the hard segment content.For example,the surface energy of SR-5 could reach-24.81mN/m.2.Preparation of POSS-reinforced and cross-linked silicone rubbers based on primary amine-cyclic carbonate cross-linking reactions?VPSR?.Firstly,the clathrene propyl polysilsesquioxane?SH-POSS?wassynthesizedbyhydrolysisof?-mercaptopropyltrimethoxysilane?KH590?under acidic conditions;Polypropylene polysilsesquioxane modified cyclocarbonate?POSS-VEC?was synthesis by SH-POSS and ethylene vinyl acetate?VEC?under UV irradiation in N,N-dimethylformamide?DMF?.VPSR was obtained by VEC-POSS and A-PDMS,which was cured at 100°C after the mixing at room temperature.The shift of-NH in FTIR and its multiple peaks proved that t hydrogen bond existed in VPSR;TGA results showed that VPSR had good thermal stability,and with the increase of VEC-POSS content,thermal stability decreased;XRD proved that VPSR had microphase separation structure;With the increase ofVEC-POSS content in VPSR,the particle cluster density of the quenched fracture surface increased,the hardness and tensile strength of VPSR increased,the elongation at break decreased and the crosslink density of VPSR increased.It was proved that VEC-POSS had good reinforcement and cross-linking effect on VPSR;VPSR was hydrophobic,its hydrophobicity increased with the increase of VEC-POSS content,and the surface energy of VPSR-5 had the lowest value of-25.36 mN/m.