Preparation And Properties Of Silicone Rubber Via The Reaction Between Amino And Cholopropyl Groups

Silicone rubber exhibits unique and excellent performances, such as resistance to extreme temperatures, ageing resistance, electrical insulation, special surface properties, etc. However, the comprehensive mechanical properties of the existing silicone rubber are poorer than those of common rubber at room temperature, which greatly restricts its application in many fields. So, how to improve the mechanical properties of silicone rubber becomes one of important research focuses. At present, changing the formulations, improving the synthesis technology or blending silicone rubber with other rubber based on peroxide curing system or hydrosilation reaction curing system are often used to enhance the mechanical properties of high-temperature vulcanization (HTV) silicone rubber. Methylvinylpolysiloxane was often used as a gum in these methods. However, developing a novel curing system to improve the mechanical properties of HTV silicone rubber is rarely reported. The formation of concentrative cross-linking in the rubber network is an effective method to improve the mechanical properties of HTV silicone rubber, especially the tear strength. Therefore, HTV silicone rubber with excellent properties can be prepared through adding concentrative cross-linkers to a novel type of curing systems.HTV silicone rubber can be prepared via the cross-linking reaction between amino groups and y-chloropropyl groups. In this curing system, polyamines were used as cross-linkers of polysiloxane containing y-chloropropyl groups (CPPS) matrix, and no catalyst is needed. Based on this curing system, we synthesized or choosed some polyamino-containing compounds with special structures (e.g., dendrimers, telechelic polysiloxane, aminopropyl-modified silica and amine-functionalized POSS) as cross-linkers of CPPS to prepare a series of HTV silicone rubber with excellent properties. The work was mainly as follows:A series of HTV silicone rubber was prepared with polyamidoamine dendrimers (PAMAM) as cross-linkers and CPPS as a gum. The effects of cross-linker concentration, curing temperature, and postcuring temperature on the mechanical properties of silicone rubber were discussed. Based on this discussion and measurement of cure characteristics, the optimal curing conditions were determined. The tensile strength, tear strength, elongation at break and hardness of vulcanizate reached 9.34 MPa,47.7 kN/m,689% and 59 HA, respectively. The results showed that PAMAM exhibit good concentrative cross-linking effect in this curing system. However, the mechanical properties slightly changed as the generation of PAMAM increased because part of amino groups in the interior layers of PAMAM were difficult to react with y-chloropropyl groups.A series of HTV silicone rubber was prepared with siloxane-polyamidoamine dendrimers (Si-PAMAM) as cross-linkers and CPPS as a gum. The effects of the used amount of cross-linkers on the comprehensive mechanical properties of silicone rubber were discussed. The results showed that the silicone rubber cross-linked with Si-PAMAM exhibited better mechanical properties than that with PAMAM. The tensile strength, tear strength, elongation at break and hardness of vulcanizate reached 10.06 MPa,47.9 kN/m,962% and 60 HA, respectively.Aminopropyl-terminated polydimethylsiloxane (APPDMS) and mult-amino-terminated telechelic polydimethylsiloxane (MATPS) were synthesized, and characterized with FT-IR and NMR. APPDMS and MATPS were subsequently used as cross-linkers of CPPS to prepare a series of HTV silicone rubber (MCSR/APPDMS and MCSR/MATPS), respectively. The appropriate curing temperature was determined through the analysis of cure characteristics. The effects of the used amount of TS530 and cross-linkers on the comprehensive mechanical properties of MCSR/APPDMS or MCSR/MATPS were discussed, respectively. The results showed that the mechanical properties of MCSR/MATPS were better than those of MCSR/APPDMS.A series of aminopropyl-modified silica (APS) with different amine contents was prepared and subsequently used as cross-linkers of CPPS to prepare HTV silicone rubber. The dispersion of APS in CPPS matrix was studied by scanning electron microscopy, and the results showed that APS was well dispersed in CPPS matrix. The cure characteristics were determined by rheometry. The effects of the used amount of TS530 and APS on the cure characteristics and comprehensive mechanical properties of silicone rubber were discussed, respectively. The optimal conditions to prepare silicone rubber were finally obtained. The obtained silicone rubber exhibited a tensile strength of 7.32 MPa, a tear strength of 40.2 kN/m and an elongation at break of 899%.Octa(aminophenyl)silsesquioxane (OAPS) and N-phenylaminomethyl POSS (NPAMS) were synthesized, and characterized with FT-IR, NMR and elemental analysis. Through the solution mixing or mechanical mixing methods, a series of HTV silicone rubber was prepared with OAPS or NPAMS as cross-linkers and CPPS as a gum. The effects of distribution of OAPS or NPAMS in CPPS matrix, the used amount of cross-linkers and the preparation method on the comprehensive mechanical properties of silicone rubber were discussed. The results showed that the silicone rubber prepared through the solution mixing method exhibited a homogeneous morphology and a favorable mechanical property. MCSR/OAPS and MCSR/NPAMS exhibited tensile strengths of 9.82 MPa and 9.85 MPa, tear strengths of 42.3 kN/m and 48.1 kN/m, respectively. The results indicated that OAPS and NPAMS were good concentrative cross-linkers in preparing HTV silicone rubber with CPPS as a gum.The thermal properties of these HTV silicone rubbers in inert atmosphere were investigated by TGA and DSC, respectively. The results showed that the obtained silicone rubber exhibited similar thermal degradation behaviors and good thermal stability. Furthermore, MCSR/POSS exhibited better thermal stability than others.