Preparation and characterization of 3-chloropropyl polysiloxane-based heat-curable silicone rubber using polyamidoamine dendrimers as cross-linkers

Abstract

A series of high-temperature vulcanization (HTV) silicone rubber was prepared with polyamidoamine (PAMAM) dendrimers as concentrative cross-linkers and polysiloxane containing 3-chloropropyl groups (CPPS) as gums in a novel curing system. The curing, mechanical, and thermal properties of this novel HTV silicone rubber (MCSR) were studied through rheometry, mechanical testing, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The curing process was analyzed on the basis of the cure curves obtained by rheometry. The optimal conditions to prepare MCSR were determined by changing curing conditions, including cross-linker concentration, curing temperature, and postcuring temperature. MCSR exhibited a tensile strength of 9.34MPa and a tear strength of 47.71kN/m when the molar ratio of [3-chloropropyl]/[N–H] was 1:1.5. These excellent mechanical properties were attributed to the concentrative cross-linking effect from PAMAM dendrimers. Meanwhile, the mechanical properties slightly changed as the generation of PAMAM dendrimers increased because of steric hindrance. In addition, TGA results indicated that MCSR was thermally stable in a nitrogen atmosphere even at high degradation temperatures, such as T5wt.% loss (MCSR-3)=451.7°C and T50wt.% loss (MCSR-3)=659.0°C. DSC analysis revealed that a glass transition peak followed by a melt was identified for MCSR at −160°C to 30°C. The experimental results showed that using PAMAM dendrimers as cross-linkers is a practical way to obtain silicone rubber with excellent properties.