Modification of liquid silicone rubber by octavinyl-polyhedral oligosilsesquioxanes and silicon sol

Abstract

To develop an efficient and bio-compatible way to improve the thermal and mechanical properties of addition type liquid silicone rubber (LSR), a series of modified LSR samples were prepared by introducing octavinyl-polyhedral oligosilsesquioxanes (VPOSS) and high purity silicon sol singly or in combination before vulcanization. Significant correlation was found between the loading rate of VPOSS and thermal properties. However, mechanical properties were negatively correlated with VPOSS content within the range experimented, which may be ascribed to material defect caused by uneven distribution and aggregation. Furthermore, test results approved that the introducing of silicon sol indeed affected the stabilities of the polymer by restraining the material defect caused by the aggregation of POSS molecules and improving cross link density. For example, adding 10%-20% of silicon sol into VPOSS(1.0%) modified LSR will increase tear resistance by 43.9%-85.7%, elongation at break by 31.7%-57.3%, residue at 800 °C in N₂ atmosphere by 32.0%-37.9%, residue at 650 °C in air atmosphere by 70.9%-91.6%, respectively. This work proves that, to incorporate VPOSS into LSR by hydrosilylation, and to use silicon sol as dispersant and reinforce filler can become an efficient way to improve the mechanical property, thermal stability and bio-compatibility of LSR in the future.