Modulus Reduction Mechanism of Trimethylsiloxy Silicates in a Polyorganosiloxane

摘要

Trimethylsiloxy silicates can be added to network forming linear polyorganosiloxane-based formulations to reduce the elastic modulus of the resulting cross-linked network without the loss of ultimate strength or excessive bleeding that typically occurs when either linear oligomers or polymer additives are used. The linear viscoelastic properties of uncured blends of a polyorganosiloxane with different loadings of silicates were characterized using time-temperature superposition to investigate the physical factors responsible for the modulus drop. The reduction in the plateau modulus of the polymer was found to be consistent with the power-law relation observed for nonentanglement-forming diluents, and was accompanied by a decrease in the frequency range of the plateau regime with increasing silicate content. Swelling and extraction studies on the corresponding cross-linked networks were conducted to help postulate the primary physical factors responsible for the modulus reduction. The modulus reduction enables lowdurometer, high-elongation elastomeric materials useful in silicone rubbers, high-movement joint sealants and pressure-sensitive adhesives.