Dow Corning Corporation

Lori Jean Conway

Phillip Joseph Griffith

William James Schulz, Jr

Jary David Jensen

Peter Lamont

Thomas E Gray

A platinum group-metal curing liquid silicone rubber compositions having improved physical properties such as tear and heat-aging, especially at durometers below about 35 and above about 65. The present inventors have unexpectedly discovered that the addition of diorganohydrogensiloxy end-blocked polydiorganosiloxanes and triorganosiloxy end-blocked polydiorganosiloxanes having a viscosity greater than about 10 Pa.cndot.s at 25.degree. C. to liquid silicone rubber compositions can provide for the described improved properties.

Use of high molecular weight organopolysiloxanes to improve physical

A method for preparing organopolysiloxane bases with high levels of fillers. The present inventors have found that by mixing the components of the base at a temperature below about 60.degree. C. for a period of time sufficient to effect essentially a homogeneous blend, a base composition is formed which can be further blended with a platinum group metal-containing catalyst, an organohydrogensiloxane, and optionally an inhibitor to form a curable liquid silicone rubber (LSR) composition. The curable LSR composition has improved flow characteristics and improved shelf life when compared to similar materials where the base is prepared at temperatures above about 60.degree. C. The improved flow characteristics allows larger quantities of fillers to be incorporated into the curable LSR composition while still maintaining acceptable flow characteristics. Silicone elastomers prepared using the curable LSR compositions can have improved swell and degradation resistance to oils, lower compression set values, and improved tear, elongation, and tensile values and require no post cure. The present organopolysiloxane bases are particularly useful as a common base for forming a group of cured silicone elastomers with a range of durometers.

Growing community of inventors

Midland, MI, United States of America

Lori Jean Conway