Dow Corning Corporation

Carl M Monroe

John Donald Blizzard

Randall P Sweet

Olgerts Skostins

Linda Denise Kennan

Peter Lamont

Roger G Chaffee

Theodore L Knapp

An improved reinforcing silica filler can be produced by treating a reinforcing silica, having a surface area of greater than 50 m.sup.2 /g and from 0.5 to 6 parts by weight of adsorbed moisture per 100 parts by eight of silica, with a volatile treating agent comprising a combination of from 0.2 to 10 parts by weight of volatile treating agent of the formula Vi.sub.x Si(OR').sub.4-x and from 0.2 to 15 parts by weight of volatile treating agent of the formula Ph.sub.x Si(OR').sub.4-x, where Vi is vinyl radical and Ph is phenyl radical. The improved reinforcing silica filler can be combined with polydiorganosiloxane and curing means to produce silicone elastomer compositions which can be cured to elastomers which have improved physical properties, such as compression set and heat aging.

Treated silica for reinforcing silicone elastomer

A silicone rubber stock, giving an elastomer upon cure by hot air-vulcanization which has a low compression set, is obtained when a silicon composition containing at least two .tbd.SiH groups is added to a silicone rubber base which contains a polydiorganosiloxane gum having at least two alkenyl groups per molecule.

Low compression set silicone rubber

A method of producing an improved extruding silicone rubber stock consists essentially of mixing together a polydiorganosiloxane having a Williams Plasticity Number of from 125 to 180 and a get slope activity of less than 25 and a reinforcing silica filler having a surface area of greater than 150 m.sup.2 /g and a hydrophobic surface from a silane treatment to give a stock which has a Garvey rating of greater than 3.5 at an extrusion rate of 20 rpm.

Silicone extrusion stock

Compositions which cure to electrically conductive silicone elastomers containing greater than 2 percent by weight of phenyl radicals, are disclosed. The compositions comprise a mixture of polydiorganosiloxane and greater than 15 percent by weight of electrically conductive carbonaceous particles of less than 20 micrometers average diameter. Electrically conductive members of controlled resistivity are manufactured using these compositions. These electrically conductive members are useful as the core for improved automotive ignition cable. The ignition cable has a long useful life.

Electrically conductive polydiorganosiloxanes

The resistance of a fluorinated silicone elastomer to the effects of exposure to hot fuel, hot oil, and elevated temperature has been improved by the addition of from 0.8 to 5 parts by weight of polytetrafluoroethylene powder to a curable fluorinated silicone elastomeric composition, consisting essentially of a fluorinated polydiorganosiloxane gum having from 45 to 50 percent of the organic radicals being 2-(perfluoroalkyl)ethyl radicals, from 50 to 55 percent of the organic radicals being monovalent hydrocarbon radicals with from 0.1 to 1 percent of the monovalent hydrocarbon radicals being aliphatic unsaturated radicals, and a treated reinforcing silica filler. The resistance is further improved by also including an alkaline earth metal oxide or hydroxide acid acceptor.

Curable fluorinated silicone elastomer

When a small amount of polytetrafluoroethylene powder is mixed with certain curable polydiorganosiloxane compositions containing a reinforcing silica and an organic peroxide curing agent and the resulting mixture is extruded and heat-cured, the resulting elastomeric article has a durometer of less than 30 and has a greatly reduced amount of porosity or bubbles.

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Midland, MI, United States of America

Carl M Monroe