Ppg Industries, Inc.

Melvin P Wagner

Thomas G Krivak

Timothy A Okel

Harlan B Johnson

Shantilal M Mohnot

Samuel B Laferty

Joseph P Tultz

Elastomeric compositions contain crosslinked poly(diorganosiloxane) and reinforced precipitated silica having, on a coating-free and impregnant-free basis, a surface area of from about 220 to about 340 square meters per gram, a pore diameter at the maximum of the volume pore size distribution function of from about 9 to about 20 nanometers, and a total intruded volume of from about 2.6 to about 4.4 cubic centimeters per gram.

Silicone rubber reinforced with reinforced precipitated silica

Reinforced precipitated silica having, on a coating-free and impregnant-free basis, a surface area of from about 220 to about 340 square meters per gram, a pore diameter at the maximum of the volume pore size distribution function of from about 9 to about 20 nanometers, and a total intruded volume of from about 2.6 to about 4.4 cubic centimeters per gram, is produced by a process wherein precipitated silica is heavily reinforced using a multiplicity of precipitation and aging steps.

Reinforced precipitated silica

Described is a porous flexible sheet of about 93 to 99.5 weight percent amorphous precipitated silica and from about 0.5 to about 7 weight percent fibrillated, unsintered polymeric material, e.g., polytetrafluoroethylene. The sheet is useful as a separator in absorbed electrolyte gas recombinant batteries, e.g., lead-acid batteries, and has a tensile strength of less than 75 pounds per square inch (0.5 MPa). The sheet preferably has a porosity of from 85 to 92 percent and exhibits an electrical resistance of less than 3.5 milliohm-in.sup.2 /10 mil when saturated with 37 percent sulfuric acid. The sheet is prepared by subjecting a dry homogeneous mixture of the silica and polymeric material, e.g., polytetrafluoroethylene, in the above proportions to mechanical shear blending forces to fibrillate the polymer and thereafter dry forming the resulting admixture into sheet form.

Gas recombinant separator

The abrasion resistance of siliceous filler-reinforced rubber vulcanizates is improved by adding to the unvulcanized rubber composition silane coupling agent comprising a mixture of a mercaptosilane, such as mercaptopropyltrimethoxysilane, and an alkyl alkoxysilane, such as methyltrimethoxysilane. The mercaptosilane is present in amounts of between 0.3 and 15 parts per hundred parts of rubber, and the weight ratio of mercaptosilane to alkyl alkoxysilane is between 0.15:1 and 15:1. Preferably, the silanes in a ratio of about 1:1 are admixed with a hydrocarbon process oil and the oil-silane mixture added to the siliceous filler-rubber mixture.

Rubber compositions

Amorphous precipitated high structure silica pigment useful in the reinforcement of silicone rubber is described. The silica pigment is treated with an aqueous solution of a metal, e.g., calcium and barium, which forms a relatively water insoluble, white or colorless sulfate salt in amounts sufficient to provide at least an equal molar amount of the metal compared to the amount of alkali metal in the silica. Silicone rubber reinforced with such silica pigment exhibits a water swell of less than 4 volume percent.

Precipitated silica pigment for silicone rubber

The abrasion resistance of siliceous filler-reinforced rubber vulcanizates is improved by adding to the unvulcanized rubber composition a silane coupling composition comprising a mixture of a silane coupling agent, such as

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Wadsworth, OH, United States of America

Melvin P Wagner