Abstract: A sealant made from a room temperature curing polydimethylsiloxane composition has a siloxaphobic surface layer at the air-sealant interface where this layer is a fluorocarbon compound and a drying oil oxidation product. Elastomeric compositions made from polydimethylsiloxanes having both low reactivity endgroups and high reactivity endgroups and a siloxaphobic agent of fluorocarbon alcohol or a reaction product of the fluorocarbon alcohol and a hydrolyzable silane, are particularly useful for sealing buildings because they can withstand the expansions and contractions. One siloxaphobic agent is the reaction product between a fluorocarbon alcohol and a methyltri(methylethylketoximo)silane and the formula of one of the reaction product compounds is ##STR1## wherein x has an average value of at least 6.

Abstract: A curable polydiorganosiloxane is reinforced by mixing with a modified polyvinylalcohol (PVA). Fully hydrolyzed PVA is modified by dissolving or swelling in solvent, then adding a silylating agent of the formula R".sub.b (R'.sub.2 SiO).sub.n SiR.sub.a X.sub.4-a where R is a group capable of undergoing hydrolysis to form a siloxane bond with the curable polydiorganosiloxane, R' is a monovalent alkyl or aryl radical having from 1 to 6 carbon atoms, optionally halogen substituted, and compatible with the curable polydiorganosiloxane, R" is either R or R', X is a radical reactive with the hydroxyl on the PVA, a and b are integers of 0 to 3 inclusive, the sum of a plus b is from 1 to 3 inclusive, and n is from 0 to 35. This modified PVA is then mixed with the curable polydiorganosiloxane. The polydiorganosiloxane is then cured and the solvent is extracted to yield a cured polydiorganosiloxane reinforced with polyvinylalcohol.

Abstract: A curable polydiorganosiloxane is reinforced by mixing with a solution of polyvinylalcohol (PVA) or a modified PVA. The polydiorganosiloxane is then cured and the solvent is extracted to yield a cured polydiorganosiloxane reinforced with PVA.

Abstract: A fine powder is obtained by first dissolving polyvinylalcohol and tetraalkoxysilicate in a common solvent to obtain a reaction product, then spraying a fine mist of a solution of the reaction product into a coagulating bath of a solvent which is miscible with the common solvent, but a poor solvent for the reaction product. After drying, the fine particles obtained are useful as filler in polydiorganosiloxane compositions.

Abstract: Polydiorganosiloxane gum, of the type produced by the alkaline metal catalyzed polymerization of organocyclosiloxanes can be reduced in hydroxyl content by mixing the gum with an acid or acid producing phosphoric component and a silylamine component, allowing the mixture to react until the hydroxyl groups are lowered to the desired extent, then devolatilizing the gum. The hydroxyl content can be lowered without causing any significant change in the molecular weight of the gum. The hydroxyl content can be lowered to essentially zero.

Abstract: Polydiorganosiloxane gum, of the type produced by the alkaline metal catalyzed polymerization of organocyclosiloxanes can be produced without hydroxyl content by mixing the gum with and acid or acid producing phosphoric component and a silylamide component, allowing the mixture to react until the hydroxyl groups are eliminated, then devolatilizing the gum. The hydroxyl content can be removed without causing any significant change in the molecular weight of the gum and producing a gum which is heat stable at temperatures such as 250.degree. C. without the addition of heat stabilizers.