Abstract: A polydiorganosiloxane gum base stock can be foamed and cured by exposing to a microwave source a composition which comprises 100 parts by weight of the stock, 3 to 25 parts by weight of an organohydrogensiloxane, 0.05 to 0.5 part by weight of an acetylenic alcohol inhibitor, 1 to 200 p.p.m. platinum as a platinum catalyst and from 0.25 to 30 parts by weight of a microwave sensible material. This method is particularly useful where it would be impractical or undesirable to use heat to foam and cure silicone compositions.

Abstract: A sponge prepared from silicone rubber using 4,4'-oxybis(benzenesulfonhydrazide) as a blowing agent has improved heat stability when calcium oxide, magnesium oxide or a mixture of these two oxides is present in the composition. The sponge prepared using these oxides has a lower compression deflection after heat aging than the compositions which do not contain the oxides.

Abstract: Polydiorganosiloxane gum base stocks which contain per 100 parts by weight of the stock, 5 to 30 parts by weight of an organic alcohol having one C--OH per molecule, 3 to 25 parts by weight of an organosiloxane having an average of at least 2.5 silicon-bonded hydrogen atoms per molecule, 0.05 to 0.5 parts by weight acetylenic alcohol inhibitor and 5 to 20 p.p.m. platinum as a platinum catalyst, can be foamed by heating the composition above 125.degree. C. The sponged products are thin skinned or no skin, elastomeric, have flame retardant properties and can be used where applicatons see relativey high temperatures.