Abstract: Organopolysiloxane compositions that are crosslinked by ultraviolet light comprising (A) an organopolysiloxane having units of the formulaHR.sup.1 C=CR.sup.2 COOR.sup.3 SiR.sub.2 O.sub.1/2,in which at least two such siloxane units are present per molecule of organopolysiloxane (A) and at least 80 percent of the number of the remaining siloxane units in organopolysiloxane (A) comprise units of the formulaR.sub.2 SiO,where R is a monovalent hydrocarbon radical or a halogenated monovalent hydrocarbon radical, R.sup.1 is hydrogen or a halogenated phenyl radical, R.sup.2 is hydrogen or an alkyl radical having from 1 to 4 carbon atoms per radical and R.sup.3 is a divalent hydrocarbon radical or a halogenated divalent hydrocarbon radical, in which the organopolysiloxane (A) has an average viscosity of from 20 to 5000 mPa.s at 25.degree. C., (B) an organopolysiloxane terminated by units of the formula R.sub.3 SiO.sub.178 , and having from 0.05 to 5 mole percent of units of the formula ##EQU1## wherein R and R.sup.

Abstract: Organopolysiloxane compositions which contain glass fibers having an average length of up to about 0.5 mm. The compositions are flowable in the absence of a solvent and can be cured at room temperature or moderately elevated temperatures to form elastomers having a high tear resistance and a high durometer.