| 摘要 |
The invention provides a novel heat curable organopolysiloxane composition capable of giving a cured product having a remarkably high hardness and excellent anti-crack resistance. The cured product is also free from surface tackiness even by heat-curing in air. The main component of the composition is an organopolysiloxane having vinyl groups, phenyl groups and silicon-bonded hydrogen atoms simultaneously in a molecule or a mixture thereof with a second organopolysiloxane having vinyl groups and phenyl groups but no silicon-bonded hydrogen atoms in the molecule. It is essential that the molar ratios of the vinyl groups, phenyl groups, silicon-bonded hydrogen atoms and, if any, alkyl groups in the organopolysiloxane or organopolysiloxanes to the silicon atoms must be within specifically defined ranges and the organopolysiloxane component is admixed with a platinum catalyst for the addition reaction between the vinyl groups and the silicon-bonded hydrogen atoms as well as an organic peroxide such as dicumyl peroxide.
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