The properties of organosilicon compositions based on alpha - omega -dihydroxy diorganopolysiloxanes, methyl polysiloxanes, fillers, amino organosilicon corss linking agents and optionally alkyl silicates or polysilicates, which are vulcanisable at ambient temperature or above, are improved by using a methylpolysiloxane in which the ratio of the R(CH3)2SiO0.5 units (R=C1-C3 alkyl or vinyl) to SiO2 units is 0.4:1 to 1.2:1 and which contains 0.5 - 3.5% by weight OH groups bonded to Si and by using an amino organosilicon compound which is an aminoorganosilane of the general formula (i) (R''O)3- pR'pSi[(CH2)nO]m (CH2)tNHQ in which R' represents an alkyl group with 1 to 4 carbon atoms, a vinyl group or a phenyl group, R'' represents a methyl, ethyl or methoxyethyl radical, Q represents a hydrogen atom or the radical -(CH2)2NH2, p and m represent 0 or 1, n represents 1, 2, 3 or 4, and t represents 2 or 3, or an aminoorganopolysiloxane produced by reacting the aminoorganosilane (i) above, in which p is 0, with a hydroxylic methylpolysiloxane polymer (ii) containing at least 2% by weight of hydroxyl groups bonded to the silicon atoms, of viscosity 1 cPo at 25 DEG C to 1,000 cPo at 25 DEG C, of the average general formula (CH3)a(HO)bSiO(4-a-b)/2 in which a represents any number from 1.6 to 2.3 and b represents any number ranging from 0.1 to 1; the amounts of aminoorganosilane (i) and hydroxylic methylpolysiloxane polymer (ii) being such that there are 0.4 to 1.2 mols of (i) per gram-(hydroxyl group) (that is to say 17 g) of (ii). The new compositions have improved fluidity characteristics and pot life, and adhere easily to most surfaces without using a primer and can be used particularly to protect electronic connections.
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