Organo-polysiloxane compsn. curing to form an elastomer - with good mechanical properties and reduced gas permeability, used as jointing material

摘要

A mono- or bi-component organosilicic compsn., hardening at room temp. into an elastomer, is prepd. by mixing (a) an oil based on alpha,omega di(hydroxy)diorganopolysiloxane with viscosity 5000-500,000 cP at 25 degrees C; (b) a crosslinking agent; (c) a mineral filler; (d) a crosslinking catalyst; and (e) an additive to reduce the permeability of the elastomer to gases and vapours. The additive contains (i) 30-95 pref. 35-90 wt. % liq. polybutylene of Mn 300-2500 pref. 350-2000, formed by polymerisation of mixt. of 4C olefins contg. =85 wt. % isobutenes; and (ii) 5-70 pref. 10-65 wt. % solid prods. of lamellar structure, with average particle dia. 0.5-500 mu. 20-100 pts. wt. additives are used per 100 pts. wt. component (a). The compsn. is used to make impervious joints e.g. for windows, containers e.g. of hygroscopic prods., pharmaceuticals, or for cases contg. delicate measuring appts.