Abstract: Liquid, linear, crosslinkable phosphazene compositions and a process for their preparation are disclosed. These liquid compositions, prepared from normally solid polyphosphazene, contain the polyphosphazene in admixture with from about 1 to about 30 parts per hundred parts of polymer of a polythiol, a polyacrylate, a polymethacrylate or mixtures thereof such that the combination has a viscosity of less than 500,000 cps at 23.degree. C. These compositions are easily handled and can be crosslinked at ambient temperatures.

Abstract: A sealant composition comprising a non-crosslinked, elastomeric mastic and an extrusion-inhibiting amount of vulcanized rubber particles of irregular shape and having sharp edges and angular surfaces. When the composition is used as a channel sealant, the ability of the particles to deform at structural gaps while offering resistance to extrusion prevents the loss of the elastomeric mastic.

Abstract: A thermostable heterocyclic polymer constituted by monomer units of the general formula ##STR1## where R.sup.1 and R.sup.2 denote an organic radical having from 2 to 1000 carbon atoms;a radical having 2 to 1000 carbon atoms, containing:1 to 1000 atoms of Si,and/or 1 to 1000 atoms of F,and/or 1 to 1000 atoms of Cl,and/or 1 to 1000 atoms of Br,and/or 1 to 1000 atoms of N,and/or 1 to 1000 atoms of S,and/or 1 to 1000 atoms of P,and/or 1 to 1000 atoms of B,and/or 1 to 1000 atoms of O,R.sup.1 and R.sup.2 being either the same or different;R.sup.3 .dbd.NH, CH.sub.2 ;R.sup.4 is a radical which, with R.sup.3 .dbd.NH, may be ##STR2## while with R.sup.3 .dbd.CH.sub.