Effect of a filler on the formation of network polyurethanes

The formation of network polyurethanes based on simple oligoglycols, trimethylolpropane and aromatic diisocyanates in the presence of aerosil has been investigated. It has been shown that the nature of the polyether does not change the way in which the filler affects structure-formation in the system being hardened. Depending on which diisocyanate is introduced into the composition of the reaction system, the introduction of the filler either prevents the formation of a gel (in the case diphenylmethane-4,4′-diisocyanate) or it creates more favourable conditions for gel-formation than those in the unfilled system (for toluylene-2,4-diisocyanate). The data from investigation of the kinetics and the dynamic viscosity during crosslinking are in good agreement with the results of a study of the volumetric swelling of cured specimens.