EFFECTS OF RUBBERS AND THERMOPLASTICS AS ADDITIVES ON CYANATE POLYMERIZATION

Several rubber (acrylonitrile-butadiene copolymer) or thermoplastic (p olyethersulfone) additives bearing different chain ends were introduce d into pure aromatic dicyanates. We studied the influence of these ini tially miscible modifiers on the polymerization kinetics, as a functio n of their chemical structure and concentration. It appears that apart from those bearing a labile hydrogen atom, the additives play almost no role on the polycyclotrimerization rate; neither does phase separat ion. However, the additives influence the structure of the final netwo rks insofar as they partially dissolve in the matrix and thus modify b oth the final T(g) and the onset of vitrification, compared with the p ure monomer. Finally, the amino- or phenolic additives can react with cyanate functions and produce adducts which are well-known catalysts f or cyanate cyclotrimerization; in their presence, a marked enhancement of the polymerization rate can thus be observed, together with the th ermal effects mentioned above.