Cyclomatrix poly(organo phosphazenes)—some aspects of synthesis, characterization and adhesive heat resistance

Structure‐property relationships of a phosphazene‐modified epoxy‐based cyclomatrix system were studied using aromatic diamine condensates of hexachlorocyclotriphosphazene (PNCl 2 ) 3 and a diglycidyl ether of bisphenol‐A. Synthesis and characterization of the condensates and difficulties associated with these aspects are described. Adhesive heat resistance and thermal stability are reported as functions of the “active hydrogen” content of the condensates, molar ratios of the epoxy and “active hydrogen,” and amine structures. Modification of the OH groups formed in the amine–epoxy reaction via cyanoethylation and transesterification was not effective in improving high‐temperature adhesion. The polymer systems were stable up to 380°C in air, exhibited higher char contents at elevated temperatures, and were optically clearer when compared with the corresponding nonphosphazene systems. Presence of phosphazene rings was also helpful in lowering the cure time and temperature.