Our previously reported one-step method of simultaneously polymerizing and molding pyrrone monomers to produce high-strength, high-modulus, dense, thermally stable moldings has been studied in more detail and improved by using crystalline 1 : 1 salts of the monomers. Interrelationships between molding powder characteristics and molding conditions required to achieve optimum polymer properties were investigated. Typical properties of the moldings obtained from the salt of pyromellitic anhydride and 3,3′-diaminobenzidine were: density, 1.29 g/cc; diametral tensile strength, 10,700 psi; ultrasonic modulus, 1.3 × 106 psi; hardness, 80 Rockwell B; and thermal stability in air (at 0.5°C/min), 400°C. Quick TGA methods, applied to the salts for estimating the thermal stability of molded polymers, before actual polymerization and molding, have been developed. No problems associated with gas release are observed when molding conditions have been optimized.