Bisphenol Fluorenone Carbonate-Silicone Block Polymers:Improved Synthesis and Further Studies of Mechanical and Flammability Properties.

摘要

Several changes in synthesis and processing procedures have been resulted in BPF carbonate-silicone plastics of controlled molecular weight and improved transparency. Ultrapurification of the BPF monomer, use of rigorously dry environments and reagents, use of ammonia as the base in the silicone endcapping step, the return to chloroform as the polymerization solvent, the addition of excess base and phosgene during polymerization, and rapid polymer isolation washing and drying minimized molecular weight reduction and allowed effective use of phenol as a polymerization chain stopper. These steps also resulted in almost complete elimination of haze in moldings. The purer BPF particularly and argon blanketing of the extruder led to much reduced color in extrudates and moldings. Dermatological problems were encountered by personnel. Creep studies were carried out on one resin over 5 to 6 decades of time at stresses up to 4200 psi and temperatures up to 80 degree C. Creep is proportional to (time)(n) where n < or = 0.03. Little temperature dependence of creep rates is seen. Critical stresses for crazing under constant load are greater than 4000 psi at room temperature but approximately this level at 50 and 80 degree C. The outstanding flammability characteristics of the BPF carbonate-silicone block polymer family have been confirmed with further testing. The mechanism previously proposed for the synergism between the BPF carbonate and the silicone blocks in raising the limiting oxygen index has been supported with the results of electron microscopy and controlled degradation studies. A layer of what appears to be vitreous SiO2 has been found lining the outer pores of the char.