A STUDY OF THERMAL-STABILITY OF POLYESTER CONTAINING PHENYL PHOSPHONATE UNIT FOR FLAME-RETARDANT FIBER

Phenyl phosphonic acid (PPA) was chosen as a comonomer to manufacture flame retardant polyester fiber. The yield based on PPA is less than 5 5% by a conventional polyester formation process. Different factors wh ich might affect the yield of the copolymerization were investigated. The phosphorus residues in the reactor during the process of polymeriz ation were monitored. It is found that the phosphorus residues decreas e sharply in the high vacuum stage. This indicates that factors which increase the molecular weight of the prepolymer containing phenyl phos phonate unit will promote the yield of the copolymerization. In order to get an insight into the low yield of the copolymerization, the comp ounds containing phenyl phosphonate unit, bis(2-naphtholyloxyethyl) ph osphonate (BNEP) and bis(p-methoxycarbonyl phenyl) phosphonate (BMPP) were synthesized for model studies. The preliminary results showed tha t these compounds decompose significantly above 240 degrees C. This su ggests that the low yield of the PPA polymerization process may be att ributed to the thermal instability of the O-P-O bond in the phenyl pho sphonate unit at the polymerization temperature. (C) 1996 Published by Elsevier Science Limited