Flame retardance comonomer structure

It has been reported that the effectiveness of copolymerized DOPO-type monomers can be further improved if the alcohol-amine derivatives of DOPO, for example, Structure 5.11, are used rather than similar structures not containing nitrogen.30 Of the FR fibers based on P-containing comonomers, it has been found that those based on Structure 5.10 are more hydrolytically stable, presumably because the P-containing group is in a cyclic structure and also should the hydrolysis of the P-0 bond occur, it will not lead automatically to a marked reduction in molecular weight.31 All the P-modified PETs appear to be subject to both the vapor-and condensed-phase mechanisms of flame retardance, with the former predominating.32 33... 

Other reactive P-containing comonomers reported to improve flame retardance in PET include aliphatic and alicyclic (spiro) bisphosphonates34 such as Structure 5.12. 

The question of the flammability behavior of similar flame retarding structures when used as additives or as comonomers in PET is discussed. For the case of structures related to tetrabromo-bisphenol-A, there was little difference, but for those containing triphenylphosphine oxide related structures a switch from volatile phase to condensed phase mechanisms was possible. 

For the case of PET flame retardation, we were interested in determining whether certain flame retardant structures functioned differently when the structure was incorporated as an additive or when it was incorporated as a comonomer into the backbone of the chain. 

The results on both the bromine and phosphorus examples indicated that differences in flame retardation could occur for similar flame retardant structures and were dependent on whether they were used as additives or comonomers. 

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