SYNTHESIS AND FLAMMABILITY OF COPOLYISOPHTHALAMIDES .1. WITH PHOSPHORUS GROUPS IN THE MAIN CHAIN

The influence of certain phosphorus substituted (OH, OMe, Me) 3,3'-diphenylphosphine oxides on flammability and thermal stability of 1,3-phenylene isophthalamide copolymers was investigated. Introduction of the above phosphorus groups along the backbone of poly (1,3-phenylene isophthalamide) was performed in a random manner to a degree of ca. 5-15 mol %. From the limiting oxygen index (LOI) measurements on copolymers, it was found that the diphenylphosphinic acid group has the highest flame retardance efficiency with an increase of LOI 44-56%. From thermogravimetric analysis (TGA), it was found that the action of phosphorus groups is limited in the solid phase, increasing the char yield to 27-42%. This was attributed to crosslinking reactions at the stage of amide bond decomposition.