Thermal degradation and flame retardancy of ethylene-vinyl alcohol copolymer blended with ammonium polyphosphate

摘要

The thermal degradation and flame retardancy of ethylene-vinyl alcohol copolymer (EVOH) blended with ammonium polyphosphate (APP) have been studied. EVOH blended with 5 wt.% or more of APP showed excellent flame retardancy. The burn time in UL-94 test and the total released heat measured by cone calorimeter decreased with increasing APP content. In particular, blended-EVOH with 15 and 20 wt.% of APP did not ignite under UL-94 test. The thermal degradation properties were observed by TGA (thermal gravimetric analysis), Py/GC/MS (pyrolysis/gas chromatography/mass spectrometry) and EA (elemental analysis). TGA curves of blended-EVOH showed three points of inflection which were considered to be due to the reaction with APP. Although 20% of the degradation temperature fell with the blending of APP, 70% of the degradation temperature rose. The results of elemental analysis showed multiple degradation reactions, one of which was the reaction of APP with OH radicals on the polymer chain to form a crosslinked structure. The effect of APP on the flame retardancy of EVOH was considered to be caused by the crosslinking as well as the dehydrogenation.