Study of the degradation of fire-retarded PP/PE copolymers using DTA/TGA coupled with FTIR

摘要

A PP/PE copolymer was successively flame retarded using Mg(OH)_2, then using brominated trimethylphenyl indane associated with Sb_2O_3 (Br/Sb), and finally using blends of equal weights of this last combination with Mg(OH)_2 or talc-containing non- hydrated fillers. Decompositions of pure and additive-containing copolymer were studied by DTA/TGA coupled with FTIR. A good correlation exists between the maxima of Gram-Schmidt curves and the derivatives of TGA curves. The coupling of techni- ques shows that the incorporation of the Br/Sb flame retardant limits strong exothermic phenomena due to sample ignition. In the case of Mg(OH)_2 associated with Br/Sb, the decomposition of the hydrated mineral occurs at a lower temperature than the reaction between brominated trimethylphenyl indane and Sb_2O_3. This delays the action of Br/Sb flame retardant towards higher tempera- tures, improving the thermal stability of the polymer. A good agreement is also found between DTA/TGA-FTIR conclusions and fire resistance tests carried out on standardized samples. When magnesium hydroxide is replaced by the fillers, the interest in using a pure talc, which appeared in fire resistance tests, is not strongly confirmed by DTA/TGA-FTIR. This discrepancy may be ascribed to the reduced influence of mass diffusion phenomena due to the small weight of the sample used in thermal analysis experiments.