Thermal stability of poly(oxyalkylene)amine-grafted polypropylene copolymers

The thermal and thermo-oxidative degradation of a family of amphiphilic cop olymers consisting of a polypropylene (PP) backbone and several poly(oxyeth ylene) /poly(oxypropylene) (POE/POP) pendants were investigated by using a thermal gravimetric analysis (TGA). Their relative stability was correlated to the chemical structures with respect to the POE versus POP in pendants and the terminal functionalities. In comparing the starting amines, molecul ar weight (Mw) and the types of polymer backbone were the main controlling factors for thermal stability in nitrogen, while the terminal amine contrib uted most to the thermo-oxidative stability in air. In the amine-grafted PP copolymers, the functional groups including the tethered amine, quaternary amine and sodium salt complexes significantly stabilized the PP copolymers , particularly in oxidative condition. The following trends of relative sta bility in air were observed: PP-g-MA/EDA > PP-g-MA/DAP much greater than PP -g-MA/ED2001 much greater than PP-g-MA/M2070 = PP-g-MA/D2000 > ED2001 > D20 00 = PEG2000 > PPG2000; PP-g-MA/Na+ > PP-g-MA. Under the condition of heliu m gas and at 550 degreesC, the representative PP-g-MA/ED2001 copolymer was pyrolyzed into fragments of olefins/dienes from PP backbone as well as viny l ethers from POE pendants, as observed by GC/mass spectroscopy. Reaction p athways for degradation and the controlling factors for the thermal and the rmooxidative stability of these functionalized PP copolymers are discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.