INVESTIGATING THE DEGRADATION OF THERMOPLASTICS BY THERMOGRAVIMETRY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY (TG-FTIR)

Themogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) has been used to study the thermal degradation of three types of synthetic thermoplastics: Poly(arylene ether)s containing art acenaphthylene mo iety, poly(arylene ether ketone)s prepared as analogues of the commerc ial polymer poly(ether ether ketone) (PEEK), and aromatic polyimides s ynthesized by a single-step solution polymerization. TG-FTIR was found to be useful in providing important structural information about the poly(arylene ether)s and polyimides, which was not apparent through co nventional NMR or FTIR techniques. Spectra obtained using air as a pur ge for insoluble and soluble poly(arylene ether)s 1 revealed that resi dual sulfur remained in both polymers after preparation through a reac tion with Lawesson's reagent. Comparison of TGMN-FTIR results of new p oly(arylene ether ketone)s 2 with previously reported data on degradat ion studies of PEEK obtained with TG-mass spectrometry (TG-MS) showed that both polymers had similar degradation patterns, with phenol being a major degradation product. TG-FTIR studies on polyimides 3 and 4 sy nthesized by one-step solution polymerization demonstrated that it was possible to determine the imidization degree by monitoring the intens ity of the water absorption band at 1795 cm(-1) as a function of the T G temperature during a weight-loss occurring near 300 degrees C. The F TIR spectra of both polyimides studied in this work showed that carbon monoxide was a significant degradation product. Other degradation pro ducts detected for polyimide 3 were ammonia, isocyanic acid and phenyl isocyanate. FTIR peaks consistent with hydrogen cyanide also appeared for polyimide 3.