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ABSTRACT:The thermooxidative degradation of poly-(oxymethylene) copolymer (CPOM-Y) powder was studied in air in 150°C. The effect of the sequence distribution of degraded poly(oxymethylene) (POM) samples on the thermal decomposition behavior was investigated with 1 H-NMR and gas chromatography/mass spectrometry. The results showed that the degradation process of CPOM-Y could be divided into three stages with a gradually increasing degradation rate. The change in the sequence molar fractions agreed with the fact that the ethylene oxide (EO) units had higher thermal stability, and the degradation of POM was due to the decomposition of formal units. At the beginning, CPOM-Y tended to split off formaldehyde, starting at the chain ends, some of which were not ended by EO units. In stage 2, the thermooxidation of POM occurred in the amorphous phase. In stage 3, no obvious rules for the changes in the sequence contents were obtained from NMR results, and this indicated further random chain scission and unzipping occurring heavily in the crystalline bulk. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: [577][578][579][580][581][582][583] 2004

Despite the development of strong, durable, and cost efficient polyisobutylene-based polyurethane (PIBbased PU) materials has yet to be achieved. The well dispersion and maximum interfacial interaction between the nanofiller and the PIB-based PU at low loading have been scarcely studied. Here, the preparation of PIB-based PU nanocomposites with Multiwalled carbon nanotubes (MWCNTs) using a simple in situ polymerization method is reported. The thermogravimetric analysis tests show that MWCNTs significantly improved the thermal stability of MWCNTs/PIB-based PU nanocomposites. Compare to the pure PIB-based PU the onset temperature of degradation for the nanocomposite was about 20 C higher at 0.7 wt% MWCNTs loading. Efficient load transfer is found between the nanofiller MWCNTs and PIB-based PU and the mechanical properties of the MWCNTs/PIB-based PU nanocomposite with well dispersion are improved. A 63% improvement of Young's modulus and slightly increased of tensile strength are achieved by addition of only 0.7 wt% of MWCNTs. The experimentally determined Young's modulus is in well agreement with the theoretical simulation. It is worth noting that the PIBbased PU and MWCNTs/PIB-based PU nanocomposites exhibit excellent damping properties (tan d > 0.3) from 245 C to 8 C. POLYM. COMPOS.,