SYNOPSISPhotodegradation of incombustible polymer materials [high-density (HD) and low-density (LD) polyethylene (PE) containing 0.5 to 2.0 phr of decabromodiphenyl ether (DBDE) or tetrabromobisphenol A (TBA) as a flame retardant] were studied using an Okazaki Large Spectrograph (OLS). Samples were irradiated in air a t 23°C with monochromatic light of wavelengths at 260, 280, 300, 320, 340, and 360 nm. Ultraviolet and Fourier transform infrared (FTIR) spectra were taken to estimate the chemical changes caused by photoirradiation. Molecular weight change was followed by gel permeation chromatography (GPC) measurements. It was found that the photostability of P E samples was reduced by the addition of flame retardants. The threshold wavelengths of photodegradation are 320 nm and 360 nm for PE-TBA samples and PE-DBDE samples, respectively. Main-chain scission is favored when the irradiation was carried out with the light of wavelength 300 nm for HDPE-DBDE and HDPE-TBA samples. The most effective irradiation wavelengths for crosslinking are found to be 300 nm and 280 nm for LDPE-DBDE and LDPE-TBA samples, respectively. 0 1995 John Wiley & Sons, Inc.

SYNOPSISPhotodegradation of incombustible materials [polystyrene ( PSt ) and polypropyrene (PP) containing 2 wt % of decabromodiphenyl oxide (DBDE) or tetrabromobisphenol-A (TBA) as a flame-cut agent] were studied using Okazaki Large Spectrograph (OLS) . Samples were irradiated in air at 23°C with monochromatic light of wavelengths at 260, 280, 300, 320, 340, and 360 nm. UV-visible spectra and FTIR spectra were measured to identify the chemical structural changes of the polymers. Number of chain scissions, which is a measure of the polymer degradation, was estimated from the results of GPC measurements. It was found that the photostability of PP and PSt was reduced by the addition of DBDE or TBA.Photodegradation of these polymers took place by the irradiation of the light of wavelengths lower than 320 and 360 nm for the polymer containing TBA and DBDE, respectively. The most effective irradiation wavelengths for main chain scission are found to be 260-280 and 300 nm for PP or PSt-TBA samples and PP or PSt-DBDE samples, respectively. 0 1993

SYNOPSISThe thermal degradation mechanisms of liquid crystalline aromatic polyesters ( LCPs ) prepared from p -hydroxybenzoic acid ( P H B ) , biphenol ( B P ) , and terephthalic acid (TA)were studied by pyrolysis-gas chromatography/mass spectrometry ( Py-GC/MS) . The LCP containing deuterated terephthalate units and the LCPs that have different comonomer ratios were examined. On the basis of the pyrolysis products determined, the origin of the main pyrolysis products (benzene, phenol, biphenyl, phenyl benzoate, etc.) from the corresponding comonomer units were estimated and their thermal degradation mechanisms were eventually discussed in detail.

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