Thermal degradation of polystyrene (PS) was carried out in the absence of oxygen between 292 and 336 "C. The formed volatile products were analysed qualitatively and quantitatively by means of gas chromatography. It was found that the composition of the volatile fraction is a function of conversion and independent of temperature for most of the products. A radical chain mechanism is proposed to explain these experimental results.

The thermal degradation of polydisperse polystyrene samples with mol. wts. (3,) between 6OOOO and 220000 has been investigated at different temperatures under oxygen free conditions. Product analysis has been carried out by GPC. The experimental degradation could be simulated by a model consisting of scission and depolymerization. The dynamical behaviour of this model is expressed in a matrix form. The ratio of scission and depolymerization is constant for all polymers and different temperatures during degradation. Therefore, a master curve could be evaluated, which gives a general relation between the decrease of mol. wt. and the mass of volatiles. Finally a radical chain mechanism has been proposed in a lumped form which is consistent with the kinetic model and the experimental results. 0025-1 16X/82/05 1207-12/%03.00

The performance of synthetic fibers cannot be completely understood without any knowledge of the structure in the noncrystalline regions. X-ray diffraction measurements led to the conclusion that the noncrystalline regions in PET fibers can be divided into isotropic noncrystalline (amorphous) and oriented noncrystalline fractions, the amount of which is dependent on the thermal and mechanical history. But x-ray diffraction data, thermal analysis, and dyeing experiments left many effects unexplained: the dependence of glass-transition and dye uptake on thermal history, the real order-disorder situation within the noncrystalline regions, certain mechanical properties, and their time-dependence such as relaxation. The glass-transition temperature Tg of PET fibers, as determined by viscoelastic measurements, runs through a maximum depending on the heat-setting conditions. This can be explained by the assumption that the average size of crystallites reaches a minimum, and therefore the number of crystallites per unit volume shows maximum values at a heat-setting temperature of about 190°C. By raising the heat-setting temperature above 190°C, the crystallites become larger. Segregation of the crystallites in the noncrystalline matrix occurs.

The absorption of water in glass fiber reinforced epoxy resins is a complex process. With dynamic-mechanical measurements it is possible to distinguish locations of water in the resin-glass interphase, in micro-cracks of the resin, and diluted in the bulk polymer. The dominant mechanism of incorporation depends on the resin/hardener system, the surface treatment of the glass fabrics, and the sorption temperature.

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