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Anionic nylon 6 modified with poly(oxypropylene) up to 40% by weight and obtained by one-shot reaction injection molding ("one-shot" RIM) was characterized by wide-angle X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, thermal gravimetric analysis, and Fourier transform infrared spectroscopy. Cross analysis by different techniques pointed out that the polymer contained only the a-form and the modifier had little, if any, influence on the crystallinity index, which was found to be about 40% when referred to the nylon 6 fraction only. Morphological changes at different modifier contents were ascribed to different block copolymer structures.

The chemical reactions occurring during the intumescent process taking place in the combustion of the poly(2,6‐dimethyl–1,4‐phenylene ether)–high‐impact polystyrene blends (PPE–HIPS) are studied in detail through the chemical characterization of the burnt and original material by infrared, pyrolysis–gas chromatography–mass spectrometry, and direct insertion probe spectrometry. Evidence is given of thermal rearrangement in the blend of the polyether PPE chains to polybenzylic structures occurring in the heating conditions of pyrolysis or combustion, as previously shown, to take place in thermal degradation of PPE. The rearranged chain segments are shown to give a larger contribution to the intumescent char, while volatile blowing products are mostly formed by polystyrene and polybutadiene components. From PPE–HIPS blends, the volatilization of the fire‐retardant triphenyl phosphate (TPP), which when heated alone volatilizes at a temperature below that of PPE–HIPS degradation, is delayed probably by hydrogen bonding with PPE. This allows TPP to play the typical flame inhibition role of volatile phosphorus compounds. Moreover, it is found that TPP favors the PPE rearrangement and henceforth increases the char yield of the burning blend, which is a typical condensed phase fire‐retardant action. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2231–2240, 1998

Kinetic investigations on the bulk polymerization of vinyl chloride initiated by exposure to 60Co γ‐rays were carried out in the temperature range of −50 to 90°C at dose rates varying from 0.15 to 50 rad/c. Some polymerization runs were also carried out in a centrifugal field. As generally reported for this polymerization system, in which the polymer is insoluble in the monomer, the polymerization rate was found to change as a function of the amount of the polymer formed in a special fashion. This particular function has been shown to be greatly influenced by the polymerization temperature and to be independent of the rate of initiation, or, more rigorously, of the dose rate. Thus, at any given temperature the equation of the polymerization conversion rate could be written in the form of the product of two separate functions, one for the polymerization conversion and the other for the dose rate. While for the latter the results gave an essentially square‐root dependence on dose rate as is normally found for homogeneous polymerization, the former has been discussed in the terms of recently advanced kinetic schemes, based on a two‐phase polymerization model. The kinetic parameters found in this work are in agreement with previous authors' data.