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Ammonium pentaborate (APB) is shown to be an effective intumescent, char- forming additive for thermoplastic polyurethanes (TPU). As little as 5 to 10 parts of APB, added to a flame retarded TPU, provides a 7 to 10-fold improve ment in burn-through resistance. The APB/TPU char is characterized by its glassy, multicellular structure which provides virtually instantaneous thermal protection to heat-sensitive substrates and is able to resist thermo-oxidative degradation. In contrast to its behavior in polyurethanes, APB is found to be somewhat less effective as an intumescent additive for several non-urethane polymers such as natural rubber, polyester resin, polyamide and polyvinyl chloride. A mechanism is proposed to account for the unique nature of the APB/TPU system. It is suggested that, via a series of chemical reactions, APB redirects the thermal decomposition of the polyurethane thereby producing less volatiles and increased char.

The susceptibility of Nd-Fe-B magnet powders to oxidation and corrosion is wen known and presents problems in processing and in service. Although the oxidation of Nd-Fe-B magnet powders can lead to severe irreversible losses, such losses can be stemmed by the application of antidegradation coatings. The effects of oxidation on Nd-Fe-B magnet powders and magnets at elevated temperatures have been examined with respect to time, particle size, and treatment, using isothermal thermogravimetric analysis and long-term oven aging. The magnetic properties of each sample were then evaluated by hysteresis testing. The effects of corrosive agents were also examined, and although the oxidation and corrosion of Nd-Fe-B magnet powders may yield similar weight gains and losses in magnetic properties, each process exhibits a different magnetic hysteresis "signature:' The correlations between the weight gain and magnetic measurements have proven quite reliable. The application of coatings to magnet powders can reduce the weight gain due to degradation by more than 98%, while the losses in magnetic properties are reduced from over 75% (for uncoated powders) to less than 10% (for coated powders).

The role of PVC in fires is currently a controversial topic because of the many negative comments made about PVC on the occurrence of any major fire disaster. Critics also use many small‐scale smoke and toxic gas tests to define the role of PVC in these fires. The purposes of this paper are (1) to summarize the current technical knowledge of real fire behavior, (2) use this understanding to interpret available data for PVC in large‐ and small‐scale fire tests, and (3) help bring a sense of technical realism to the issues involved.

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