Abstract: An envelope system for protecting a substrate from fire or other thermal extreme. The system includes a screen, which surrounds the entire substrate and which is set off from the substrate by ridges folded into the screen, and a thermal protective coating applied to the screen and spaced from the substrate by the screen to form an air gap between the substrate and the coating.

Abstract: A method of continuously producing ammonium polyphosphate by the reaction of urea and polyphosphoric acid, over a wide range of molecular weights, in a pre-mix slurry, under controlled temperature of about 315.degree.+/-15.degree. C. The slurry is reacted on a hot, continuously moving surface and forms ammonium polyphosphate in an ammonia atmosphere. Preferably, the pre-mixed slurry is added to a screw-type extruder, where the material comes in contact with the ammonia along the preheated moving surfaces of the extruder. The ammonium polyphosphate is scraped from the extrusion screw into a container with minimum handling. The material can be ground to a finer consistency if desired.

Abstract: Reaction of an aromatic dianhydride with a polycyclic aromatic primary diamine at a controlled reaction rate yields a diamic acid dianhydride oligomer. The oligomer may be a precursor for an imide foam which forms at low temperature, has outstanding physical characteristics, and is extremely heat resistant. The diamic acid moiety may be converted to diimide, and other modifications of the oligomer are disclosed. Other derivatives of the oligomers are also disclosed.

Abstract: An envelope system for protecting a substrate from fire or other thermal extreme. The system includes a screen, which surrounds the entire substrate and which is set off from the substrate by ridges folded into the screen, and a thermal protective coating applied to the screen and spaced from the substrate by the screen to form an air gap between the substrate and the coating.