No abstract

A simple analytical technique has been developed to determine the amount of carboxyl groups present in degraded polyethylene film. This procedure is based upon the relative reactivities of the various carbonyl groups present, in oxidized polyethylene film, to sulfur tetrafluoride gas. The quantity of the carboxyl groups in the film is then measured as a function of the absorption at 5.45 μ.

synopsisA structure occurs in radical-polymerized polyethylene which leads to formation of a triene on ultraviolet radiation. An inhibition of oxidative processes is observed while the triene or its precursor are being consumed. Subsequent formation of oxygenated products-hydroxyl, carbonyl, and carboxyl-is well behaved and arisea from short wavelength light. A crosslinking reaction is initiated by light of -4000 wavelength. ExperimentalFilms were prepared in the thickness range 25-250 p, with most experiments performed on samples of 150 f 5 p (6 mils). The major studies were on a branched polyethylene of density 0.919 g/cc with 37 methyls, 0.1 vinyl, 0.06 trans olefins, and 0.32 vinylidene groups/2OOO carbon atoms.

H‐Film is a polypyromellitimide which results from polycondensation of pyromellitic dianhydride and an aromatic diamine. Its unique blend of thermal, physical, and electrical properties make it an outstanding candidate for a variety of electrical and non‐electrical end‐use applications. These properties recommend H‐Film for use as Class H (220°C) electrical insulation. Thermal aging of this polymeric film to embrittlement in air will require on the order of ten years at 250°C (482°F), one year at 275°C (527°F), and three months at 300°C (572°F). Even greater thermal durability in inert atmospheres has been observed. Our continuing thermal characterization studies on this polypyromellitimide have resulted in data relating to weight loss and decomposition products.