Abstract: Composites comprising structural fibers such as carbon fibers and, as the matrix resin, an aryl ether sulfone polymer comprising a 4,4'-bis-phenylsulfonyl biphenyl and at least two additional arylene structural units. The matrix resins exhibit improved toughness and stress crack resistance and a reduced tendency toward crystallization. The polymers are soluble and film-forming from solution, and may be used as coating and impregnating resins for producing the laminates and fiber-reinforced composites of this invention.

Abstract: A method and device are disclosed for the determination of the environmental stress crack resistance (ESCR) of polymer articles made from polymers such as acrylonitrile-butadiene-styrene copolymers, polycarbonate, polystyrene and blends thereof. The method and device involve the external application of stress to an unstressed test article which has been exposed to a stress cracking agent. The stress is induced by means of a weight located below the horizontal plane of the plastic article. The time between the application of stress and the cracking of the test article is measured to compute a characteristic ESCR parameter and thereby evaluate the environmental stress crack resistance of the article.