Glass-reinforced composites, based on synthetic resins such as phenolics, areas, melamines, and unsaturated polyesters, generally became available in the 1940s, when dramatic improvements in strength-to-weight ratios were first observed. Nowadays, the crucial importance of composite products in a number of areas, particularly in aircraft and marine applications, is accepted, as today's materials prove superior to their aluminium or steel counterparts. Although the specific dry strength and modulus of recent reinforced composites exceed those of aluminium or steel, upon prolonged exposure to humid environments, a dramatic decrease in these properties can still sometimes occur. Early composite products were very susceptible to moisture, even in ambient humidity. The bonding of polymeric materials to inorganic surfaces such as glass has been intrinsic to many products, but the interfacial bond strength and durability remain susceptible to moisture during processing. Yet it is this same interfacial bond strength that is also linked to the product's acceptance and eventual success in the marketplace.
