Field of the Invention
This invention relates to the bonding of two dissimilar polymeric resin composition surfaces. In a particular embodiment, the invention relates to a process for bonding an epoxy resin matrix reinforced with glass fibers to the surface of polyvinyl chloride pipe whereby the pipe is reinforced and withstands high pressures without rupture of the interface bond between the epoxy resin and the polyvinyl chloride surface.
For some time plastic pipe made of one or more layers each of polyvinyl chloride and epoxy-impregnated glass fibers has been widely used in the construction and plumbing industries. Light weight and resistance to corrosion have been among the desirable properties of this type of pipe. This pipe conventionally consists of an inner hollow cylinder of polyvinyl chloride overlaid with a wrapping of epoxy-impregnated glass fibers. In some cases only a single layer of each material is used; in other cases, however, the first layer of epoxy-impregnated glass fibers is overlaid with a second polyvinyl chloride layer, which is itself then overlaid with a second layer of epoxy-impregnated glass fiber. Any number of such multiple alternating layers may be thus built up.
Bonding between each pair of dissimilar surfaces of the alternating layers of epoxy-impregnated glass fiber and polyvinyl chloride has, however, been a serious problem, often reaching critical dimensions where the pipe consists solely of a relatively thin polyvinyl chloride inner cylinder overlaid with only one or two layers of an epoxy-impregnated glass fiber wrapping. Since polyvinyl chloride and epoxy do not substantially chemically bond with each other, mechanical forces were depended upon to maintain the integrity between the layers of the pipe. However, these mechanical forces were insufficient to withstand the countervailing forces produced by the fluid pressure within the pipe, and the layers of the pipe would become separated. This was particularly aggravated whenever it was necessary to cut into the pipe, as with a conventional pipe joint, thereby exposing the interface in the cut cross-section of the pipe to the full line pressure carried within the pipe.