GB813311A - - Google Patents

Abstract

813,311. Foamed polyurethane. AGRICOLA REG. TRUST. June 29, 1956 [July 6, 1955; Aug. 23, 1955], Nos. 19546/55 and 24257/55. Class 2 (5). [Also in Group VIII] An expanded plastic (e.g. foamed polyurethane) incorporates a net or other fabric of net-like structure which is extensible in all directions and which allows an initial freedom of movement and thereafter inhibits further stretch and consequent tearing of the plastic. The net may be embedded in the plastic, or as shown (Fig. 1) may be secured to the surface of the plastic 2 or may be enclosed between two sheets 4 and 5 of plastic. The net may be secured by means of an adhesive, e.g. a polyurethane foam adhesive, or by melting the surface of the plastic by radiant heating and then applying the net, or by incorporation in the plastic during manufacture. Where the net is used on the surface of the plastic, the plastic may be caused to bulge through the apertures in the fabric. If the net has square apertures, as shown in Fig. 1, the threads must have a limited elasticity or must be puckered during insertion by stretching the plastic before applying the net, and releasing it after that application. The net may have apertures of other shapes (e.g. hexagonal) and may be a knotted net, a twisted net or a lace net. A number of spaced layers of net may be embedded in a block of plastic, which may be subsequently split between these layers to produce thinner reinforced sheets. In a modification (Fig. 5) the net or fabric is replaced by co-operating layers of parallel threads positioned at an angle to one another in parallel planes. The layers of threads may be in contact as shown, or may be separated by a layer of expanded plastic. The threads themselves may have limited elasticity or the layers may be stretched to the desired limited extent before the threads are attached and then released so that the threads pucker. The two layers may be attached to one another when relaxed or when stretched.