Abstract: A method of joining, repairing or reinforcing substrates, particularly polymeric pipes for transporting fluids, e.g. natural gas and water. The method makes use of an article, preferably a heat-recoverable article, which comprises a conductive polymer composition and which is heated to its recovery temperature by passing electrical current through the conductive polymer. Preferably the article is a heat-shrinkable coupler. The coupler may make direct contact with and fuse to the pipes, or there may be an insert between the coupler and the pipes. The article preferably comprises carbon black dispersed in either a sintered polymer, particularly ultra high molecular weight polyethylene or a very high molecular weight polymer, particularly polyethylene having a molecular weight greater than 150,000.

Abstract: The resistivity/temperature characteristics of PTC conductive polymers which have little or no cross-linking can be modified by stretching. The rate at which resistivity rises with temperature is increased, and the peak resistivity is decreased; however, the decrease in peak resistivity is substantially smaller than that observed with PTC conductive polymers having a high degree of cross-linking. Therefore, heat-recoverable electrical devices, particularly for covering telephone and other cable splices, comprise (a) a layer of a PTC conductive polymer which has little or no cross-linking, (2) an adjacent heat-recoverable layer of a PTC or ZTC conductive polymer which has a relatively high level of cross-linking, and (3) electrodes which can be connected to a power supply so that current passes through the layers and causes recovery of the device; preferably an uncrosslinked PTC layer is sandwiched between two cross-linked ZTC layers. Non-recoverable devices, e.g.

Abstract: A piezoelectric device comprising a first conductor, a conductive polymer member which contacts the first conductor, a piezoelectric polymer member which contacts the conductive polymer member but which is separated from the first conductor and which has been rendered piezoelectric by stretching and polarizing it while it is in contact with the conductive polymer member, and a second conductor which contacts the piezoelectric polymer member but which is separated from both the conductive polymer and the first conductor.

Abstract: An article comprising vinylidene fluoride polymer which has been rendered piezoelectric by stretching the article to a final draw ratio of less than about 6:1 and polarizing and has an equivalent activity A* of at least 6, where A* is given byA*=d.sub.3h -50(d.sub.o -d)where d.sub.3h is the hydrostatic coefficient of the stretched and polarized vinylidene fluoride polymer after heating at 120.degree. C. for 1 hr, in units of pC/N; d.sub.o is the density of the unstretched and unpolarized polymer, in units of g/cc; and d is the density of the stretched and polarized polymer before heating at 120.degree. C. for 1 hr, in units of g/cc, said article having an aggregate dimensional change of less than 15% upon heating at 120.degree. C. for 1 hr, as measured by the sum of the absolute dimensional changes along three orthogonal coordinate axes, one of which is a principal direction of stretching.

Abstract: A piezoelectric coaxial cable comprises a conductive polymer core comprising a high molecular weight polymeric material having conductive particles dispersed therein, a piezoelectric polymer layer surrounding the conductive polymer core, and an outer conductor surrounding the piezoelectric polymer layer. The high molecular weight polymeric material of the conductive polymer core comprises a polymer capable of being intimately bonded to the piezoelectric polymer.

Abstract: A piezoelectric coaxial cable comprising a metallic helically wound inner conductor, the volume within the helix being filled with a solid material; a continuous piezoelectric polymer layer circumferentially surrounding the inner conductor; and an outer conductor in contact with the piezoelectric polymer layer but separated from the inner conductor.