Abstract: A method of improving the mechanical properties of polymers is described. The method involves heat treating the polymer at a temperature below the glass transition temperature in a wet or in a dry environment. Polymer articles capable of moisture uptake in humid environments, as well as polymer articles less susceptible to moisture uptake, have improved mechanical properties, particularly improved stress relaxation behavior and set properties, when treated in accord with the heat treatment method.

Abstract: A method of improving the mechanical properties of polymers is described. The method involves heat treating the polymer at a temperature below the glass transition temperature in a wet or in a dry environment. Polymer articles capable of moisture uptake in humid environments, as well as polymer articles less susceptible to moisture uptake, have improved mechanical properties, particularly improved stress relaxation behavior and set properties, when treated in accord with the heat treatment method.

Abstract: A conductive polymer composition which has a resistivity at 20.degree. C. of at most 1.0 ohm-cm and a PTC anomaly of at least 104 contains at most 64% by volume of a crystalline polymeric component and at least 36% by volume of a particulate conductive filler. A preferred conductive filler is carbon black having a DBP number of 60 to 120 cm.sup.3 /100 g. Compositions of the invention, as well as other conductive polymer compositions are preferably prepared by a method in which the polymeric component and the filler are blended in a first step at a temperature greater than the melting temperature of the polymer, the mixture is then cooled, and the mixture is then mixed in a second step. The resulting composition has a PTC anomaly that is at least 1.2 times the PTC anomaly of the first mixture.

Abstract: A conductive polymer composition which has a resistivity at 20.degree. C. of at most 1.0 ohm-cm and a PTC anomaly of at least 10.sup.4 contains at most 64% by volume of a crystalline polymeric component and at least 36% by volume of a particulate conductive filler. A preferred conductive filler is carbon black having a DBP number of 60 to 120 cm.sup.3 /100 g. Compositions of the invention, as well as other conductive polymer compositions are preferably prepared by a method in which the polymeric component and the filler are blended in a first step at a temperature greater than the melting temperature of the polymer, the mixture is then cooled, and the mixture is then mixed in a second step. The resulting composition has a PTC anomaly that is at least 1.2 times the PTC anomaly of the first mixture.