Abstract: A product having a positive temperature coefficient of resistance is formed by etching a carbon black at an elevated temperature to remove less crystalline portions and thereby to increase the specific surface area of the carbon black. The resulting carbon black is called porous carbon black. The porous carbon black is blended with a crystalline polymer to form a product having the desired positive temperature coefficient of resistance. Production of a material suitable for use as a resettable fuse is described.

Abstract: A semiconductor encapsulating epoxy resin composition comprising an epoxy resin, a curing agent, and an inorganic filler is improved in melt flow and moldability when the filler comprises spherical silica having a mean particle size of 5 to 35 .mu.m and a specific surface area of up to 1.4 m.sup.2 /g. A mixture of (A) spherical silica having a mean particle size of 0.1 to 2 .mu.m, and (C) ground silica having a mean particle size of 2 to 15 .mu.m is also useful as the filler. A cured product thereof has a low coefficient of expansion and improved crack resistance upon soldering after moisture absorption.

Abstract: Certain polyether polyols are used in polyurethane-forming binders to improve the shakeout of molds and cores, made by cold-box and no-bake processes. Such molds and cores are used to make metal castings, particularly from low melting metals such as aluminum.