Abstract: A method for producing a tube preform using an injection molding method. An injection molding method is used to produce tube preforms which can be constructed with either one layer or a plurality of layers. The preform subsequently is heated and biaxially expanded by compressed air. A tube can be obtained which, on the one hand, has a tube shoulder with the strength provided by an industrial thread and, on the other hand, has a side wall which exhibits the softness desired for a tube.

Abstract: In order to make it possible to produce superconducting coils with small overall height, they are made from a plurality of coil subunits, optionally with a plurality of layers for each coil subunit, in particular in the case of the low-voltage coil of a transformer. The coil subunits contain as electrical conductor a high-temperature superconductor, around which a fibrous glass is spun and which is embedded in a glass-fiber reinforced epoxy resin or in a plastic. The coil subunits are placed around a transformer core in a cryostat.

Abstract: An electrical resistance element having a resistance body between two contact terminals. The resistance body has PTC behavior and is composed of a polymer matrix and a filler component embedded in the polymer matrix. The filler component is composed of electrically conducting particles. Although the element is of simple and inexpensive construction, the resistance element is notable for good electrical conductivity in the low-resistance state and for a low response time for the PTC transition from the low-resistance to the high-resistance state. This is achieved as a result of the fact that at least some of the electrically conducting particles are formed as composite bodies having electrically conducting surfaces and/or as hollow or porous bodies composed of electrically conducting material. These particles have a lower specific density and/or lower specific heat capacity than solidly formed particles composed of conductive material.

Abstract: An electrical insulator including a thermosetting matrix and a filler composed primarily of powdered material embedded in the thermosetting matrix. The insulator has a high service life in spite of severe mechanical stressing at temperatures of up to 105.degree. C. This is achieved as a result of the thermosetting matrix having a glass transition temperature exceeding 140.degree. C. and the inclusion of a powdered filler, which has a reduced rigidity compared with the thermosetting matrix, embedded in the thermosetting matrix.