Abstract: A process for manufacturing foils for coatings from high and ultra-molecular polyethylene, polypropylene and/or poly(vinylidene difluoride) in which the powdered polymer, optionally with the addition of colours and/or additives, is spread on a sintering belt circulating in a sintering furnace, thermally sintered and compacted by smoothing rollers to form a foil material with a porosity of 0 to 10%, preferably <1%. In preferred embodiments the foil web is combined with other foil materials, fleeces or the like during the compacting step. The foils according to the invention are particularly suitable for ski and snowboard linings and bearing coatings.

Abstract: Abrasive material with particularly high abrasive performance is obtained in that the ceramic material contains an additive of 0.01 to 15 percent by weight, preferably 0.1 to 3 percent by weight of a chromium compound.

Abstract: Ceramic sintered body, in particular abrasive grain, based on .alpha.-Al.sub.2 O.sub.3, said body being arranged in such a manner that improved abrasive results are achieved, said body being bound into a structure by means of a glass-like ceramic binder and showing a drop in hardness from its center to its edge of less than 1800 N/mm.sup.2, preferably less than 1000 N/mm.sup.2, and, in particular, less than 500 N/mm.sup.2.

Abstract: Sintered microcrystalline ceramic material based on .alpha.-Al.sub.2 O.sub.3 with an addition of 0.01 to 2.0 weight percent of a cerium compound, consisting of a microcrystalline matrix and 0.1 to 30 volume percent whisker-like needles, whereby said cerium compound is mainly present in the needles. The whisker-like needles give this material a special tenacity combined with good abrasive results.

Abstract: Sintered microcrystalline ceramic material based on .alpha.-Al.sub.2 O.sub.3 with an addition of 0.01 to 2.0 weight percent of a cerium compound, consisting of a microcrystalline matrix and 0.1 to 30 volume percent whisker-like needles, whereby said cerium compound is mainly present in the needles. The whisker-like needles give this material a special tenacity combined with good abrasive results.

Abstract: An abrasive material of great hardness and high tenacity particularly suitable for high-pressure grinding consists essentially of a sintered, microcystalline .alpha.--Al.sub.2 O.sub.3 abrasive material having a purity of least 98.5% and a density of at least 95% of theoretical density, the .alpha.--Al.sub.2 O.sub.3 crystallites of the material being smaller than 4.mu., preferably smaller than 3.mu..