in a method and apparatus for making highly densified compression sheets from thermoplastic polymeric compounds preferably together with reinforcement fiber mats in a continuous fashion in a double - band press in which the compound material is heated and compressed between two compression bands which extend between reversing inlet and outlet drums and define between adjacent sections a wedge - shaped precompression zone adjacent the inlet drums wherein the compound material is increasingly compressed and also heated and a final compression zone adjacent the precompression zone , wherein the compound is heated under pressure such that the thermoplastic melts and fully wets any fibers in the sheet and an end compression zone in which the sheet is cooled which the pressure is maintained and the compound material is retained in the space between the compression bands by seal bands extending along the side edges of the compression bands and maintained in sealing engagement therewith .