Abstract: A heat exchanger of thermoplastic materials, e.g. polypropylene, comprises two spaced-apart headers interconnected by an extruded board comprising a plurality of tubular passages extending from one end of the board to the other; each header having a longitudinal groove in its exterior surface and a plurality of holes spaced along the groove, interconnecting the groove and the interior of the header; each end of the board being located along the groove of one of the headers and held in position by a sealing bead adhering to both the header and the board, the bead extending continuously right round the mouth of the groove where adjacent to the board, to seal against loss of any fluid flowing between the header and the tubular passages. The heat exchanger can be readily adapted for use as a solar energy collector. The board and headers are preferably polypropylene extrusions secured together and sealed by extrusion welding using an extruded bead of a polypropylene composition.

Abstract: polyolefin compositions filled with from 10 to 85% by weight of particulate (preferably coccolithic) calcium carbonate have less adversely affected impact strengths if the weight mean particle diameter of the calcium carbonate is from 1.40 to 1.90 .mu.. The calcium carbonate is preferably coccolithic. The preferred polyolefins are copolymers of propylene with 10 to 20% by weight of ethylene. The composition may also contain from 2 to 15% calculated on the weight of the calcium carbonate, of fiberous vegetable matter.The filled compositions are useful for conversion into press-formable sheet, for example, having a thickness of 0.5 to 2 mm, which may be melt bonded to a textile cloth and thermoformed into an article such as a piece of motor vehicle trim. The large amounts of filler in the composition allow freshly formed hot sheets to be conveniently laminated to woven or non-woven natural synthetic cloths without the use of adhesives.