Abstract: A device for improving the possibilities of process control in blown film manufacture is described. In blown film manufacture, the plastic material is extruded in the form of a tube from a slot die and is pulled off while maintaining an internal pressure in the tube as it cools during chemical formation of the film material. According to the invention, the film tube is flushed on all sides in this cooling area with an air stream that has been conditioned in terms of temperature and air purity, and this flushing air stream, in turn, is shielded against outside influence by a partition surrounding the area. Preferably, the flushing air stream is divided into a number of partial air streams.

Abstract: A composite slab made of plastic, especially polypropylene, for construction purposes and packing purposes for example is described, said slab according to a preferred embodiment comprising a plurality of layers, each of which consists of a composite that is extruded in a plurality of layers and of which two plane layers and the others are profiled, namely layers that have a corrugated profile with peak lines that are located in a plane, with these layers being welded together along the peak lines on one side of the profiled layer and/or at the intersections of the peak lines of adjacent profiled layers. Layers consisting of a plane slab can be provided between the profiled layers. The composite extruded in several layers comprises two outer layers and a middle layer made of polymers from the same material group, whose middle layer consists of a highly crystalline polymer with incorporated stretch-resistant fibers, whose melting point is at least 15.degree. C.