Abstract: In a process for the production of an optical coupler for polymeric optical fibers using ultrasound welding, the fibers are warmed, before the welding, to a temperature of from 50.degree. to 250.degree. C. for from 0.2 to 3 hours. The polymeric optical fibers are introduced into a plastic tube which melts with the fibers during the welding operation to form a unit. In another embodiment, a connector bar which has the same refractive index as the core material of the polymeric optical fibers can be inserted into the plastic tube, the polymeric optical fibers are brought into contact with the connector, and the plastic tube, the connector bar and the fibers are welded to one another under the action of ultrasound.

Abstract: In composites comprising at least one solid base layer of a propylene polymer and a foam layer likewise of a propylene polymer, these layers can be bonded by softening only the side of the base layer facing the foam layer and optionally provided with relief structures by warming, and pressing the base layer and foam layer together, giving a very strong bond.

Abstract: Multi-layer radiator of plastic material consisting of planar elements comprising an array of vertical water pipes horizontal collecting channels, wherein the planar elements are first connected by straps fastened in the readily accessible border zones of the elements to form units which are then welded together at their end-faces. The radiator can be produced with a few operating steps and the manufacturing costs are considerably reduced.

Abstract: A device for the transmission of solar energy to a liquid medium is composed of a platelike, flat hollow piece made from a plastics material and being provided with tubular flow channels, which is mounted in a flat-bottomed box under a translucent covering while being insulated.

Abstract: A multi-element radiator of plastic material wherein the elements are closed of a plurality of vertical water pipes which discharge at their upper and lower ends into cylindrical tube sections and the end-faces of adjacent tube sections are connected to form the upper and lower horizontal collecting channels.

Abstract: The thermostability of shaped articles of thermoplastic material is determined by the visible alteration of the surface of the article caused by a focused hot gas jet which is blown onto the surface. The temperature of the gas and the gas rate hitting the surface per unit of time, and also the residence time of the shaped article under the influence of the hot gas jet are a measure for the thermostability.