The phenomenon of molecular orientation is known since the 50's. It consists in a re-arrangement of the polymeric chains resulting in a preferred alignment of the structure. The mechanical behavior of the material is then greatly enhanced, resulting in a drastic improvement of all the mechanical properties, mainly in the direction of the alignment. This alignment is induced by stretching the material in the same direction, at certain conditions of temperature, speed, etc, which are specific for every material. The PVC, a polymer with an amorphous structure, is very suitable for orientation purposes, and the application for pipes is one of the most popular. The systems for PVC-0 piping to this day are clearly defined in two: in-batch and in-line systems. In batch systems, stable, flexible, allowing a high . orientation degree and important raw material savings, are at the same time not much efficient in terms of energy, labor, output, and are highly penalized by internal logistics. The development of new systems, air based, dramatically improves the speed and efficiency and brings about important energy & labour savings, allowing the integration of these on a standard extrusion line. The result is a stable and reliable process, highly profitable, working on a continuous way and achieving the efficiency of an in-line process.
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