Melting virgin polymers

Most off-quahty or scrap polypropylene fibers may be repeUetized and blended in small percentages with virgin polymer to produce first-grade spunbonded fabrics. The economics are of great importance in a process where high yields are required in order to be competitive. Some manufacturing equipment direcdy recycles edge-trim back into the extmder where it is blended back into the polymer melt (see Fibers, olefin). 

The thermophysical properties, such as glass transition, specific heat, melting point, and the crystallization temperature of virgin polymers are by-and-large available in the literature. However, the thermal conductivity or diffusivity, especially in the molten state, is not readily available, and values reported may differ due to experimental difficulties. The density of the polymer, or more generally, the pressure-volume-temperature (PVT) diagram, is also not readily available and the data are not easily convertible to simple analytical form. Thus, simplification or approximations have to be made to obtain a solution to the problem at hand. 

Polymers from carpet waste produced by melt processing may be used to make products in a molding process, either alone or blended with virgin polymers. The recycled polymers may also be used as matrices in glass fiber reinforced composites. For such applications, the properties of the composites are dominated by the reinforcement (glass fibers), and therefore even recycled polymers without compatibilization could provide the composites with satisfactory mechanical properties. ... 

This equation can be directly applied to properties, such as the melt flow index or the fiber s length, that can be determined in the virgin polymer, hence in the feed stream of the first cycle. However, in the case of other properties, such as the tensile or the impact strengths, that can only be measured after processing to produce test pieces, Pq cannot be... 

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