ISSN:
0021-8995
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Maschinenbau
,
Physik
Notizen:
Reprocessing of used polyethylene serves as a promising solution to a severe ecological and economical problem. This material, however, has frequently been exposed outdoors and demonstrates poor workability and inferior mechanical properties. In this study, we attempt to explore ways for the improvement of flow and product performance by intensive shear processing. When shearing reclaimed polyethylene (LDPE) containing some degree of crosslinking and oxidation, either by repetitive injection molding, extrusion or roll milling, the fluidity of the recycled polymer is gradually increased, frequently with rising ductility of the product and a decrease in melt elasticity. As a result, a practical way of reclaiming poor-flowing, partially gelled polymer has been found. Additionally, the recycled material can be blended with virgin polyethylene, preferably of the linear low density type. Virgin polyethylene by itself, however, demonstrated an opposite response to intensive shear. There was a drop in fluidity, a rise in melt elasticity, and usually a decrease in ductility. All this is believed to result from the degradation processes that may consist of initiation of microgels and recombination of polymer chains by free radicals, as shown by an actual increase in intrinsic viscosity and in the higher modes of molecular weight averages. It was noted that the controlling mechanism of shear modification of virgin polymer differs from that occurring with a partially crosslinked structure. Results of the shear modification of both virgin and reclaimed polyethylene, by continuous kneading in a Brabender Plastograph, indicate mainly a chain scission mechanism. In all cases the melt viscosity dropped together with the ductility of the final product.
Zusätzliches Material:
18 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/app.1984.070290807
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