Melt methods polyolefins

Presented here are only the methods that the author has tested in practice on plastics wastes. The first attempts were undertaken in 1986 in a small pilot unit that dealt with wastes of polyolefin films used for packaging. Those wastes were nonpigmented, transparent and rather clean. They were provided by waste collectors in blocks of approximately 30 kg, intended for factories producing regenerated granules (recyclate). The intention was to show the potential of producing a polyolefin wax to be used in polish applications or in hot-melt glues from those wastes. 

As shown by Price (6), rejected noncrystallizable impurities will be pushed ahead of the growing spherulite as a wave, leaving a lower concentration within the spherulite than in the original melt. Frank and Lehner (8) and Curson (9) have used UV transmission microscopy to observe additive distributions in crystalline polyolefins. This method can be used to observe the redistribution process in action by quenching partially crystallized polypropylene to freeze the additive concentrations... 

Polyolefin blends of commercial importance are normally made via two methods blending in the melt either during polymerization or mechanically after the polymerization process. The first method, called in-reactor blending, involves the blending of different polyolefins (homopolymers, random, and block copolymers) in a polymerization reactor. This is enabled by the presence of multiple catalyst species... 

Mixing of natural rubber with polyolefin is one of the methods used to prepare thermoplastic natural rubber (TPNR). TPNR behaves like vulcanized rubbers at ambient conditions, but at elevated temperatures they melt and flow like a thermoplastic material. Thus TPNR could be processed using conventional thermoplastic processing machinery without requiring vulcanization, and these materials could be reprocessed. Thus there is low level of wastage, as scrap too can be recycled. 

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