Polyolefins, waste recycling

The same technique can be used to dye a material that is otherwise difficult to dye. An ethylene-propylene copolymer rubber was reacted first with maleic anhydride, then with an aromatic amine dye in an extruder to produce a dyed rubber.81 Dye sites can also be inserted into polyolefins by grafting them with dimethylaminoethyl methacrylate, using azo or peroxide catalysts in an extruder.82 jV-Vinylimidazole has been grafted to polyethylene in an extruder with the help of dicumylperoxide.83 The product was mixed with an acrylic acid-modified polypropylene and used to compatibilize polyethylene and polypropylene. This could be helpful in the recycling of mixed polyolefins from municipal solid waste. Recycling of cross-linked (thermoset) polymers is more of a problem because they cannot be remelted in an extruder. However, they can be if... 

Mixtures of polyolefins and polystyrene - relevant components in the packaging plastics waste recycling problem - are antagonistically immiscible. The phase diagram... 

Mixed polyolefin waste (HDPE + LDPE -I- PP) was compatibilized by adding recycled paper fibers to increase modulus [72]. 

Z Krulis, D Michalkova, F Lednicky, Z Horak, M Sufcak. Recycling of polyolefin waste using malei-nized liquid polybutadiene. Symposium on Recycling of Polymers, Institute of Macromolecular Chemistry, Prague, 1997, p 20. 

Noteworthy, one of the greatest research interests in advanced polymeric materials was dedicated to studies of properties and morphology of polyolefin blends. This was not only due to wide industrial applicability of these materials but also due to their rich and fascinated morphology depending on molecular structure, thermal history, and external stress field [5]. Nowadays when plastic waste recycling is one of the main issues of envirorunental concerns, stndies of polypropylene (PP) and polyethylene (PE) blends play important role, due to their consmned amoimt and difficult separation of these materials apart [6]. 

Details are given of a visit by RECOUP to BP Chemical s feedstock recycling demonstration unit in Sunbury. The feedstock recycling technology has been developed by a consortium of companies, and will enable polyolefin rich plastic waste from domestic and commercial sources to be vapourised and then condensed to form a hydrocarbon wax. This can then be used to feed existing petrochemical crackers to produce polymers indistinguishable from virgin material, it is claimed. 

Okamato et al. [110] developed a new mbber recycling technology to produce a polyolefin TPE-based on EPDM waste and PP. Pine mbber powder can also be obtained from the sanding process of... 

Another important factor that distinguishes this separation is that it is not environmentally or economically feasible to simply return a rejected stream to the environment, as in a typical aqueous RO process where the brine can be returned to the ocean. The federal regulations mandate that C02 emissions from refineries and chemical plants be reduced to low levels therefore, facilities can no longer afford to dispose of waste hydrocarbon streams in their flare systems. Pure streams from polyolefin reactors and vents from polymer-storage facilities, which were once flared, must be redirected to recovery systems. To reduce the economic penalty of environmental compliance, these paraffin and olefin mixtures must be recovered and recycled. In other words, two products must be made, a useful fuel and a useful chemical product, hence more process engineering is required in order to achieve such an objective. 

A major application of these types of molded products would be for interior uses in automobiles, such as head liners, door panels, and dashboards. Although this is a low-cost, low-performance application, it represents a very laige-volume market. Indeed, wood is already utilized in applications of this type, but as a finely ground flour that serves as a filler (up to 40%) in extrusion-molded polyolefin products. The use of recycled fiber in this process and the one described above offers the potential of even greater cost reductions, combined with alleviation of solid waste disposable problems. 

To recover a maximum of olefins and butadiene from recycling polyolefins, it is necessary to have a short residence time of the product gases in the fluidized bed zone to avoid no secondary reactions. The pyrolysis gas should not be circulated and used as fluidizing gas. For the experiments, steam was used as fluidizing gas [13, 14]. An easy separation of the hydrocarbon products is possible by condensation to water in a cooler. The results are shown in Table 17.6. As feedstock a light plastic fraction from household waste separation was used which contains 95.8% of PE and PP, 3% of PS, and 0.2% of PVC. 

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. 

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