Recychng, polymer

A. Bourmaud, C. Baley, Rigidity analysis of polypropylene/vegetal fibre composites after recychng. Polym. Degrad. Stab. 94(3), 297-305 (2009)... 

In the search to develop new materials for immobilization of homogeneous transition metal catalyst to facilitate catalyst-product separation and catalyst recychng, the study of dendrimers and hyperbranched polymers for application in catalysis has become a subject of intense research in the last five years [68], because they have excellent solubility and a high number of easily accessible active sites. Moreover, the pseudo-spherical structure with nanometer dimensions opens the possibility of separation and recycling by nanofiltration methods. Although dendrimers allow for controlled incorporation of transition metal catalysts in the core [69] as well as at the surface [70], a serious drawback of this approach is the tedious preparation of functionalized dendrimers by multi-step synthesis. 

Anon., Plastics recycling struggles for profitability, Chem. Eng., August 23, (1993). M. Heathcote, Back to basics for polymer recychng, Chem. Eng. News, 59, 1556, 28 (1993). 

Zeolites are widely used in acidic processes and they are an obvious catalyst choice. The suitability of commercial cracking catalysts to degrade polymer waste is vital as one of the options of commercializing this polymer recychng method is to co-feed polymer waste to existing refinery crackers [13]. Furthermore, in the search for cheaper catalysts, clays and their pillared analogues are also introduced in the polymer catalytic degradation [16, 17]. 

Several enantioselective reductions that use polymer-supported chiral catalysts have been reported. A maj or advantage of performing enantioselective reactions with polymer-supported catalysts is that their use allows both the recycHng of the catalysts and the easy separation of the low molecular weight chiral products. One of the most attractive methods to carry out asymmetric synthesis is the continuous flow system by using an insoluble, polymeric catalyst. 

Polymer recychng, also known as mechanical recycling. The method is the most desirable, and it should be used whenever it is ecologically, commercially, and technically feasible. 

One of the major benefits of polymer-supported catalysis is the recovery and the reuse of immobihsed catalysts, especially when dealing with chiral catalysts which can be extremely expensive [17]. Therefore effective separation methods are required [1]. However, one has to keep in mind that even the best separation technique can t overcome all the problems that can occur in polymer-sup-ported catalysis. For example, metal leaching is one major problem associated with the use and the recycHng of metal-based, polymer-supported catalytic systems and often the addition of fresh metal species to the recovered catalysts is... 

The main advantage of polyampholytes related to the protein separation process is the realization of the forcing out effect at the lEP of polyampholytes which will fadhtate polymer recychng after protein separation. 

In some cases, a cradle-to-cradle approach about these renewable polymers (i.e., from raw material extraction through materials processing, manufacturing, distribution, use, repair and maintenance, and final disposal or recychng) can be addressed by life-cycle assessment (LCA) [8]. 

Are there circumstances that would be likely to shift this balance That would require either that recycling become less expensive or that the production of virgin polymers become more expensive, or both. The cost of virgin materials has its roots in the price of the petroleum from which the needed feedstocks are obtained. So a significant rise in oil prices would tend to drive up the cost of nearly all plastics, too. But because many of the costs of recycling are energy related, they are also tied in one way or another to oil prices. So it is not immediately clear that plastic recycHng can be made more economically attractive in the near term. 

One of the problems with recychng automotive plastics is paint removal. This applies not only to end-of-life vehicles but also to thermoplastic olefin (TPO) painted parts, which have a high scrap rate. Polymer Sciences Inc. announced plans in late 1999 to build recycling facilities in Duncan, SC, and somewhere in Europe, using the company s mechanical process for stripping paint from TPO parts before they are gronnd and pelletized. However, the plant was not built, and the company now fists paint removal as a technology that it has available for sale or license. ... 

Moller, J. Stromberg, E. Karlsson, S. Comparison of extraction methods for samphng of low molecular compounds in polymers degraded during recychng. Eur. Polym. J. 2008, 44, 1583-1593. 

The recycling of mixed waste presents a fmther market opportunity for compatibilisers. European Directives on the recychng of end-of-life products encourage the recycling of plastics products, although in practice this does not often involve mixed waste. This is because the lack of compatibility between polymers degrades the mechanical properties and drastically reduces the market for the recyclate. 

Polymer blends offer the possibility to prepare polymeric materials with properties tailored to specific needs. In plastics recychng, blending of different polymers is in some cases necessary because the separation of a single component can be difficult or expensive. In most cases, however, the polymers are immiscible and this leads to blends having poor properties. 

The difficulties arising in recychng of mixture of HDPE, PVC, and PET are due to the incompatibility of these polymers, their different melting points, ranging from 130 to 260 C, and thus different processing temperatru-es, and degradability of PVC at temperatures above 200 C. 

The recycled polymer can also be contaminated by pigmented constituents in the feedstock. In the recychng of RDPE bottles by melt reprocessing, a major effort has been directed towards producing a naturally-colored recycle stream. The major barrier to overcome to reach this end is the removal of the colored bottle caps. Typically blue and red caps are used to differentiate the fat contents of... 

Chemical recycling is a process by which the polymer starting chemicals are retrieved from the plastic with high temperatures and in the absence of oxygen. The chemical recycling process can produce primary chemicals to produce new polymers. Chemical recychng process can be used for petroleum-based and biobased plastics. 

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