Recycle Polymer

Blends of PET and HDPE have been suggested to exploit the availabiUty of these clean recycled polymers. The blends could combine the inherent chemical resistance of HDPE with the processiag characteristics of PET. Siace the two polymers are mutually immiscible, about 5% compatihilizer must be added to the molten mixture (41). The properties of polymer blends containing 80—90% PET/20—10% HDPE have been reported (42). Use of 5—15% compatbiLizer produces polymers more suitable for extmsion blow mol ding than pure PET. 

Copolymer technology is progressing along two "fronts." First, new appHcations for copolymers are being found to increase the volume of materials that are already commercially available. One example of this is the rapid growth of styrenic block copolymers sold as asphalt (qv) and polymer modifiers over the past 10 years (Fig. 7). Another is the increased interest in graft and block copolymers as compatihilizers for polymer blends and alloys. Of particular interest are compatihilizers for recycled polymer scrap. 

Furthermore, increased governmental scmtiny of chemical substances will make it more difficult to bring a new product to market. The choice of comonomers and copolymers maybe based pardy on EPA, EDA, OSHA, and TSCA rulings. In addition to these regulations, the thmst toward recycling polymers is expected to impact copolymer production. The abiUty to recover and reprocess these materials will be a key factor for economic success. 

To increase the average molecular weight of somewhat degraded recycled polymer. ... 

Polyesters are now one of the economically most important classes of polymers, with an overall world production between 25 and 30 million tons in 2000, consisting mostly of PET. This production is rapidly increasing and is expected to continue to do so during the next decade, driven by packaging applications, due to a very favorable image of environmentally friendly and recyclable polymers in western countries, and by textile applications, due to a strong demand in the far-east area to satisfy the needs of an increasing population. 

Hie ester linkage of aliphatic and aliphatic-aromatic copolyesters can easily be cleaved by hydrolysis under alkaline, acid, or enzymatic catalysis. This feature makes polyesters very attractive for two related, but quite different, applications (i) bioresorbable, bioabsorbable, or bioerodible polymers and (ii) environmentally degradable and recyclable polymers. 

In America there are promising signs for certain polymers. For example, poly(ethylene terephthalate) drinks bottles can be cleaned and recycled to give an acceptable grade of PET resin in a process that is economically viable. The recycled polymer is used as carpet fibre, furniture stuffing, or insulation. Waste nylon can also be recycled profitably. 

The difference between chemical and feedstock recycling is pecuhar. As we will see in the next sections, there is, in essence, hardly any technology that recycles polymers into its own monomers. In this report we will concentrate on feedstock recycling, but in this broad definition we will include chemical recycling as well, see Section 5. 

Dissolution/reprecipitation processes were evaluated for the recycling of poly-epsilon-caprolactam (PA6) and polyhexamethyleneadipamide (PA66). The process involved solution of the polyamide in an appropriate solvent, precipitation by the addition of a non-solvent, and recovery of the polymer by washing and drying. Dimethylsulphoxide was used as the solvent for PA6, and formic acid for PA66, and methylethylketone was used as the non-solvent for both polymers. The recycled polymers were evaluated by determination of molecular weight, crystallinity and grain size. Excellent recoveries were achieved, with no deterioration in the polymer properties. 33 refs. 

On completion of the first life cycle of plastics, various recycling processes are available for further utilisation of these valuable materials. The choice of process will depend upon the materials to be recycled. In chemical recycling polymers are degraded to basic chemical... 

Recycling polymers is one way to minimize the disposal problem, but not much recycling occurs at present. Only about 25% of the plastic made in the United States is recycled each year, compared with 55% of the aluminum and 40% of the paper. A major obstacle to recycling plastics is the great variation in the composition of polymeric material. Polyethylene and polystyrene have different properties, and a mixture of the two is inferior to either. Recyclers must either separate different types of plastics or process the recycled material for less specialized uses. Manufacturers label plastic containers with numbers that indicate their polymer type and make it easier to recycle these materials. Table 13-5 shows the recycling number scheme. 

Reversible Phase Separation Driven by Photodimerization of Anthracene A Novel Method for Processing and Recycling Polymer Blends... 

Products Made from Post-Consumer Recycled Polymers... 

In gas phase reactors, the monomer is introduced to the bottom of reactor where it percolates up through a fluidized bed of polymer granules and inert-media supported catalyst. A fraction of the monomer reacts to form more polymer granules, the remaining monomer being drawn from the top of the reactor, cooled, and recycled. Polymer granules are continuously wthdrawn from the bottom of the fluidized bed and the catalyst is replenished. 

Shen, L. Bio-based and Recycled Polymers for Cleaner Production— An Assessment of Plastics and Fibres. Ph.D. Thesis, Department of Science, Technology and Society (STS)/Copernicus Institute, Utrecht University, 2011. 

Scheme 7.111 Recyclable polymer-supported imides for amide synthesis.

Carboxylic Acids Obtained by Fermentation of Carbohydrates Lactic (2-hydroxy-propionic) acid obtained by fermentation of glucose and polysaccharides is used by NatureWorks (Cargill/Dow LLC) to prepare polylactide (PLA), a biodegradable or recyclable polymer with a potential production of 140000 t a-1 (Scheme 3.4) [23], This and other potential useful reactions from lactic acid have been reviewed by Datta and Henry [24],... 

Olefin Metathesis in Non-degassed Solvent Using a Recyclable, Polymer Supported Alkylideneruthenium, J. Dow-DEN, J. Savovic, Chem. Comm. 2001, 37-38. 

Simply Assembled and Recyclable Polymer-Supported Olefin Metathesis Catalysts, L. Jafarpour, S.P. Nolan, Org. Lett. 2000, 2, 4075-4078. 

Highly Efficient and Recyclable Polymer-Bound Catalyst for Olefin Metathesis Reactions, S. Randl, N. Buschmann, S.J. Connon, et at, Synlett 2001, 1547-1550. 

In this section, we describe the mechanical properties of a class of materials that continues to grow in terms of use in structural applications. As issues related to energy consumption and global warming continue to increase demands for lightweight, recyclable materials, the development of new polymers and the characterization of recycled polymers will continue to dominate research and development efforts in this area. 

Gallet G, Perez G, Karlsson S. 2001. Two approaches for extraction and analysis of brominated flame retardants (BFR) and their degradation products in recycled polymers and BFR containing water. 

Although the main focus of our programs have been on issues of reactivity and enantioselectivity, we have recently begun to address the important issue of practicality in Mo-catalyzed asymmetric metathesis. Two key advances have been reported in this connection (1) The availability of a general chiral Mo catalyst that can be prepared in situ from commercially available compounds. (2) The synthesis of a recyclable polymer-supported chiral Mo catalyst. These advances are summarized below. 

There is a demand for quality assurance of recycled polymers, not only for high-grade applications. The properties of the recyclate must be specified and guaranteed within narrow tolerances by the manufactures according to the needs of their customers. 

To a plastic producer (i.e. processor), melt index is one property that is needed in order to evaluate whether the same process can be used irrespective of whether it uses virgin or recycled polymers. This will tell if it is possible to process the recycled polymeric materials in the same set-up as usual. Several other properties are needed in order to quality mark the materials. The melt index is related to what final tensile properties a product obtains, this in turn has an impact on the expected life-time. The purity of a recyclate stream with respect to the amount of foreign polymer in the stream has an impact on melt-index, but will also be an important factor for the final mechanical properties. Another very important property is the amount of low molecular weight compounds, which may be of vastly different types. Typically such an analysis will show the presences of additives and their degradation products, degradation products of the polymeric matrices, traces of solvents, initiators, or catalysts, compounds related to the use of the plastics and others. 

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