Polymer blends recycling

Recycling of manufactured polymer blends Recent concepts in polymer blends recycling Jose et al. 2011... 

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. 

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

The feasibility of diffuse reflectance NIR, Fourier transform mid-IR and FT-Raman spectroscopy in combination with multivariate data analysis for in/ on-line compositional analysis of binary polymer blends found in household and industrial recyclates has been reported [121, 122]. In addition, a thorough chemometric analysis of the Raman spectral data was performed. 

Rather than worry about whether a copolymer of two different monomers is heterogeneous or not, why not just make homopolymers of each and mix them together (make a polymer blend) The answer is easy Most polymers do not like other polymers, and, on mixing, each will tend to segregate into a phase that excludes any other polymers (will phase separate). These different phases tend not to stick to each other very well, resulting in a polymer sample with poor physical properties. We will discover the practical consequences of this in Chapter 7 when we discuss the properties of certain block copolymers called thermoplastic elastomers and in Chapter 9 when we discuss the recycling of plastics. 

Fig. 10 Strain at break Vs. UV exposure time for polypropylene copolymer bars made from (a) virgin polymer (V) (b) virgin polymer + undegraded recyclate (U) (c) virgin polymer + photodegraded recyclate (P). Results for blends with recyclate contents of 10% and 25% are shown. (More details in Craig, I.H. White, J.R. Mechanical properties of photo-degraded recycled photo-degraded polyolefins. J. Mater. Sci. 2006, in press.)...

Much effort is being expended on polymer blends to reduce the need for separation and to improve the properties of the recycled materials. Because most polymers are incompatible with one another, this usually requires the addition of a compatibilizer,151 or the preparation of one in situ. (Com-... 

Radiation processing may help to overcome theoretical and technological difficulties, in the way of creating new multicomponent polymeric systems. In the present work, we focused on solving the major obstacle, the inherent thermodynamical incompatibility of partners in polymer blends, alloys, composites and recycled products. 

Compatibilization and upgrading of commingled plastics for reprocessing, and (3) Recycling of polymer blends [Akovali et al., 1998]. 

The term reactive processing is used to describe a polymer processing that involves chemical reactions. In principle, any processing operation can be conducted as a reactive process, viz. reactive injection molding (RIM). However, most often the term refers to reactive extrusion, and in particular, to the reactive compatibilization of immiscible polymer blends, usually conducted in a TSE. During the last 50 years, the latter machines have been used as chemical reactors for the polymerization, depolymerization (chemical recycling), polymer modification and compatibilization [Brown, 1992, Xanthos, 1992 Utracki, 1989, 1991, 1994, 1997]. 

One of the more recent applications of polymer blends and alloys is in plastics recycling. The current solid waste crisis has resulted in public demands for industrial solutions that would result in a reduction of all landfilled solid waste, while minimizing alternate negative environmental impact. It has been perceived by the public that plastic materials account for the overwhelming majority of the landfilled solid mass, when plastics account for only approximately 7 wt% of 18 vol%. 

Improving the recyclability and reprocessability aspects of polymer blends, particularly with respect to the retention of properties after multiple processing histories, to increase the efficiency of regrind use. 

Role of Polymer Blends Technology in Polymer Recycling... 

The experience indicates that it is easier to recycle unfilled than filled polymers. In all cases re-stabilization of the resin is required. Some polymers e.g., PI, PPS, POM, and LCP) are less susceptible to degradation than others. By contrast, the condensation polymers, viz. PA, and PEST, are difficult to reprocess without loss of performance. In most cases, the engineering resins and polymer blends require upgrading. 

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