Recycling of Commingled Plastics

As mentioned earlier, for some applications it is possible to use recycled plastics that contain a mixture of different types of resins. Since different plastic resins are generally not compatible with each other, such mixtures tend to contain small regions of individual types of polymers within a matrix of another polymer. Adhesion between these regions can be poor, resulting in a substantial decrease in performance. Two general approaches have been taken to producing usable materials from such mixtures. 

The second approach to the use of incompatible mixtures of recycled plastics is to compatibilize them in some way, and thereby improve their performance. One 

---

Recycling of Commingled Plastics 20.3.1 With a Compatibilizing Method... 

Most processes for recycling of commingled plastics depend on a predominance of polyolefin in the mix to serve as a matrix within which the other components are dispersed. One of the early processes was the Mitsubishi Reverzer, which was developed in Japan. This process used a short-time, high-temperature, high-shear machine which could handle up to 50% filler. The plastics were first softened in a hopper and then mixed in an extruder. Products were formed in a variety of shapes by flow molding, extrusion, or compression molding. However, the equipment was never successfully marketed. The Klobbie process, developed in the Netherlands in the 1970s, consisted of an extruder... 

Basic problems associated with the equilibrium and interfacial behavior of polymers, compatibilization of immiscible components, phase structure development, and the methods of its investigation are described herein. Special attention is paid to mechanical properties of heterogeneous blends and their prediction. Commercially important types of polymer blends as well as the recycling of commingled plastic waste are briefly discussed. 

Smith, R. Overview of Feedstock Recycling of Commingled Waste Plastics, Presentation at the consortium for fossil fuel Liquefaction Science, P " Annual Meeting, Pipestem. WV, August, (1995). 

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

Some new technology is being developed by which mixed plastics may be depolymerized at high temperatures into monomers that pan be easily separated and repolymerized. Pyrolysis is also effected on commingled plastics, as well as on thermosets, wherein the product consists of a fuel, that will be used for energy. In summary, the concept of tertiary recycling may be practical for some polymers while also effective for better recycling of mixed plastics or thermosets. 

Recycled plastic lumber (RPL) was developed as a substitute for treated wood [51]. RPL, being a product of commingled plastics, can contain as much as 100% post-consumer plastics (or a blend of recycled plastic and recycled wood waste), while structural plastic lumber is... 

Lynch, J., and Nauman, E. "Separation of Commingled Plastics by Selective Dissolution" Proceedings of Society of Plastics Engineers RETEC Conference - New Developments in Plastics Recycling. Charlotte, NC. 1989. 

The prodegradant structural inhomogeneities and nonpolymeric impurities may negatively affect the recyclate lifetime. With the formation of new pro-oxi-dative functional moieties a substantial part of the stabilizers added for the first lifetime are simultaneously consumed. As a consequence the mechanical properties of commingled plastic recyclates generally do not meet material expectations. Increase in resistance to degradation by proper restabilization and the recovery of... 

In 1993, over 41 million pounds of polystyrene was recycled into new plastics products in the U.S. (77). Eor commingled plastics, gasification comes closest to competing with low cost landfilling (57). 

It is not tme either that vinyl is the problem in municipal recycling because it contaminates other resins. Contamination occurs whether or not vinyl is present. Other resins are just as much a contamination problem as vinyl. Except for commingled plastics apphcations, different plastic materials caimot be mixed successfiJly in most recycled products apphcations. This is why it is cmcial to separate efficientiy one plastic from another. Because of the chlorine that is present in it, vinyl lends itself very weU to automated sorting technology. 

Commercial tellurium, 24 408, 414 Commercial vaccines, 25 487 Commercial waste, 25 864 Commingled plastic wastes recycling, 21 453-456 thermal cracking of, 21 454 thermal degradation of, 21 454 Commingled recyclables, 21 368 in waste collection, 25 869-870 Comminution, 16 135... 

Mixed, or commingled, plastics must be dealt with differently to find end uses. Several technologies exist for mixed plastics, such as the ET/1 extrusion process from Advanced Recycling Technology of Belgium and a compression-molding process from Recycloplast of West Germany. At... 

Still, the demand for recycled plastics is low, mainly due to a general uncertainty of the quality of the recycled material. The possibility of offering high quality recycled polymeric materials relays on a reliable and selective collection and sorting, an efficient recycling process and of course an available end-market. The basic technological development, thus, lies in the development of fast, reliable and relatively cheap methods for characterisation of separated and commingled plastic fractions. Recently, it was demonstrated that separation, at home, of a very small amount of products can mean a decreased use of raw oil and less emission of CO2 to the environment [11]. If... 

Pyrolysis recycling of mixed waste plastics into generator and transportation fuels is seen by many as the answer for deriving value from unwashed, commingled plastics as well as managing their desired diversion from landfill. 

---