Composite products from post-consumer carpet

Composite products from post-consumer carpet 

Landfilling carpet waste, as well as many other thermoplastic wastes, is not sustainable. A key issue is whether post-consumer carpet (PCC) should be separated into its primary thermoplastic base polymers or used as a mixture. A composite with a matrix based on a mixture of incompatible polymers is a way of upgrading the polymer mix and is potentially inexpensive. If the reinforcing fibers dominate the composite properties, then having a matrix comprised of incompatible polymers can be tolerated. The results presented here indicate composites with attractive properties can be made using a matrix of mixed incompatible polymers. 

Most carpet consists of face fiber, usually nylon 66, nylon 6 or polypropylene (PP), with polypropylene backing fabrics and a calcium carbonate filled styrene/ butadiene rubber (SBR) latex binder. It is feasible to sort carpets by the type of face fiber, but it is difficult to separate the face fiber from the backing fabrics and latex adhesive. Therefore, the focus of this chapter is on inexpensive techniques to recycle post-consumer carpet without separating the face fibers from the backing fabrics. 

A carpet separation process is illustrated in Fig. 13.1. First the carpet is sorted by face fiber. A near infrared sensor can identify the face fiber within a second even though nylon 6 and nylon 66 have similar infrared spectra. These two types of nylon carpet must be separated since they are incompatible. Next a guillotine is used to cut the carpet into small enough pieces to feed a shredder. After shredding some of the latex, calcium carbonate and dirt will separate from the carpet. To improve the purity of the carpet, fine grinding is necessary. Then a density separator can be used to remove more filler and dirt. Since there is a significant difference in the densities of nylon and polypropylene, a density separator can be used to separate nylon face fibers from polypropylene backing fabrics. Hydrocyclones can separate these polymers rapidly. Sink-float baths can accomplish this 

Up to 25% by weight of the relatively pure recycled nylon is compounded with virgin nylon and reinforcements and is sold commercially as an injection molding resin. This resin with recycled content is not cheaper than virgin nylon due to the cost of separation and purification. While it is used to make engine manifolds, it is not sold in sufficient quantities to divert much carpet from landfills. Therefore, less pure and potentially less expensive composite materials and products based on post-consumer carpet are considered next. 

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Composite products from post-consumer carpet... 

This research on composite products from post-consumer carpet was supported by the State of Georgia s Traditional Industries Program (TIP), specifically the Consortium on Competitiveness of the Apparel, Carpet, and Textile Industries (CCACTI). The provision of carpet by Wellman, Inc. and glass mat by Eleison... 

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