Recycling carpet waste

Cost is another concern associated with the use of recycled carpet waste fibers in concrete. Currently a vast amount of carpet waste is disposed of each year and therefore the cost of raw material for the recycled fibers is negligible. The disassemble process to convert the waste into fibers suitable for concrete reinforcement requires only simple, inexpensive shredding operation. Therefore the cost of the recycled fibers will remain very competitive with virgin fibers for FRC. 

FRC using recycled carpet waste fibers has also been used in the construction project of a 11,000 m2 building. Conventional equipment and procedures were used in the construction. The project consumed about 20 tons of carpet waste as concrete additives. The waste fibers were directly added into concrete mixing trucks. The mixing, pouring and finishing went smoothly the compressive and flexural strengths exceeded specifications and improved ductility and shatter resistance of the material were evident. This project has demonstrated that low-cost carpet waste... 

Products from recycled carpet waste. [Data from Riccirdelli, X E King, M H ... 

Figure 16.4. Extrusion process developed by Monsanto for recycling carpet waste [63],...

In a study on concrete reinforcement with carpet waste fibers [78, 79], recycled carpet waste fibers about 12-25 mm in length and fiber volume fractions of 1 and 2% were used. FiberMesh, a virgin polypropylene (PP) fiber (19 mm long), at 0.5 and 1% volume fractions was included for comparison. 

Chen T. (1996), Recycling Carpet Waste hy Reactive Extrusion , M. S. Thesis, School of Textile and Fiber Engineering, Georgia Institute of Technology, March. 

Utilization of recycled carpet waste fibers for reinforcement of concrete and soil... 

Wang Y. (1999), Utilization of Recycled Carpet Waste Fibers for Reinforcement of Concrete and Soil , Journal of Polymer-Plastics Technology Engineering, Vol. 38, No. 3, 533-546. 

In both the materials used and the construction process, sustainability and efficiency will become standard. Improvements mjob site management and building design will reduce waste and cost of construction. Materials such as engineered wood, recycled carpeting, and cellulose insulation, which have lower environmental impact, will become cheaper and more widely available. Not only are buildings constructed with such material friendlier to the environment, they also provide higher-quality, lower-cost solutions. 

DSM and Allied Signal have developed carpet identification equipment that can identify specific plastics. Particularly carpet made of nylon 6 (or nylon 66) fibres are separated, cut into pieces, isolated, and converted by polycondensation into their monomeric components. The monomers can then be reused in the production of nylon. DSM and Allied Signal opened the world s first large scale carpet recycling plant in Augusta, Georgia, US in November 1999. This plant has a capacity of 90,000 tpa nylon 6 carpet waste (109). 

Polymer Engineering and Science 41, No.9, Sept.2001, p.1457-70 REVIEW RECYCLING OF NYLON FROM CARPET WASTE... 

The problem of carpet recycling is considered and the different methods being proposed or commercially utilised are discussed. The main component of the carpet waste is fibres of nylon-6 and nylon-66. The review of the literature includes a limited amount of journal publications, which focus primarily on fundamental aspects, and a large number of patents, which describe the available technologies. The most promising recycling techniques (depolymerisation, extraction, melt blending and mechanical separation) are described. 48 refs. 

This fall, the closed-loop Evergreen Nylon Recycling plant will start up in the US, a joint venture of DSM Chemicals North America and AlliedSignal. The facility will recover 45,000 m.t./year of caprolactam by depolymerising the fibres from 100,000 m.t./year of discarded nylon-6 carpets. Meanwhile in Germany, Lurgi is building the Polyamid 2000 AG facility. It will process 120,000 m.t./year of carpet waste and recover 10,000 m.t./ year of caprolactam from nylon-6 carpets and 13,000 m.t./ year of nylon-6-6 from nylon-6-6 carpets. 

A three-year joint European project, RECAM, recommends that it should be possible to colleet more than 50% of carpet waste in Western Europe. High-grade materials such as PA and PP could be recovered for the manufacture of engineering plastics compounds and more than 8 million Gigajoules of energy could be reeovered from the remainder. At the heart of the proj ect are ehemieal recycling processes developed by both DSM and Enichem. 

This study is limited to application of unwanted materials such as carpet wastes and recycled glass in cement-based composites. 

Waste carpet typically contains large quantities of Nylon 6, which can be converted back into caprolactam. Recycling processes are described in U.S. 7,115,671, U.S. 6,111,099 (both to DSM B.V.), and U.S. 5,359,062 (to BASF). Determine the economics of recovering caprolactam from carpet waste if the waste is available at a cost of -30/metric ton (i.e., you are paid 30/ton to accept it). How does this compare to burning the waste carpet in an incinerator with a steam turbine cogeneration plant ... 

Other materials in waste that is thermally processed also were studied by pyrolytic techniques, typically with the purpose of regenerating the monomers or of obtaining other useful small molecules. For example, pyrolytic studies were performed for the evaluation of the possibilities for re-utilization of nylon carpet waste [7], the recycling of thermoset polymeric composites [8], the recovery of methyl methacrylate from poly(methyl methacrylate) waste [9], as well as for other raw material recovery from pyrolysis of plastic waste [10]. The results of incineration of various other types of waste also were studied at model scale [11, 12). These studies were applied to specific waste materials associated with the manufacturing process or to municipal solid waste [13-15)... 

This paper summarizes the results of an experimental program to evaluate the effectiveness of using recycled fibers from carpet waste for concrete reinforcement. It also discusses issues that need to be addressed for the application of such FRC in large scale construction projects. It then reports on a building construction project using carpet waste fiber reinforced concrete. The results suggest that using carpet industrial waste fibers in construction would not only improve the reliability and life of the concrete structure, it but also could reduce the landfill spaces needed to dispose the waste material. 

The carpet industrial waste generated each year and that accumulated in landfills represent an abundance of useful resources, as they can provide effective reinforcement for concrete. As to be discussed in the following sections, concrete reinforced with recycled fibers from hard carpet waste is indeed a suitable material for construction. It suggests that using carpet waste in construction could be a very cost-effective way to improve the durability and performance of the concrete structure, and to reduce the needs for landfill spaces. 

Besides for building constructions, the carpet waste FRC can also be used for highway construction as pavements, columns, bridge decks and barriers, and for airport construction as runways and taxiways. Recycled fibers from carpet waste could become a standard additive for concrete. 

YoujiangW (1993) Fiber reinforced concrete using recycled carpet industrial waste and its potential use in highway construction. Symp Proc on Recovery and effective reuse of discarded materials and by-products for construction of highway facdities, October 1993, Denver, CO... 

Many carpet manufacturers, fiber and chemical suppliers, recycling companies, and academic institutions are actively pursuing various methods to recycle fibrous waste. The approaches include chemical processes to depolymerize nylon and other polymers, recovery of plastic resins from carpet fibers, direct extrusion of mixed carpet waste, composites as wood substitutes, fibers for concrete and soil reinforcement, waste-to-energy conversion, and carpet as feedstock for cement kilns. 

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