Carpet waste

Ammonolysis is the preferred route currently in use at the DuPont Company for the depolymerization of nylon-6,6 carpet waste. McKinney13 has described the reaction of nylon-6,6 and nylon-6 mixtures with ammonia at temperatures in the range of 300-350°C at a pressure of about 68 atm in the presence of an ammonium phosphate catalyst to form a mixture of nylon-6,6 and nylon-6 monomers (HMD A, A A, and s-caprolactam) and adiponitrile, 5-cyanovaleramide, 6-aminocapronitrile, and 6-aminocaproamide. 

Carboxylic-sulfonic anhydrides, 80 Cardiovascular surgery, 27 Cardo diamines, 277, 278 Carothers, Wallace, 198 Carothers equation, 11, 59 Carothers group, 1 Carpet waste... 

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. 

In an industrial application dissolution/reprecipitation technology is used to separate and recover nylon from carpet waste [636]. Carpets are generally composed of three primary polymer components, namely polypropylene (backing), SBR latex (binding) and nylon (face fibres), and calcium carbonate filler. The process involves selective dissolution of nylon (typically constituting more than 50wt% of carpet polymer mass) with an 88 wt % liquid formic acid solution and recovery of nylon powder with scCC>2 antisolvent precipitation at high pressure. Papaspyrides and Kartalis [637] used dimethylsulfoxide as a solvent for PA6 and formic acid for PA6.6, and methylethylketone as the nonsolvent for both polymers. 

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 U.S. carpet industry produces about 1 billion m2 of carpet and consumes about 1 million tons of synthetic fibers per year. About 70% of the carpet produced is for replacement of used carpet, which translates into about 2 million tons of used carpet for disposal. In the Dalton, Georgia area where many carpet manufacturers are located, over 40, 000 tons of carpet waste has to be disposed of each year. Significant amount of carpet trim waste is also being disposed of by other industries such as the automobile manufacturers. Because of the high cost of developing and managing landfills, waste disposal in landfills has become increasingly difficult. 

Previous studies reported in the literature have indicated that nylon and polypropylene fibers can provide effective reinforcement for concrete [1-5]. The configurations of the fibers in carpet, nylon face yam being highly crimped and polypropylene fibers being of flat tape shape, help improve the fiber-matrix interlocking which is essential for effective reinforcement. All the major components of the carpet waste are shown to have good durability in Portland cement [1,4]. 

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. 

The results for compression and flexural tests of various mixes are given in Table 1. Six or seven specimens were tested for each setup. In the one day compressive test, similar strength values were observed for plain concrete and various FRCs. It appeared that the 28 day compressive strengths of carpet waste FRCs were lower than that of plain concrete. The plain concrete specimens failed in a brittle manner and shattered into pieces. In contrast, all the FRC samples after reaching the peak load could still remain as an integral... 

Use of carpet waste FRC in full scale construction projects... 

First, the carpet waste must be disassembled into short fibers of appropriate length. By optimizing the fiber length and fiber/matrix bond properties, improved toughening effect can be achieved [8, 9], This generally means that the... 

A most important requirement for using carpet waste FRC is, of course, that its properties must meet or exceed specifications. As for conventional concrete, field and laboratory testing for quality control must be carried out. 

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. 

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. 

A large amount of carpet waste is disposed of in landfills each year. This not only poses economical and environmental problems to the industry, it also represents a severe waste of resources because the waste material can prove to be valuable for construction applications. This study focused on the use of carpet waste fibers in fiber reinforced concrete and demonstrated that such reinforcement can effectively improve the shatter resistance, toughness, and ductility of concrete. Performance enhancement has also been observed in the drying shrinkage test. Such improvements in concrete performance is especially beneficial for concrete structures in seismic zones as the increased toughness could improve the reliability and shock resistance of the structures. 

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... 

The carpet industry in the United States produces about 1 billion square meters of carpet per year. Of this, approximately 70% is used to replace existing carpet this translates into 1.2 million t (1.32 million T) of carpet waste produced annually [49]. Additional wastes produced by the carpet making industry increase the total amount of waste fibers to an estimated 2 million t (2.2 million T). Several research efforts are addressing ways to include these waste fibers in both asphalt pavements and Portland cement concrete. 

The results indicated that using 2% carpet waste in the mix had no 23-25... 

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

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