Carpet fiber recycling

PP polypropylene yogurt containers, grocery bags, carpet fiber, food wrap, luggage compost bins, curbside recycling bins... 

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. 

Realff M. (2004) Regional Fiber Recycling System , Presentation at 9th Annual Conference on Recycling of Polymer, Textile and Carpet Waste, Dalton, GA, May 10-11. 

Recycled fibers from various sources have been studied as reinforcement in concrete, including tire cords, carpet fibers, feather fibers, steel shavings, wood fibers from paper waste, and high-density polyethylene."... 

The restrained shrinkage cracking behavior was measured by the total crack width of each ring specimen with respect to time. The crack widths were significantly reduced in the fiber composites, including all recycled fibers except those with rubber strips. In the recycled carpet fiber composites, the crack width and spacing were evenly distributed. The crack widths were much larger than those with steel fibers, and about one half of those with FiberMesh. 

Test curves for the triaxial compression test with a 34.5 kPa confinement pressure (a) reinforced with recycled carpet fibers, (b) reinforced with fibrillated polypropylene fibers. 

Shaw selected a combination of polyolefin resins from Dow Chemical as the base polymer of choice for EcoWorx due to the low toxicity of its feedstocks, superior adhesion properties, dimensional stability, and its ability to be recycled. The EcoWorx compound also had to be designed to be compatible with nylon carpet fiber. Although EcoWorx may be recovered from any fiber type, compatibility with nylon-6 provides a significant advantage. Polyolefins in EcoWorx are compatible with known nylon-6 depolymerization methods, whereas PVC interferes with those processes. Nylon-6 chemistry is well known and not addressed in first-generation production. 

The majority of polyamides used commercially are nylon-6,6 or nylon-6. The largest supply of waste for recycling of nylons is obtained from used carpets. Approximately 30-40% of die nylon produced in the world is used as carpet face fibers.1 Carpets consist of a multicomponent construction of face fibers and a primary and secondary backing. The face fibers are generally made of... 

Chemical recycling of nylon-6 carpet face fibers has been developed into a closed-loop recycling process for waste nylon carpet.5 The recovered nylon-6 face fibers are sent to a depolymerization reactor and treated with superheated steam in the presence of a catalyst to produce a distillate containing caprolactam. The crude caprolactam is distilled and repolymerized to form nylon-6. The caprolactam... 

Important solvolysis reactions for nylons are hydrolysis, methanolysis, glycolysis, aminolysis, ammonolysis, transamidation, and acidolysis.17 Hydrolysis of nylon-6 with steam in the presence of an acid catalyst to form caprolactam is tlie preferred depolymerization approach. However, when recycling carpet face fibers, file fillers in the polymer may react with file acid catalyst and lower the efficiency of the catalyst. 

When the new product to be manufactured is the same as what it started as, for example a new bottle made from bottle scrap, the recycling is referred to as closed-loop. When the new application is different from the starting one, the process is referred to as open-loop recycling, as is the case when the polyethylene terephthalate bottle is used to produce polyester fiber for carpeting. 

This PCT fiber has better resiliency than PET, without compromising high-temperature resistance. It successfully competed in the carpet yam market against nylon, where PET was limited by its relatively lower wear resistance. Recycling of PET bottles has provided a source of low-cost resins that are used for carpets in less critical markets. 

In contrast, PET end-use markets have been developing for at least 10 years. When the PET bottle was introduced in 1978 and was collected in states with deposit laws, the industry for recycling them and reusing them began to develop. PET resins can be reused to make polyols for insulation and unsaturated resins for bathtubs, shower stalls, boat hulls, and auto panels. Reclaimed PET is also used for strapping, paint brushes, geotextiles, fibers for fiberfill and carpets, and other textile applications. 

Acrylic and modacrylic fibers have a wool-like appearance and feel, and excellent resistance to heat, ultraviolet radiation, and chemicals [Bajaj and Kumari, 1987]. These fibers have replaced wool in many applications, such as socks, pullovers, sweaters, and craft yams. Other applications include tenting, awning fabric, and sandbags for rivershore stabilization. The use of acrylic and modacrylic fibers in carpets is low since these materials do not hold up well to recycling through hot-humid conditions. This also prevents its use in the easy-care garment market. 

You can participate in a massive recycling effort just by purchasing carpeting made of polyester rather than nylon fibers, which is made from recycled plastic bottles. 

In order to decrease human consumption of petroleum, chemists have investigated methods for producing polymers from renewable resources such as biomass. Nature Works polylactic acid (PLA) is a polymer of naturally occurring lactic acid (LA), and LA can be produced from the fermentation of corn. The goal is to eventually manufacture this polymer from waste biomass. Another advantage of PLA is that, unlike most synthetic polymers which litter the landscape and pack landfills, it is biodegradable. PLA can also be easily recycled by conversion back into LA. It can replace many petroleum-based polymers in products such as carpets, bags, cups, and textile fibers. 

Although FRC has become widely available from concrete suppliers, its use has been limited primarily due to cost considerations. Effort to reduce the cost includes limiting the fiber dosage and developing inexpensive fibers. A very attractive alternative, however, would be to use suitable recycled fibers from industrial waste which otherwise would be discarded, the carpet industrial waste being an example. 

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. 

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