Carpet Waste Research Articles

Nylon recovery from carpet waste through pyrolysis under the presence of zinc oxide and the roll-milling treatment

Recycling of carpet waste is not extensively carried out because of its complex combination of materials. A representative type of carpet consists of three layers: nylon fibers, adhesives, and backing materials made of poly(vinyl chloride), PVC. Thermal treatment of carpet waste, thus, leads to the emission of hazardous chlorinated compounds. In the present work, we have employed the one-directional thermal treatment of the backing materials under the presence of zinc oxide, which promotes the thermal degradation of PVC. Nylon fibers could be effectively recovered by the consequent milling treatment from the brittle backing materials. The influence of process parameters, such as pyrolysis temperature and reaction time, on the separation efficiency is discussed.

Effect of nylon fibres on mechanical and thermal properties of hardened concrete for energy storage systems

The use of recycled materials in new concrete production is very appealing because of the low cost of the raw materials and the landfill space saving, as well as the enhancement of the resulting concrete’s properties. This paper focuses on the production of concrete for thermal energy storage systems using polyamide fibres from post-consumer textile carpet waste. We investigated the influence of a fibre content of 5kg/m3 on the mechanical and thermal properties of fresh and hardened concrete with a w/c ratio of 0.35, comparing it with plain concrete. The nylon fibre-reinforced concrete was slightly more ductile and tougher than the plain concrete because the fibres have an important role after failure. The tensile strength, maximum load-bearing capacity and modulus of elasticity decreased slightly with the addition of nylon fibres, but drying shrinkage was lower than for plain concrete. Given that heat capacity and thermal conductivity are the most important parameters for thermal energy storage purposes, we measured these parameters for all the samples at 25°C, and after a thermal treatment at 300°C. The heat capacity values were 0.63 and 0.81Jg−1K−1 for fibre-reinforced concrete (FC) and plain concrete (C), respectively, and the thermal conductivity values were 1.16 and 1.02Wm−1 K-1.

Impact of Carpet Waste Fibre Addition on Swelling Properties of Compacted Clays

Municipalities and recycling and environmental authorities are concerned about the growing amount of carpet waste produced by household, commercial and industrial sectors. It is reported that 500,000 tonnes of carpet waste fibre are plunged into landfills annually in the UK. In the United States of America, around 10 million tonnes of textile waste was generated in 2003. In geotechnical engineering, expansive clay soils are categorised as problematic soils due to their swelling behaviour upon increase in the moisture content. The problematic nature of such soils is intensified with the increase in the plasticity index. This paper presents results of a comprehensive investigation into utilisation of carpet waste fibres in order to improve the swelling characteristics of compacted cohesive soils. Therefore, two different clay soils with markedly different plasticity indices (i.e. 17.0 and 31.5 %) were treated with two different types of carpet waste fibre. Waste fibres were added to prepare specimens with fibre content of 1, 3 and 5 % by dry weight of soil. Soil specimens with different dry unit weights and moisture contents were prepared so as to the swelling behaviour of fibre reinforced compacted clays is completely attained under various scenarios. The results indicated that the behaviour of the fibre reinforced soils seems highly dependent on the initial compaction state and secondary on the moisture content. It was found that the swelling pressure drops rapidly as the percentage of fibre increases in samples prepared at the maximum dry unit weight and optimum moisture content. Reducing the dry unit weight, while maintaining constant moisture content or increasing the moisture content at constant dry unit weight was found to reduce the swelling pressure.

Unconfined Compression Strength of Reinforced Clays with Carpet Waste Fibers

This paper presents results of a comprehensive investigation on the utilization of carpet waste fibers in reinforcement of clay soils. Effects of adding proportionate quantities of two different types of shredded carpet waste fibers to clay soils (i.e., 1, 3, and 5% by dry weight of the soil) were investigated and evaluated. The investigation was conducted on specimens prepared at their maximum dry unit weight and optimum moisture content, as well on specimens prepared at variable conditions of dry unit weight and moisture content. A comparison was also made on specimens prepared at the same fiber content by changing dry unit weight while moisture content was kept unchanged or by changing both dry unit weight and moisture content. The investigation revealed that inclusion of carpet waste fibers into clay soils prepared at the same dry unit weight can significantly enhance the unconfined compression strength (UCS), reduce postpeak strength loss, and change the failure behavior from brittle to ductile. The results also showed that the relative benefit of fibers to increase the UCS of the clay soils is highly dependent on initial dry unit weight and moisture content of the soil. Failure patterns were gradually transformed from the apparent classical failure for unreinforced soil specimens to barrel-shaped failures for reinforced specimens at 5% fiber content.

Fabrication of structural composites from waste carpet

AbstractVacuum‐assisted resin transfer molding (VARTM) has been used to fabricate engineered composite materials from postconsumer carpet waste. The process is unique and applicable to any type of carpet. This method utilizes the three‐dimensional material architecture of carpet to result in composites with improved mechanical properties, as compared to other recycled carpet‐based materials. The technique can be used to make laminated structures for load‐bearing applications. As a result, this can lead to the recycling of waste carpet with the potential of reduced environmental impact. The potential applications of these composites include low‐cost containers, civil infrastructure components, and materials for impact protection. Moreover, the simplicity of the fabrication technique makes it attractive for commercialization. © 2011 Wiley Periodicals, Inc. Adv Polym Techn 31: 380–389, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20261

Research on Mechanical Properties of Recycled Fiber Concrete

At present, green energy saving idea, aimed at protecting environment and saving energy, now has become the guiding philosophy of modern architecture. Based on this, recycled carpet waste fibers for textile mechanical properties of concrete were discussed in this paper. The application of polypropylene fiber concrete abroad has been widely used, which is becoming more and more popularly in China recent years. Meanwhile, research on the application of recycled polypropylene fiber concrete is still scarce. The experiment of this paper adopt waste polypropylene fibers as reinforcing fiber, and we make the standard specimen which size is . We use the specimen to do the research of mechanical properties of compressive strength and observing the variation of compressive strength of concrete specimen in different fiber volume. We discovered that when we add volume of 0.12% recycled polypropylene fiber and the length is 19mm, the compressive strength of concrete increases greatly. We draw the conclusion that the compressive strength of recycled fiber concrete is better than ordinary one from the experiment. In addition, if such concrete was used widely, we may reach the goals of conserving resources and protecting the environment.

Utilization of recycled post consumer carpet waste fibers as reinforcement in lightweight cementitious composites

Purpose – A large amount of post‐consumer carpet waste is discarded into landfills. The need to recycle this waste is increasing due to the lack of available landfill spaces in many parts of the world, environmental concerns, and resource conservation. The purpose of this paper is to explore the use of this waste for a low‐cost, high‐volume application.Design/methodology/approach – Fibers from carpet waste have been successfully used as reinforcement in concrete, typically at 0.1‐1 per cent volume fraction (fractions by weight are even lower), for enhanced toughness. In this study, lightweight cementitious composites were fabricated that were reinforced with recycled carpet fibers at up to 20 per cent fiber to cement weight ratios. Flexural, toughness, and impact properties of the lightweight cementitious composites were characterized.Findings – The density of the composites decreases with the increase of fiber content. In the three‐point bending test, lightweight cementitious composites exhibited a ducti...

The influence of the precursor and synthesis method on the CO2 capture capacity of carpet waste-based sorbents

Adsorption is one of the most promising technologies for reducing CO(2) emissions and at present several different types of sorbents are being investigated. The use of sorbents obtained from low-cost and abundant precursors (i.e. solid wastes) appears an attractive strategy to adopt because it will contribute to a reduction not only in operational costs but also in the amount of waste that is dumped and burned in landfills every year. Following on from previous studies by the authors, in this work several carbon-based adsorbents were developed from different carpet wastes (pre-consumer and post-consumer wastes) by chemical activation with KOH at various activation temperatures (600-900 °C) and KOH:char impregnation ratios (0.5:1 to 4:1). The prepared materials were characterised by chemical analysis and gas adsorption (N(2), -196 °C; CO(2), 0 °C), and tested for CO(2) adsorption at temperatures of 25 and 100 °C. It was found that both the type of precursor and the conditions of activation (i.e. impregnation ratios, and activation temperatures), had a huge influence on the microporosity of the resultant samples and their CO(2) capture capacities. The carbon-based adsorbent that presented the maximum CO(2) capture capacities at 25 and 100 °C (13.8 wt.% and 3.1 wt.%, respectively), was prepared from a pre-consumer carpet waste and was activated at 700 °C using a KOH:char impregnation ratio of 1:1. This sample showed the highest narrow microporosity volume (0.47 cm(3) g(-1)), thus confirming that only pores of less than 1 nm are effective for CO(2) adsorption at atmospheric pressure.

Water absorption behavior of carpet waste jute-reinforced polymer composites

This article deals with the water absorption behavior of low-cost polymer composite composed of carpet waste jute yarns and thermoset matrices (i.e., epoxy and polyester). The water absorption behavior of the composites and deviation of their flexural and impact properties after aging in distilled water were investigated. The magnitude of diffusion parameters such as n and K were evaluated to assess the mode of water transport. It was found that the composites follow Fickian diffusion behavior. Both maximum water content (Mmax) and effective diffusion coefficient (Deff) values increased with increasing fiber content. Epoxy matrix composites showed higher Mmax and D eff values when compared to those of polyester matrix composites. D eff value increased remarkably with an increase in immersion temperature, whereas temperature had relatively little impact on Mmax value. Thermodynamics of diffusion process was investigated using Arrhenius plots and the magnitude of the activation energy for the process of diffusion (E a) was evaluated. Ea increased with temperature increment, suggesting fast access of water into polymer segments at elevated immersion temperatures. NaOH treatment of jute yarns was also investigated in terms of the water absorption behavior of the composites. It was shown that alkali treatment reduces water absorption of the composites remarkably, which was attributed to interface improvement. Flexural strength and modulus of the composites decreased up to 40% and 60%, respectively, whereas Charpy impact strength increased up to 30% after 168 h of water immersion.

Mechanical Characterization of Carpet Waste Natural Fiber-reinforced Polymer Composites

This investigation deals with the property characterization of polymeric composites from abundantly available and renewable jute fibers. The aim of this article is to explore the possibility of using carpet waste jute yarn for value added fiber-reinforced composite materials and to investigate the physical and mechanical properties of these low-cost composites. Jute yarn was treated with 25 wt% NaOH solution to improve fiber—matrix interface. NaOH-treated jute yarn was crimpier, bulkier, more hairy, and flexible. The investigation of the mechanical properties of composites was performed as a function of yarn type, reinforcement form, matrix type, alkali treatment, and fiber content. For this purpose, the tensile, flexural and charpy impact tests were performed. It was found that composite samples from alkali treated reinforcement had better mechanical properties based on the investigated parameters. SEM analyses showed that alkali treatment improves bonding across the fiber—matrix interface. Jute—epoxy composites showed better tensile and flexural strength in comparison to jute—polyester composites, whereas impact strength of epoxy matrix composites were almost half that of polyester matrix composites. Composites from double ply jute yarns showed better flexural strength. Taking into account the reinforcement form, jute composites from random reinforcement form showed higher tensile strength and modulus. The study strongly suggests that the jute fiber waste-reinforced polymer composite materials are quite capable to serve as a potential cost effective, technologically viable, and attractive substitute to the conventional glass fiber composites.

Utilization of Carpet Waste in Reinforcement of Substandard Soils

In the UK, 400 million tonnes of waste are generated each year. A considerable amount of this waste is attributed to construction and demolition wastes that are destined for landfill sites. Textiles, including carpet waste, on the other hand, account for only 2% of all wastes by weight but because of their high volume-to-weight ratio, once dumped into landfills they occupy large spaces. Besides, given the high added values of carpets, carpet waste account for almost £70 million of lost revenue per year in the UK. Increasing public concern for the environment and higher taxations imposed on landfill dumping are forcing manufacturers of various disciplines to seriously reduce their waste and/or find new applications for their inevitable waste. This article reports on one such application where carpet fibrous waste is included in clayey or substandard soils with the intention of enhancing soil cohesion and reinforcement. The findings suggest that inclusion of as much as 10% fibers can be tolerated and would enhance internal cohesion, shear and comprehensive strength as well as load-bearing capacity of this kind of soils. Soil moisture content is also reported to play an important role in enhancing cohesion and compressive strength of such combinations.

Emissions from Carpet Combustion in a Pilot-Scale Rotary Kiln: Comparison with Coal and Particle-Board Combustion

The use of post-consumer carpet as a potential fuel substitute in cement kilns and other high-temperature processes is being considered to address the problem of huge volumes of carpet waste and the opportunity of waste-to-energy recovery. Carpet represents a high volume waste stream, provides high energy value, and contains other recoverable materials for the production of cement. This research studied the emission characteristics of burning 0.46-kg charges of chopped nylon carpet squares, pulverized coal, and particle-board pellets in a pilot-scale natural gas-fired rotary kiln. Carpet was tested with different amounts of water added. Emissions of oxygen, carbon dioxide, nitric oxide (NO), sulfur dioxide (SO2), carbon monoxide (CO), and total hydrocarbons and temperatures were continuously monitored. It was found that carpet burned faster and more completely than coal and particle board, with a rapid volatile release that resulted in large and variable transient emission peaks. NO emissions from carpet combustion ranged from 0.06 to 0.15 g/MJ and were inversely related to CO emissions. Carpet combustion yielded higher NO emissions than coal and particle-board combustion, consistent with its higher nitrogen content. SO2 emissions were highest for coal combustion, consistent with its higher sulfur content than carpet or particle board. Adding water to carpet slowed its burn time and reduced variability in the emission transients, reducing the CO peak but increasing NO emissions. Results of this study indicate that carpet waste can be used as an effective alternative fuel, with the caveats that it might be necessary to wet carpet or chop it finely to avoid excessive transient puff emissions due to its high volatility compared with other solid fuels, and that controlled mixing of combustion air might be used to control NO emissions from nylon carpet.

Properties of cementitious composites containing polypropylene fiber waste

The carpet waste fibers and waste glass that create a serious environmental problem can be converted into useful products. The use of these waste materials in a cement-based composite can be a promising direction for waste reduction and resources conservation. In this study, several tests have been carried out to investigate the performance of control mortar using recycled glass and fibers as a fraction of aggregates in a cement-based composite. These tests included compressive strength, flexural strength, flexural toughness and water absorption. The results revealed that carpet waste fiber and waste glass could be reused as substitutes for conventional materials in cement-based composites.

Recykling odpadow dywanow i wykładzin dywanowych

The analyses of the global and domestic markets of post-production and post-consumer carpet wastes and the methods of their recycling were presented (Table 1 and 2). The results of the own investigations concerning mechanical recycling of post-consumer carpet wastes are discussed. Defibered carpet wastes were applied as the fillers for thermoplastics' composites. The carpet wastes of polypropylene nap or polyacrylonitrile:polyamide 66 (80:20) one (Table 3) were used. Polypropylene or low-density polyethylene (primary one or agglomerate made of packaging film) were applied as polymer matrices. The dependence of mechanical properties of the composite on the type of polymer matrix and filler as well as on these components mutual ratio (Table 5-8, Fig. 5) was investigated. Polypropylene composites show the character of constructional plastics. The structures of the composites obtained (Fig. 6-9) as well as of the fibers obtained as a result of carpet waste' defibering (Fig. 4) were characterized by SEM method. Acoustic properties of the materials obtained were also studied (Table 9, Fig. 10). It was found they were fit to be the sound absorbing screens (acoustic insulating power > 30 dB).

Characterization of fuel gas products from the treatment of solid waste streams with a plasma arc torch

This work addresses the plasma treatment of two solid waste streams and production of fuel gases from the process. In this study, carpet waste and simulated solid wastes generated by a United States Air Force Basic Expeditionary Airfield Resources Base deployment were used. Waste was treated in a furnace fitted with a 100 kW plasma arc torch. The off gas was analyzed to determine its composition. The product gas was composed primarily of carbon monoxide and hydrogen, with small amounts of methane, benzene and toluene also detected. These experiments demonstrate the feasibility of producing fuel gases by plasma treatment of the solid waste streams. While the thermal energy value of the fuel gas produced in these experiments was less than the energy input, a higher waste-to-fuel gas conversion efficiency is expected in full-scale application.

ACOUSTIC UNDERLAY MANUFACTURED FROM CARPET TILE WASTES

Abstract Carpet waste has successfully been converted into acoustic underlay materials that compete with commercial counterparts both in terms of performance and costs. This paper builds on an earlier paper [Miraftab et al, Autex Res.J.5(2), 96-105 (2005).] where granular/fibre mixing ratios, binder concentration and particle size distribution were shown to play a major role in maximising impact sound insulation capabilities of developed underlays. Product optimisation with respect to the particle size as governed by the aperture dimension and mean effective fibre length is further explored in this paper, and the developed underlay is compared with a selection of commercially available acoustic underlays. The results show that a 2mm-aperture screen at the granulating chamber output yields a waste stream with grains in the size range of 0.5-1.0mm and a mean effective fibre length of 2.75 mm which was most suitable to work with, and gave rise to samples with the best impact sound reduction performance. The optimised sample of 10mm recycled underlay (U2) appeared to perform better than most commercial systems tested. The manufactured underlay withstood, and in some instances, outperformed, during the standard tests as required within the BS 5808 protocol. The study concludes that recycling carpet waste to produce quality acoustic underlay with desirable impact sound insulation characteristics is technically feasible, and a viable alternative to landfill or incineration.

Impact sound insulation and viscoelastic properties of underlay manufactured from recycled carpet waste

This paper reports an investigation of the impact sound insulation performance of a range of materials made from recycled carpet tiles and provides a comparison with the performance of some commercially available acoustic underlays. The impact testing is carried out using a specially designed rig. It is demonstrated that good quality acoustic materials can be successfully manufactured from a granulated mix of industrial carpet waste. The effects of the grain to fibre (G:F) mass ratio, binder concentration and particle size distribution on the acoustic performance is investigated. It is shown that the optimum G:F ratio should be close to the mass ratio of the backing material to the pile material in many types of commercial carpet tiles (60:40). Sieving the granular waste and producing samples containing a single class of particle size does not enhance the impact sound insulation performance. These are important findings, which should ensure an efficient, cost-effective, full-scale manufacturing process. A formulation has been developed which yields samples with optimum impact sound insulation capability. This optimised sample compares favourably with the commercial underlays tested on the impact rig. The dynamic mechanical properties of the developed underlays have also been investigated to provide a better understanding of their influence on the impact sound insulation.

Soil reinforcement with recycled carpet wastes.

A root or fibre-reinforced soil behaves as a composite material in which fibres of relatively high tensile strength are embedded in a matrix of relatively plastic soil. Shear stresses in the soil mobilize tensile resistance in the fibres, which in turn impart greater strength to the soil. A research project has been undertaken to study the influence of synthetic fibrous materials for improving the strength characteristics of a fine sandy soil. One of the main objectives of the project is to explore the conversion of fibrous carpet waste into a value-added product for soil reinforcement. Drained triaxial tests were conducted on specimens, which were prepared in a cylindrical mould and compacted at their optimum water contents. The main test variables included the aspect ratio and the weight percentage of the fibrous strips. The results clearly show that fibrous inclusions derived from carpet wastes improve the shear strength of silty sands. A model developed to simulate the effect of the fibrous inclusions accurately predicts the influence of strip content, aspect ratio and confining pressure on the shear strength of reinforced sand.

Emissions study of co-firing waste carpet in a rotary kiln

Post-consumer carpet represents a high volume, high energy content waste stream. As a fuel for co-firing in cement kilns, waste carpet, like waste tires, has potential advantages. Technological challenges to be addressed include assessing potential emissions, in particular NO emissions (from nylon fiber carpets), and optimizing the carpet feed system. This paper addresses the former. Results of pilot-scale rotary kiln experiments demonstrate the potential for using post-consumer waste carpet as a fuel in cement kilns. Continuous feeding of shredded carpet fiber and ground carpet backing, at rates of up to 30% of total energy input, resulted in combustion without transient puffs and with almost no increase in CO and other products of incomplete combustion as compared to kiln firing natural gas only. NO emissions increased with carpet waste co-firing due to the nitrogen content of nylon fiber. In these experiments with shredded fiber and finely ground backing, carpet nitrogen conversion to NO ranged from 3 to 8%. Conversion increased with enhanced mixing of the carpet material and air during combustion. Carpet preparation and feeding method are controlling factors in fuel N conversion.

Effects of Inorganic and Polymer Filler on Tertiary Damage Development in Asphalt Mixtures

Two methods, a three-parameter (work-hardening) model and a pseudostrain energy model, were used to characterize permanent deformation-related damage potential of asphalt mixtures. The three parameters were calculated by fitting a curve that describes permanent strain accumulation during repeated load compressive testing. The pseudostrain energy was calculated using the linear viscoelastic constitutive equation. Both methods are appropriate and predict permanent deformation and tertiary damage in asphalt mixtures due to plastic deformation and microcrack development. The effects of a waste carpet coproduct and hydrated lime on permanent deformation were evaluated using the two techniques. The coproduct reduced damage potential in both a dense-graded mix and in a mix designed to exhibit early tertiary damage (tender mix). The coproduct was effective with two compositionally different bitumen within each mixture. Hydrated lime was effective in reducing tertiary damage potential in the dense-graded mixture, but its effectiveness was mixture and bitumen dependent.