Biodegradability Study on Cotton and Polyester …

1 Journal of Engineered Fibers and Fabrics Volume 5, Issue 4 - 2010 42 Biodegradability Study on Cotton and Polyester Fabrics Lili Li1, Margaret Frey1, Kristie J Browning2 1 Department of Fiber Science and Apparel Design, Cornell University, Ithaca, NY 14853-4401, United States 2 Cotton Incorporated, Cary, NC 27513, United States. Correspondence to: Margaret Frey, Email: ABSTRACT The purpose of this Study was to measure and compare the Biodegradability of fabrics in laboratory and large scale composting environments. Cotton jersey fabrics with three levels of finishing treatments (scoured and bleached, softener added and resin added) and a Polyester jersey fabric were tested. Under controlled laboratory conditions, the carbon dioxide produced was monitored and integrated to determine the biodegradation rate by ASTM D 5988-03 method in natural soil, and the weight losses were measured after biodegradation in enzyme solutions.

2 The same set of fabrics was buried in the Cornell University Composting Facility for 3 months. The weight losses and the fabric morphology after biodegradation were used to assess and compare the Biodegradability with the results obtained under laboratory conditions. The Polyester fabric showed a slight initial degradation, but the fabric remained intact under both laboratory conditions and the compost environment. The Cotton fabric with softener had an accelerated degradation rate, while the Cotton fabric with resin showed a relatively slow degradation rate. All Cotton samples were more significantly degraded in the compost environment than under the laboratory conditions and confirmed to be compostable . Keywords: biodegradation; ASTM D 5988-03; Compost; Enzyme; Cotton ; Polyester ; fibers INTRODUCTION The disposal of the fabric materials used in textiles [1-3] is a serious challenge to waste management.

3 Conventional methods for fabric waste management include land-filling, recycling and incineration. Increasingly, large scale composting is emerging as a viable disposal method for biodegradable materials. Currently, food, animal and other biodegradable waste streams are being successfully diverted from land-filling to composting waste streams. However, few textile materials are assessed in large scale composting streams although laboratory testing has confirmed their Biodegradability [4-7]. ASTM D 5988-03 standard (Standard Test Method for Determination of Aerobic Biodegradation in Soil of Plastic Materials or Residual Plastic Materials after Composting) is designed to Journal of Engineered Fibers and Fabrics Volume 5, Issue 4 - 2010 43evaluate the extent and rate of aerobic biodegradation of fabric materials in contact with natural soil under controlled laboratory conditions.

4 The CO2 produced is monitored and measured for each material. The degree of Biodegradability is assessed by the amount of CO2 produced and expressed as a fraction of the measured and calculated carbon content with respect to time [8, 9]. The enzyme biodegradation process is another feasible laboratory method to measure the Biodegradability of fabrics. Enzymes have different active components to decompose the corresponding chemical bonds of polymer materials and produce low molecular weight products [10-12]. Composting as an option for waste treatment is a potential way to test biodegradation of the fabrics [13-15]. Compared with these laboratory conditions, the Composting Facility will have more significant microbial and enzymatic active components.

5 The compost is created by: combining organic wastes ( , yard trimmings, food wastes, manures) in proper ratios into piles, rows, or vessels; adding bulking agents ( , wood chips) as necessary to accelerate the breakdown of organic materials; and allowing the finished material to fully stabilize and mature through a curing process. The composting facility used in this work uses a mature compost which contains approximately 850 tons of pre and post-consumer food scraps and compostables, 3300 tons of animal manure and bedding, and 300 tons of plant materials and soil. The mature compost is a stable material with content called humus that is dark brown or black, and has a soil-like, earthy smell. The production of high temperatures to destroy pathogens and weed seeds is controlled from 50-65 oC.

6 If the temperature drops below 50 oC or increase above 65 oC, the piles are turned by a self powered elevating face turner. The purpose of this Study is to compare the results achieved under laboratory conditions with large scale composting facility conditions in terms of the fabrics Biodegradability . All fabrics were laundered 30 times to simulate garments at the end of their useful lives prior to testing. The results of the weight loss obtained in enzyme and composting conditions and the biodegradation rate under ASTM D 5988-03 conditions were used to assess and compare the Biodegradability of Cotton fabrics and the Polyester fabric. The structures of these fabrics before and after degradation by the three testing methods were analyzed by IR spectra. The morphologies of fabric materials after biodegradation by different testing methods were observed by Scanning Electron Microscopy (SEM).

7 EXPERIMENTAL Materials Four knit fabric samples were tested: 1. 100% Cotton jersey, scoured and bleached, no finish ( Cotton nf). 2. 100% Cotton jersey, scoured and bleached, softener only ( Cotton softener only). 3. 100% Cotton jersey, scoured and bleached, resin plus softener ( Cotton resin). 4. 100% Polyester shirt purchased at retail ( Polyester ). Finish formulations for the Cotton samples with softener only and resin plus softener are shown in Ta b l e s I and II. All fabric samples were washed 30 times prior to testing. The Cotton samples were laundered Journal of Engineered Fibers and Fabrics Volume 5, Issue 4 - 2010 44according to AATCC 135 with a warm wash (105 oF), using the normal cycle, and tumble-dried ( Cotton cycle) for 30 minutes. The Polyester shirt was laundered according to the manufacture s instructions including a cold wash (80 oF), using the normal cycle, and tumble-dried low for 30 minutes.

8 AATCC standard liquid detergent was used for all washes and ballast was added to equal a 4-1b load. TABLE I. Cotton Softener only Generic Name % on weight of the bath (owb) Nonionic wetting agent Amino functional silicone softener Cationic softener Cationic emulsified polyethylene Pad-apply finish. Dry only. TABLE II Cotton Resin plus Softener Generic Name % on weight of the bath (owb) Nonionic wetting agent Amino functional silicone softener Cationic softener Cationic emulsified polyethylene Capped, DMDHEU resin MgCl2 Catalyst Pad-apply finish. Dry. Cure at 340 F for 15 seconds. For the ASTM D 5988-03 test, natural soil was supplied by the College of Agriculture and Life Sciences at Cornell University. The soil was sieved to less than 2 mm particle size, and stored at 4 oC for 7 days prior to use. 2 g soil samples were dispersed in 10 mL of distilled water and the pH value of the liquid was measured by a pH meter (Model 215 Denver Instrument).

9 The ash content of the soil was obtained by measuring the remaining weight after incineration at 550 oC for 3 h. The moisture of the soil was determined from the weight loss after drying in the oven at 105 oC for 24 h. The water content in the soil was adjusted to 61% by adding water. The chemicals used were both analysis reagents. The solutions were prepared by adding g ammonium phosphate (98%, Sigma-Aldrich) and 28 g potassium hydroxide (98%, Mallinckrodt Baker Inc.) to 1 L distilled water, respectively. Elemental analyzer Elemental analyses of the fabrics were performed on a Carlo Erba NC2500 elemental analyzer. Fabrics samples were introduced to the combustion column via a Costech Zero-Blank autosampler. IR analysis Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) technique was utilized to collect IR spectra of the samples.

10 The fabric sample was put into the microcup of the diffuse reflectance accessory on a PerkinElmer Nicolet Magana 560 IR spectrometer (Madison, WI), and IR information for the sample was collected and processed with OMNIC software. Biodegradation methods ASTM D 5988-03 The evolution of CO2 from samples was used as a measure of biodegradation according to ASTM D 5988-03. All samples were cut into 25 strips with 2 2 cm dimensions. The tests were carried out in desiccators at room Journal of Engineered Fibers and Fabrics Volume 5, Issue 4 - 2010 45temperature. For every sample, a blank, a positive control, and a specimen in positive control were introduced in the desiccators. The blank was only natural soil; the positive control was natural soil in which ammonium phosphate solution was added. The specimen in positive control was the natural soil in which fabric samples and ammonium phosphate solution were added.