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True Cotton vs. Other Fibers

Bleached vs. Unbleached Cotton

While TJ Beall Company believes that cotton fibers, especially from US producers, is the most sustainable fiber on earth, our company recognizes that the textile finishing processes have several downfalls in regard to water quality and energy use. When cotton is harvested, it typically undergoes a number of processes, including scouring and bleaching. Cotton was traditionally whitened with chlorine bleach, a process that releases dioxin, a carcinogen and hormone disruptor, into the environment. Nowadays, cotton fibers are mainly scoured with an alkali treatment and then bleached using hydrogen peroxide. Such hydrogen peroxide based processes yield waste effluents, potentially hazardous to the environment.

Cotton is scoured to remove natural waxes, pectins and other non-cellulosic components using hot alkaline solutions (usually caustic soda) containing detergents or soaps. Cotton scouring waste liquors are chemically aggressive and may be toxic (1).  Their solids content, resulting from the alkali and from impurities in the raw cotton material, is generally high. Cotton scouring generates very high BOD concentrations. (2) Bleaching removes the natural yellowish colouring of cotton fibers, thereby increasing whiteness. This operation is generally required if the finished cotton material is to be white or dyed a light color. It is an oxidation process usually brought about using hydrogen peroxide or more historically sodium hypochlorite or sodium chlorite. Auxiliary chemicals such as sulfuric acid, hydrochloric acid, caustic soda, sodium bisulfite, surfactants and chelating agents are generally used during bleaching or in the final rinses, contributing to the pollution load (3). Bleaching wastewater usually has a high solids content with low to moderate BOD levels (3) (4). The dissolved oxygen content of these effluents can be unusually high due the decomposition of hydrogen peroxide. Nevertheless, chloride or hydrogen peroxide can cause toxicity problems in biological treatment processes (3) (4).

As previously discussed, bleached cotton has several negative aspects when compared to True Cotton such as less desirable price point, poor processing characteristics, and a higher coefficient of friction (less soft).

REFERENCES

  1. Comparison of Effectiveness Between Conventional Scouring & Bio-Scouring On Cotton Fabrics  A. M. K. Bahrum Prang Rocky  International Journal of Scientific & Engineering Research Volume 3, Issue 8, August-2012
  2. Membranes for Industrial Wastewater Recovery and Re-use edited by S. Judd, Bruce Jefferson Elsevier Science Inc NY 2003
  3. Chemical Technology in the Pre-Treatment Processes of Textiles  by S.R. Karmakar  Elsevier Science, the Netherlands 1999
  4. Zaharia Carmen and Suteu Daniela (2012). Textile Organic Dyes – Characteristics, Polluting Effects and Separation/Elimination Procedures from Industrial Effluents – A Critical Overview, Organic Pollutants Ten Years After the Stockholm  Convention - Environmental and Analytical Update, Dr. Tomasz Puzyn (Ed.), ISBN:978-953-307-917-2

 

True Cotton vs. Rayon

The most common way to produce rayon is known as the viscose process. In this process, cellulose material such as wood pulp is dissolved in a strong solvent to make a thick, viscous solution that is forced through spinnerets into a quenching solution where strands solidify into fibers. This is sometimes called hydrolysis alkalization or wet spinning because the fiber is “spun” in a chemical solution. The solvent used for this process is carbon disulfide, a toxic chemical that is a known human reproductive hazard (1) (2). It can endanger factory workers and pollute the environment via air emissions and wastewater unless great care is taken. The recovery of this solvent in many viscose factories is around 50%, which means that the other half goes into the environment (2) (3). Other potentially hazardous chemicals which are also used in the viscose process include sodium hydroxide and sulfuric acid. Because of these environmental issues, Patagonia does not use rayon fabric or fibers made by the viscose process (1). Therefore, the production of rayon can actually have a very negative impact on the environment. In use, viscose fibers exhibit “wet collapse” unlike cotton and True Cotton which in turn can result in a characteristic surface slimyness and a discomfort against the skin. This is clearly manifested when some viscose nonwoven products are in their wet state (4).

However, there are new closed-loop processes for making rayon which have excellent environmental benefits over traditional processes. Lenzing AG from Austria in particular uses this process to make lyocell, which is sold under the trademark Tencel. We look forward to working with this new fiber to create better bio-based substrates for the nonwovens industry.

REFERENCES

  1. Patagonia 2013 at http://www.patagonia.com.au/environment/footprint-chronicles/bamboo-and-rayon/
  2. WHO Regional Office for Europe, Copenhagen, Denmark, 2000 at http://www.euro.who.int/__data/assets/pdf_file/0019/123058/AQG2ndEd_5_4carbodisulfide.PDF
  3. Vigliani E C. Carbon disulphide poisoning in viscose rayon factories. Br J Ind Med 1954. 11235–244.244.
  4. C. R. Woodings, The Effect of Fibre Properties on the Absorbency of Nonwovens (Der Einfluß der Fasereigenschaften auf das Absorptionsvermögen von Nonwovens), LENZINGER BERICHTE August 1990

 

True Cotton vs. Polyester

Most polyesters are made from petroleum from which the constituent acids and alcohols are derived. The types of processes that manufacturers use vary, and little is known about specific manufacturing processes because the companies want to keep them a secret in order to remain competitive (1). In a general description of how polyester is synthesized, in the older processes, dimethyl terephthalate and a dihydric alcohol undergo a condensation polymerization when these materials are reacted in a vacuum at high temperatures. Today over 70 to 75% of polyester is produced by CP ( continuous polymerisation) process using PTA (Purified Terephthalic Acid) and mono Ethylene Glycol (MEG). Catalysts like Sb3O3 (Antimony Trioxide) are used to start and control the reaction. The polymerized material is extruded in the form of a ribbon which in turn is converted into chips and melt spun and subsequently drawn into filaments and fibers.

From a safety point of view, great care needs to be exercised in polyester production. It is worth noting that polyester is produced using antimony as a catalyst.  Antimony is a carcinogen, and toxic to the heart, lungs, liver and skin.  Long term inhalation can cause chronic bronchitis and emphysema (2).  Also, as noted, Ethylene glycol (MEG) is a raw material used in the production of polyester.  In the United States alone, an estimated 1 billion lbs. of spent ethylene glycol is generated each year (3).  The MEG distillation process creates 40 million pounds of still bottom sludge. When incinerated, the sludge produces 800,000 lbs of fly ash containing antimony, arsenic and other metals (4).

Notable disadvantages compared to True Cotton:

  • Not consumer preferred
  • Not anually renewable
  • Not biodegradable
  • Not hypoallergenic
  • Not perceived as comfortable
  • Poor breathability

REFERENCES

  1. Kristin Boekhoff  “Peter Schwartz's TXA 337: Structural Fabric Design”,  Cornell University o1996 http://schwartz.eng.auburn.edu/polyester/manufacturing.html
  2. ANURAG VARSHNEY  “FUTURE PROSPECTS OF POLYESTER YARN Roll” No.: 510928963 at http://www.scribd.com/doc/79539269/56989536-Future-Prospects-of-Polyester-Yarn   
  3. O EcoTextiles  at http://oecotextiles.wordpress.com/2013/02/06/antimony-in-fabrics/
  4. Sustainable Textile Development at Victor, http://www.victor-innovatex.com/doc/sustainability.pdf

 

True Cotton vs. Polypropylene

Polypropylene is an example of a thermoplastic olefin fiber in which the long chain synthetic polymer is basically composed of at least 85% by weight of propylene units, These are products of the polymerization of propylene gas, a product of the petroleum industry. Polypropylene has over the years found great versatility as a fiber forming material.
Following the catalytic reactions ((using Ziegler-Natta catalysts) to produce polypropylene, the thermoplastic chips of polymer can be converted into fibers or filaments by traditional melt spinning or by modern derivatives of this as seen in nonwoven spunbonding or melt-blowing.
The use of polypropylene does not have any significant effect from an occupational health and safety point of view in terms of chemical toxicity(1) . The manufacture of the polymer at high temperatures can release irritating vapors to the respiratory system and eyes. There are no known effects from chronic exposure to polypropylene.

Notable disadvantages compared to True Cotton:

  • Not consumer preferred
  • Not annuaully renewable
  • Not biodegradable
  • Not hypoallergenic
  • Not perceived as comfortable
  • Poor breathability
  • Poor "slick" handle

REFERENCES

  1. Polypropylene at Lenntech See http://www.lenntech.com/polypropylene.htm