Deniz Duran1, Hatice Aktekeli2
1,2 Ege University – Faculty of Engineering – Textile Engineering Department.
The rapid increase in the world population leads to the depletion of our natural resources and to the increase of environmental pollution. In recent years, many studies have been carried out to produce alternative solutions to these problems. Community awareness is growing and accordingly, interest is growing towards safe, biodegradable synthetic materials that are either recyclable or that do not harm the environment. In this study, the researches about the polylactic acit(PLA), which are obtained by using natural based raw materials which are self-destructive in natüre, and PLA’s usage areas.
Population growth and industrialization in the world has brought environmental problems. For this reason, sustainability has become an important issue of the whole world in recent years. The textile industry is also in search of solutions that support sustainability, from raw material selection to production methods, like many other industrial areas(Erten, 2004; Kalaycı et al., 2016).
Petroleum-derived raw materials, which take many years of decay in nature and when they start to deteriorate, causing to emit harmful chemicals to the environment and slowly pollute our food chain, as well as the non-renewable energy, are a serious threat to their living life as well as environmental pollution. In this context, the use of natural based raw materials instead of petroleum based synthetic fibers is one of the methods that can create an alternative to sustainable textile production. For this reason, biodegradable polymers which do not harm the environment and which can disappear without leaving waste in nature are important(Kalaycı et al., 2016; Çebin, 2016).
Polylactic acid (PLA) is the most commonly used biodegradable polymer in textile industry.
2.Polylactic Acid (PLA)
Polylactic acid(PLA), a repeating unit of lactic acid, is a polymer entering the group of aliphatic polyesters. One of the most important characteristics is that it is a biodegradable and compostable thermoplastic polymer produced from starch rich vegetable sources such as corn, sugar cane and wheat.
The lactide monomer forming the polylactic acid can be produced by carbohydrate fermentation or chemical synthesis. Produced lactic acids today are produced by fermentation. PLA polymer is made by ring opening polymerization mechanism. By this method, high molecular weight PLA is obtained(Ray, 2005).
General Features of PLA
- PLA is synthesized from renewable sources.
- PLA is a 100% biodegradable polymer. In nature, it disappears spontaneously in a short period of time such as 0-2 years.
- PLA is an ecological polymer that can decompose in nature without any danger and does not contaminate the soil during its degredation.
The degradation of the PLA in nature takes place in 2 steps:
- High molecular weight (Mn> 4000) chains are hydrolyzed to low molecular weight oligomers (the reaction continues by accelerating with the addition of acid or alcali and the effect of temperature and humidity).
- When Mn <4000, the microorganisms in the environment continue to deteriorate by releasing smaller molecular weight compounds such as carbon dioxide, water and humus(Farrington et al., 2005).
3. Nonwoven Surface Production Techniques
Polylactic acid polymers can be applied to the surface with nonwoven surface technologies and they are widely used. For this purpose, needling and melt blowing methods are mostly used.
3.1. Needle punching method
In the needle punching method, fiber bundles are fed to the cards by air flow after opening and blending. After the carding, with the structure called camel back, the web comes to the laying and folding band and is laid on top according to the desired thickness. Needling is carried out throughout the thickness of the web which is formed by the unbonded fiber. The notched needles move the fibers from one face of the web to the other face to form a complex structure, during the needling, some of the fibers and filaments move up to the needles and another part remains in place and the fibers are pulled down with repeatedly immersed needles. In this way, mechanical bond of the fibers is carried out.
3.2. Meltblowing method
The most common and current definition used for the meltblown method is the one-step process, also it is surface forming method by the way of the thermoplastic raw material is melted in the extruder and self-bonded by spraying the microfibers onto the cylinder from nozzle with high-speed air flow.
Polymer material being melted in the extruder, is sprayed through the nozzle holes with high speed hot air flow and the micro-size fibers are cooled and solidified as they move towards the collection cylinder. The solidified fibers form a randomly oriented non- woven surface in the collection cylinder. Due to the turbulence created by the air flow, the fibers are placed highly complex. Usually a vacuum placed in the collector retracts hot air(Duran, 2004).
4.Usage Areas of Biodegradable Nonwovens
Nonwovens produced by biodegradable PLA which is obtained by using needling and melt blown techniques find a wide range of applications. Textile fibers can be used for growing different human organs. This process involves the planting and cultivation of cells living in human organs on a textile scaffold. This skeleton consists of biodegradable polymers made of biocompatible and degradable polymers and fibers such as biodegradable PLA.
Apart from these, applications where PLA fibers are used in medical field are given below:
- Special membranes for use in nerve injuries,
- In parts which can be implanted to the body,
- In controlled drug release systems,
- Bandage, wound closure etc. materials (Farrington et al., 2005). It is also used as top layer and additive layers in the diaper and women’s hygiene market due to its elastic properties.
PLA has the opportunity to be applied in the automotive field.
- In 2003, PLA was used as a floor covering for Toyota Raum and Prius models. Here, the last group of PLA was closed to prevent hydrolysis.
- In 2008, PLA fiber was used for the Mazda door sill.
- Mitsubishi used a floor covering with Nylon 6 and PLA fibers in a special production vehicle (Auras et al., 2010)
In the agricultural field, PLA is used in applications such as sandbags, weed prevention networks, plant nets and pots. Important features for such applications; it is the process of maintaining structural integrity during use and degradation under the soil after use (Üner and Koçak, 2012).
In recent years, many studies have been carried out in order to generate alternative solutions to the rapid growth of the world population, the depletion of our natural resources and the increase of environmental pollution. Accordingly, there is growing interest in safe, biodegradable synthetic materials that are either recyclable or that do not harm the environment.
In the production of nonwovens can be produced in a short time and at a more affordable cost since it does not contain the stages such as yarn preparation, warp preparation, finishing process and so on. In recent years, the importance of biodegradability in the production of nonwovens with the use of mostly petroleum-derived raw materials has started to be used in the self-destructing raw materials in nature.
In the result of these, researchers are conducting research on the use of these environmentalist raw materials in a wider field. Thanks to their superior fiber properties, the use of these environmentally friendly fibers, which are expanding day by day, is expected to become more widespread.
Auras, R., Lim, L.T, Selke, S.E.M., and Tsuji, H., 2010, Poly(lactic acid): Synthesis, Structures, Properties, Processing, and Applications, A John Wiley & Sons,Inc., Publication.
Çebin B., 2016, Plastik Poşet Kullanımının Çevreye Verdiği Zararlar, (Erişim Tarihi: 10 Mayıs 2017).
Duran, K., 2004, Dokusuz Yüzeyler, Teknik Fuarcılık Yayınları, İzmir, 408s.
Erten, S., 2004, Çevre Eğitimi Ve Çevre Bilinci Nedir, Çevre Eğitimi Nasıl Olmalıdır?, Çevre ve İnsan Dergisi, Çevre ve Orman Bakanlığı Yayın Organı, 65-66.
Farrington, D. W., Lunt, J., Davies, S., Blackburn, R. S., 2005, Biodegradable Sustainable Fibers, Chap-6,Poly(lactic acid) fibers, 191-220.
Kalaycı, E., Avinc, O. O., Bozkurt, A., Yavaş, A., (2016). Tarımsal atıklardan elde edilen sürdürülebilir tekstil lifleri: Ananas yaprağı lifleri. Sakarya Üniversitesi Fen Bilimleri Dergisi, 20(2), 203-221. Ray S.S., Bousmina M., 2005, Biodegrable Polimer/Layered Silicate Nanocomposites, Progress in Materials Science, Vol. 50, No. 8. Tipper, M., Gullemois, E., 2016, Advances in Technical Nonwovens, Developments in the use of nonofibers in nonwovens, 115- 132.
Üner, İ., Koçak, E.D., 2012, Poli(Laktik Asit)’in Kullanım Alanları ve Nano Lif Üretimdeki Uygulamaları, İstanbul Ticaret Üniversitesi Fen Bilimleri Dergisi, 11(22), 79-88.
URL-1: www.total-corbion.com/about-pla/pla-lifecycle/, (Erişim Tarihi: 29 Ağustos 2018). URL-2: www.nptel.ac.in, (Erişim Tarihi: 17 Ağustos 2018).