Fibers & Textiles The potential of PLA for the fiber market Injection molders know polylactic acid (PLA) as a stiff, brittle, splintering material with an elongation at break of 3 to 4%. Spun into fibers, a completely different picture presents itself: the fibers obtained are silk-like and the fabrics produced are smooth, skin flattering and with a pleasing drape. Elongation at break can be adjusted between 20% and 200% depending on the degree of stretching. PLA resembles PET (polyethylene terephthalate) in many properties. Similar to PET, PLA can readily be melt-spun into filaments, staple fibers, spunbond nonwovens. As a textile, PLA has many attractive properties, which are similar or sometimes even superior to PET. Such properties include a higher tenacity than natural fibers, excellent moisture transport away from the skin (wicking), natural UV resistance, low flammability and low smoke formation [1]. The annual PET consumption for textile applications amounts to 41 million tonnes (Mt) (2012), which is more than twice the demand for packaging applications (18 Mt). In 2011 the world cotton consumption was 24 Mt, in strong competition to PET. Substitution of only 1% of the world production of PET and cotton would generate a huge growth potential for textile PLA. Given these facts why does textile PLA still only play a limited role in the market – apparently for no obvious reasons? There are convincing environmental arguments in favor of PLA: Its advantages of reducing emissions of greenhouse gases are shown in Fig. 1. Its performance is superior to petrochemical or even natural fibers like cotton. Only cellulose based fibers show lower greenhouse gas emission figures. Fig. 1: Global Warming Potential (from literature review) Source: nova-Institute, Germany, 2013 Fig. 2: Land use of fibres (from literature review) Source: nova-Institute, Germany, 2013 Global warming potential (in kg CO 2 -eq / kg fibre) 5 4 3 2 1 0 -1 PET fibre Range of results Cotton fibre PP fibre PLA fibre Tencel Lenzing Modal Lenzing Viscose 2 1,8 1,6 1,4 1,2 1 0,8 0,6 0,4 0,2 0 0,8 0,9 0,9 > 31 0,7 0,25 ? 0,2 Differences in crop yields! 0,17 0,16 0,42 Cotton fibre Flax fibre Hemp fibre Wool Viscose fibre Lycocell fibre PP / PET fibre PLA fibre (corn) PLA fibre (sugar beet) PLA fibre (sugarcane) PLA fibre (wheat) 12 bioplastics MAGAZINE [05/13] Vol. 8
Fibers & Textiles By Rainer Hagen Product Manager PLA Uhde Inventa-Fischer Berlin, Germany Advantages in land use are commonly not attributed to PLA. It is well known that PLA is made from starch or sugar containing crops which need land for growing. Agricultural land is a limited resource and PLA has to compete with food crops (until non-food raw materials will be available). Fig. 2 represents the findings of a literature review conducted to compare land requirements per ton of fiber, including various natural fibers, cellulose based fibers and PLA fibers. Of course, petrochemical fibers do not require land apart from the industrial site plot where the production plants for the polymer and its precursors are located. PLA and Lyocell (cellulose based) fibers show the lowest land use, less than half of all natural fibers and viscose. Wool has the highest requirement (pastures) because of its specific production conditions. As some scientists consider, fresh water will be mankind‘s most limited resource in future, various fiber materials are compared in Fig. 3 as to their water consumption per kilogram. Apart from wool (almost no water consumption), PLA fibers show advantages over petrochemical (especially PET) and cellulose based fibers. Cotton requires the highest amount of water. This is explained by the need for irrigation of the crop which is done excessively in some parts of the world. The crops for PLA production usually do not need any irrigation. Environmental aspects should, at least in part, drive substitution of PET and cotton by PLA. Other nonenvironmental growth driving factors for textile PLA will be discussed below. Fig. 3: Water use of fibres (from literature review) Source: nova-Institute, Germany, 2013 Water consumption (in l / kg fibre) 1000 900 800 700 600 500 400 300 200 100 0 Range of results Single score 20,000 Cotton fibre Flax fibre Hemp fibre Wool Viscose fibre Lyocell fibre Modal fibre PP / PET fibre Nylon fibre Acrylic fibre PLA fibre Info: Dr. Rainer Hagen is Product Manager of Uhde Inventa- Fischer’s proprietary polylactic acid technology, PLAneo ® . The engineering company is part of ThyssenKrupp Uhde’s Polymer Division and offers together with ThyssenKrupp Uhde Biotechnology cost-efficient processes for the production of non-petroleum-based chemicals as well as plastics, such as lactic acid, lactide and polylactic acid together with succinic acid and polybutylene succinate to fulfill the vision of sustainably replacing a considerable amount of conventionally produced materials in the near future. bioplastics MAGAZINE [05/13] Vol. 8 13
