PLA fiber is made from lactic acid derived from starch. It belongs to the type that completes the natural cycle and is a biodegradable fiber. This fiber does not use chemical raw materials such as petroleum at all. Under the action of microorganisms in soil and seawater, its waste can be decomposed into carbon dioxide and water without polluting the earth's environment. Since the initial raw material of this fiber is starch, its regeneration cycle is short, about one to two years, and the carbon dioxide it produces can be reduced in the atmosphere through the photosynthesis of plants. When burning PLA fiber, there is almost no nitrogen monoxide, and its combustion heat is about one-third of that of polyethylene and polypropylene.
Uses of corn fiber:
Polylactic acid fiber is a lactic acid polymer synthesized from lactic acid contained in the human body, and it is absolutely safe for the human body. Through testing, the circular knitted fabric made of corn fiber does not irritate the skin, is beneficial to human health, and provides a sense of comfort.
Polylactic acid fiber has superior properties, with excellent drapability, smoothness, moisture absorption and breathability, natural antibacterial properties, a weakly acidic property that makes the skin feel at ease, good heat resistance and anti-ultraviolet function, and is full of luster and elasticity. The drapability of the PLA fiber fabric, the smooth feeling close to the skin, the softness of the fabric, hydrophilicity, and color luster are all excellently reflected, giving corn fiber significant development advantages in close-fitting underwear, sportswear, etc. In 2004, three well-known domestic brands, Shanghai Duocai, Qingdao Nuanbeier, Shanghai Kelefei, etc., had already launched thermal underwear using corn fiber.
Blending corn fiber with natural fibers such as cotton and wool to make new textile products, it has good shape retention, better gloss, an excellent silk-like hand feel, good moisture absorption and quick-drying effect, combining the effects of being stiff, having good elasticity, and being glossy.
In addition to being used in clothing, it can also be widely applied in civil engineering, buildings, agriculture and forestry, aquaculture, the paper industry, healthcare, and household items. PLA fiber can also be used to produce biodegradable packaging materials.
Renewable raw materials:
PLA fiber uses natural and renewable plant resources as raw materials, reducing the dependence on traditional petroleum resources and meeting the requirements of sustainable development in the international community. It combines the advantages of synthetic fibers and natural fibers, and at the same time has the characteristics of a complete natural cycle and biodegradability. Compared with conventional fiber materials, corn fiber also has many unique properties, so it has received extensive attention from the international textile industry.
Environmental protection:
With the enhancement of human awareness of protecting the earth, awareness of energy depletion, safety awareness, and clothing hygiene awareness, as well as the large-scale industrial production of PLA resin and the continuous expansion of the application fields of corn fiber, it has been recommended by many experts as an "environmental cycle material in the 21st century" and is an ecological fiber with great development potential.
Advantages and Application Key Points of Polylactic Acid (PLA) Fiber
Since the National Economic and Trade Commission issued the "Plastic Restriction Order" in 1999, the Chinese government has issued several plastic ban orders. On January 19, 2020, the National Development and Reform Commission and the Ministry of Ecology and Environment announced the "Opinions on Further Strengthening the Management of Plastic Pollution". Starting from February 2020, many provinces and cities such as Hainan Province, Hebei Province, Guangxi Zhuang Autonomous Region, Qinghai Province, Inner Mongolia Autonomous Region, Yunnan Province, Guangdong Province, Shandong Province, Henan Province, Zhejiang Province, etc. successively introduced strict plastic pollution management measures, aiming to significantly reduce the consumption of disposable plastic products.
Polylactic acid is a typical synthetic fully biodegradable material. Due to its reliable biological safety, biodegradability, environmental friendliness, good mechanical properties, and ease of processing and forming, it has broad application prospects in biomedical polymers, the textile industry, the plastics industry, the furniture industry, agricultural mulch films, and the packaging industry.
I. Introduction to Polylactic Acid Fiber
Polylactic acid (Polylactic acid, PLA) fiber, abbreviated as PLA fiber, is a fiber obtained through processes such as fermentation, condensation, polymerization reaction, and melt spinning from crops represented by corn. Since lactic acid is a natural substance existing among animals, plants, and microorganisms and is easy to degrade naturally, polylactic acid fiber has the characteristics of environmental protection and sustainability.
Polylactic acid can replace some petroleum-based chemical fibers and plastics. The packaging bags made of polylactic acid are biodegradable and pollution-free and can replace traditional plastic bags; the fabrics spun from polylactic acid are non-toxic, antibacterial, anti-mite, and difficult to burn; the daily necessities and building materials products made of polylactic acid are green, environmentally friendly, and safe. It not only opens up broad space for the leapfrog development of industries such as cotton textile, petroleum chemical fiber textile, and plastic daily necessities but also provides an important solution to the problem of "white pollution".
II. Application Fields
- Spinning Field
In the aspect of spinning, polylactic acid fiber can be spun pure or blended. It can be blended with various other fibers such as cotton, linen, silk, wool, viscose, and lyocell to produce fabrics with different styles.
- Clothing Field
Based on the friendly performance of polylactic acid fiber to human skin, as well as the functions of moisture wicking and quick drying, lightweight warmth, and fluffiness and softness brought by special profiled cross-section fibers, it will be widely used in a series of clothing textiles such as sports and leisure clothing, school uniforms, underwear, home textiles, baby and children's clothing, gloves and socks, and thermal clothing.
- Home Textile Field
The natural antibacterial, anti-mite, anti-mildew, and difficult-to-burn properties of polylactic acid fiber are also suitable for decorative textiles (indoor products, bedding, and outdoor products), including carpets, sofa covers, curtains, towels, bath towels, bed sheets, quilt covers, quilt surfaces, pillow cores, quilt cores, hotel linen, as well as a series of products such as outdoor blankets and tents.
- Nonwoven Fabric Field
Polylactic acid fiber is also suitable for producing nonwoven fabrics, such as spunlaced nonwoven fabrics, hot air/hot rolling nonwoven fabrics, spunbonded, and melt-blown nonwoven fabrics. Polylactic acid fiber is also widely used in industrial textiles and can be applied to facial masks, cotton soft towels, dry/wet wipes, baby diapers, and female hygiene products; it is also suitable for the medical and health field: PLA protective masks, protective clothing, protective caps, protective foot covers, disposable medical mattresses, disposable hygiene products, and air filters, etc.
In addition, in the elderly care field: mainly used for special quilts, cushion towels, clothes for the elderly, as well as daily necessities such as curtains, carpets, tableware, and furniture; in agriculture, forestry, animal husbandry, and fishery: mainly playing a role in the form of nonwoven fabrics, making biodegradable agricultural textile products, and being applied to ecological agriculture, soil and water conservation, environmental governance, etc.; in the construction field: used for ground covering reinforcement materials; in the paper industry field: PLA fiber is added to pulp to produce various types of paper.
III. Application Key Points
- Spinning Process
When blending polylactic acid fiber with modal, the weighing fiber mixing and sliver mixing methods are used to produce blended yarns, and the two have different impacts on the yarn quality. Generally speaking, when using the loose fiber weighing mixing method, the quality deviation of the produced yarn is small, the unevenness of single yarn strength is small, and there are fewer neps and hairiness; while the yarn produced by the sliver mixing method has higher strength and fewer thin places. Both mixing methods have their own advantages and disadvantages. In actual production, the appropriate mixing method can be selected according to product requirements, and attention also needs to be paid to controlling the temperature and humidity in the workshop.
When blending polylactic acid fiber with negative ion viscose fiber, in the spinning process, the opening and cleaning process and carding process of polylactic acid fiber and negative ion viscose fiber adopt the same process. To ensure the quality of the blended yarn of polylactic acid fiber, negative ion viscose fiber, and cotton, the quality of semi-finished products should be strictly controlled, and each workshop should maintain stable and appropriate temperature and humidity to ensure the smooth progress of the spinning process. Blending polylactic acid fiber and negative ion viscose fiber with cotton can make full use of their respective advantages, such as the moisture absorption of cotton fiber. The clothing produced from the blended yarn is a functional health product with good breathability, stable size, and comfortable wearing.
When blending polylactic acid fiber with spandex to produce elastic core-spun yarn, select spandex filament as the core filament and polylactic acid staple fiber as the outer wrapping fiber to spin the core-spun yarn, and a polylactic acid fiber/spandex elastic core-spun yarn with better elasticity, wear resistance, and excellent hand feel than ordinary staple fiber yarn can be obtained. When spinning the core-spun yarn of polylactic acid fiber, its spinning process flow is not much different from that of ordinary chemical fiber. The entire process flow is similar to that of cotton-type fiber spinning, which is: opening and cleaning → carding → drawing → roving → spinning. Improve each process. When the fineness of the spandex core filament is 77dtex, through spinning practice, when the content of the core filament accounts for 5.658% of the core-spun yarn, the pre-draft multiple of the core filament is 3.91 times, and the yarn twist is 680 twists/m, the breaking strength and breaking elongation of the spun yarn are the highest, the evenness is good, and an ideal covering effect and elasticity can be obtained.
- Nonwoven Process
The unique advantages of polylactic acid fiber determine the broad prospects for the development of its deep-processed products. The spunlaced nonwoven fabric developed and produced with it has the advantages of no pollution in the production process, which not only has far-reaching significance for environmental protection but also will have an immeasurable impact on human health. Appropriate adjustments to key processes such as the opening and cleaning process, carding process, and spunlacing process during the production process can produce products of different specifications and qualities that meet the needs of users. For example, the adjustment of the opening and cleaning process: According to the characteristics of polylactic acid fiber, the principle of formulating and adjusting the opening and cleaning process is to loosen more and discharge less, feed in thin layers and quickly, and beat lightly and move quickly, while removing impurities (defects) during the loosening process. Drying temperature: The melting temperature of polylactic acid fiber is lower than that of other spunlaced raw materials, and the drying temperature should be controlled within 110°C.
- Dyeing and Finishing Process
For the pre-dyeing treatment, dyeing, and post-finishing of knitted/woven, interwoven/blended fabrics, the principles of low temperature, low alkali, and short process should be followed. Polylactic acid fiber has a low dyeing temperature, a low setting temperature, and does not use strong alkali, so it conforms to the trend of energy conservation and emission reduction.
IV. R&D Trends
Polylactic acid fiber has many advantages such as high strength, large elongation, excellent drapability, good resilience, good anti-ultraviolet performance, low smoke generation, and low flammability, but it has some deficiencies such as low moisture regain, poor moisture absorption, poor conductivity, poor cohesion, low glass transition temperature and melting point, and poor resistance to strong alkali. In order to give full play to the excellent properties of polylactic acid fiber, the process should be improved and adjusted in spinning, weaving, dyeing and printing, and sewing according to its characteristics to meet the needs of new fiber production.
Although the dyeing performance of polylactic acid fiber is similar to that of polyester, it is different from the polyester dyeing process currently used in dyeing factories. Polylactic acid is prone to hydrolysis at high temperatures and is scrapped during high-temperature setting, and the special dyes for polylactic acid are not yet mature, resulting in an increased risk of dyeing. Polylactic acid fiber is prone to degradation during the dyeing and processing process and has poor alkali resistance. How to improve the dye uptake rate and fastness of polylactic acid fiber and reduce the cost is a key technical issue that urgently needs to be solved for the industrialization of polylactic acid and its products.
In addition, chemical modification can be carried out, mainly cross-linking and grafting on the molecular chain; or physical modification, including graft modification, cross-link modification, toughening modification, filling modification, and reinforcement modification, which can effectively improve the toughness, flexibility, strength, etc. of polylactic acid products and expand their application range.
