Polylactic acid fiber, commonly known as "corn fiber", named after the Japanese bell spinning in the 1990s introduced a blend of polylactic acid fiber and natural fibers (CornFiber).
As the name suggests, PLA and corn are "relatives", the first generation of raw materials for PLA is corn, which can be traced back to: corn a>starch a>sugar a>lactic acid a>polylactic acid. All contain starch, cellulose and hemicellulose natural biomass raw materials, can be used to produce lactic acid, and then polymerization production of polylactic acid. In order to avoid "competition for food, food and land", can also use non-food crops (such as cassava) as raw materials, and even rice straw, straw and other agricultural waste as raw materials for the production of lactic acid, and then the production of polylactic acid.
Polylactic acid fiber process and application
Currently, the mainstream PLA fibers are prepared by using high optical purity levulinic acid (PLLA) as the raw material, taking advantage of its high crystallinity and high orientation characteristics, and through different spinning processes (melt spinning, wet spinning, dry spinning, dry and wet spinning, electrostatic spinning, etc.).
Among them, melt-spun PLA fibers (filaments, staple fibers) can be used in apparel, home textiles and other fields, the production equipment and process close to polyester, with good spinnability as well as moderate performance. After appropriate modification, PLA fibers can obtain superior flame retardant (self-extinguishing) and natural antibacterial properties. However, there is still room for improvement of melt-spun PLA fibers in terms of mechanical strength, high temperature dimensional stability, resilience and aging resistance.
Wet spinning, dry spinning, wet and dry spinning and electrostatic spinning polylactic acid fiber (membrane) is mainly used in the field of biomedical applications, representative products include: high-strength absorbable sutures, drug carriers, anti-adhesion septum, artificial skin, tissue engineering scaffolds and so on. With the surge in demand for disposable nonwoven fabrics in medical, sanitary materials, filtration, and decorative fields, PLA nonwovens have become one of the hotspots for research and development.
Characteristics of Lactic Acid Fiber
The mechanical properties of melt-spun PLA fibers are moderate, the tensile strength is usually 2.0-4.0cN/dtex, close to wool but lower than polyester, nylon, Young's modulus is usually 50-70cN/dtex, the elongation at break is usually 20-40%, and other properties such as moisture retention and moisture absorption are close to polyester. After appropriate modification, polylactic acid fiber can obtain better flame retardant (self-extinguishing) and anti-bacterial and anti-mite properties. There is still room for improvement of PLA fibers in terms of strength, high-temperature dimensional stability, resilience and aging resistance.
One of the widely touted benefits of PLA fibers is that they are biodegradable or absorbable in the body. Biodegradation properties must be measured under standard composting conditions, and the degradation products are water and carbon dioxide. Conventional PLA fibers undergo only slow hydrolysis or even imperceptible hydrolysis in normal use or in most natural environments, e.g., they basically do not degrade when buried in natural soil for 1 year, while they degrade in room temperature composting conditions in about 1 week.
The degradation and absorption of PLA fibers in vivo is greatly affected by their crystallinity, and simulated in vitro degradation experiments show that highly crystalline PLA fibers still basically maintain their shape and nearly 80% of their strength after 5.3 years, and that it may take 40-50 years for them to degrade completely.
Plastarch PLA fibers can be composted in 1~2 months with a household garbage disposal and in 1~2 weeks with a factory garbage disposal.
As a research and development production of more than half a century of chemical fiber varieties, polylactic acid fiber current actual use is still less than one-thousandth of polyester, the cost factor is certainly in the foreground, the performance of the short board can not be ignored. Through the modification to avoid the shortcomings of the development of PLA fiber is the way to go.
