Production process of polylactic acid fiber
Polylactic acid, as a linear straight-chain macromolecule, has a variety of stereostructures due to the presence of chiral carbon atoms in its structural units, including polydextrorotatory lactic acid (PDLA), polylevorotatory lactic acid (PLLA) and polyracemic lactic acid (PDLLA). In the production of polylactic acid fiber, PLLA is usually selected, and its isotactic molecular structure gives it strong crystallinity, while the structures and properties of the other two polylactic acids are not suitable for spinning.
Polylactic acid fiber is made by converting polylactic acid resin into synthetic fiber by solvent spinning or melt spinning. Under suitable conditions, PLA can be prepared into a colloidal solution or melted into a melt, then extruded into a thin stream through a spinneret, and solidified into fiber in a specific medium. Although solvent-spun fibers perform better in mechanical properties, the complexity of the solvent spinning process, the difficulty of solvent recovery, and the harshness of the spinning environment make its cost relatively high and unsuitable for large-scale industrial production. Therefore, the commercial production of polylactic acid fiber currently mainly adopts the melt spinning process. This method not only has good reproducibility, low environmental pollution, and low production cost, but also facilitates automated and flexible production.
In the industrial production of polylactic acid fiber, a one-step high-speed spinning method or a two-step spinning-stretching method is usually used. The one-step method has a higher yield, which is 6 to 15 times that of the two-step method; and the two-step method can provide better fiber mechanical properties.
Structural characteristics of polylactic acid fiber
Polylactic acid fiber presents a unique full-core structure, and its longitudinal surface is covered with irregular spots and discontinuous stripes. The formation of these spots and stripes is mainly attributed to the large amount of non-crystalline parts in polylactic acid. When water, bacteria and oxygen are present, these non-crystalline parts will decompose rapidly to produce carbon dioxide and water. In addition, the cross-section of polylactic acid fiber is approximately circular, but there are also some spots on its surface. These spots and the unique structure of the fiber together constitute the characteristics of polylactic acid fiber.
Chemical structure of polylactic acid fiber
The chemical structure of polylactic acid fiber is also unique. There are a large number of active groups such as carboxyl and hydroxyl groups in its molecular chain, which make polylactic acid fiber show high activity in chemical reactions. It is the existence of these active groups that gives polylactic acid fiber excellent performance in biodegradation. When polylactic acid fiber encounters water, bacteria and oxygen, these active groups will guide the fiber to biodegrade rapidly, and finally produce harmless carbon dioxide and water. This characteristic makes polylactic acid fiber have broad application prospects in the field of environmental protection.
Longitudinal structure of polylactic acid fiber
The longitudinal structure of polylactic acid fiber presents certain characteristics. There are many tiny grooves and holes on the surface of the fiber, which increase the specific surface area of the fiber, thereby improving the adsorption performance of polylactic acid fiber. At the same time, these grooves and holes also provide more attachment sites for bacteria and enzymes, further promoting the biodegradation process of polylactic acid fiber. In addition, the longitudinal structure of polylactic acid fiber also has a certain regularity, which enables the fiber to maintain good physical properties during processing.
Cross-sectional characteristics of polylactic acid fiber
The cross-section of polylactic acid fiber presents a unique morphology. Its compact structure and high regularity make polylactic acid fiber excellent in physical properties. In addition, its special structure on the cross section also has a significant impact on the performance of the fiber, such as the improvement of adsorption performance and biodegradability. At the same time, this compact and regular structure also makes polylactic acid fiber have a wide range of application potential in the textile field.
Comparison of the performance of common textile fibers and PLA fibers
By comparing the performance of polylactic acid fiber with other common textile fibers, we can find that polylactic acid fiber has shown superiority in many aspects. Its unique longitudinal and cross-sectional structure gives it high adsorption and easy biodegradability, making it highly regarded in the field of environmental protection. At the same time, its excellent physical properties also make polylactic acid fiber have broad market prospects in textile applications.
(1) Moisture conductivity and air permeability
The official moisture regain of polylactic acid fiber is between 0.4% and 0.6%, indicating that its hygroscopicity is relatively weak, while its hydrophobicity is relatively good, so that the product remains dry during use. However, the polar carbon-oxygen bonds of polylactic acid fibers can combine with water molecules to promote the transfer of water vapor inside the fiber, thereby achieving the function of quickly discharging moisture from the human body surface, showing excellent wicking effect and breathability. Its transverse cross-section is flat and circular, and the middle is approximately circular. The longitudinal surface is smooth and uniform, and is columnar, but the surface is distributed with grooves, holes or cracks of varying depths. These characteristics enable the fiber to form a significant capillary effect, further enhancing its wicking and diffusion capabilities. In addition, the curling characteristics of polylactic acid fibers also bring a fluffy feeling to its products, thereby improving the moisture conduction ability of the fabric, making PLA fibers perform well in wicking and diffusion.
(2) Biodegradability
As a polymer material, polylactic acid is polymerized from small molecule lactic acid generated by microbial fermentation of biomass raw materials such as cassava, beets, sucrose, and straw cellulose. Polylactic acid fibers are prepared from polylactic acid raw materials through melt spinning and other technologies. Since the raw materials of PLA fiber are all derived from biomass, it can be completely degraded in the natural environment. Its final products are H2O and CO2, which are environmentally friendly and can be absorbed by natural cycles.
(3) Combustion performance
The combustion heat of PLA fiber is 19kJ/kg, and the smoke density is 63m2/kg. During the combustion process, it produces CO2 and H2O, and no toxic gases are released, so it is a low-pollution fiber. Its limiting oxygen index is 26%, which is higher than most fiber materials.
Dongguan Liansheng Non woven Technology Co., Ltd. was established in May 2020. It is a large-scale non-woven fabric production enterprise integrating research and development, production, and sales. It can produce various colors of PP spunbond non-woven fabrics with a width of less than 3.2 meters from 9 grams to 300 grams.
Post time: Apr-09-2025