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What is the melting point of polylactic acid fiber
source：www.artisanleather.com.cn | Release time：2025-09-231、 Core influencing factors: key factors determining melting point differences
The stereoregularity of raw materials (the most important factor) is that polylactic acid is polymerized from lactic acid monomers. Lactic acid exists in two configurations: "L-lactic acid" and "D-lactic acid", and their ratio directly affects the crystallinity of polylactic acid, which in turn determines its melting point
High left-handed content PLA (L-PLA, L-lactic acid content>95%): high stereoregularity, strong crystallization ability (crystallinity of about 30% -40%), high melting point. Conventional commercial fibers are mostly of this type, with melting points concentrated between 160 ℃ -175 ℃ (such as PLA short fibers for clothing and long fibers for textile fabrics, with melting points usually between 165 ℃ -170 ℃);
L-D-mixed PLA (DL-PLA, L/D-lactic acid ratio close to 1:1): low stereoregularity, low crystallinity (<5%), even amorphous structure, significantly reduced melting point, about 150 ℃ -155 ℃, and wide melting point range (no obvious sharp melting point peak), mainly used in fields with low heat resistance requirements (such as disposable non-woven fabrics).
Co polymerization modification (a common method to lower the melting point) is used to improve the toughness or processability of PLA fibers by introducing a small amount of co monomers (such as caprolactone, ethylene glycol, etc.). Co polymerization can disrupt the regularity of molecular chains, reduce crystallinity, and thus lower the melting point
For example, after copolymerization of PLA with 5% -10% caprolactone, the melting point of the fibers can be reduced from 170 ℃ of pure L-PLA to 145 ℃ -155 ℃, while the toughness is improved, making it suitable for producing textile products that require low-temperature heat setting (such as knitted underwear, to avoid damage to the fibers during high-temperature setting);
The higher the copolymerization ratio, the more significant the decrease in melting point (such as when the copolymer monomer content is greater than 15%, the melting point may be lower than 140 ℃), but it is necessary to balance the melting point and fiber strength (excessive copolymerization ratio can lead to a decrease in strength).
The fiber processing technology (slightly affecting the melting point), fiber spinning (melt spinning/solution spinning), and the temperature and stretching ratio during the stretching and shaping process can affect the crystalline perfection of the fibers, thereby fine-tuning the melting point:
During melt spinning, if the spinning temperature is too high (>200 ℃) or the stretching ratio is insufficient, it can lead to low fiber crystallinity, and the melting point may be 5 ℃ -10 ℃ lower than conventional products;
After spinning, high-temperature setting (such as 120 ℃ -140 ℃ hot stretching) can improve the crystal perfection, and the melting point will slightly increase (usually by 2 ℃ -5 ℃, such as the melting point of PLA filament after setting rising from 165 ℃ to 168 ℃ -170 ℃).
2、 Key considerations: The correlation between melting point and actual use
Heat resistance limitations: The melting point of PLA fibers (150 ℃ -175 ℃) is lower than that of conventional synthetic fibers (such as polyester melting point of 255 ℃ -260 ℃, nylon melting point of 215 ℃ -225 ℃). When using, it is necessary to avoid prolonged exposure to high temperatures above 150 ℃ (such as ironing temperature recommended to be ≤ 120 ℃, otherwise it is easy to soften and deform);
Balance between melting point and degradability: Although high melting point PLA fibers (high crystalline L-PLA) have good heat resistance, their degradation rate is relatively slow (taking 1-2 years in natural environments); Low melting point DL-PLA or copolymer PLA fibers have a faster degradation rate (3-6 months) and are suitable for disposable or short-term use scenarios.
summary
The melting point core of polylactic acid fibers is concentrated between 150 ℃ and 175 ℃, among which:
The melting point of PLA fibers (high L-lactic acid content) commonly used in commercial textiles is mostly between 160 ℃ and 170 ℃;
Low crystalline, co polymerized or disposable PLA fibers have a low melting point, about 145 ℃ -155 ℃;
When selecting, it is necessary to combine the heat resistance requirements of the application scenario (such as clothing, industrial use) with the processing requirements (such as spinning, composite), and balance the melting point and fiber properties.
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