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What are the key differences in dyeing and finishing processes between polylactic acid fiber and pol
source：www.kingcharmgroup.com | Release time：2026-08-101. Differences in pre-treatment processes
The desizing and refining of polyester can be carried out at high temperatures, using weak alkali to medium strong alkali systems, with a processing temperature of 95-100 ℃. Alkali reduction technology can also be used to etch the fiber surface through high-temperature concentrated alkali, improving the texture of the fabric.
Polylactic acid fibers do not allow strong alkaline and high-temperature alkaline environments. Under high-temperature alkaline conditions, molecular chains will undergo hydrolysis, resulting in a decrease in fabric strength and brittleness. Only weak alkaline or neutral refining agents can be used for refining, and alkaline reduction processes cannot be used at all. The pre-treatment temperature should be controlled within 80-90 ℃, and the treatment time should not be too long. When bleaching with hydrogen peroxide, it is also necessary to strictly control the temperature and pH value, as a high pH can damage PLA fibers. The core difference is that polyester is resistant to alkali treatment, while PLA needs to avoid strong alkali throughout the process.
2. Dyeing process
Polyester uses high-temperature dispersed dyes, with a conventional dyeing temperature of 125-135 ℃ under high temperature and pressure conditions, insulation for 30-60 minutes, and a dye bath controlled at weak acidity. The pH tolerance range is relatively wide, and there is no strict limit on the heating rate.
Low temperature dispersed dyes must be used for polylactic acid fibers, and the upper limit of dyeing temperature should be controlled at 100-110 ℃. It is strictly prohibited to exceed 115 ℃. Excessive temperature can cause significant shrinkage of the fabric, strength attenuation, and even fiber stickiness. The insulation time should be controlled at 40-60 minutes and should not be too long. The dyeing bath maintains weak acidity and pH is controlled at 4-6. Once it becomes alkaline, it will accelerate hydrolysis. The heating process needs to be gentle to avoid wrinkles and discoloration. At the same time, PLA has limited ability to dye dark colors, and the overall color fastness of the finished product is weaker than that of polyester.
Reduce and clean after dyeing
Polyester is commonly cleaned using alkaline reduction, combined with insurance powder and caustic soda, at a temperature of 80-95 ℃, to efficiently remove surface floating colors from the fabric and improve color fastness.
Polylactic acid fibers cannot be cleaned with alkaline reduction, as the combination of alkalinity and high temperature can directly damage the fibers. Only neutral or acidic reduction cleaning solutions can be used, and the amount of insurance powder added must be strictly controlled; The difficulty of removing floating colors is greater, and the color fastness of dark products is the main weakness.
3. Heat setting process
The heat setting temperature of polyester can reach 180-210 ℃, and excellent dimensional stability can be obtained in a short period of time.
The setting temperature of polylactic acid fibers can only be controlled between 80-110 ℃ and cannot exceed 120 ℃. Excessive temperature can cause problems such as fiber softening, shrinkage, loss of strength, and hardening of the hand feel. Due to low temperature setting, the thermal dimensional stability of PLA fabric is not as good as that of polyester. The drying process also requires temperature control and high-temperature drying is prohibited.
4. Printing process
When using polyester for sublimation transfer printing and direct steam printing, high temperature steam evaporation at 170-180 ℃ is used.
When using polylactic acid fiber for thermal sublimation transfer printing, the temperature can only be reduced to 140-150 ℃ while shortening the processing time; The direct steaming process also requires synchronous temperature reduction, as high temperatures can cause fiber damage.
5. Additives and wastewater control
Polyester is compatible with conventional polyester dyeing and finishing auxiliaries, with a large tolerance for pH in the dyeing bath.
Polylactic acid avoids strong alkaline environments throughout the process, prohibits additives that release alkalinity, and maintains a weakly acidic environment throughout the entire process; The dyeing bath should not be left at high temperatures for a long time to prevent fiber hydrolysis and aging.
6. Post production organization of finished products
Polyester can undergo high-temperature pre shrinking treatment and is suitable for various post finishing processes.
The pre shrinking temperature of polylactic acid fibers should not be too high, and weak acidic systems should be preferred as softeners; Finished products are not allowed to be hot pressed at high temperatures.
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