Sea-island composite fibers have better properties than natural fibers. They are becoming more popular in the textile industry.
1. Common Problems with Sea-Island Composite Fibers
Most sea-island composite fibers use alkaline-soluble polyester (COPET) as the sea component. These fibers need strong alkaline conditions at high temperatures (≥95°C, pH value ≥13) to break down COPET. However, PET also degrades under these conditions, losing mechanical strength. When using COPET as the sea component and PET as the island component, the PET partially hydrolyzes, reducing strength and elongation at break. This makes it hard to produce high-quality sea-island composite fibers.
2. New Production Process
A new process for making PET/COPET sea-island composite fibers includes these steps:
- Preparation: Polyester resin chips are crystallized and dried. They are mixed with a modifier and melted in a screw extruder to form PET melt.
- COPET Treatment: Alkaline-soluble polyester resin chips (COPET) are crystallized and dried. They are melted in a screw extruder to form COPET melt.
- Melt Combining: The PET and COPET melts are transported to a sea-island composite component. They combine through a spinneret to form a composite melt.
- Fiber Formation: The composite melt is extruded through spinneret holes to form fiber bundles. These bundles are cooled, oiled, and wound to create the fiber composite precursor.
- Post-Treatment: The fiber composite precursor is treated in an alkaline solution, then washed and dried to get PET/COPET sea-island composite fibers.
3. Features of Sea-Island Composite Fibers
These fibers use alkaline-soluble polyester as the “sea” component and modified polyester as the “island” component. They have higher mechanical strength, better elasticity, and stronger resistance to acids and alkalis compared to regular PET/COPET fibers.
4. Innovative Modified Polyester Resin
The modification process uses propionyl peptide ester and 1,5-pentanediol to create a diol ester. ( I previously wrote an article about the applications of 5-pentanediol, details here.)This reacts with isophorone diisocyanate and 1,4-butanediamine to produce propionyl peptide polyester urea. This is combined with polyester resin to make modified polyester resin. The modified resin has many urea groups, which form strong hydrogen bonds, making the polyester structure more stable. This improves resistance to acids and alkalis and enhances mechanical properties.
Conclusion
The new method and materials greatly improve traditional sea-island composite fibers. These fibers are more durable, elastic, and resistant to harsh conditions, opening new possibilities for high-performance textiles.
