e-Newsletter 55

TECHNOLOGY INSIGHTS

Cellulose-based PFC-free Water Repellent Surface Finish

Durable water-repellent (DWR) finishes add value by conferring a water repellent property to textile products.

Such finishes rely on the unique water repellent property of long-chain perfluoroalkyl groups, and are usually achieved by the application to textiles of perfluorochemicals (PFCs) such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA).

However, PFCs have two significant drawbacks:

  1. They are non-biodegradable; studies show that PFCs are bio-accumulative and harmful to marine species.
  2. They are classified as potentially carcinogenic to humans.

These serious issues have led many countries to ban the use of PFC-based materials in the manufacture of DWR textiles.

To create a sustainable alternative, this project has developed a novel water-repellent surface finish that makes use of PFC-free recycled cellulose material.

The recycled cellulose materials are derived from a hydrothermal treatment (developed by HKRITA) which selectively decomposes cotton polyester blends into cellulose powders and polyester fibres; the latter remain intact during the treatment.

The recycled cellulose powders can be converted to a high- value DWR surface finish through a two-step chemical process.

  1. The first step involves carrying out hydrophobic modification of the recycled cellulose powders to make them water repellent. This is achieved via laccase/TEMPO-catalyzed oxidation and grafting reaction.
  2. The second step involves adding functional additives to improve the washing durability properties of the fabric.

Finally, the surface finish solution is applied to the fabric by a pad-dry-cure or dip coating process.

The water-repellent properties achieved are comparable to those of existing commercial products.

This project demonstrates that a water-repellent function can be achieved by a PFC-free process that uses natural and recycled materials. The project puts forward a sustainable solution to a serious problem and constitutes another step in the journey towards a circular economy.

 
Research Institution:  The Hong Kong Research Institute of Textiles and Apparel
Enquiry: info@hkrita.com
Website: www.hkrita.com
 
Project video of the Cellulose-based PFC-free Water Repellent Surface Finish Cellulose-based PFC-free water repellent surface finishes add value to textile products