Developments in functional finishing of cotton fibres – wrinkle-resistant, flame-retardant and antimicrobial treatments

Abstract

Natural fibres, especially cotton, are still the most important kinds of fibres because of their numerous advantages such as high tensile strength, good abrasion resistance, high moisture absorption, quick drying and absence of static problems. However, cotton has poor elasticity and resilience, i.e. poor wrinkle recovery property. It is weakened easily by acids and resin chemicals used in finishing processes. In addition, fabrics made from untreated cotton fibres burn easily with a high flame velocity and are prone to being attacked by mildew and bacteria. Reducing wrinkling, flammability and microbial attacks of cotton fibre have been the major challenge facing the textile industry. The aim of this paper is to provide an overview of the current status of developments in functional finishing of cotton fabrics. Functional finishing agents, especially cross-linking agents, are embedded in cotton fabrics with the aid of acid catalysts, followed by drying and curing at high temperatures. The treated cotton fabrics often suffer from decrease in tensile strength, tear strength, abrasion resistance and sewability with a stiff, harsh and uncomfortable feel. Moreover, chemicals present in finishing agents react in the curing process to form some residues, which may even release free formaldehyde, which is of carcinogenic nature. The amount of formaldehyde remaining in the finished product depends largely on the amount and kind of finishing agents and catalysts used, as well as the curing conditions. Over the last decade, there have been many changes in the textile industry. The importance of environmental issues, which influence the direction of chemical finishing and reshaping the types of speciality chemicals used in textile wet processing, is a dominant theme in the market. Apart from the trend towards the use of environment-friendly chemical finishes, chemicals are being specially formulated for ease of application and high quality finishing. In this paper, the latest developments in textile functional finishing of cotton fabrics are critically reviewed and precisely described. The use of plasma surface treatment is one of the easiest and the most efficient ways to improve post-finishing of cotton fabrics. In general, the active species produced in plasma carry high energy to promote surface functionalisation reactions causing a sputtering or etching effect on cotton fabrics. The altered surface characteristics can still retain inherent advantages of cotton substrates and enhance material properties by incorporating with a large variety of chemically active functional groups. Furthermore, it may be necessary to add a suitable co-reactant to enhance the performance of chemical finishing and minimise the side effects. Recently, some finishing formulations involving catalytic effects induced by co-reactants have been developed. The aim of this paper is to critically and comprehensively examine the existing developments in textiles functional finishing, with special focus on wrinkle-resistant, flame-retardant and anti-microbial finishing of cotton fabrics. In addition, further developments of these finishing processes are discussed.

Keywords:

• wrinkle-resistant
• flame-retardant
• antimicrobial
• plasma treatment
• metal oxide

Acknowledgement

The work described in this paper was supported by grants from the Research Grants Council of The Hong Kong Special Administrative Region, China (Project Nos. PolyU 5192/08E and PolyU 5173/11E) and The Hong Kong Polytechnic University (Project No. RP4S).