Shanmugam ANANDAPRIYA1 & Sivalingam THAMBIDURAI2

1.Asst. Professor, Dept. of Textile Chemistry,
SSM College of Engineering, Komarapalayam, T.N., India.

2.Professor, Dept. of Industrial Chemistry,
Alagappa University, Karaikudi, T.N., India

Abstract:

Textile industry is one of the glooming industries and the demand for manmade fibres and its blends has been significantly increasing in the world market due to their increased applications for various end uses. The high crystalline nature of synthetics and physically hydrophobic nature serves as barrier for easy processing. Several attempts have been made in the last few years to increase the ecofriendliness in the dyeing and finishing process. Biotechnology finds a solution for this problem. Much research literature is not available about the usage of enzymes for manmade fibres. This paper discusses a general overview of enzymes and enzymatic treatment. The paper focuses on ester cleaving enzymes like cutinase, polyesterase, lipase, which are found to be effective in improving the properties of polyester and its P/C blends.

Key words: Manmade fibres, biotechnology, enzymes.

Introduction:

Biotechnology is defined by experts as the application of scientific and engineering principles to the processing of materials by biological agents to provide goods and services [1]. Enzymes are biocatalyst that accelerates the chemical reaction [2]. Among the variety of chemical and mechanical energy and process used in textile wet processing, enzymes are gaining importance due to its ecofriendly production of fibres and finishing agents, biological degradation, the use of renewable resources, saving of fossil resources, Saving water and energy[3].

The application of enzymes in industrial textile processes began around 1857, when malt extract was used to remove size from fabrics. Enzymes have been used for desizing, scouring, polishing, washing, degumming, peroxide degradation in bleaching baths for natural fibres and as well as for decolourisation of dyehouse wastewaters, bleaching of released dyestuff and inhibiting dye transfer [4]. In this paper it is intended to understand and discuss about the major enzymes under development for manmade fibres and its blends.

Enzymes Properties & Mechanism of Action:

The Enzymatic Proteins are composed of amino acids with a variety of side chains ranging from non-polar to acidic, basic and neutral polar, aliphatic and aromatic compounds. The activities of enzymes are determined by their three-dimensional structure[2]. Enzymes are very specific and it was suggested by Emil Fischer in the 1890s that this was because the enzyme had a particular shape into which the substrate(s) fit exactly. This is often referred to as "the lock and key" model. An enzyme combines with its substrate(s) to form a short-lived enzyme-substrate complex [6].

Need for Enzymatic Treatment for Synthetic Fibers

Synthetic fibers represent almost 50%of the worldwide market of textile fibers. Major characteristics of synthetic fibers are their hydrophobicity and low reactivity with most common chemical agents1. The low hydrophilicity makes those fibers less suitable to be in contact with the human skin and the low reactivity makes the fiber unsuitable to act as carrier to other chemical finishing agents. Strong alkaline treatments can improve hydrophilicity and chemical reactivity of synthetic fibers but the treatment extension is hard to control, leading to unacceptable levels of strength loss [5].

Biotechnological Treatments for Polyester Materials:

Among all the synthetic fibers we can find that the demand for PET textile fibres increasing, but also the desire for improved textile properties such as wettability or hydrophilicity. Furthermore, effects like better dyeability with water-soluble dyes or surface functionalisation for special purposes like coupling of flame retardants are desirable from the perspective of the textile industry. Besides textiles, enzymatic modification of synthetic materials has immense potential for specialty applications such as the different screening in medical devices and electronics [7, 8]

In recent years, there have been major research efforts to find technologies that can meet these demands. Two technologies suitable for this purpose have been identified, which are plasma technology on the one hand, and enzymatic technologies on the other hand [9,10]. Both innovative technologies show the advantage of lower energy consumption and avoid the use of harsh chemicals, when compared to a chemical surface treatment. Potentially a great variety of enzymes could be used to modify the surface of PET: Amongst the hydrolytic enzymes, besides esterases and lipases, enzymes acting on natural polyesters such as cutinases or polyhydroxyalkanoate depolymerases could have potential [11,12]. However, there are a number of reports on the hydrolysis on synthetic aliphatic polyesters while aromatic polyesters seem to be more recalcitrant to microbial/enzymatic attack [13, 14].

Previously, treatment of PET with lipases has been shown to improve wetting and absorbency of PET fabrics while strength was retained [15]. Compared to chemical hydrolysis by alkali treatment, enzymatic surface hydrolysis has the advantage of maintaining mechanical stability, because the enzyme cannot penetrate into the fibre and is therefore restricted to reacting on the very surface only. Improved stain resistance, wettability and/or dyeability of PET fabrics treated was reported with so-called polyesterases (lipases, esterases or cutinases) [16]. Pilling properties of polyester fabrics were found to be improved by treatment with enzyme preparations from Humicola sp. Candida sp. and Pseudomonas sp. [17].

Oxidative enzymes, such as laccases, have also been shown to hydrophilize the PET surface [18]. Although oxidative modification with laccases would be especially interesting since functionalization could be achieved without cleavage of the polymer, there is no detailed mechanistic or application related data available yet. The dyeability of polyester fabrics were found to be improved by treatment with cutinase enzyme preparations from Fusarium solani pisi due to hydroxyl groups formation at the fiber surface [19].

Polyethylene terephthalate (PET) can be modified by a polyesterase from Thermobifida fusca.

Biocatalysis and Biotransformation 22: 347-351 (2004)

Property Enhancement of Polyester/Cotton Blends by using Enzymatic Treatments:

The Polyester is often added to cotton fabric to improve product economics while increasing tenacity and resiliency. This increase in tenacity can be troublesome with respect to pilling. Cotton fibers have a lower tenacity, and as the pills are formed the anchor fibers can be easily broken with further mechanical action. Once the tenacity of the fabric is increased with added polyester, the pill break-off rate is much lower[20,21]. Furthermore, 100% polyester fabrics can be notorious for pilling problems and because of the high tenacity of the polymer, the anchor fibers rarely break releasing pills.
Work published by Bazin and Sasserod [22] revealed a reduction in fuzz level which resulted in a dramatic reduction in pilling on both 100% cotton and polyester cotton blends using cellulase. Work Published by Stefanie G. Mccloskey et al. reveals that polyester cotton blend fabric can be treated with a cellulase combined with a cutinase to impart a bio-polished finish[23].

Deo et al., uses cellulase as an alternative to carbonization of disperse/reactive dyed polyester/cotton blended fabrics. Their paper reveals that the K/S values of enzyme treated and H2SO4-carbonised samples indicate that the action of enzyme is almost uniform on all the blends, irrespective of the cotton content[24].

Enzymatic Treatments for Acrylic Fibers:

Polyacrylonitrile or acrylic fiber is gaining importance because of its wool-like handle, easy care properties, good colourfastness, dimensional stability, moth and mildew resistance, pressed-in crease retention, resiliency, warmth, wrinkle resistance, and chemical resistance. Like polyester, acrylic has the undesirable properties of poor abrasion resistance, pilling resistance and strength [5]. Several attempts have been made to improve the eco-efficiencies of acrylic fiber production processes, including its subsequent dyeing. The chemical methods tried to make acrylic more hydrophilic, and thereby enhance dye uptake, have not been successful. In turn, these methods affected the physio-chemical properties of acrylic because of elevated temperatures, aggressive chemicals and higher concentrations of dimethyl sulfoxide (DMSO) [25].

Hydrolysis of nitrile groups under strong alkali treatment leads to irreversible yellowing of fabrics. In addition, the mild alkali treatment for an extended period reduces the dye uptake. In contrast, acidic hydrolysis causes minimum changes in the dye uptake.

The enzymatic hydrolysis of surficial nitrile groups of acrylic fibers can offer a promising alternative to chemical processes.The enzymesnitralase, nitrile hydratase, and amidasecatalyse the hydrolysis of nitriles to corresponding amides, carbonic acid and ammonia. Studies have demonstrated that these enzymes improve many undesirable properties of acrylic under mild conditions. Surficial nitrile groups of acrylic fibres were hydrolysed by the enzyme preparation to a maximum of 16%, although acrylonitrile was known to be a very good substrate for both nitrilases and nitrile hydratases from these organisms [26, 27]. However, the enzyme action on polyacrylonitrile is restricted to certain factors relating to the properties of the polymer. Firstly, rate of adsorption and desorption of enzymes to the polymer may affect the hydrolysis rate. Secondly, the crystallinity and hydrophobicity of acrylic fibres may limit the accessibility of nitrile groups to the enzyme. More research is required to explore the high potential of nitrile degrading enzymes in the modification of acrylic fibers[28] .

Cavaco-Paulo et l., reported for the first time the action of cutinase on vinyl acetate, co-monomer in acrylic commercial fiber. The cutinase hydrolysis of acrylics (constituted by polyacrylonitrile and 7% of vinyl acetate as co-monomer) yields acetic acid, leaving vinyl alcohol at the fiber surface.

Enzymes & Polyamide Fibres:

Polyamide fibres are obtained by the condensation of adipic acid and hexamethylenediamine. These fibres are hydrophobic and have poor wettability in an aqueous medium. Alkaline hydrolysis is an effective way to improve fibre wettability, but the action of concentrated solutions of NaOH or KOH is hard to control and extensive damage can result [5].

The use of hydrolytic enzymes can lead only to superficial hydrolysis of polyamide fibres. This is due to the fact that enzymes are relatively large molecules and do not penetrate into the tight hydrogen bonded structure of polyamide. These superficial changes would improve the fibre hydrophilicity and chemical reactivity towards other agents for new finishing effects of polyamide, without causing significant damage. It is been reported cutinase can be used to modify the surface of polyamide fibers by hydrolysis of the amide linkages with the formation of amino and carboxylic groups [19]. Enzyme action produces some superficial cuts along the polymer, corresponding to breakage of the amide linkages. From the breakage of these linkages two hydrolysis products might result, adipic acid and hexamethylenediamine. Enzymatic hydrolysis of polyamide fabrics was followed by determination of amino groups in the solution and on the fibre surface [29]

Conclusion:

The demand for manmade fibres in the world market is increasing and necessity to explore for eco-friendly processing is required. This paper presents the various biotechnological studies that are carried out all over the world till dated. But the studies are at R&D level; more research is necessary to commercialize these enzymatic treatments to improve the desired properties that are very much essential. The future for enzymatic treatment for synthetic fibres is not far away, but it takes sometimes for actual implications.

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