The most important property of any apparel is comfort and handle. Due to the hydrophobicity and soiling properties of synthetic and its blends, it gives the wearer less comfort. Synthetic materials have the ability to resist most bacteria, microbes and insects, as the synthetic is not digestible. However, soiled synthetics can cultivate microbes because of the added source of food. This makes the wearer even less comfortable. To overcome this, moisture management, stain/ soil release and antimicrobial treatment on synthetic and its blends are necessary. Therefore multifunctional finishes using specialty chemicals are needed.
Moisture management often refers to the transport of both moisture vapour and liquid away from the body. Moisture management can be defined as 'The controlled movement of water vapour and liquid water (perspiration) from the surface of the skin to the atmosphere through the fabric'. When a synthetic material is subjected to this moisture management treatment, it develops improved hydrophilicity followed by very fast drying behaviour. In case of synthetic blends subjected to this treatment, their drying rate becomes much faster. In the case of natural fibres it is the reverse - very good absorbency and slow drying rate. The drying rate of polyester is four times greater than cotton. P/C blends subjected to moisture management treatment will have increased absorbency. The polyester will dry more quickly than cotton and while it dries it keeps on absorbing from cotton and quickens the drying process. Wicking, wetting and drying rate are test methods through which we can find out moisture management efficiency.
Soil/ Stain Release
When a textile substrate is made repellent in nature, it is able to repel only the liquid stains or soils. But, dry stains like grease, paint, grass stain, etc, leave their mark on the textile. These are difficult to remove from a surface made repellent in nature. Hence, the need for soil/ stain release finishes. Like the name implies, a soil release finish keeps dirt from binding to the substrate fibre and allows it to be more easily removed through vacuuming, laundering and other cleaning methods. Soil release finishes tend to come in either fluorochemical or silicone type varieties. Fluorochemical treatments protect against both water and oil-based soils and resist wetting by oily and watery liquids. Silicone treatments protect against water-based soils and watery liquids only.
Soil release chemicals help in easy laundering by releasing water and oil-based stains. Today, stain release finish for cotton fabric apparel is mostly imparted by the incorporation of low surface energy fluorochemicals. Stain release fluorochemical finishes allow oil and water stains to penetrate the fabric. However, when the fabric is laundered, the stains are easily removed. Fluorochemicals have the unique property to provide fabrics with a low surface energy film with both high oil and water repellency properties to resist penetration of oil and water-based stains (polar and non polar liquids). The 'repellent' products prevent the textile substrate from wetting and soiling by repelling the soiling substances and the adhesion of dry soil. Fluorochemical hybrid finishes, also called 'dual effect', and containing hydrophilic groups, have also been developed and improved successfully over recent years to impart both stain repellency and stain release properties.
The concept of soil release finish comes into play here. Originally, the soil release finish imparts hydrophilic properties to the substrate and lowers its static charges. The result is that the oil and water-based stains do stick, and penetrate but are very easily washed off in normal home laundering. Synthetic fibres such as polyester have more hydrophobic properties which limit their scope of usage. If such fibres are imparted with more hydrophilic properties, especially water/ perspiration absorbency with wash-fast resistance, their use will further broaden. Superior hydrophilic properties (water/ perspiration absorbency) will allow varieties of fibre materials, knits, wovens and industrial materials a broader scope of use.
The uniqueness of this material is related to the tendency of non-polar perfluoro alkyl side chains to orient outward towards the air. During the drying and curing stage, polymer mobility allows the tails to orient outwards. The oxyethylene segments are forced towards the interior of the film and so the outermost film layer is richly populated by the low interfacial energy perfluoro segments. This provides a low critical surface tension, which favours oil repellency. In water, the polyoxyethylene segments swell, causing the polymer to 'flip-flop'. The surface is now hydrophilic, favouring the release of soil. The flip-flop mechanism is shown in the figure.
The inherent properties of textile fibres provide room for growth of micro-organisms. Besides, the structure of the substrates and the chemical processes may also induce the growth of microbes. Humid and warm environments aggravate the problem. Infestation by microbes cause cross infection by pathogens and induce odour where the fabric is worn next to skin. In addition, staining and loss of the performance properties of textile substrates is the result of microbial attack. Basically, with the view to protect the wearer and the textile substrate itself an antimicrobial finish is applied to textile materials.
Micro-organisms are small forms of life that generally cannot be seen by the human eye. This includes bacteria, fungi, algae and viruses. Bacteria are uni-cellular organisms, which grow very rapidly under warmth and moisture. Further, sub-divisions in the bacteria family are Gram positive (Staphylococcus aureus), Gram negative (E-Coli), spore bearing or non spore bearing type. Some specific types of bacteria are pathogenic and cause cross infection. Fungi, molds or mildew are complex organisms with slow growth rate. They stain the fabric and deteriorate the performance properties of fabrics. Algae require continuous sources of water and sun light to grow and develop darker stains on the fabrics. Dust mites are eight legged creatures and occupy household textiles such as blankets, bed linen, pillows, mattresses and carpets. Dust mites feed on human skin cells and liberated waste products can cause allergic reactions and respiratory disorders.
Multifunctional Specialty Finish
This multifunctional specialty finish was tried on different synthetic substrates and following are the substrate and chemicals used.
1) 65/35 P/V WOVEN FABRIC GREY COLOUR DYED (30S X 30S EPI-80* PPI*76), GSM - 200
2) 100 % PES WOVEN BLEACHED FABRIC (60S X 40S EPI-76* PPI*60), GSM -60
3) 100% 70 de PES HEAVY S/J KNIT, GSM 250
4) 60/40 70 de P/C PIQUE KNIT, GSM- 220
5) 94/6 70 de/20 de NYLON/ LYCRA POPCORN KNIT, GSM 90
TG-996 is a stain-release agent, which imparts excellent stain-release property and wickability to textile substrates. RESIL ULTRAFAB UPE is a hydrophilic polymer that can be applied on synthetic fibre and it blends. ULTRAFRESH NMV2 is an antimicrobial agent applied along with fluorocarbon and hydrophilic polymer in one bath process.
Dosage and Process Conditions
The finishing was carried out by using TG-996: 10-40 gpl, Ultrafab UPE: 5-15 gpl, Ultrafresh NMV2: 20-30 gpl by dry on wet padding; one dip one nip; expression achieved was between 60-70% pickup; pH 4.5-5 using Ultrafab FP (Fabric Protector). After padding the fabric was dried at 120C and followed by curing at 160C for 3 minutes. For all tests the fabric was kept under standard atmospheric conditions - temperature 232C and 65% humidity.
For wicking test, the in-house vertical method, stain release AATCC 130 and anti-microbial AATCC 147 were followed.
Different recipes were tried by varying the fluorocarbon, hydrophilic polymer and antimicrobial. By varying the parameters a performance study was done.
WICKING RESULTS BY VARYING FLUOROCARBON DOSAGES ON DIFFERENT SUBSTRATES
STAIN RELEASE RESULTS BY VARYING FLUOROCARBON DOSAGES ON DIFFERENT SUBSTRATES
The dosage of fluorocarbon plays a vital role in the stain release/ wicking results. By increasing the dosage of fluorocarbon, the stain release rating achieved is between good and best; and wicking height is decreased. But it does not affect the unfinished wicking results. A fabric with less initial absorbency for finishing shows very good wicking results. The usage of antimicrobial agents along with fluorocarbon and hydrophilic polymer passes AATCC 147 test method at initial and after 20 HL. As this is a functional finish and the results differ from substrate to substrate with respect to count, construction, weave, type of knit, etc, this multi-specialty finish is substrate specific. Hence, work has to be done individually for the different substrates.
1) Mr Tirtha Ghosh, 'Moisture Management and Wicking: a Closer Look', Resilient, Vol.- 4, Issue-3, 2004
2) Mr Saville, Physical Testing of Textiles
1) Antimicrobial Textiles an Overview by Dr T Rajendran, IE (I) Journal. TX, Vol. 84, February 2004
2) B Clemo, Applying Ultra Fresh, Resilient, pp 13-16
3) Chemistry & Technology of Fabric Preparation & Finishing by Dr Charles Tomasino, Chapter-10
4) Resilutions Issue from Resil Chemicals Pvt Ltd
About the Author:
The author is in the Final Year, M. Tech in SSM College of Engineering.
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