Performance-enhancement finishes for nonwoven fabrics

Abstract

In recent years, with the improvement of standard of living and the pace with which human life is moving, customers require more and more functional fabrics. The nonwovens sector is one of the fastest-emerging and exhilarating in the textile market. Nonwovens are extensively used materials for technical textile applications, ranging from medical textiles to geo textiles.

Depending on the fibres used for the manufacturing of nonwovens and their end uses, various functional finishes can be imparted to nonwoven fabrics to enhance their performance and serviceability. Performance properties include functional characteristics such as moisture management, water repellency, flame retardancy and antimicrobial finishes. This paper focuses on some of the functional finishes that are critical for nonwoven fabrics.

1. Introduction

Nonwovens are defined as distinctive, high-tech, engineered fabrics made from fibres used for manufacturing various products for numerous applications. The term "nonwoven" is coined for fabrics that are neither knitted nor woven. They are materials having similar properties of fabrics such as woven and knitted, but in this case the fabric is manufactured by bonding fibres with each other chemically, mechanically or through heat or solvent treatment. These fabrics are mostly porous sheets, directly made from fibres that do not require transforming fibres into yarn.

Nonwovens offer many advantages over woven fabrics – one of the most important being that it is economical, as it involves direct conversion of fibre to fabric that leads to cost savings, lesser production time and possibility of large volume production.
Fibres, namely cotton, viscose, polyester and polypropylene, are extensively used in the manufacturing of nonwovens by needle punch technique, hydro entanglement, thermal bonding and chemical bonding. Nonwovens used for technical textiles are primarily made from synthetic polymers, as strength and flexibility is of major importance.

Nonwovens have a wide application areas in the field of technical textiles, including:

• Agrotech - Crop covers, weed control fabrics, greenhouse shading and root bags, etc
• Buildtech - Roofing and tile underlay, thermal and noise insulation, vertical drainage, textile construction and building components etc
• Clothtech - Shoe components, sewing products, interlining, clean room garments, etc.
• Geotech - Drainage, sedimentation and erosion control, pond liner, separation, reinforcement, filtration, offshore land reclamation, roadside, rail side, river and canal banks, and reservoirs
• Hometech - Carpet components, furniture components and consumer wipes etc
• Meditech - Drapes and gowns, sterile wrap, swabs and dressing, cleaning, cover stock, wound-care, protective apparel, bedding and sheets and masks
• Mobiltech - Airbags, cabin air filters, engine intake and exhaust air filters, silencer pads, insulation materials, car covers, under padding, car mats, tapes, backing for tufted carpets, seat covers, door trim and insulation, floor coverings, protection and composites
• Protech - Chemical and biological protection, particulate protection, flame retardant, cut resistant, shields and gowns worn in emergency response, chemical handling, hazardous waste control, cleaning and filtration

For the above applications, some physical or chemical finishes are vital. Thus, in this paper we focus on some of the functional finishes that are required to meet the performance of the nonwoven material.

2. Chemical finishing

2.1. Antimicrobial finishes

Nowadays, nonwoven fabrics are the most commonly used textiles for surgical gowns, patient drapes, laboratory coats and coveralls etc. The need for hygienic clothing is of great demand for the materials used in domestic and industrial applications. Textile materials are a source of food material for micro-organisms, so having an antimicrobial property is obligatory.

Fabrics affected by bacteria are a major cause of skin infections and irritations. Strength loss in fabric, discoloration and bad odour are some of the sources of microbial attack on the fabric. Thus, the application of anti-microbial agents on fabric are of prime importance so that the growth of micro-organisms, namely bacteria and fungus, can be inhibited. These types of finishes are used to prevent the biological degradation of fabric by bacterial or fungal growth. Mostly, these finishes are based on silane, metallic compounds or natural biopolymer.

Understanding the requirement and need of today's market, Sarex has developed an antimicrobial agent, named Saraguard 5700, which is a methanol-free, durable, non-leaching antimicrobial and fungicide for broad-spectrum microbes such as Escherichia coli, Staphylococcus auerus, Methicillin-resistant Staphylococcus aureus (MRSA) and Klebsiella pneumoniae. This finish can be applied on substrates by padding, exhaust, spray or coating techniques. Saraguard 5700 passes AATCC 100 test method.

2.2. Flame-retardant finish

Nonwovens are finding more and more applications in areas that were once ruled by woven materials. Nonwoven products are mainly manufactured using synthetic fibres such as polyolefin, polyester or nylon, which are highly flammable. The use of nonwovens manufactured with synthetic fibres can therefore lead to an increased fire risk in many cases. This needs to be taken into account even more nowadays, since there is a trend to replace high-cost materials by lower-cost materials, for example polypropylene.

Flame-retardant finishes help to reduce flame propagation and suppress smoke emission. They are mainly made of nitrogen phosphorous compound. Many of these finishes are available in fibre form to be blended in the fabric during the process or manufacturing. They are also present in polymer dispersion form to be applied through padding or coating. These types of finishes are mainly applied on car interiors, carpets, artificial turfs, ballooning fabric, parachutes, tents and fire fighters etc.

Considering the need of the hour for flame retardants, Sarex has developed a unique flame retardant, Flamguard-DPS, which is a halogen-free, durable flame-retardant finishing chemical for synthetic fibres that gives minimum shade change. It can be applied by padding and spray methods.

Flamguard-DPS passes BS-3119 (1959) & BS-3120 Vertical flame test for flame-proof materials.

2.3. Water and oil repellent finish

Nonwovens possess many characteristics, such as soft handle, drapability, hydroscopic properties, ventilation properties and slippery appearance, but are deprived of many functional properties including water and oil repellency. Water and oil can act as pollutant to the fabrics that can impair the performance and serviceability of the fabric. Thus, to improve the serviceability and meet the product requirements, water and oil repellent finish can be imparted. This type of finish is used to inhibit wetting of fabrics. They mainly consist of silicone or fluorocarbon compounds.

Conventionally, wax finishes were applied to reduce the breathability of fabrics. Fluorocarbon compounds also provide repellency to oil, diesel and gasoline to synthetic fibres. They can be applied by coating, spraying and padding.

Sarex has developed a new-generation flurocarbon C6 water and oil repellent, Careguard-66 (New). It imparts durable water and oil repellency on various substrate, namely polyester, cotton, nylon, wool fibres and their blends, without affecting the original handle of the fabric. It can be applied by pad foam and spray technique. The performance of Careguard-66 (NEW) will be closer to that of C8 Chemistry Fluorocarbons.

2.4. Fragrance finishes

Fragrance finishing of textiles is the process where we enhance the value of the product by adding aroma. The active material-giving fragrance and the essential oil are volatile substances, and therefore the most difficult task in preparing the fragrance-emitting textile is how to prolong its durability. Micro-encapsulation technique is an effective way of solving this problem.

Microcapsules are minute containers that are normally spherical if they enclose a liquid or gas, and roughly of the shape of the enclosed particle if they contain a solid. It can be considered as a special form of packaging, in that the particulate matter can be individually coated for protection against environment, and release the volatile substance from the enclosed capsule as required. This property has enabled microcapsules to serve many useful functions and find applications in different fields of technology.

The uses of aromatherapy in textiles are diverse. Interior textiles such as sheets, quilt covers, curtains, carpets and bed gowns are suitable for the attachment of lavender, citrus or cinnamon microcapsules, which are good for hypnogenesis and eliminating fatigue. The fabrics finished with the above fragrances can be used in apparel, leisurewear, daywear and partywear. For sportswear, fragrances may be orange or lemon, which will keep them energised on the ground for a longer period. Perfumed toys make it easier for children to get closer to nature.

Considering the above market, Sarex has developed a range of Superfresh finishes in Lavender, Peppermint, Jasmine and Rose flavours. Superfresh finishes are odour-absorbing and refreshing, and impart a durable fragrance to the fabric. Fragrance is released from micro capsules due to abrasion, which occurs under normal wearing conditions. They are applicable on synthetic and natural fabrics by padding and spraying.

2.5. Abrasion-resistance finish

Nonwoven fabrics have a common disadvantage when fabric properties are compared with woven and knitted fabric, particularly in terms of surface abrasion, pilling and durability in multiple-use applications. Nonwoven materials used in car interiors and home furnishings require such durability, as they constantly come under abrasion and friction, due to wear and tear. They also experience a loss of strength, as pills are formed and the breakdown of fabric takes place.

To avoid such conditions, Sarex has developed an anti-pilling agent, Helafin-42, which improves resistance to pilling, snagging and tearing. Helafin-42 can be applied by exhausts, as well as pad applications. It can be applied in combination with water-repellent agents and with resins. Finishes obtained with Helafin-42 are resistant to washing and dry cleaning.

Conclusion

The world’s market place is continuously changing, and so are the demands of consumers. People desire change, ie something new and unique, and the successful and effective implementation of change needs to happen within the market. Advances in nonwovens have resulted in a new strain of textiles with high functionality. Advanced composite materials containing a combination of fibres and fabrics have been developed for applications where biocompatibility and strength are required. It is predicted that nonwoven materials will continue to have greater impact in this sector, owing to the large number of characteristics and performance criteria required from these materials and functional finishing.

• Sarex Chemicals can be a solution provider to its customers to meet the requirement of various functional finishes on nonwoven substrates

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