Polyurethane Use in the Textile Industry

Overview of Textiles in the World and Turkey

The textile industry played an important role in the development of developed countries in the 18th century. Today it plays the same role in developing countries. Due to high production and labour costs, textile production has shifted from developed to developing countries since the 1970s. Developed countries are now a good market for the textile sector rather than producers. However, these countries maintain their position and influence in the sector through activities such as modernization in production processes, advanced technology, R&D work, creation of new trends, and development of standards for finished products. The textile sector encompasses fibres, yarns, knitted-woven fabrics, felt, tufting (looped weaving), nonwoven surfaces such as wet wipes, home textile products, carpets for all needs; and at the same time technical textiles such as twine, rope, nets, cables, hoses, conveyor belts, tarpaulins, canvas, car covers, protective cloth, filter cloth, parachute cloth, brake cloth.

Synthetic Fibres (Chemical Fibres, Man-Made Fibres) 2.1. Regenerated Fibres

• Regenerated cellulose, viscose silk, modal, tencel, bamboo, • Cellulose esters, acetate silk, • Regenerated protein, vicara, ardil, lanital.

2.2. Synthetic Fibres

• Acrylic Fibre: Orlon, perlon, dralon, acrilan, creslan. • Polyvinyl Fibre: Polyamide, nylon. • Polyester: Terylene, trevira. • Polyurethane: Lycra • Polyvinyl Fibre: Polyvinylidene chloride, mod acrylic (dynel), polyvinyl chloride.

1- Synthetic Fibres 1.1. Regenerated Cellulose Fibres A- Viscose Silk- Rayon

Also known as floss. It is produced using wood cellulose, primarily birch, along with cotton waste and linter cotton. Cellulose obtained at 90-94% purity is converted to alkali cellulose with caustic. After a series of processes, highly lustrous fibre is obtained. Similar to silk, soft and drapeable, does not pill.

B- Viscon

Produced from birch wood. The cellulose structure does not change after production. Resembles cotton. Has superior moisture absorption properties to cotton. However, dry strength is low, wet strength is weak. Very suitable for dyeing. The resulting fabric is elegant and comfortable. Used in t-shirt, dress and underwear production.

C- Tencel Fibre- Lyocell Fibre

A regenerated cellulose product produced from eucalyptus wood. Excellent wet strength, high moisture absorption properties and resistance to mechanical pressure. Used in apparel production.

D- Bamboo Fibre

Obtained from bamboo wood. A new generation fibre type. Shows natural anti-bacterial properties. UV absorbing. Production similar to viscose. Has high wet strength. Has a lustrous appearance without requiring mercerization. Elastic. As soft as silk and cashmere. Used in towel, underwear and sock production.

E- Modal

Produced from birch wood. High wet-dry strength, flexible and soft. Finishing process similar to cotton. Shows natural whiteness. Has lustre without requiring mercerization.

F- Acetate Silk

Obtained through acidification of cotton waste and wood pulp. A quality and expensive type of silk.

G- Copper Silk

Wood cellulose, copper carbonate, ammonia or caustic is steeped and precipitated, then copper is removed in a sulphuric acid bath. A fibre with a structure resembling natural silk but with poor resistance to water and chemicals.

H – Milk Protein Fibre- Casein Fibre

A new generation fibre. Combines natural and synthetic fibre properties. Obtained from milk cream.

I – Zein Fibre

A new generation fibre. Corn flour is dissolved in isopropyl alcohol to obtain zein protein. Processed with defatted cottonseed flour to be converted into fibre.

J- Alginate Fibre

A new generation fibre. Obtained from seaweed. The structure of alginic acid resembles cellulose. Can be dyed. Heat resistant, used in non-flammable fabric production. No alkaline resistance. With this property it is used in lace and fine fabric production.

K – Soy Cellulose

A new generation fibre, an invention of the 20th century. Inexpensive, appearance resembles silk/cashmere. But in terms of durability resembles synthetic fibre. Balances body moisture and heat. Antibacterial and UV protective. Has wound-healing properties.

1.2. Polyester Fibre

A polycondensation product of dicarboxylic acids (terephthalic acid) with diols (glycols). The fibre withstands heat up to 200°C. High strength. Does not break easily. Resistant to chemicals other than phenols, moisture, bacteria. Not suitable for cooking. Resistant to acids. Can undergo saponification reaction in alkali. However, cotton/polyester blends can be mercerized with minimal damage. Wool/polyester blends do not require ironing. Not affected by moisture.

1.2. Polyamide Fibre

Obtained as a result of polycondensation of amino carboxylic acids or their lactams. Similar to protein fibres in that it contains acid amide groups. Polyamide 66 is called nylon 66 or simply nylon. Because it is alkaline resistant it is used as filter cloth in industry. Sensitive to air and light. Resistant to decay, bacteria and insects, used in canvas, car cover and fishing net production. Not acid resistant at high temperatures. Sensitive to peroxides, therefore care should be taken not to use active oxygen detergents when washing white garments made of polyamide. Absorbs very little water, as a result dries quickly. Due to this property it is used in swimwear and raincoat production. Mixed with other fibres to increase durability.

1.3. Polyurethane Fibre – Elastane Fibre

A polyurea copolymer. Obtained by adding diamines to diazocyanate. Withstands heat up to 240°C. Its proper name is SPANDEX fibre in English, a word meaning stretchable, elastic. High tear and rupture resistance. Can be stretched to 500-800% of its length, when pressure is released it returns to the original length without deformation. Does not degrade when melted and cooled again. Has industrial applications in thermal jackets, valve jackets, polyurethane-coated glass fibre.

1.4. Nomex

A polycondensation product of metaphenylene diamine and isophthalic acid. Insoluble in organic solvents and phenol. Resistant to dilute alkali and acids. Very high heat resistance. Due to these properties, used in ironing board covering cloth, military-specific clothing, hot gas filter production.

1.5. Polypropylene Fibre

A propylene polymerization product. Has the lowest density among all fibres. Very good wet and dry strength. Not suitable for dyeing. Coloured while in molten state during fibre production. Used in carpets, coverings, indoor and outdoor clothing, filling material. Polyethylene fibre, a polyethylene polymerization product. Suitable for filter cloth, floating rope, fishing net production.

1.6. Polyvinyl Alcohol Fibre

Obtained as a result of saponification of polyvinyl acetate. Hardened by reaction with aldehyde or ketones. Suitable for dyeing. Hygroscopic. Its non-hardened form is water-soluble, therefore used in surgical suture thread production (self-dissolving surgical suture thread). Mixed with wool, cotton and other synthetic fibres for use in textiles.

1.7. Polyvinyl Chloride Fibre- Movil, Envilon, Talon

Obtained through vinyl chloride polymerization. This polymer is not usable because it can only be dissolved in high boiling point solvents. Made soluble through modification. Good resistance to acids and alkali, due to this property used in protective work clothing and filter cloth production. Rot-resistant Pe-Ce fibre is used to produce fishing materials, sail cloth, canvas, awnings, car covers. Used as filling material in eiderdowns. Mixed with other fibres and used in dress and underwear production.

1.8. Polyvinylidene Chloride Fibre- Saran, Velon, Harlan

Water and chemical resistant but heat resistant. Hydrophobic, therefore not suitable for dyeing. A very inexpensive fibre. Resistant to sun, biological agents, acid-base, therefore suitable for car upholstery, curtains, mosquito netting, awnings, filter cloth and industrial hose production.

1.9. Acrylic Fibre

Among synthetic fibres, it most closely resembles wool. The one containing 100% acrylonitrile polymer is rigid, brittle, difficult to dye. Must be modified to be usable. A polymer product of acrylonitrile and a comonomer is made. Used in sportswear, clothing, costumes, curtaining, upholstery production.

1.10. PAN Fibre

A modified form of acrylonitrile polymerized product. Recycled Fibre: As in every sector, the declining raw material resources in textiles has developed the concept of recycling.

Textile Recycling

It is of two types: from textile waste and from non-textile waste. 1. Obtained from textile waste. Turkey has approximately 750,000 tonnes of textile waste annually. Regenerated cellulose fibre types are produced by sorting these. 2. Synthetic fibre produced from waste such as PET (polyethylene terephthalate) bottles is converted into yarn (polyester) and used in sock and blanket production. Currently in Turkey, approximately 30% recycling recovery is achieved from PET bottle waste. Given that we are dependent on imports for polyester fibre, the contribution to the economy from increasing this is clear. Besides this, the importance of the contribution of the factor of removing PET waste from the environment, which is very difficult to decompose in nature, should not be forgotten. PET bottle to fibre recovery facilities are located in Uşak, Gaziantep and Thrace.    

Obtained from Plant Seeds

1- Cotton Fibre Obtained from the pod of the cotton plant. The cotton plant is a bush-type plant with a long lifespan that can produce flowers and pods for many years under suitable conditions. The structure of cotton extracted from the pod contains 88-96% cellulose. Cotton is converted into pure cellulose yarn through various processes. Cotton fibre is durable, moisture-absorbing, suitable for dyeing. Good heat and moisture resistance. It is important as the oldest known fibre.

2- Organic Cotton Fibre

A new generation fibre. Obtained from cotton grown in fertilizer-free fields in special regions, with limited finishing processes and dyes selected in accordance with ecological restrictions. Thus harmful agents to humans and nature have been eliminated or minimized.

Polyester

Synthetic organic polymers containing an ester group in the polymer chain. When classified according to use, it is divided into two: polyester fibre and polyester plastic. Polyester was first sold in America under the name dacron, and at the same time in England under the name terylene. According to American standards, the polyester forming the fibre must contain at least 85% by weight of an ester of a dihydric alcohol and terephthalic acid. In the standard process for making polyester fibre, dimethyl terephthalate and ethylene glycol are polymerized, cut into small particles, melted, (at 256°C) forced through fine holes under pressure, and thus long fibres are obtained. If a second dicarboxylic acid is used in addition to terephthalic acid, a copolyester is obtained. Polyester obtained by using aliphatic dicarboxylic acids instead of terephthalic acid has a melting point of 100°C. Fully aromatic polyesters where both the alcohol and acid are aromatic (such as polyhydroquinone-terephthalate) melt above 400°C. Polyester fibre withstands 200°C. Does not break easily. Resistant to most chemicals other than phenols, moisture and bacteria.

Although resistant to acids, it is not resistant to strong alkalis (due to saponification reaction). Mercerization can be achieved with cotton-polyester blend.

  However, durability decreases. Fabrics made of polyester, polyester-wool or cotton blend do not require ironing and given shapes do not deform with washing. Commercial names of polyesters are diolen, trevira, terylene, tergal, terlonka, dacron, lavsan, teteron, frtrel and avitrон. Enkaterm is a modified polyester that withstands temperatures up to 1500°C. Early polyester resins appeared in Berzelius's work in 1847 and in Gay-Lussac and Pelouze's work in 1883. The unsaturated polyester resins used in today's reinforced plastics (RP) are combinations of reactive monomers. Carleton Ellis, proposed the combination idea in the 1930s. Ellis discovered that unsaturated polyester resins formed by the reaction of glycols with maleic anhydride could be improved to insoluble solids by adding a peroxide catalyst. Applied for a patent for this idea in 1936. Ellis later discovered that by combining unsaturated polyester alkyd with reactive monomers such as vinyl acetate or styrene, the addition of catalyst could be facilitated and a more useful product could be made. The first use of glass-fibre reinforced polyester composites was seen in aircraft and boat hulls. The invention of the pultrusion line allowed unsaturated polyester-based materials to be developed in new application areas such as oil wells and electrical insulation devices. The filament winding process further expanded the potential market for unsaturated polyester resins. This technique was initially developed for the manufacture of military rocket cases and nozzles, but the potential for use in pipe and storage tank construction was soon discovered. In the 1960s, after these BMC (Bulk Moulding Compounds) and DMC (Dough Moulding Compounds) techniques, PMCs (Polyester Moulding Compounds) were also adopted by the industry. Systems of this structure are applied in many areas from simple material packs to the moulding of complex details.

Technical Textiles

Over 80% of global polyester fibre production capacity is realized in China and India. Technical textiles have a history as old as conventional textiles. For example, ship sails are actually in the technical textiles category. After the discovery of the first synthetic fibre in 1939, technical textiles production and application areas increased. Today approximately 30% of technical textiles are based on synthetic fibres. With the discovery of rubber and polymer materials and developments in the chemical sector, products with different properties and different application areas were obtained. Technical textiles are resistant to chemicals, weather, microorganisms, have superior performance and functional properties, high added value and are expensive. Lamination and coating techniques are applied in technical textiles production in order to impart functional properties to fabrics and increase application areas.

Coated Fabrics

Coated fabrics are obtained by coating one or both surfaces of fabric produced as woven, knitted or nonwoven with a chemical substance. Coating and lamination are applied to improve and change the physical and aesthetic properties of fabrics, to extend the application area by combining the advantages of fabrics, polymers, foam and films.

Lamination

The lamination process is based on the principle of combining fabric layers or fabric and material to create a composite material. Polymer materials that cannot be formed as coating paste are first converted into film form and then laminated to the fabric. Adhesives used in lamination are generally water-based, solvent-based substances or substances that are solid or gel and molten at heat. These substances that are molten at heat are produced in film, granule, powder or gel form. These substances can be polyolefin, polyurethane, polyester, polyamide or a combination of different polymers or copolymers.  

Table 1. Substances used in coating, their properties and application areas [5, 7, 8, 17]

Prepared by: Nükhet Sezer

References 1- "Textile Production and Auxiliary Chemicals" Müjgan İlter, May 2015, İzmir 2- "General Properties and Performance Tests of Fabrics Produced with Coating or Lamination Techniques", Yasemin BULUT, Vildan SÜLAR, Dokuz Eylül University, Textile Engineering Department/İzmir 3- "Real Village Return Project: Hemp", Author: Erdem Ulaş