Fibres from Natural Polymers

The most common natural fibre is viscose, which is made from the polymer cellulose obtained mainly from farmed trees. Other cellulose based fibres are cupro, acetate, triacetate, lyocell and modal. The production processes for these fibres are given later. Less common natural polymer fibres are made from rubber, alginic acid and regenerated protein.

Fibres from Synthetic Polymers

The inorganic man-made fibres are fibres made from glass, metal, carbon or ceramic. These fibres are often used to reinforce plastics to form composites. Viscose is made from cellulose from wool pulp. The cellulose is ground up and reacted with caustic soda. After a period of time carbon disulphate is added which helps to form a yellow crumb known as cellulose xanthate. This is easily dissolved in more caustic soda to give a viscous yellow solution. This solution is pumped through a spinneret into a dilute sulphuric acid bath where cellulose is regenerated as fine filaments as the xanthate decomposes.

Viscose fibres, like cotton, have a high moisture regain. It dyes easily, it does not shrink when heated and it is biodegradable. It is often blended with other fibres and used on apparel and hygienic disposable products. It is used very little in home furnishings because of its thermal stability and a high modulus version of viscose is still the main product used in Europe to reinforce high speed tyres.

Lyocell – This fibre is made up from a solvent spinning process. The fibres, like other cellulosics are moisture absorbent and biodegradable. They retain 85% of their strength when wet and are mostly used for apparel fabrics, especially outerwear.

Cupro – Cotton cellulose is first bleached by boiling in an alkaline solution. This is then dissolved in a mixture of copper oxide and ammonia. The blue viscous liquid is pumped through the spinneret into a spinning tube in which alkaline water is flowing. This water flow stretches the filaments before they are dried and wound up.

Cupro fibres have a good drape and are easy to wash. The main production is in filament yarn form for woven fabrics, largely used in linings.

Acetate and Triacetate – the term acetate fibres is used to describe fibres made from cellulose acetate. Wood cellulose is swollen by acetic acid and then converted to cellulose acetate using acetic anhydride. It is then dissolved resulting in viscous solution that is pumped through spinnerets into warm air to form filaments. These fibres are different to viscose in that they melt, are dyed using disperse dyes, absorb little water and can be textured. Although the dry strength of the two types is similar, triacetate has a higher wet strength. Main end uses for the filament yarns are linings and dress wear.

Acrylic – The starting materials for acrylic are propylene and ammonia, which are reacted with oxygen in the presence of catalysts. The substance is then polymerised and spun into fibres from a solution with a solvent. The fibres are then stretched, washed and crimped.

Acrylic fibres are soft, flexible and have a high loft. For this reason they are widely used in knitted apparel such as socks and sweaters. In addition to this, home furnishing and blankets are important applications. Acrylic fibres are also used as a precursor for producing carbon fibre.

Polyamide – to produce fibres from the polyamide polymers the often polymer is pumped through spinneret holes at 300 degrees centigrade to form filaments that are cooled and solidified in a quench air stream. Different processes are then used to obtain the desired texture, strength and wearability required. The end use for polyamide are in outerwear and technical fabrics.

Polyster – these yarns are made up in a similar way to polamide. In Europe, apparel accounts for a large share of the polyester fibres. Industrial use, such as tyre fabrics and unspun uses such as furniture fillings and non-wovens are expanding rapidly.

Elastane – these fibres are able to recover when stretched. Elastane was first synthesised in 1937 but was not commercialised as a fibre until 1958. Apart from having properties of stretch and recovery the yarn can also resist oils found in cosmetics and perspiration.

Aramids – the development of aramids took place in the USA in the 50’s and 60’s. There are two types of aramids, meta-aramids and para-aramids. The fibres were developed due to a demand for high performance fibres for air and space travel. The main end uses for meta-aramids are protective clothing and electrical insulation. Para-armaids are used to replace asbestos in brake and clutch linings, tyre reinforcements and in composites such as materials for aircraft, boats, high performance cars and sports equipment. Members of the police forces and armed forces wear anti-ballistic aramid apparel.

Glass – is the most important inorganic fibre. There are several types of glass fibre production. Glass is used extensively for insulation in the form of felt and also for reinforcing plastics to make boats and caravans. Other lesser uses are in flame-resistant curtains and décor fabrics.

Carbon – the fibres are characterised by having high moduli and high strength. They are also brittle and have a low density and are used as reinforcement fibres in composites for the aircraft and aerospace industries and sports items, Dupont® produce a number of products such as Nomex® and Keviar®, which have properties to protect the wearer against heat, flames and cuts.

Kevlar® - has characteristics of outstanding strength and cut resistance properties, making it an ideal product when used in conjunction with areas such as construction, automotive and body armour protection. When used in the construction sector, garments made of Kevlar® can be found in brakes and transmission parts, tyres, belts and hoses. Kevlar® exceptional strength also makes it an important component when used in the production of bullet-proof vests.

Nomex® - products provide the wearer with protection against heat and flames, which is why it is used in occupations such as fire fighting, racing car driving and plant operatives. The thermal flame resistance properties of Nomex® enable the product to be used also in the interiors of rail and aircraft, car interior textiles and upholstery, floor coverings and contract furnishings for hotels, offices and hospitals.

Teflon® - this fibre is used for demanding applications throughout industry where its outstanding properties of low friction, extremely high loading capacity, heat tolerance and chemical resistance are instrumental in economic resolution of many intractable design problems. The fibres exhibit some markedly different properties from its polymeric resin counterpart which is perhaps best known for its use as non-stick surfacing compound. In particular it is stronger and more resistant to deformation.