10 min readPathway sheetOften a 10-mark answer (one fibre at a time); comparisons for 5 marks

Rayon, nylon and polyester: manufacture, properties and uses

Man-made fibres are made by forcing a polymer liquid through a spinneret. Rayon is regenerated cellulose (wet spun); nylon and polyester are synthetics (melt spun).

SpinneretA metal cap with many tiny holes, like a shower head

Viscose raw materialWood pulp or cotton linters

Nylon 6,6 made fromHexamethylene diamine + adipic acid

Polyester (PET) made fromTerephthalic acid + ethylene glycol

Three ways to spin man-made fibres

Method	How the filament sets	Fibres
Wet spinning	Solution is pushed into a chemical bath that sets the fibre	Viscose rayon, some acrylics
Dry spinning	Solution in a volatile solvent is pushed into warm air; the solvent evaporates	Acetate, some acrylics, spandex
Melt spinning	Melted polymer is pushed into cool air and hardens	Nylon, polyester, polypropylene

Viscose rayon process

Rayon was the first man-made fibre. Chardonnet of France is called the father of the rayon industry; Cross, Bevan and Beadle of England found the viscose method in 1892.

1
Steeping: sheets of purified wood pulp are soaked in caustic soda (about 18%) to form alkali cellulose.
2
Pressing and shredding: extra alkali is squeezed out and the sheets are shredded into white crumbs.
3
Ageing: the crumbs stand for a set time so the cellulose chains shorten.
4★
Xanthation: the crumbs are churned with carbon disulphide and turn orange as cellulose xanthate forms.
5
Dissolving and ripening: the xanthate is dissolved in dilute caustic soda to give a thick, honey-like liquid, viscose, which is ripened, filtered and freed of air bubbles.
6★
Wet spinning: viscose is pumped through spinnerets into an acid bath (sulphuric acid with sodium and zinc sulphates), and cellulose is regenerated as filaments.
7
Finishing: filaments are stretched, washed, desulphurised, bleached and dried, then wound as filament or cut into staple.

★ one-way, controls the pace

Nylon and polyester (melt spinning)

Nylon was developed by Wallace Carothers at DuPont (USA) in the 1930s. Polyester was developed by Whinfield and Dickson in England in 1941 and sold as Terylene and Dacron.

1
Polymerisation: nylon 6,6 joins hexamethylene diamine and adipic acid (nylon 6 uses caprolactam); polyester (PET) joins terephthalic acid and ethylene glycol. Both are heated in a reactor (condensation polymerisation).
2
Chips: the polymer is pushed out as a ribbon, cooled and cut into chips.
3★
Melting and extrusion: chips are melted and pumped through a spinneret.
4
Cooling: the filaments harden in a stream of cool air.
5★
Drawing: filaments are stretched several times their length so the molecules line up, giving strength and elasticity.
6
Texturing or cutting: filaments are crimped for bulk and stretch, or cut into staple for blending with cotton or viscose.

★ one-way, controls the pace

Properties and uses compared

Property	Viscose rayon	Nylon	Polyester
Strength	Fair; much weaker when wet	Very strong; best abrasion resistance	Strong
Absorbency (regain)	High, about 13%; comfortable	Low, about 4%	Very low, about 0.4%; sticky in heat
Elasticity and resiliency	Poor; creases	Excellent elasticity	Excellent resiliency; wrinkle-free, drip-dry
Heat	Does not melt; medium iron	Melts; low iron; sparks make holes	Melts; heat-set pleats stay
Other points	Drapes well, dyes brightly; mildew possible	Static, pilling; weakened by sunlight	Static, pilling, holds oily stains; resists sunlight, moths and mildew
Uses	Saris, dress material, linings, kurtas; wipes and sanitary products	Hosiery, sportswear, ropes, fishing nets, parachutes, carpets, toothbrush bristles	Polyester-cotton shirting and uniforms, saris, curtains, pillow fibre-fill, sewing thread

Regenerated and synthetic

RegeneratedA natural polymer (cellulose) is dissolved and re-formed. Absorbent and cotton-like; burns like cotton. Viscose, modal, lyocell.

SyntheticA polymer built from petrochemicals. Strong, low absorbency, thermoplastic (melts). Nylon, polyester, acrylic, spandex.

Acrylic (polyacrylonitrile) is the wool-like synthetic: light, warm and cheap, used for sweaters, shawls and blankets, but it pills and melts.

In daily life

Do not wear nylon or polyester while cooking or in a hospital kitchen: they melt and stick to skin if they catch fire. A polyester-cotton blend is fine for front-office uniforms, and viscose and polypropylene non-wovens make disposable caps, masks and wipes.

Exam angle

2 marks: “What is a spinneret?” A metal cap with many tiny holes through which a polymer solution or melt is forced to form man-made filaments.

5 marks: “Compare the properties of nylon and polyester.” Both melt-spun, strong, thermoplastic, low regain, static, pilling. Nylon: more elastic, best abrasion resistance, harmed by sunlight. Polyester: wrinkle-free, regain 0.4%, oily stains, resists sunlight. Uses of each.

10 marks: “Explain the manufacture of viscose rayon. Add its properties and uses.” Steeping, pressing, shredding, ageing, xanthation, dissolving, ripening, wet spinning in an acid bath, finishing; flow chart; properties; uses.

Remember it

Viscose steps: 'Some People Shred And Xerox Documents Rather Slowly': Steep, Press, Shred, Age, Xanthate, Dissolve, Ripen, Spin.