Synthetic Fibres, Chemistry tutorial

Synthetic fibres

Introduction

Synthetic or man-made fibres usually come from synthetic materials these as petrochemicals.  But several kinds of synthetic fibres are created from natural cellulose; including rayon, modal, and the more recently developed Lyocell. Cellulose-depend fibres are of 2 kinds, regenerated or pure cellulose these as from the cupro-ammonium process and modified cellulose- the cellulose acetates.

Definition of Synthetic Fibres

Synthetic fibres are subsets of man-made fibres that are depend on synthetic chemicals (often from petrochemical sources) rather than arising from natural materials via a purely physical procedure. 

While, Synthetic dyes are manmade dyes that impart better properties upon the dyed materials.

Kinds of Fibres

(a) Cellulose fibres are a subset of man-made fibres, regenerated from natural cellulose. The cellulose comes from various sources. Modal is made from beech trees, bamboo fiber is a cellulose fiber made from bamboo, soy silk is made from soybeans, and seacell is made from seaweed, and so on.

(b) Mineral fibres

Fiberglass made from specific glass, and optical fiber, made from purified natural quartz, are also man-made fibres that come from natural raw materials. Metallic fibres can be drawn from ductile metals such as copper, gold or silver and extruded or deposited from more brittle ones, these as nickel, aluminum or iron.

Carbon fibres are often depends on carbonized polymers, but the end product is pure carbon.

(c) Polymer fibres

Polymer fibres are a subset of man-made fibres that are based on synthetic chemicals (often from petrochemical sources) rather than arising from natural materials through a purely physical process. Such fibres are made from:

Polyamide nylon, PET or PBT polyester phenol-formaldehyde (PF) polyvinyl alcohol fiber (PVA) polyvinyl chloride fiber (PVC) polyolefins (PP and PE) acrylic polyesters, pure polyester PAN fibres are utilized to make carbon fiber via  roasting  them  in  a  low  oxygen  atmosphere. Traditional acrylic fiber is employed more often as a synthetic replacement for wool. Carbon fibres and PF fibres are noted as 2 resin-based fibres that aren't thermoplastic; most others can be melted aromatic polyamids (aramids) these as Twaron, Kevlar and Nomex thermally degrade at high temperatures and don't melt. Such fibres have strong bonding between polymer chains polyethylene (PE), eventually by very long chains / HMPE (for example Dyneema or Spectra). Elastomers can even be utilized, for instance spandex although urethane fibres are starting to replace spandex technology. polyurethane fiber

(d) Microfibres: Micro fibres in textiles refer to sub-denier fiber (such as polyester). Denier and Detex are 2 measurements of fiber yield depend on weight and length. If the fiber density is known we as well have a fiber diameter, otherwise it is simpler to measure diameters in micrometers. Microfibres in technical fibres refer to ultra fine fibres (glass or melt blown thermoplastics) often utilized in filtration. Newer fiber designs contain extruding fiber that splits into multiple finer fibres. Most synthetic fibres are round in cross-section, but special designs can be hollow, oval, star-shaped or trilobal. The latter design gives more optically reflective properties. Synthetic textile fibres are frequently crimped to provide bulk in a woven, non woven or knitted structure. Fiber surfaces can as well be dull or bright. Dull surfaces reflect more light while bright tends to transmit light and build the fiber more transparent.

Properties and Applications of Synthetic Fibres

Table: Application of Synthetic Fibres

Polymer

family and

type

Polyamide

s

Common

Names

& Trade

Names

Deniers

 

(gm/9,0

00 m)

 

Tensil

e

Streng

th

(gm/d

enier)

Elong

ation

at

Break

 

(%)

Initial

 

Modu

lus

(gm/d

enier)

Apparel and

Home-

Furnishing

Applications

Industrial

Applications

Polycaprol

actam

(textile

fibre

nylon 6

(textile)

1.5-5

4.5-

6.8

23-43

25-35

hosiery,

lingerie, sports

garments,

soft-sided

luggage,

upholstery

no significant

applications

Polyhexa

methylene

adipamide

 

(textile

fibre)

nylon 6,6

(textile)

1.5-5

4.5-

6.8

23-43

25-35

hosiery,

lingerie, sports

garments,

soft-sided

luggage,

upholstery

no significant

applications

Polycaprol

actam

(industrial

fibre

nylon 6

(industrial)

1.5-5

8.5-

9.5

12-17

33-46

no significant

applications

tyres, ropes,

seat belts,

parachutes,

fishing lines

and nets,

hoses

Polyhexa

methylene

adipamide

 

 

nylon 6,6

(industrial)

1.5-5

8.5-

9.5

12-17

33-46

no significant

applications

tyres, ropes,

seat belts,

parachutes,

fishing lines

and nets,

hoses

(industrial

fibre)

Aramids

 

 

 

 

 

 

 

Poly-p-

phenylene

tereph-

Kevlar,

Twaron,

1.0-1.5

 

25-30

3-6

500-

1,000

no significant

applications

radial tyre

belts,

bulletproof

vests,

reinforcement

for

boat hulls

and aircraft

panels

thalamide

Technora

 

 

 

 

 

 

Poly-m-

phenylene

isoph-

Nomex,

Conex

 

2-5

3-6

2-30

130-

150

no significant

applications

filter bags for

hot stack

gases, flame-

resistant

thalamide

Polyesters

Polethylen

e

terephtalat

e

Dacron,

Terylene,

Trevira

1.5-5

 

4.7-

6.0

35-50

25-50

 

permanent-

press clothing,

fibre fill

insulation,

carpets

sewing thread,

seat belts,

tyre yarns,

non-woven

fabrics

Polyacrylo

nitrile

 

Acylic

(>85%)

acrylonitri

le

Acrilan,

Creslan,

Courtelle

2-8

 

2.5-

4.5

27-48

25-63

substitute for

wool--e.g., in

sweaters,

hosiery,

blankets

 

filters, battery

separators,

substitute for

asbestos

in cement

Modacryli

c (35-

85%)

acrylonitri

le

Verel, SEF

2-8

2.5-

4.5

27-48

22-56

flame-resistant

clothing--

e.g.,

artificial fur,

children's

sleepwear

flame-resistant

awnings,

tents, boat

covers

Polyolefin

s      

Polypropy

lene

Herculon,

Marvess

2-10

5-9

15-30

29-45

upholstery,

carpets, carpet

backing

ropes, nets,

disposable

non-woven

fabrics

Polyethyle

ne

 

Regular

High-

Modulus

Dyneema,

Spectra

2-10

2-4

30-35

20-40

2.7-3.5

1,370-2016

No significant applications no significant 

applications

Cordage, webbing

Reinforcement

For boat hulls, bulletproof  vests

Polyuretha

ne

spandex,

Lycra

2.5-20

0.6-1.5

400-600

 

stretch fabrics-

-e.g.,  for

sportswear,

swimsuits

no significant

applications










Kinds of Synthetic Dyes

There are diverse types of synthetic dyes that impart colours on dyed materials. These are:

a. Acid Dyes: They come in a wide variety of colours; it is fairly fast to light and to washing. It is named acid dyes since they work best when applied in an acid bath. It is mostly utilized on nylon, silk and wool.

Azoic (or Naphthol) Dyes: This kind of dyes is enormously fast to light,  it  is  generally  utilized  to  dye  a  material  red,  orange  or maroon. It is mostly employed in cotton.

c. Basic Dyes: This kind of dye is just fair when it comes to fastness to light and to washing, however this type can create a brilliant colour. It is mainly used on natural and acrylic fibres; it is as well sometimes utilized for wool and silk. This dye is as well utilized to colour paper. Acetic acid is generally added to the dyebath to assist in the quick penetration of the dye onto the fiber.

d. Chrome (or Mordant) Dyes: This kind of dye is fairly fast to light and to washing, it is especially helpful for black and navy shades. The choice of mordant is extremely significant as different mordants can alter the final colour significantly; it is significant to recognize as well that many mordants, particularly those in the hard metal category can be hazardous to health that is why caution should be followed when using it. It is largely utilized for wool and silk.

e. Mordant is a chemical that is mixed through the dye and the fiber, the modern mordants are dichromates and chromium complexes, that is why it is as well termed chrome dye.

f. Developed (or Diazo) Dyes are employed to treat assured dyed fabrics to improve their fastness to light and to washing and as well to change fabric's colour. The treatments are employed primarily on cotton. Diazotizing is the treatment that involves the employ of chemical termed a developer. It is essentially employed on cotton.

g. Direct Dyes this kind is one of the easiest to utilize and has a wide range of colours, it isn't fast to washing, but its fastness is often improved through more treatment. It is mainly utilized on cotton, rayon leather, wool, silk and nylon. It is too employed as pH indicators and as biological stains.

h. Disperse (or Acetate) Dyes  this dyes is finely ground in the presence of dispersing agent, its dyeing rate is seriously influenced through the dispersing agent utilized during the grinding. Disperse dyes were developed since other dyes would not work with acetate it is as well employed on different manmade fibres, including acrylic, acetate, and polyester fibres.

i. Reactive (or Fiber-reactive) Dyes:  Such kinds of dye have a good fastness to light and to washing. Reactive dyes create strong chemical bonds through the material being dyed that builds it the most permanent of dyes. This dye is via far the best choice for dyeing cotton, nylon, wool and other cellulose fibres at home or in the art studio.

j. Sulphur Dyes: Such dyes are especially fast to washing and the best for material that is washed frequently. Sulphur dyes are colourless (upon application), but upon exposure to air they are oxidized and turn into their relevant colours. They come mostly in dark, dull colours and utilized on cotton, linen and rayon.

k. Vat Dyes: This kind is superior compared to the other dye when it comes to its fastness to light and to washing. Vat dyes like sulphur dyes must be oxidized before their real colour comes out. This dye is mainly employed for cotton, linen, wool and silk. The indigo colour of blue jeans is vat dye.

Dyes for Man- Made Fibres

The 1st man-made fibre to attain commercial significance was viscose rayon, in the early 1900s. This is chemically alike to cotton (in other words it is a cellulosic fibre) and so the dyes already available for cotton were utilized on viscose rayon. At the time such were mainly direct, vat, azoic and sulphur dyes, but since the year 1960s fibre-reactive dyes have come to be extensively utilized on all cellulosic fibres. In the year 1930s, when acetate rayon appeared, the existing dyes were not very suitable, with the notable exception of the natural dye logwood black, which was already being used on silk and wool. A new class of dyes eventually to be called disperse dyes, was developed which allowed a full range of shades to be successfully applied to acetate rayon.

In the year 1940s and 1950s the truly synthetic fibres, these as the polyamides (nylon), polyesters and acrylics, began to appear commercially. Disperse dyes proved to be particularly appropriate for polyester and so the importance of this class of dye amplified enormously. Since both fibres and dyes have been modified since then, polyamides are now dyed mainly by acid dyes, and acrylics mostly through modified basic dyes.

Over the last twenty to thirty years, developments in dye chemistry have enabled the man-made fibre to be dyed through better fastness to light and washing, and in an ever rising range of colours.

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