Plastics and Fibres

Plastics are polymeric materials that can reform or reshape by applying heat or pressure. Different kinds of plastics have different types of monomeric units. The arrangement of these monomeric units can be in the cross-link, chain or sheet forms. Plastics have a vast number of uses in almost every field. Plastic can directly or indirectly alter environmental changes.

Similarly, fibres are chemical compounds made up of small units of monomers. Fibres can broadly be categorised into two types: natural and synthetic. Natural fibres are naturally occurring fibrous materials extracted from wool, cotton, grains, etc. On the other hand, synthetic fibres are man-made fibres that are synthetically manufactured to perform certain functions or enhance the properties of natural fibres.

Both plastics and fibres are polymers, and they share similar classification criteria like chemical composition, arrangements of monomers, physical properties, etc.

Classification of Plastics 

Plastics can be classified based on different criteria, such as the chemical structure of polymeric backbone, the chemical structure of polymeric side chains, or their chemical synthesis process. These criteria apply to fibres as well.

Different processes such as condensation, crosslinking and polyaddition can synthesise plastics. 

Physical properties such as strength, density, resistance to temperature, pressure, and chemicals are also used as criteria to classify plastics. 

Generally, plastics can be classified as thermoplastics and thermosetting polymers. 

Thermoplastic:

• Thermoplastics can be reshaped repeatedly by heating until they are converted into thermosets. 

• There is no internal chemical change in thermoplastics on heating.

• Examples include polystyrene, polypropylene, polyvinyl chloride, polyethene, and polytetrafluoroethylene (PTFE). 

• The mass of thermoplastic has a range of 20,000 to 50,000 amu. 

Thermosets: 

• Thermosets, on the other hand, can be heated and shaped once. 

• After moulding, thermosets are solidified and retain their form. 

• An irreversible reaction occurs in thermosets which restrict the plastic to reshape. 

• Examples include bakelite; a cross-linking polymer formed by heating Novalac with formaldehyde.

Classification of Fibres 

Natural fibres:

Natural fibres are generally classified based on their origin, i.e., from where they are extracted. The cellulosic fibre is extracted from vegetables, cotton, jute, flax, etc. the protein-based or animal fibres are extracted from silk, wool, etc.

Synthetic fibres: 

Synthetic fibres are composed of monomeric units attached via covalent bonds.

Therefore these fibres are classified based on the arrangement of monomers. They are linear, branched or cross-linking (network) polymers. The arrangement of monomers attached from one end to another in a straight line is called the linear structure of the polymer. When these linear chains emerge as branches, they form branched structures. These branches can crosslink with other units and form a network structure.

Both plastics and fibres are significant contributors to society today. Some applications of plastics and fibres are listed below.

Applications of Fibres

Synthetic fibres:

• Factory synthesised cellulosic fibres are used to manufacture paper, tire cords, rugs, suit coat linings, cigarette filters, or a substitute for cotton.

• Polyamide, a synthetic fibres category, is used to make hosiery, sports garments, luggage, tires, seat belts, ropes, nets, fishing lines, hoses, etc. 

• Aramid (synthetic fibre) is used to manufacture aircraft panels, bulletproof vests, radial tire belts, flame resistant clothing, etc.

• Polyester, another category of synthetic fibres, are used in the manufacture of carpets, tire yarns, nonwoven fabrics, sewing threads, permanent-press clothing etc. Polyacrylonitrile, a substitute for wool, is used to manufacture battery separators, blankets, sweaters, filters, hosiery, etc.

• Polypropylene is used to manufacture carpets, nets, ropes, nonwoven fabrics, upholstery etc. 

• Polyurethane is used as stretch fabric in sportswear and swimsuits.

Natural fibres:

Natural fibres on exposure to light and moisture become yellow and lose their strength. This is the reason for preferring synthetic fibres over natural fibres.

• Horsehair, a natural fibre, is used to make a string of violin bows.

• Natural fibres are used to manufacture brushes of industrial, paint or domestic grade.

• Natural fibres are also used in mattresses and furniture.

Applications of Plastics

• Like fibres, plastics have a large number of applications. From commodities to industries require plastic due to its versatile nature.

• Plastics such as Plastomers, HDPE, LDPE, organoleptic polymers are used in the manufacture of bottles, geomembranes, bags, sheets, etc.

• In the manufacture of stationery items like pens, Petri dishes, packaging, medical items, protective packaging, disposable food containers, furniture components, household goods, automotive components, appliance components, swimming pool parts etc., plastics like HIPS, GPPS, ABS, EPS, metallozine are used.

• PA6, PET, PC(Polycarbonate), PBT, PUR(Polyurethane), SAN, TPE(Thermoplastic Elastomers) etc., are used in the manufacture of number plates, fishing line, automotive components, industrial appliance components, footwear, roof sheeting, gears, plugs, protective gears, cosmetic jars, castor wheels, carbonated drink bottles, ear tags, mining, conveyor belts, etc.

• Thermosets are used in Cookware Handles, Appliances, Industrial Components, Toilet Seats, etc.

Conclusion 

Plastics and fibres are essential categories of compounds because of their broad applications. Plastics and fibres are categorised under polymers. Both plastics and fibres share similar classification criteria like chemical composition, arrangements of monomers, physical properties, etc. Fibres are either artificially synthesised or naturally occurring. Different polymerisation processes can also help understand the basic compositions of plastics and fibres. Plastics are broadly categorised as thermosetting and thermoplastic. Thermoplastic is more flexible for industrial use. Competitive to thermosets, thermoplastics are more environmentally friendly.