Synthetic Fibers

Synthetic Fibers

• Synthetic fibers can be produced in large quantities and are cheaper than some natural fibers like pure silk.
• Examples of synthetic fibers include polyamide nylons, polyesters, PVC, phenolformaldehyde resin, and polyethylene.

Polyester (Terylene or Polyethylene Terephthalate)

• Polyester is a category of polymers with ester linkages in their main chain.
• It takes 18% of the market share of synthetic polymers.
• Preparation: Terylene is made from ethylene glycol and terephthalic acid.
• Properties:
  • Occurs as a colorless, rigid substance.
  • Highly resistant to mineral and organic acids, but less resistant to alkalis.
  • Hydrophobic in nature.
  • High melting point due to the presence of aromatic rings.
• Uses:
  • Mostly used for making synthetic fibers.
  • Can be blended with wool, cotton for better use and wrinkle resistance.
  • Other applications include electrical insulation.

Nylon (Polyamide Resin)

• Nylon is a polyamide resin containing recurring amide groups in its structure.
• Produced by copolymerization of di-amine with di-acid.
• Different types of nylons include nylon 6,6, nylon 6,10, etc.
• Nylon 6:
  • Synthesized by ring-opening polymerization of caprolactam.
  • Properties:
    • Tough and possessing high tensile strength and elasticity.
    • Wrinkleproof and highly resistant to abrasion and chemicals like acids and alkalis.
    • Can absorb up to 2.4% of water.
  • Uses: Making tire cords, textiles, and in the automobile industry.
• Nylon 6,6:
  • Prepared by condensation polymerization of adipic acid and hexamethylene diamine.
  • Properties:
    • Translucent, whitish, and high melting point.
    • Possesses high temperature stability and good abrasion resistance.
    • Has good strength and is insoluble in common organic solvents.
  • Applications:
    • Textile industry.
    • Mechanical engineering applications like gears, bearings, and machine parts.
    • Flexible tubing for conveying petrol, etc.
    • Used as electrical insulators and in the automobile industry.

Biodegradable Polymers

• Generally, polymers are not affected by the environment.
• Natural polymers are biodegradable, but synthetic polymers and plastics are not prone to biodegradation and cause pollution.
• Biodegradable polymers are defined as degradable polymers in which degradation is caused by the action of naturally occurring microorganisms.
• Examples of biodegradable polymers:
  • Poly-lactic acid (PLA)
  • Polyvinyl acetate (PVA)

Poly-lactic Acid (PLA)

• An aliphatic thermoplastic polyester.
• Derived from renewable resources like corn starch, tapioca roots, or sugarcane.
• Properties:
  • Crystallinity of around 37%.
  • Melting temperature between 173-178°C.
  • Soluble in chlorinated solvents, benzene, and tetrahydrofuran.
• Applications:
  • Biomedical applications like drug delivery devices and dialysis media.
  • Production of compost bags, food packaging, and disposable tableware.
  • Can be used in the form of fibers and non-woven textiles.

Polyvinyl Acetate (PVA)

• Obtained by the addition polymerization of vinyl acetate.
• Properties:
  • A rubbery synthetic polymer with the formula (C4H6O2)n.
  • Water soluble, colorless, and transparent.
  • Has excellent mechanical properties and good heat resistance.
  • Harmless if taken orally.
• Applications:
  • Adhesives for porous materials, particularly wood, paper, and cloth.
  • Wood glue, known as "white glue" or PVA glue.
  • Paper adhesive during paper packaging.
  • Used in making chewing gums, paint emulsions, etc.

Conducting Polymers

• Classified into two types: intrinsic conducting polymers and doped conducting polymers.
• Intrinsic conducting polymers:
  • Characterized by intensive conjugation of π-bonds in their structure.
  • Examples: polyacetylene, polythiophene, and polyaniline.
• Doped conducting polymers:
  • Conducting polymers having e-s in their backbone can be easily oxidized or reduced.
  • Doping can be done by oxidation or reduction, resulting in p-doping or n-doping.

Classification of Polymers based on Tacticity

• Stereochemical arrangement of atoms.
• Isotactic polymers: All substituents are located on the same side of the macromolecular backbone.

Natural Rubber

• A high molecular weight hydrocarbon polymer represented by the formula (C5H8)x.
• Obtained from the milk emulsion called latex by tapping the bark of the tree "Hevea brasiliensis."
• The main composition of natural rubber is polyisoprene.
• Isoprene in natural rubber exists in two geometrical isomeric forms, cis and trans.

Vulcanization of Natural Rubber

• Advantages:
  • Good tensile strength and load-bearing capacity.
  • Excellent resilience.
  • Better resistance to moisture, oxidation, and abrasion.
  • Resistance to organic solvents like CCl4, benzene, and petrol.
  • Good elasticity.
  • Good electrical insulator.
• Applications:
  • Manufacture of tires.
  • Heavy-duty tires.
  • Tank linings in chemical plants.
  • Reducing machine vibrations.
  • Foam rubber for making cushions, mattresses, padding, etc.

Neoprene

• A class of synthetic rubbers made from chloroprene polymerization.
• Properties:
  • High tensile strength.
  • Resistant to chemicals, water, heat, fires, oxygen, and ozone.
  • More resistant to water, chemicals, and heat than natural rubber.
  • Resistant to weather and sunlight, making it last longer.
• Applications:
  • Industrial settings and other places with a lot of movement.
  • Neoprene extrusions and neoprene sheets.