Polymers and Plastics

Elastomers are rubber–like solids with elastic properties. In these elastomeric polymers, the polymer chains are held together by the weakest intermolecular forces. These weak binding forces permit the polymer to be stretched. A few ‘crosslinks’ are introduced in betweenthe chains, which help the polymer to retract to its original position after the force is released as in vulcanised rubber. Examples are buna-S, buna-N, neoprene, Bromo Isobutylene Isoprene (bromobutyl), Viton (a brand of synthetic rubber and fluoropolymer elastomer commonly used in O-rings and other molded or extruded goods), etc.

P. Neoprene is a synthetic rubber and used in the formation of waterproof seat covers, manufacturing gaskets, corrosion resistant coatings. Q. Urea formaldehyde resin is prepared from the condensation reaction of urea and formaldehyde. R. Glyptal is the copolymer (condensation polymer) of Ethylene glycol and Phthalic acid. Hence, only statement P is false.

Polyacrylonitrile (PAN) is made from the addition polymerisation of acrylonitrile and is manufactured under the brand name of orlon. Vectran is the brand name of aromatic polyester used as reinforcing fibres for ropes and sailcloth. It is also used in manufacturing badminton strings, bike tyres and in electronics applications.

Epoxy resins, also known as polyepoxides are a class of reactive prepolymers and polymers, which contains  epoxide groups. Epoxy resins may be reacted (cross-linked) either with themselves through catalytic homopolymerisation, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols, and thiols. Examples are - Bisphenol A (BPA), Bisphenol F (BPF), Epoxy phenol novolac (EPN), etc. Examples of polyvinyl resins are - PVA (poly vinyl alcohol), PVAc (poly vinyl acetate), etc.

(P) Vulcanization is a chemical process for converting natural rubber or related polymers into more durable materials via the addition of sulphur or a solution of S₂Cl₂ in CS₂. (Q) Buna-N is the copolymer of butadiene and acrylonitrile. (R) Cellulose is treated with sulfuric acid and potassium nitrate to give cellulose mononitrate. This was used commercially as Celluloid, a highly flammable plastic used in the first half of the 20^th Century for lacquers and photographic film. Hence, statement P is only incorrect.

(P) Poly methyl methacrylate (PMMA) is produced by the homopolymerisation of methyl methacrylate. PMMA is a transparent thermoplastic and used as a glass substitute. (Q) Kydex is a line of thermoplastic acrylic-polyvinyl chloride materials manufactured by Kydex LLC. It has a wide variety of applications, including for firearm holsters and sheaths for knives. (R) Polyvinyl acetate (PVAc) is made by polymerization of vinyl acetate. In a water suspension, this is used as a glue. Polyvinyl chloride (PVC) is made by polymerization of the monomer vinyl chloride and is used in the formation of pipes. Hence, only statement R is false.

Since, statement R is the only false statement, then this option is not correct.

Poly methyl methacrylate (PMMA) is produced by the homopolymerisation of methyl methacrylate. PMMA is a transparent thermoplastic and used as a glass substitute. Hence, only polymer S is used as a glass substitute.

A large number of polymers are quite resistant to environmental degradation processes and are thus responsible for the accumulation of polymeric solid waste materials. It is obtained by the copolymerisation of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid. PHBV is used in speciality packaging, orthopaedic devices and in controlled release of drugs. PHBV undergoes bacterial degradation in the environment. The examples of non-biodegradable polymers are - PMMA (poly methyl methacrylate), PVC (polyvinyl chloride), PVAc (polyvinyl acetate), PFR (phenol formaldehyde resin), PP (polypropylene), etc.

P. Nylon 2–nylon 6 (nylon 2,6) is an alternating polyamide copolymer of glycine and amino caproic acid. It is biodegradable. Q. Glyptal is the condensation polymer of ethylene glycol and phthalic acid. It is used in the manufacture of paints and lacquers. Bakelite is the condensation polymer of phenol and formaldehyde. It is used in the making of combs, electrical switches, hardness of utensils and computer discs. R. Urea formaldehyde resin (UFR) is the condensation polymer of urea and formaldehyde and is used in the making of unbreakable cups and laminated sheets. Hence, only statement Q is not true.

Step growth polymerisation - This type of polymerisation generally involves a repetitive condensation reaction between two bi-functional monomers. These polycondensation reactions may result in the loss of some simple molecules as water, alcohol, etc., and lead to the formation of high molecular mass condensation polymers. Examples are - the formation of terylene or dacron by the interaction of ethylene glycol and terephthalic acid, the condensation polymerisation of hexamethylenediamine with adipic acid under high pressure and at high temperature (Nylon 6,6), etc. Hence, both Dacron and Nylon 6,6 are made from step growth polymerisation.

Polymers are defined as high molecular mass macromolecules, which consist of repeating structural units derived from the corresponding monomers. These polymers may be of natural or synthetic origin. Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic Examples of natural polymers are - starch, glycogen, cellulose, pectin, wool, silk, rubber, chitin, rayon, etc.

(P) PA 6/66 (nylon 6/66) is a copolymer and is made from caprolactam, hexamethylenediamine and adipic acid. (Q) PA 6I (nylon 6I) is an amorphous polymer made from the polymerisation of hexamethylenediamine and isophthalic acid. PA 66/610 (nylon 66/610) is made from hexamethylenediamine, adipic acid and sebacic acid. (R) Amodel from Solvay industries and Trogamid from Evonik Industries are semi-aromatic polyamides and are made from the polymerisation of hexamethylenediamine and terephthalic acid. Hence, Q and R are false.

Natural rubber is a polymer of isoprene (cis-1,4-polyisoprene). Thiokol is a synthetic rubber, Theo pentene is not a polymer, and artificial wax is not an isoprene polymer.

This is correct statement about tissue conditioning materials.