Both assertion as well as reason statement is true. Natural rubber may be considered as a linear polymer of isoprene (2-methyl-1, 3 butadiene) and is also called as cis-1, 4-polyisoprene. On vulcanization, sulphur forms cross links at the reactive sites of double bonds and thus, the rubber gets stiffened. Thus, this option is correct.

Buna-S, NBR and neoprene: All are examples of elastomers.

Yes, it is correct., as all are used as blowing agent for polymers. Zinc carbonate is an inorganic chemical blowing agent which decomposes at higher temperature than bicarbonates. 5-phenyltetrazole (5-PT) has been widely used as a blowing agent for foaming high temperature-processing polymers. The principal use of azodicarbonamide is in the production of foamed plastics as a blowing agent.

Poly β-hydroxybutyrate – co- β -hydroxy valerate (PHBV) is a biodegradable polymer obtained by the copolymerisation of 3-hydroxybutanoic acid and 3 - hydroxypentanoic acid. Nylon 2–nylon 6 is an alternating polyamide copolymer of glycine (H₂N–CH₂–COOH) and amino caproic acid [H₂N (CH₂)₅ COOH] and is biodegradable.

Calcium carbonate is mainly used as filler in the plastics sector. Aluminium hydroxide also finds use as fire retardant filler for polymer applications.

Elastic deformation in polymers is due to slight adjustment of molecular chains. High-density polyethylene is more crystalline than low-density polyethylene because it contains fewer branches.

Polyether ether ketone (PEEK) is a semicrystalline thermoplastic polymer with excellent mechanical and chemical resistance properties that are retained till high temperatures. Thus, this option is correct.

Melamine resin, polyurethanes, polyepoxides: All are examples of thermosetting polymers.

Glass transition temperature (T_g) of polytetrafluoroethylene (PTFE) is 115 ^oC.

Citric acid ethyl ester is used as a plasticizer for polyvinylchloride and similar plastics. Dibutyl sebacate is a dibutyl ester of sebacic acid. Its main use is as a plasticizer in production of plastics such as cellulose acetate butyrate, cellulose acetate propionate, ethyl cellulose, polyvinyl butyral, polyvinyl chloride, polystyrene, and many synthetic rubbers and other plastics. Polybutene and polyisobutylene are liquid oligomers widely used as plasticizers for high-molecular weight polymers, such as polyethylene. n-Butyl benzyl phthalate is an ester of phthalic acid, benzyl alcohol and n-butanol. It is mostly used as a plasticizer for PVC.

Melac is used in the manufacture of unbreakable crockery. PTFE is used in making oil seals and gaskets and also used for non-stick surface coated utensils. PAN is used as a substitute for wool in making commercial fibres as orlon or acrilan. Glyptal is used in manufacture of paints and lacquers. Thus, this option is correct.

Nahcolite (sodium bicarbonate) is commonly used as a blowing agent in the manufacture of rigid foams which are chiefly polystyrene polyurethane, epoxy and polyvinyl chloride. Dioctyl phthalate (Bis(2-ethylhexyl) phthalate) is the most common of the class of phthalates which are used as plasticizers. Titania (titanium dioxide) is the most important white pigment used in the polymer industry. Salol (phenyl salicylate) is used as UV stabilizer for commercial polymers and sun tanning lotions.

Polycarbonate (Lexan) is highly transparent to visible light, with better light transmission than many kinds of glass. Polycarbonate (Lexan) has a glass transition temperature of about 147°C, so it softens gradually above this point and flows above about 155°C.

Polyphenylene oxide is an amorphous standard thermoplastic polymer. Polyetherimide (PEI) is an amorphous thermoplastic with high mechanical strength and rigidity. Polyamide-imide (PAI) are amorphous thermoplastic high performance polymers characterized by high thermal stability.

This option is correct because the correct match is: [CH₂CH(OH)]_n - 230^oC [F₂C—CF₂]_n - 326.8^oC [(CO)C₆H₄(CO₂CH₂CH₂O)]_n - 260^oC [CH₂O]_n - 175^oC.