Polymers — Part 2: Important polymers, rubber and biodegradable polymers: visual lesson, CBSE Class 12 Chemistry

Lesson

Polymers in daily life

Part 2 — the polymers we make, use and throw away.

In this lesson you will

Describe the preparation and uses of polythene, Teflon, polyacrylonitrile, nylons, terylene, Bakelite and melamine
Explain natural rubber, vulcanisation and synthetic rubbers (neoprene, Buna-N, Buna-S)
Calculate number-average and weight-average molar masses and the polydispersity index
Describe biodegradable polymers such as PHBV and nylon-2–nylon 6

Concept

Polythene, Teflon and polyacrylonitrile

LDPE (low density): ethene at 1000–2000 atm, 350–570 K with a peroxide initiator; highly branched, soft, used for squeeze bottles, carry bags, insulation. HDPE (high density): ethene at about 333–343 K and 6–7 atm with a Ziegler–Natta catalyst; linear, tougher, used for buckets, pipes. Teflon from tetrafluoroethene: chemically inert, used for non-stick coatings. Polyacrylonitrile (PAN) from acrylonitrile: fibre (orlon, acrilan) used as a wool substitute.

Table of addition polymers with monomers, structure and uses
Polymer	Monomer	Structure	Use
LDPE	Ethene	Branched	Carry bags, squeeze bottles
HDPE	Ethene	Linear	Buckets, pipes, dustbins
Teflon	CF₂=CF₂	Linear	Non-stick pans, seals
PAN	CH₂=CHCN	Linear	Acrylic fibres (wool substitute)
PVC	CH₂=CHCl	Linear	Pipes, raincoats, flooring

Concept

Nylons and terylene

Nylon 6,6: hexamethylenediamine + adipic acid at high temperature (polyamide; amide links –CO–NH–); used in sheets, bristles, textiles. Nylon 6: from caprolactam heated with water. Terylene (Dacron): ethylene glycol + terephthalic acid at 420–460 K with a catalyst (polyester; ester links); used in crease-resistant fabrics and safety belts.

\text{polyamide link: } \mathrm{-CO-NH-} \qquad \text{polyester link: } \mathrm{-CO-O-}

Table of nylon 6,6, nylon 6 and terylene with monomers, linkages and uses
Polymer	Monomers	Link	Use
Nylon 6,6	H₂N(CH₂)₆NH₂ + HOOC(CH₂)₄COOH	Amide	Bristles, ropes, fabrics
Nylon 6	Caprolactam	Amide	Tyre cords, fabrics, ropes
Terylene	HOCH₂CH₂OH + HOOC–C₆H₄–COOH	Ester	Clothes, sails, seat belts

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