polymers

Question 1

mass of polymer range

Answer 1

10³ to 10⁷

Question 2

natural polymers

Answer 2

found in plants and animals
e.g. proteins, cellulose, starch, resins, rubber

Question 3

semi-synthetic polymers

Answer 3

cellulose derivatives like cellulose acetate (rayon) and cellulose nitrate etc

Question 4

synthetic polymers

Answer 4

plastic (polythene), synthetic fibres (nylon 6.6), synthetic rubbers (Buna-S)

Question 5

free radical mechanism- what is formed

Answer 5

alkenes, dienes and their derivatives

Question 6

free radical mechanism- how does it take place + catalysts

Answer 6

alkenes, dienes, derivatives as polymerised in the presence of a free radical generating initiator (catalyst) like benzoyl peroxide, acetyl peroxide, tert-butyl peroxide

Question 7

what is the intermediate formed in free radical mechanism, chain initiation step from benzoyl peroxide

Answer 7

phenyl radical

Question 8

homopolymer

Answer 8

addition polymers formed by polymerisation of a single monomeric species are known as homopolymers. e.g. polythene

Question 9

copolymers

Answer 9

polymer formed from addition product of two different monomers are called copolymers

e.g. Buna-S

Question 10

under what conditions is a low density polythene obtained

Answer 10

• obtained by polymerisation of ethene
• under high pressure of 1000 to 2000 atm
• at a temperature of 350 K to 570 K
• in the presence of dioxygen or a peroxide initiator (catalyst)

Question 11

structure of low density polythenes

Answer 11

highly branched
straight chain structure with some branches

Question 12

Low density polythene properties

Answer 12

• Chemically inert
• tough but flexible
• poor conductor of electricity

Question 13

use of low density polymers

Answer 13

1. insulation of electricity carrying wires
2. manufacture of squeeze bottles, toys, flexible pipes

Question 14

high density polyhene formation how

Answer 14

• addition polymerisation of ethene takes place in a hydrocarbon solvent
• in the presence of a catalyst such as triethylaluminium and titanium tetrachloride (Ziegler-Natta catalyst)
• at a temp of 333 to 343 K
• under a pressure of 6-7 atm

Question 15

HDP structure

Answer 15

linear molecules and has high density due to close packing

Question 16

HDP properties

Answer 16

inert and more tough and hard

used for manufacturing buckets, dustbins, bottles, pipes, etc

Question 17

Teflon

Answer 17

polytetrafluoroethene

Question 18

how is teflon manufactured

Answer 18

by heating tetraflurorethene with a free radical or persulphate catalyst at high pressures

Question 19

uses of teflon

Answer 19

chemically inert and resistant to attack by corrosive reagents so used in making oil seals and gaskets and non stick sruface

Question 20

Polyacrylonitrile

Answer 20

The addition polymerisation of acrylonitrile in presence of a peroxide catalyst leads to its formation

Question 21

use of polyacrylonitrile

Answer 21

substitute for wool in making artificial fibres as orlon or acrilan

Question 22

addition polymerisation also called

Answer 22

chain growth polymerisation

Question 23

condensation polymerisation also called

Answer 23

step growth polymerisation

Question 24

what happens in condensation polymerisation

Answer 24

result in loss of simple molecules like water, alcohol, hydrogen chloride etc

Question 25

what is the product of each step in condensation polymerisation

Answer 25

a bi-functional species

Question 26

terylene other name

Answer 26

dacron

Question 27

monomer of terylene

Answer 27

ethylene glycol and terephthalic acid

Question 28

polyamides

Answer 28

polymers possessing amide linkages are examples of synethetic fibres and are termed as nylons

Question 29

Nylon 6,6 preparation how? type of polymerisation monomers

Answer 29

condensation polymers monomers; hexamethylenediamine with adipic acid under high pressure, temp

Question 30

why does nilon 6,6 have high tensile strength

Answer 30

* strong intermolecular forces like hydrogen bonding * these strong forces lead to close packing of chains and thus impart crystalline nature

Question 31

nylon 6 formation

Answer 31

obtained by heating caprolactam w water at high temp

Question 32

polyesters formation

Answer 32

polycondensation products of dicarboxylic acids and diols e.g. dacron/terylene

Question 33

dacron/terylene formed in the presence of what catalyst

Answer 33

zinc acetate-antimony trioxide catalyst

Question 34

dacron fibre

Answer 34

crease resistant used in blending w cotton and wool fibres also as glass reinforcing materials

Question 35

phenol formaldehyde polymer formed how

Answer 35

condensation rxn of phenol with formaldehyde in the presence of either acid or base catalyst

Question 36

initial product ontained in formation of phenol-formaldehyde polyer

Answer 36

Novolac as used in paints

Question 37

novolac on heating with formaldehyde undergoes cross linking to form an infusible solid mass called ___

Answer 37

bakelite it is a termosetting polymer which cant be reused or remoulded

Question 38

melamine formation how

Answer 38

formaldehyde polymer formed by condensation of melamine and formaldehyde

Question 39

Buna-S formed from

Answer 39

1,3-butadiene and styrene

Question 40

elastomeric polymer

Answer 40

natural rubber

Question 41

natural rubber structure

Answer 41

linear polymer of isoprene (2-methyl-1,3-butadiene) also called cis-1,4-polyisoprene

Question 42

temp at which natural rubber becomes soft

Answer 42

greater tahn 335K

Question 43

temp at which natural rubber becomes brittle

Answer 43

less than 283K

Question 44

what is natural rubber soluble in

Answer 44

non-polar solvents and non resistant to attack by oxidising agents

Question 45

vulcanisation of rubber

Answer 45

heating raw rubber with sulphur on vulcanisation sulphur forms cross links at the reactive sites of double bonds and thus rubber gets stiffened

Question 46

neoprene

Answer 46

synthetic rubber neoprene or polychloroprene formed by free redical polymerisation of chloroprene