Define thermoplastics and thermo setting polymers with two examples of each
Thermoplastics polymers are linear polymer which can be repeatedly melted and moulded again and again on heating without any change in chemical composition and mechanical strength. Examples are polythene and polypropylene.
Thermosetting polymers, on the other hand, are permanently setting polymers. Once on heating in a mould, they get hardened and set, and then cannot be softened again. This hardening on heating is due to cross- linking between different polymeric chains to give a three dimensional network solid. Examples are bakelite, melamine-foimaldehyde polymer etc.
Which of the following polymers are used as fibre?
(a) Polytetrafluoroethane (b) Poly chloroprene
(c) Nylon (d) Terylene
Write the monomers used for gettingThe following polymers:
(i) Polyvinylchloride
(ii) Teflon (iii) Bakelite
Which of the following polymers are condensation polymers?
(a) Bakelite (b) Teflon
(c) Butyl rubber (d) Melamine formaldehyde resin
Name the polymers used in laminated sheets and give the name of monomeric units involved in its formation.
Out of chain growth polymerisation and step growth polymerisation, in which type will you place the following.
What is a biodegradable polymer ? Give an example of a biodegradable aliphatic polyester.
Which of the following polymers soften on heating and harden on cooling? What are the polymers with this property collectively called? What are the polymers with this property collectively called? What are the structural similarities between such polymers? Bakelite, urea-formaldehyde resin, polythene, polyvinyl, polystyrene.
Which of the following polymers are thermoplastic?
(a) Teflon (b) Natural rubber (c) Neoprene (d) Polystyrene
Assertion (A): Olefinic monomers undergo addition polymerization.
Reason (R): Polymerisation of vinyl chloride is initiated by peroxides/ persulphates.
Which of the following are characteristics of thermosetting polymers?
(a) Heavily branched cross linked polymers.
(b) Linear slightly branched long chain molecules.
(c) Become infusible on moulding so cannot be reused.
(d) Soften on heating and harden on cooling, can be reused.
Write the names and structures of the monomers of the following polymers:
(i) Buna-S (ii) Buna-N (iii) Dacron (iv) Neoprene
What is the role of benzoyl peroxide in addition polymerization of alkenes? Explain its mode of action with the help of an example.
Assertion (A): Polyamides are best used as fibres because of high tensile strength.
Reason (R): Strong intermolecular forces (like hydrogen bonding within polyamides) lead to close packing of chains and increase the crystalline character, hence, provide high tensile strength to polymers.
Assertion (A): For making rubber synthetically, isoprene molecules are polymerised.
i Reason (R): Neoprene (a polymer of chloroprene) is a synthetic rubber.
Which of the following monomers form biodegradable polymers?
(a) 3-hydroxybutanoic acid +3-hydroxypentanoic acid
(b) Glycine + aminocaproic acid
(c) Ethylene glycol + phthalic acid
(d) Caprolactam
Which of the following are examples of synthetic rubber?
(a) Polychloroprene (b) Polyacrylonitrile
(c) Buna-N (d) cis-polyisoprene
What is the structural difference between HDP and LDP? How does the structure account for different behaviour and nature, hence the use of a polymer?
How is the following resin intermediate prepared and which polymer is formed by this monomer unit?
A natural linear polymer of 2-methyl-l,3-butadiene becomes hard on treatment with sulphur between 373 to 415 K and -S – S – bonds are formed between chains. Write the structure of the product of this treatment?
Which type of biomolecules have some structural similarity with synthetic polyamides? What is this similarity?
Phenol and formaldehyde undergo condensation to give a polymer (A) which on heating with formaldehyde gives a thermosetting polymer (B). Name the polymers. Write the reactions involved in the formation of (A). What is the structural difference between two polymers?
Which of the following are addition polymers?
(a) Nylon (b) Melamine formaldehyde resin
(c) Orion (d) Polystyrene
How does the presence of double bonds in rubber molecules influence their structure and reactivity?
Why should the monomers used in addition polymerisation through free radical pathway be very pure?
