Low density polythene and high density polythene, both are polymers of ethane but there is marked difference in their properties. Explain.
Low density and high density polythenes are obtained under different reaction conditions. LDP is obtained through free radical addition at high pressure (1000 to 2000 atm) and a temperature of 350 K to 570 K and is highly branched structure. LDP is chemically inert and tough but slightly flexible.
High density polythene or HDP is obtained by addition polymerisation of ethene in presence of hydrocarbon solvent at low pressure of hydrocarbon solvent at low pressure (6-7 atm) and a temperature of 333 K to 343 K in presence of Ziegler-Natta catalyst. Under these conditions the polymer is linear and has high density due to close packing. It is tougher, and harder than LDP.
Write the monomers used for gettingThe following polymers:
(i) Polyvinylchloride
(ii) Teflon (iii) Bakelite
Which of the following polymers are used as fibre?
(a) Polytetrafluoroethane (b) Poly chloroprene
(c) Nylon (d) Terylene
Which type of biomolecules have some structural similarity with synthetic polyamides? What is this similarity?
Name the polymers used in laminated sheets and give the name of monomeric units involved in its formation.
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.
Assertion (A): Olefinic monomers undergo addition polymerization.
Reason (R): Polymerisation of vinyl chloride is initiated by peroxides/ persulphates.
Which of the following polymers are condensation polymers?
(a) Bakelite (b) Teflon
(c) Butyl rubber (d) Melamine formaldehyde resin
Which of the following are addition polymers?
(a) Nylon (b) Melamine formaldehyde resin
(c) Orion (d) Polystyrene
Out of chain growth polymerisation and step growth polymerisation, in which type will you place the following.
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.
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.
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?
Which of the following polymers, need at least one diene monomer for their preparation?
(a) Dacron (b) Buna-S (c) Neoprene (d) Novolac
Which of the following polymers are thermoplastic?
(a) Teflon (b) Natural rubber (c) Neoprene (d) Polystyrene
Which of the following are examples of synthetic rubber?
(a) Polychloroprene (b) Polyacrylonitrile
(c) Buna-N (d) cis-polyisoprene
Which of the following polymers have vinylic monomer units?
(a) Acrilan (b) Polystyrene (c) Nylon (d) Teflon
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?
Why should the monomers used in addition polymerisation through free radical pathway be very pure?
Assertion (A): Olefinic monomers undergo addition polymerization.
Reason (R): Polymerisation of vinyl chloride is initiated by peroxides/ persulphates.
Assertion (A): For making rubber synthetically, isoprene molecules are polymerised.
i Reason (R): Neoprene (a polymer of chloroprene) is a synthetic rubber.
Assertion (A): For making rubber synthetically, isoprene molecules are polymerised.
i Reason (R): Neoprene (a polymer of chloroprene) is a synthetic rubber.
Classify the following as addition and condensation polymers:
Terylene, Bakelite, Polyvinyl chloride,Polythene
Write the name and structure of one of the common initiators used in free radical addition polymerisation.
Which of the following polymers can have strong intermolecular forces?
(a) Nylon (b) Polystyrene (c) Rubber (d) Polyester
Assertion (A): Network polymers are thermosetting.
Reason (R): Network polymers have high molecular mass.
