Discuss the main purpose of vulcanisation of rubber.
Natural rubber has the following disadvantages:
(a) It is soft and sticky and becomes even more so at high temperatures and brittle at low temperatures. Therefore, rubber is generally used in a narrow temperature range (283-335 K) where its elasticity is maintained.
(b) It has large water absorption capacity, has low tensile strength and low resistance to abrasion.
(c) It is not resistant to the action of organic solvents.
(d) It is easily attacked by oxygen and other oxidising agents. .
To improve all these properties, natural rubber is vulcanised by heating it with about 5% sulphur at 373-415 K. The vulcanized rubber thus obtained has excellent elasticity over a larger range of temperature, has low water absorption tendency and is resistant to the action of organic solvents and oxidising agents.
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.
Assertion (A): Olefinic monomers undergo addition polymerization.
Reason (R): Polymerisation of vinyl chloride is initiated by peroxides/ persulphates.
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.
Out of chain growth polymerisation and step growth polymerisation, in which type will you place the following.
Which of the following polymers are thermoplastic?
(a) Teflon (b) Natural rubber (c) Neoprene (d) Polystyrene
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.
Write the names and structures of the monomers of the following polymers:
(i) Buna-S (ii) Buna-N (iii) Dacron (iv) Neoprene
Which of the following are examples of synthetic rubber?
(a) Polychloroprene (b) Polyacrylonitrile
(c) Buna-N (d) cis-polyisoprene
How is the following resin intermediate prepared and which polymer is formed by this monomer unit?
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.
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?
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 addition polymers?
(a) Nylon (b) Melamine formaldehyde resin
(c) Orion (d) Polystyrene
Which type of biomolecules have some structural similarity with synthetic polyamides? What is this similarity?
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 does the presence of double bonds in rubber molecules influence their structure and reactivity?
Which of the following polymers can have strong intermolecular forces?
(a) Nylon (b) Polystyrene (c) Rubber (d) Polyester
Assertion (A): Polytetrafluoroethene is used in making non-stick cookware. Reason (R): Fluorine has highest electronegativity.
Synthetic polymers do not degrade in the environment for a long time. How can biodegradable synthetic polymers be made. Differentiate between biopolymers and biodegradable polymers and give examples of each type.
