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15.20  What is a biodegradable polymer ? Give an example of a biodegradable aliphatic polyester.

Polymers which are decomposed by bacteria are called bio-degradable polymers. Their degraded product does not cause any serious effect on the environment.  Bio-degradable aliphatic polyesters are - 1.  poly -hydroxybutyrates-co--hydroxy valerate(PHBV) 2. Nylon-2-Nylon-6

15.19  How is dacron obtained from ethylene glycol and terephthalic acid ?

Dacron(terelyne) is obtained from polymerisation of ethylene glycol and terepthalic acid at around 420 to 460 K. Also used in blending of cotton and wool fibres.

15.18 (ii)Identify the monomer in the following polymeric structures.

 

The above polymer is melamine So, the monomer is melamine  and fomaldehyde()

 18 (1)   Identify the monomer in the following polymeric structures.

                

It is Nylon10, 6 So, the monomer is Decanoic acid []and hexamethylene diamine []

15.17   Write the names and structures of the monomers of the following polymers:
                (iv) Neoprene

Monomer of Neoprene is Chloroprene.(2-chloro-1, 3-butadiene) Structure- 

Q17  Write the names and structures of the monomers of the following polymers:
               (iii) Dacron

The monomer of Dacron is- -Ethylene glycol -Terephthalic acid Structures are-                          

15.17  Write the names and structures of the monomers of the following polymers:
                  (ii) Buna-N

The momomeric unit of buna-N is 1, 3-Butadiene Acrylonitrile The structure of the monomer are-                         

15.17   Write the names and structures of the monomers of the following polymers:
             (i) Buna-S  

Name  of monomer of Buna-S -(a) (1,3 butadiene)                                                    (b) Styrene                             

15.16   What are the monomeric repeating units of Nylon-6 and Nylon-6,6?

The monomeric repeating unit of Nylon 6 is caprolactam and the monomers of Nylon6, 6 is adipic acid and hexamethylene diamine.  

15.15  Discuss the main purpose of vulcanisation of rubber.

The natural rubber has many flaws in following ways like- it becomes soft at high temperature and brittle at low temperature (<283K). And show very high water absorption capacity soluble in a non-polar solvent and poor resistant to the attack of oxidising agents. To improve all these physical properties we do vulcanisation of rubber. During this process, sulphur cross-links are formed, which...

15.14  How does the presence of double bonds in rubber molecules influence their structure and reactivity?

Natural rubber is a linear polymer of isoprene  (2-methyl-1, 3-butadiene) and is also called as cis - 1, 4 polyisoprenes. Due to the cis configuration about the double bond, it is difficult to come closer for effective compactness due to the weak intermolecular attraction (van der Waals). Thus natural rubber has a coiled structure and it can be stretched like spring(show elastic nature).  

15.12  Write the monomers used for getting the following polymers.
                 (iii) Bakelite

The monomeric unit of abkelite is phenol and formaldehyde. (a) phenol-  (b) formaldehude- 

15.12   Write the monomers used for getting the following polymers.
                (ii) Teflon 

The monomeric unit of Teflon (PTFE) is tetraflouroethene (). It is resistant to heat and chemical attack.

15.12   Write the monomers used for getting the following polymers.
               (i) Polyvinyl chloride

For PVC (polyvinyl chloride) we use vinyl chloride as a monomer.

15.11  Define thermoplastics and thermosetting polymers with two examples of each.

Thermoplastic polymers are linear or slightly branched chained molecules. It can be repeatedly softened and hardened on heating. Thus they can be modified again and again. Examples- polyethene and polystyrene. These polymers have intermolecular forces of attraction intermediate between elastomers and fibres. Some examples of common thermoplastics are polyethene, polystyrene, polyvinyls,...

15.10  Write the free radical mechanism for the polymerisation of ethene.

In free radical mechanism, there are three main steps- Chain initiation Chain propagation Termination 1. Chain Initiation- the polymerisation of ethene to polythene consists of heating or exposing to light a mixture of ethene with a small amount of benzoyl peroxide initiator. Generating new and larger free radicals. 2. Chain Propagation Step-   As the radical reacts with another molecule of...

 15.9  Explain the term copolymerisation and give two examples.

The process of formation of polymers of two or more different monomeric units is known as copolymerisation. For example, Buna-S is formed by the copolymerisation.

 15.8  How can you differentiate between addition and condensation polymerisation?

Addition Polymerisation- The process of repeated addition of monomer, having a double or triple bond to form polymers. For example, polyethene is formed by the addition polymerisation of ethene. Condensation Polymerisation- Process of formation of polymers by repeated condensation reaction between two different monomers, having bi-functionality or tri-functionality. A small molecule is...

 7  Why do elastomers possess elastic properties?

In elastomers, the polymeric chains are held by weak intermolecular forces of attraction. These weak binding forces allow them to stretch and a few cross-links are there in between the chains, which helps them to retract after stretching or releasing forces. Due to this elastomers are elastic in nature. Example- Buna-S, Buna-N and Neoprene etc.

15.6  Is ( NH-CHR-CO )_n , a homopolymer or copolymer?

, is a homopolymer because it is  obtained from a single monomer of 
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