37.4. Technical Questions

Q. 1. Mention the merits and demerits of Emulsion Polymerization w.r.t. other polymerization processes ?

Ans: One of the major advantages of Emulsion Polymerization is that it has good heat control over the entire polymerization process. The heat control occurs by transfer to the aqueous phase, and this enables little change in the viscosity of the emulsion medium.

Secondly, in this process, the reaction mass is emulsified with soap in a continuous aqueous medium. Soap has a stabilizing action, and hence, the emulsion obtained is stable and no agitation is necessary. Due to this, extra cost incurred in employing agitators is avoided.

Moreover, Emulsion Polymerization overcomes the difficulty of low degree of polymerization, as encountered in Solution and Bulk Polymerization. Since the degree of polymerization directly depends upon the droplet sizes, and in this process, spherical monomer particles (micelles) in the range of 1 – 10 μ , are yielded ; hence, the degree of polymerization is sufficiently higher than in the other two processes.

However, Emulsion Polymerization has certain disadvantages. It blocks the emulsifiers used in the process. In addition, the process has poor capacity and low electrical resistance , which sometimes create major problems.

 

Q.2. What are stereospecific Polymers ? How are they achieved ?

Ans: Stereospecific Polymer are specially oriented polymers which have certain properties that are completely different from the usual polymers. These special properties include high density and melting points , crystallinity and improved mechanical properties.

The reason for having these special property in the polymers is because of tailored atomic arrangements, which are achieved by the addition of catalysts like Ziegler catalysts or supported metal oxide catalysts. Even, X-ray and ¥ - ray radiations can bring about stereospecificity in the polymers.

The stereospecific polymers can be realized by examining the spatial arrangement of atoms on the main chain.

 

References :

1. Ullmann F., Encyclopedia of Industrial Chemistry, Wiley – VCH, 1999-2012

2. Kirk R. E., Othmer D. F., Encyclopedia of Chemical Technology, John Wiley and Sons, 1999-2012