Question

Which of the following is not employed in the commercial production of linear poly vinyl chloride?

• A. Emulsion polymerisation
• B. Suspension polymerisation
• C. Addition polymerisation
• D. Condensation polymerisation

Hint:

Vinyl monomers containing a single carbon-carbon double bond (like vinyl chloride, styrene, ethylene, and propylene) always undergo addition polymerisation to form linear polymers.
Condensation polymerisation is reserved for monomers with functional groups, such as diacids, diamines, diols, and amino acids (producing nylons, polyesters, etc.).

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
This question asks us to identify the polymerisation mechanism or method that is not used in the commercial manufacture of linear Polyvinyl Chloride (PVC).
PVC is a widely used synthetic plastic polymer made from the polymerisation of vinyl chloride monomers.

Step 2: Key Formula or Approach:
We must review the chemical structure of PVC and the corresponding industrial polymerization techniques:
1. Vinyl chloride monomer (VCM) has the chemical formula \(\text{CH}_2 = \text{CHCl}\), containing a carbon-carbon double bond.
2. Polymers containing double bonds typically undergo addition (chain-growth) polymerisation rather than condensation (step-growth) polymerisation.
3. Industrially, addition polymerisation is executed using various heterogeneous phase techniques such as suspension, emulsion, or bulk polymerisation to control the high exothermic heat of reaction.

Step 3: Detailed Explanation:
Let us analyze each of the options in detail:
- Addition polymerisation is the fundamental chemical mechanism by which vinyl chloride monomers react with one another. The double bond opens up to form a continuous linear chain of repeating unit \([-\text{CH}_2-\text{CHCl}-]_n\) without forming any by-products. Therefore, addition polymerisation is employed.
- Suspension polymerisation is the primary industrial method used commercially, accounting for about \(80\%\) of global PVC production. In this process, VCM is suspended as small droplets in water using dispersing agents and polymerised using oil-soluble initiators.
- Emulsion polymerisation is another commercial method used to produce fine, paste-grade PVC (about \(10\%\) to \(15\%\) of global production), where surfactant micelles are used to disperse the monomer in water.
- Condensation polymerisation involves the reaction of bi-functional or multi-functional monomers with the elimination of small molecules like water or hydrochloric acid. PVC is a homopolymer formed solely by the chain growth of VCM, and no small molecules are eliminated during its synthesis. Thus, condensation polymerisation is physically impossible for the production of linear PVC.

Step 4: Final Answer
Therefore, condensation polymerisation is not employed, which corresponds to option (D).