18 What is the concept of swelling in degradation of polymer

18. What is the concept of swelling in degradation of polymers?

Solution

Swelling is a partial dissolution of polymer in the solvent. There is a limited solubility of polymer in the solvent. For example hydrocarbon rubber easily absorbs hydrocarbon solvent like gasoline. The greater the similarity between the chemical structure of polymer and solvent greater are the chances of swelling, as seen in the previous example polymer would underwent swelling for hydrocarbon solvent but is resistant to attack by acid and alkaline solutions that are metal. For this reason hydrofloric acid is stored in plastic bottles.

Swelling also depends upon the temperature and molecular structure. More the temperature more is the dissolution resulting in more swelling. In general, increasing molecular weight, increasing degree of crosslinking and crystallinity, and decreasing temperature result in a reduction of these deteriorative processes.