Polymer Expansion
Absorption of liquid chemicals into a plastic or rubber structure causes a measurable increase in volume and a decrease in mechanical strength. The process of solvent swelling occurs when the molecules of a liquid penetrate the spaces between polymer chains and push them apart. This reaction is a critical consideration for coatings and seals used in industrial textile machinery.
Chemical Compatibility
Degree of expansion depends on the similarity between the chemical nature of the solvent and the polymer. If the solubility parameters match, the solvent swelling will be extensive and may lead to the total failure of the material. Testing involves immersing a sample in a specific chemical for a set time and measuring the change in mass or dimensions.
Technicians use this data to predict the service life of gaskets and hoses in chemical processing environments.
Structural Impact
Softening of the material usually accompanies the increase in volume as the solvent acts as a plasticizer. While solvent swelling is often a sign of damage, it can also be used in laboratory settings to determine the cross link density of a polymer. A more tightly cross linked material will swell less than one with fewer molecular bonds.
Operational Boundary
Protective equipment and industrial fabrics must be rated for resistance to specific chemicals to prevent accidental failure. Because solvent swelling is often reversible once the liquid evaporates, the material may appear undamaged after it dries. The internal structure remains weakened, which makes verification of chemical exposure essential for safety.
