Corrosion of Thermosets

Unreinforced, unfilled thermoset polymers can corrode by several mechanisms. The type of corrosion can be divided into two main categories physical and chemical. 

Physical corrosion is the interaction of a thermoset polymer with its environment so that its properties are altered but no chemical reactions take place. The diffusion of a liquid into the polymer is a typical example. In many cases, physical corrosion is reversible after the liquid is removed, the original properties are restored. 

When a polymer absorbs a liquid or gas, that results in plasticization or swelling of the thermoset network, physical corrosion has taken place. For a cross-linked thermoset, swelling caused by solvent absorption will be at a maximum when the solvent and polymer solubility parameters are exactly matched. 

Temperatures might have to be modified depending on the corrodent. 

Chemical corrosion takes place when the bonds in the thermoset are broken by means of a chemical reaction with the polymers environment. There may be more than one form of chemical corrosion taking place at the same time. Chemical corrosion is usually not reversible. 

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