D11. Discuss the changes in physical properties due to cross-linking and describe any structural similarity between a cross-linked polymer and a thermoset polymer.

A cross-linked polymer goes from a solid to an elastomeric stage when the glass transition temperature is reached, while a linear polymer goes from a solid to a liquid (more or less viscous) stage. Cross-links improve the strength properties of a polymer and decrease its ability to dissolve in different media. Cross-linkages also decreases the swelling ability of the resin.

The reason why some polymers are so called thermoset resins is simply that they form cross-linkages when they are heated to a certain temperature. That means that the thermoset resin is a cross-linked resin with the properties discussed above.