Question

What is the difference between bulk and surface degradation? How do the properties of ceramics and polymers affect which mechanism is favored?

Answer 1

In bulk degradation, corrosion happens uniformly throughout the whole material. In surface degradation, the corrosion of the material starts at the surface and proceeds inwards towards the bulk.

Two properties of polymers and ceramics decide which degradation would take place. They are : degradation of the polymer in water and diffusion of water into the polymer. If degradation is greater than diffusion, then surface degradation would occur because the polymer would degrade by the time water reaches the bulk. If diffusion rate is greater than degradation rate, then bulk degradation would occur.