Bulk erosion of polylactic acid (PLA) involves hydrolytic degradation of ester bonds, leading to molecular weight reduction and loss of mechanical properties, often accelerated by autocatalysis from degradation products. Water penetration facilitates this process throughout the material, resulting in structural changes such as increased crystallinity and altered surface morphology.

The bulk erosion process of polylactic acid (PLA) occurs when the material degrades uniformly throughout its structure. This process begins as water penetrates the polymer, breaking down its ester bonds through hydrolysis. Since water can diffuse through the entire polymer matrix, degradation occurs from the inside as well as the surface, leading to a gradual loss of molecular weight and mechanical integrity over time. This is different from surface erosion, where degradation happens only at the material’s surface. Bulk erosion can result in a rapid breakdown once the polymer reaches a critical threshold of degradation.