Influence of Degradation of Poly-L-lactide on Mass Loss, Mechanical Properties, and Crystallinity in Phosphate-Buffered Solution

A bulk degradation of poly-L-lactide (PLLA) rectangular bars was studied by incubating them in phosphate-buffered solution at 37C for different periods. The characteristics of the mass, water uptake, mechanical properties, thermal behavior, and crystallinity of the PLLA samples were investigated. The results indicate that mass loss and water uptake of PLLA increase with increasing time; however, pH value and mechanical strength decrease. The melting temperature, melting enthalpy, and crystallinity of PLLA firstly increase and then decrease with increasing degradation time. There is no new diffraction peak formed with increasing degradation time, which indicates that the degradation could occur in the amorphous regions firstly and then in the crystalline regions.