Structure development and biodegradability of uniaxially stretched poly(l-lactide)

The effects of uniaxial drawing conditions on the orientation of various poly(l-lactide) (PLLA) samples were investigated using Fourier transform infrared dichroism and thermal analysis. The results showed that the orientation in uniaxially stretched PLLA was determined by the drawing rate, drawing temperature, and draw ratio. For the amorphous sample, a higher orientation was obtained at a lower drawing temperature due to the slower chain relaxation. On the other hand, a higher orientation was achieved for the precrystallized samples at a higher drawing temperature due to the larger deformation of spherulites. The hydrolysis tests of PLLA films showed that the rate of hydrolysis was dependent on the degree of orientation as well as the percent crystallinity. After preferential hydrolysis of the amorphous regions, the surface of oriented PLLA samples might be covered by a layer of relatively inactive crystal lamellae, causing a reduction in the rate of hydrolysis.