Poly(L-Lactide), 8. High-Temperature Hydrolysis of Poly(L-Lactide) Films with Different Crystallinities and Crystalline Thicknesses in Phosphate-Buffered Solution

Hydrolytic Degradation

“…c The T 0 m value obtained by Marand et al procedure [286,287]. (T h < T m ) [66] and PLLA hydrolytically degraded in the melt at 200 C (T m T h ) [70]. At 97 C (in the solid state), the molecular weight distribution peak shifted as a whole to a lower molecular weight, specific peaks due to the chains in the crystalline residues appeared at 24 h and that at 1 Â 10 4 g/mol remained (Figure 21.11a), as in hydrolytic degradation at 37 C [30,31].…”

“…In the late stage of hydrolytic degradation, wherein the crystalline residues are degraded, the effect of crystalline thickness is direct and crucial. The molecular weight of crystalline residues (or extended-chain crystallites) increases with an increase in the initial crystalline thickness before degradation [31,49,66,67]. As expected from Equation 21.1, the hydrolytic degradation time required for the crystalline residues to become lactic acid increases with an increase in their initial molecular weight.…”

“…11 GPC profiles of crystallized PLLA films hydrolytically degraded in the solid state at 97 C (T h < T m )[66] and PLLA hydrolytically degraded in the melt at 200 C (T m < T h )[70].…”

In-line monitoring of the thermal degradation of poly(l-lactic acid) during melt extrusion by UV–vis spectroscopy

“…the sample has dissolved completely) [36e38]. In vitro experimentation at elevated temperatures can accelerate the degradation process while causing no change in the hydrolysis mechanism, allowing direct comparison of the degradation rate of various polymers [36,39,40]. In this study, the degradation of PLLA was performed at 60 C. The selected extrudates correspond to processing conditions of 180 C, 0.34 kg/h, and 50 or 400 rpm, respectively.…”

Comparative study on hydrolytic degradation and monomer recovery of poly(l-lactic acid) in the solid and in the melt

“…To reduce the energy consumption for recycling, low degradation temperature below T m of PLLA is favored. However, the PLLA crystalline residues remaining after the removal of amorphous chains will prolong the reaction period required for giving a high yield of L-lactic acid [19][20][21]. Moreover, as far as we are aware, the hydrolytic degradation near the T m , i.e., just below and above the T m of PLLA has not been studied so far.…”