PROGRESS OF POLYMERIZATION OF D,L-LACTIDE THROUGH DIFFERENTIAL SCANNING CALORIMETRY AND GEL-PERMEATION CHROMATOGRAPHY

Melt polymerization conditions for D,L-lactide initiated with tetraphe nyltin were studied with regard to polymer molecular weight. The prese nt study was undertaken to investigate the progress of polymerization of D,L-lactide through differential scanning calorimetry (DSC), and al so to explore the correlation between melt polymerization conditions a nd molecular weight. The physical characteristics, such as glass trans ition temperature (T-g) Of the polymer and melting transition (T-m) of D,L-lactide are correlated with GPC data. DSC data shows that the T-m of D,L-lactide is 122.8 at 150 degrees C polymerization time. Delta H -f is 83.2 J g(-1), and T-g of polymer is untraceable. At 180 degrees C the T-m is 101.4 degrees C, Delta H-f is 34 J g(-1), and T-g is arou nd 29.5 degrees C. The drop in T-m and Delta H-f clearly shows the con version of D,L-lactide to polymer. The maximum increment to molecular weight of polymer is achieved at 160 degrees C and 8 h. After a short induction period, the slow polymerization of D,L-lactide resulted in m aximal molecular weight followed by an almost constant value of molecu lar weight.