Kinetics of direct polycondensation preparing polylactic acid by using lactic acid

Reactive kinetics of direct polycondensation of lactic acid was studied.The direct polylactic acid(PLA) was made from lactic acid under atmospheric pressure and with no catalyst.The results show that the polycondensation of lactic acid proceeds as a third order reaction at 124 ℃ with 14.15%-62.75% conversion and according to a kinetic equation: -d[COOH]/dt=k[COOH]3.The rate constant of reaction,k,at different temperature and the activation energy E of 4.34 kJ/mol were calculated.Finally the relationship of number-average molecular mass to time have been compared by using theoretical calculated and practical measured values.