JOURNAL OF POLYMER ENGINEERING

 Vol. 23, No. 6, 2003, page 413

Increasing the molecular weight of poly(L-lactic acid) by solid state polycondensation in a closed system

Gang Qian, Xing-Gui Zhou*, Ling-Bo Zhu and Wei-Kang Yuan

UNILAB Research Center of Chemical Reaction Engineering,
East China University of Science and Technology,
Shanghai 200237, China

ABSTRACT

             In this paper a direct condensation process is presented for the production of high molecular weight poly (L-lactic acid) (PLLA). It constitutes two steps: pre-polymerization in melt state and post-polymerization in solid state. The distinct feature of this new process lies in the second step, where water, the byproduct of polycondensation, is removed by a dehydrant. Continuous vacuum supply or purging by inert gases is avoided. Through this process, we obtain a PLLA product with molecular weight higher than 300,000, characterized by low monomer content, high crystallinity and small distribution index.

 Keywords: PLLA; solid-state polycondensation; closed system 

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