Pyrolysis mechanism of Poly(lactic acid) for giving lactide under the catalysis of tin

Publication date: Available online 9 October 2018Source: Polymer Degradation and StabilityAuthor(s): Lidong Feng, Songyang Feng, Xinchao Bian, Gao Li, Xuesi ChenAbstractIn order to obtain the mechanisms of the pyrolysis reaction that poly (lactic acid) (PLA) gives lactide in the presence of Sn, the four types of low molecular weight PLAs (L-PLA) with different end-groups were prepared, including HO-L-PLA-COOH, R-L-PLA-OH, R-L-PLA-COOH, and R-L-PLA-R, and depolymerized by thermogravimetry at different heating rates. As for the pyrolysis reactions of the L-PLAs, their activation energy (Ea) were estimated by the several isoconversional model-free methods and their kinetic models were also explored by the Malek method. The random degradation behavior of L-PLAs was determined by the plots of ln{−ln[1−(1−w)0.5]}vs. 1/T for experimental data from TG for L-PLAs and model reactions. The experimental results showed that the Ea values and the possible kinetic models for the pyrolysis reactions of the L-PLAs were different due to the different end-groups and thereof the mechanisms for the pyrolysis reactions of PLA that give lactide were proposed under the catalysis of Sn. The pyrolysis reactions of R-L-PLA-OH and R-L-PLA-R trend to be controlled by a single kinetic model. The pyrolysis reactions of HO-L-PLA-COOH and R-L-PLA-COOH are more complex and controlled by not less than two kinetic processes. The pyrolysis reaction of PLA selectively produces lactide through the unzipping ...
Source: Polymer Degradation and Stability - Category: Chemistry Source Type: research
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