Characterization of poly(lactic acid)s with reduced molecular weight fabricated through an autoclave process |
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| Institution: | 1. Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan 333, Taiwan, ROC;2. Department of General Dentistry, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan, ROC;3. Graduate Institute of Nanomedicine and Medical Engineering, Taipei Medical University, Taipei 110, Taiwan, ROC;1. Department of Polymer Science and Rubber Technology, Cochin University of Science and Technology, Kochi 682022, Kerala, India;2. Department of Chemistry, K.K.T.M.Govt College, Pullut, Kodungallur, India;1. Department of Wood Science and Technology, Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran;2. Department of Chemical Technologies, Iranian Research Organization for Science and Technology (IROST), P.O. Box 15815-3538, Tehran, Iran;1. Department of Mechanical Engineering, Faculty of Engineering of Bilbao, University of the Basque Country (UPV/EHU), Rafael Moreno “Pitxitxi” 2-3, 48013 Bilbao, Spain;2. Department of Mining, Metallurgy and Science of Materials, Faculty of Engineering of Bilbao, University of the Basque Country (UPV/EHU), Rafael Moreno “Pitxitxi” 2-3, 48013 Bilbao, Spain;3. Materials Testing and Simulation, Leartiker (Lea-Artibai Development Center), Xemein Avenue 12-A, 48270 Markina, Xemein, Spain |
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| Abstract: | Poly(lactic acids) (PLAs) with different molecular weights (MWs) were prepared by autoclaving a commercial PLA for different time periods. The harvested PLAs were characterized by different techniques. Gel permeation chromatography results showed that the MW of PLA decreased with increasing autoclaving time. The Mark–Houwink parameters for PLA in dichloromethane at 25 °C were determined for the first time. The melting endotherms, revealed by differential scanning calorimetry, were observed for the 60 and 120 min-autoclaved PLAs (cf. PLA60 and PLA120) but hardly detected for the original and 30 min-autoclaved PLA (PLA30). The PLA120 exhibited higher crystallinity than that of PLA60. Thermogravimetric analysis showed that the activation energy for thermal degradation decreased from 186 kJ mol−1 to 140 kJ mol−1 for original PLA and PLA120. The hydrophilicity of the PLA increased, indicating higher number of COOH groups, with increasing autoclaving time, as revealed by the contact angle measurement. Rheological data showed that the complex viscosity and storage modulus of PLA decreased with increasing autoclaving time due to the decreasing MW. Unlike original PLA and PLA30, PLA60 and PLA120 exhibited Newtonian fluid behavior at all test frequencies. |
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| Keywords: | Poly(lactic acid) Molecular weight reduction Autoclaving Physical properties |
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