Influence of crystal polymorphism on crystallinity calculation of poly(l-lactic acid) by infrared spectroscopy |
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| Affiliation: | 1. CAS Key Laboratory of Engineering Plastics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. School of Materials Science and Mechanical Engineering, Beijing Technology and Business University, Beijing 100048, China;4. Department of Chemistry and Industrial Chemistry, University of Genova, via Dodecaneso, 31, 16146 Genova, Italy;5. POLYMAT and Polymer Science and Technology Department, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, 20018 Donostia-San Sebastián, Spain;6. Ikerbasque, Basque Foundation for Science, Bilbao, Spain;1. KIT-ITEP, Germany;2. KIT-IKET, Germany;3. Pro-Science, Germany;1. Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, PR China;2. University of Science and Technology of China, Hefei, 230026, PR China;1. Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Łódź, Poland;2. International Institute for Nanocomposites Manufacturing, WMG, University of Warwick, CV4 7AL, UK |
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| Abstract: | Vibrational spectroscopic methods have been used to determine the crystallinity of poly(l-lactic acid) (PLLA), which is the most popular bio-plastic today. However, it is found that influence of crystal polymorphism of PLLA on the quantitative method proposed for crystallinity calculation based on IR technique has seldom been considered. Herein, by preparing a set of PLLA specimens with different crystallinity and crystal forms, the absorption coefficient ratios between amorphous and crystal bands for evaluating the absolute crystallinity of PLLA α and α′ crystal form have been derived, respectively. In addition, a comparison of the proposed IR method with other techniques used to analyze crystallinity of PLLA such as X-ray diffraction (XRD) and differential scanning calorimetry (DSC) is presented. The origin of the disagreement on the results of quantitative measurements of crystallinity by different methods is also discussed. This study provides a simple spectral method to determine the crystallinity of PLLA with various crystal modifications. |
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| Keywords: | FTIR Crystallinity Polymorphism |
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