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Effects of molecular weight,stereo configuration of PLA,and processing on the dispersion of multiwalled carbon nanotubes and properties of corresponding nanocomposites |
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| Authors: | Mojtaba Mohammadi Yingjie Li Jed Randall Mohammadreza Nofar Marie-Claude Heuzey Pierre J Carreau |
| Affiliation: | 1. Center for High Performance Polymer and Composite systems (CREPEC), Department of Chemical Engineering, Polytechnique Montréal, Montreal, Québec, Canada
Contribution: Conceptualization, Formal analysis, Investigation, Methodology, Validation, Writing - original draft, Writing - review & editing;2. Center for High Performance Polymer and Composite systems (CREPEC), Department of Chemical Engineering, Polytechnique Montréal, Montreal, Québec, Canada Contribution: Investigation, Validation, Writing - original draft;3. NatureWorks LLC, Plymouth, Minnesota, USA Contribution: Formal analysis, Validation, Visualization, Writing - review & editing;4. Sustainable and Green Plastics Laboratory, Metallurgical and Materials Engineering Department, Faculty of Chemical and Metallurgical Engineering, Istanbul Technical University, Istanbul, Turkey Contribution: Formal analysis, Validation, Visualization, Writing - review & editing;5. Center for High Performance Polymer and Composite systems (CREPEC), Department of Chemical Engineering, Polytechnique Montréal, Montreal, Québec, Canada |
| Abstract: | Multiwalled carbon nanotubes (MWCNTs) were dispersed and distributed via a co-rotating twin-screw extruder (TSE) in high (h)- and low (l)-molecular-weight amorphous and semicrystalline polylactides (PLAs) (aPLA and scPLA, respectively). Effects of PLA molecular weight and D-lactic acid equivalents content (D-content), as well as processing parameters, were examined on the MWCNT dispersion quality in PLA. The effectiveness of the MWCNT dispersion in various PLA matrices was investigated using scanning electron microscopy (SEM) and small-amplitude oscillatory and transient shear flow rheometry in the molten state. The results showed a better dispersion of MWCNTs in the low-molecular-weight PLA grades (aPLAl and scPLAl). In addition, better MWCNT dispersion was observed in aPLA grades when processed at a higher temperature of 190°C than at 150°C. At 150°C, while MWCNT bundles in aPLAl could be broken down, a good dispersion could not be achieved in aPLAh due to the lower molecular mobility at such a temperature. The electrical conductivity of the samples was also shown to increase as the MWCNT dispersion was improved. The existence of crystallites in scPLA-based nanocomposites, however, disrupted the connectivity of the MWCNTs and decreased the final electrical conductivity. The lower molecular weight aPLAl prepared at 190°C showed the highest electrical conductivity (~10−5 S/m) at a low loading of 0.5 wt.% MWCNTs. |
| Keywords: | D-content dispersion molecular weight PLA-MWCNT nanocomposites processing temperature |
