Mechanisms contributing to mechanical property changes in composites of polypropylene reinforced with spray-dried cellulose nanofibrils
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This study revealed the effects of spray-dried cellulose nanofibril (SDCNF) addition (3,10 and 30 wt%) and maleic anhydride polypropylene (MAPP) coupling agent (2 wt%) on the mechanical properties of polypropylene (PP). Results indicated that the elastic moduli of the PP composites increased as the SDCNF content increased above 10 wt%. The addition of MAPP into the SDCNF/PP composites did not improve the elastic moduli. Flexural strength of PP was improved when the SDCNF content increased above 10 wt%, while the tensile strength of PP decreased as the SDCNF content increased. The addition of MAPP into the SDCNF/PP composites increased the strength of the composites when the SDCNF content was above 10 wt%. Without the addition of MAPP, the composite’s impact strength did not exhibit a significant increase among the pure PP and SDCNF/PP composites. No significant differences in crystallinity or crystal forms were found in the pure PP and PP/MAPP/SDCNF composites. The spherulitic size of PP was reduced after adding SDCNF into the PP.
KeywordsSpray drying Cellulose nanofibrils Crystal morphology Impact strength Composites
Funding is provided in part by the Maine Agricultural and Forest Experiment Station (MAFES) Project ME0-M-8-00527-13 and the USDA ARS Forest Products Research Agreement 58-0202-4-003. Authors thank Kelly Edwards in the Electron Microscopy Lab for section cutting and Dr. Mehdi Tajvidi in the School of Forest Resources for polarized light microscope observation at the University of Maine.
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