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J. Compos. Sci. 2018, 2(1), 7; https://doi.org/10.3390/jcs2010007

Spray-Dried Cellulose Nanofibril-Reinforced Polypropylene Composites for Extrusion-Based Additive Manufacturing: Nonisothermal Crystallization Kinetics and Thermal Expansion

1
Advanced Structures and Composites Center, University of Maine, 35 Flagstaff Road, Orono, ME 04469-5793, USA
2
School of Forest Resources, University of Maine, 5755 Nutting Hall, Orono, ME 04469-5755, USA
3
Department of Chemistry, University of Maine, 171 Aubert Hall, Orono, ME 04469, USA
*
Author to whom correspondence should be addressed.
Received: 17 January 2018 / Revised: 5 February 2018 / Accepted: 7 February 2018 / Published: 9 February 2018
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Abstract

Isotactic polypropylene (iPP) is a versatile polymer. It accounts for the second-largest polymer consumption worldwide. However, iPP is difficult to 3D print via extrusion-based processing. This is attributable to its rapid crystallization rate. In this study, spray-dried cellulose nanofibrils (SDCNF) and maleic anhydride polypropylene (MAPP) were investigated to reveal their effects on the nonisothermal crystallization kinetics and thermal expansion of iPP. SDCNF at 3 wt % and 30 wt % accelerated the crystallization rate of iPP, while SDCNF at 10 wt % retarded the crystallization rate by restricting crystal growth and moderately increasing the nucleation density of iPP. Additionally, adding MAPP into iPP/SDCNF composites accelerated the crystallization rate of iPP. The effective activation energy of iPP increased when more than 10 wt % SDCNF was added. Scanning electron microscopy and polarized light microscopy results indicated that high SDCNF content led to a reduced gap size among SDCNF, which hindered the iPP crystal growth. The coefficient of thermal expansion of iPP/SDCNF10% was 11.7% lower than the neat iPP. In summary, SDCNF, at 10 wt %, can be used to reduce the warping of iPP during extrusion-based additive manufacturing. View Full-Text
Keywords: additive manufacturing; fused deposition modeling; 3D printing; polypropylene; crystallization retardant; transcrystallization; nucleation additive manufacturing; fused deposition modeling; 3D printing; polypropylene; crystallization retardant; transcrystallization; nucleation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Wang, L.; Gramlich, W.M.; Gardner, D.J.; Han, Y.; Tajvidi, M. Spray-Dried Cellulose Nanofibril-Reinforced Polypropylene Composites for Extrusion-Based Additive Manufacturing: Nonisothermal Crystallization Kinetics and Thermal Expansion. J. Compos. Sci. 2018, 2, 7.

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J. Compos. Sci. EISSN 2504-477X Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
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