Synergistic Mechanisms Underlie the Peroxide and Coagent Improvement of Natural-Rubber-Toughened Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Mechanical Performance
1
The Ohio State University, Department of Food Science and Technology, 2015 Fyffe Road, Columbus, OH 43210, USA
2
The Ohio State University, Department of Horticulture and Crop Science, 1680 Madison Avenue, Wooster, OH 44691, USA
3
The Ohio State University, Department of Food, Agricultural and Biological Engineering, 1680 Madison Avenue, Wooster, OH 44691, USA
*
Author to whom correspondence should be addressed.
Polymers 2019, 11(3), 565; https://doi.org/10.3390/polym11030565
Received: 23 January 2019 / Revised: 15 March 2019 / Accepted: 19 March 2019 / Published: 26 March 2019
(This article belongs to the Special Issue Recent Advances in Bioplastics)
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a promising bio-based and biodegradable thermoplastic with restricted industrial applications due to its brittleness and poor processability. Natural rubber (NR) has been used as a toughening agent, but further physical improvements are desired. In this study, rubber toughening efficiency was significantly improved through the synergistic use of a trifunctional acrylic coagent and an organic peroxide during reactive extrusion of PHBV and NR. The rheological, crystallization, thermal, morphological, and mechanical properties of PHBV/NR blends with 15% rubber loading were characterized. The peroxide and coagent synergistically crosslinked the rubber phase and grafted PHBV onto rubber backbones, leading to enhanced rubber modulus and cohesive strength as well as improved PHBV–rubber compatibility and blend homogeneity. Simultaneously, the peroxide–coagent treatment decreased PHBV crystallinity and crystal size and depressed peroxy-radical-caused PHBV degradation. The new PHBV/NR blends had a broader processing window, 75% better toughness (based on the notched impact strength data), and 100% better ductility (based on the tensile elongation data) than pristine PHBV. This new rubber-toughened PHBV material has balanced mechanical performance comparable to that of conventional thermoplastics and is suitable for a wide range of plastic applications.
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Keywords:
poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV); bioplastic; natural rubber; reactive extrusion; toughening
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MDPI and ACS Style
Zhao, X.; Cornish, K.; Vodovotz, Y. Synergistic Mechanisms Underlie the Peroxide and Coagent Improvement of Natural-Rubber-Toughened Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Mechanical Performance. Polymers 2019, 11, 565.
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