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Biodegradable PHB-Rubber Copolymer Toughened PLA Green Composites with Ultrahigh Extensibility Jayven Chee Chuan Yeo, Joseph Kinyanjui Muiruri, Beng Hoon Tan, Warintorn Thitsartarn, Junhua Kong, Xikui Zhang, Zibiao Li, and Chaobin He ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b03978 • Publication Date (Web): 03 Oct 2018 Downloaded from http://pubs.acs.org on October 4, 2018
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ACS Sustainable Chemistry & Engineering
Biodegradable PHB-Rubber Copolymer Toughened PLA Green Composites with Ultrahigh Extensibility
Jayven Chee Chuan Yeo†‡, Joseph K. Muiruri†‡, Beng Hoon Tan‡, Warintorn Thitsartarn‡, Junhua Kong‡, Xikui Zhang‡, Zibiao Li*,‡ and Chaobin He*,†‡
†
Department of Materials Science and Engineering, National University of Singapore, 9
Engineering Drive 1, Singapore 117576 ‡
Institute of Materials Research and Engineering, Agency for Science, Technology and
Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634 Correspondence to
[email protected]; or
[email protected] 1 ACS Paragon Plus Environment
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Abstract Sustainable biopolymers, Poly(lactide) (PLA), has been intensely researched over the past decades, due to its excellent biodegradability, renewability, and sustainability. The boundless potential of this sustainable biopolymer could resolve the adverse negative impact caused by the petroleum-based polymers. However, the inherent drawback of PLA such as brittleness, low heat distortion temperature and slow recrystallization rate narrowed the broad applications in biomedical, automotive and structural. In this study, we successfully synthesized a PHB-based filler (PHB-di-rub) displaying synergetic functions of (1) effective nucleating and (2) extreme toughening of the PLA matrix at only 5% (1.5 wt% PHB content). Remarkably, the storage modulus improves by 15%; tensile elongation extends by 57-fold (300% strain) and toughness by 38-fold while maintaining its original strength and stiffness. Likewise, 10% of PHB-di-rub (3 wt% PHB content) has an even higher improvement with storage modulus improve by 32%, elongation by 128-fold (680% strain) and toughness by 84-fold, with a marginal change in strength and stiffness. NMR results confirmed the ‘brick and mortar’ structure of PHB-di-rub, where PHB act as the rigid core and the poly(lactide-cocaprolactone) (DLA-co-CL) random copolymer confer the flexibility. DSC, WAXD, and POM display the excellent nucleating ability of PHB-di-rub. SEM shows the morphology of elongated fibrils structure with strong matrix-filler interaction and homogenous filler dispersion. SAXS, WAXS and WAXD elucidate the extreme toughening mechanism to be a combination of rubber-induced crazing effect and highly orientated PLA matrix with PHB-dirub. The Herman’s orientation function further quantify the extreme elongation (680%) owing to the perfect alignment. This highly biodegradable biocomposite with high strength and toughness show potential in replacing the current petroleum-based polymers, which open up to broader prospects in the biomedical, automotive and structural application. Keywords: Extreme stretched, Biodegradable, Polylactic acid, Polyhydroxybutyrate, Material toughening, Nucleating
2 ACS Paragon Plus Environment
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ACS Sustainable Chemistry & Engineering
Introduction Sustainability paradigm with a vision to substitute petroleum-based polymers has always been a challenging research area in the material science field for the past decades. The heavy usage of petroleum-based polymers, such as polypropylene (PP) and polyethylene (PE), has accelerated the strain on the depleting natural resources. Leading to severe negative consequences to the environment that we live.1 In this context, significant research efforts to find an alternative polymer with greater sustainability and renewability in polymers become a crucial mission.2 Bio-based polymers from renewable resources are classified as the potential candidate, in particular, Polylactic acid (PLA) and Polyhydroxybutyrate (PHB).3–6 These two biopolymers are a popular choice, attributable to its excellent biodegradability, biocompatible and mechanical properties comparable to polypropylene (PP). However, the primary weakness is the fragility, with an elongation at break of
