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Natural Rubber Toughened Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Bioplastic for Food Packaging Applications

Zhao, Xiaoying
http://orcid.org/0000-0003-3709-3143
http://rave.ohiolink.edu/etdc/view?acc_num=osu154344332353769

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Food Science and Technology.
The packaging industry is searching for bio-based alternatives. Poly-(ß-hydroxybutyrate-co-valerate) (PHBV) is a promising bioplastic made from bacterial fermentation of renewable resources. It has mechanical properties similar to propylene (PP) but is more brittle. PHBV toughness and flexibility must be improved before it can be commercially used for packaging. An industrially viable and economically effective way to toughen PHBV is blending it with flexible and ductile materials. Natural rubber (NR) is a promising toughening material due to its unique combination of ductility, flexibility, and renewability. NR has various packaging applications such as films and tapes. Blends from rubber and thermoplastics, such as polyethylene and PP, with improved toughness, flexibility, and other properties have been used in packaging industry. Therefore, the objective of this work is to improve PHBV toughness and flexibility through NR incorporation, elucidate the reaction mechanism of the coagent-assisted peroxide-induced reactive extrusion of NR and PHBV, optimize the PHBV/NR blends, and evaluate their suitability for food packaging applications. In this study, 2-25 wt. %NR was incorporated into PHBV through reactive extrusion in the presence of peroxide to improve PHBV flexibility and toughness. The PHBV/NR blends had two phases with crosslinked rubber being dispersed in PHBV matrix. Rubber addition restricted PHBV crystallization and decreased its degree of crystallinity. The blend had improved flexibility, toughness, thermal stability, and melt strength, but decreased tensile strength than pristine PHBV. The blend performance had clear rubber loading-dependent differences. To improve rubber toughening efficiency and the PHBV/NR blend strength, a trifunctional acrylic coagent was synergistically used with the peroxide during the melt blending process. The reaction mechanism was investigated through FTIR and NMR analysis. Coagent and peroxide synergically crosslinked rubber phase and grafted PHBV onto rubber backbones. The presence of coagent improved peroxide crosslinking efficiency and suppressed peroxy-radical caused polymer degradation, leading to a homogeneous rubber dispersion, increased rubber modulus and cohesive strength, and improved PHBV-rubber compatibility. The peroxide-coagent treatment decreased PHBV crystallinity and crystal size. The new PHBV/NR blends had a 70% better impact strength than pristine PHBV, 40% better tensile strength then peroxide-only cured blend, and a broadened processing window. Mechanical properties of the peroxide-coagent treated PHBV/NR blends were optimized using a response surface methodology (RSM) with a Box-Behnken design. Ascending coagent loading led to increased toughness and tensile strength, but decreased flexibility of the PHBV/NR blends. Ascending rubber loading led to increased flexibility, decreased tensile strength, and maximal toughness at 15 wt. % loading. Peroxide had minimal effect on tensile strength and flexibility, but increased toughness. The optimal PHBV/NR blend was obtained at 15 wt. % NR, 4.2 phr peroxide, and 3 phr coagent, with a tensile strength of 28.1 MPa, notched impact strength of 27.5 J/m, flex modulus (1% secant modulus) of 8,679 MPa. The blends degraded by ~15% in 53 days in a lab-scale aerobic composting system at 58 °C. Trays made from the optimized PHBV/NR blend had water vapor permeability and sealability comparable to polypropylene, good stabilitywith acid food under freezing and microwave heating. Migration studies indicated that the trays were safe for food-contact applications. This research demonstrated that the bio-based and bio-degradable PHBV/NR blends potentially can be used as bio-alternatives to the petroleum-based plastic packaging materials.
Yael Vodovotz (Advisor)
Katrina Cornish (Advisor)
206 p.
Food Science
PHBV; natural rubber; reactive extrusion; toughen; bioplastic; biodegradable; food packaging

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Citations

  • Zhao, X. (2018). Natural Rubber Toughened Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Bioplastic for Food Packaging Applications [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu154344332353769

    APA Style (7th edition)

  • Zhao, Xiaoying. Natural Rubber Toughened Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Bioplastic for Food Packaging Applications. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu154344332353769.

    MLA Style (8th edition)

  • Zhao, Xiaoying. "Natural Rubber Toughened Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Bioplastic for Food Packaging Applications." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu154344332353769

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.