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1 8 A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 2 2 attained by integrating particulates and fibers in the biopolymer matrix. For example, particles, short fibers, and continuous fibers can be integrated in the matrix (Fig. 5a-c). Multilayered structures can be created by stacking fibers in different orientations (Fig. 5d). In addition, it is also possible to tailor the porosity and design various types of derivatives based on the results (Fig. 5e-f). Notta-Cuvier et al. used a tributyl citrate (TBC) plasticizer and halloysite nanotubes (HNTs) synergistically in the PLAmatrix to enhance rigidity, strength, ductility, and toughness[22]. See Fig. 5a for an example of this type of microstructure. Abu Aldam et al. showed that with solvent casting, a PLA matrix can be reinforced with crystalline PHA— another example of the Fig. 5a microstructure[23]. Efendy et al. designed PLA composites by using discontinuous harakeke and hemp fibers[24] (Fig. 5b). They subsequently designed mats by alternating layers of PLA and PLA reinforced with up to 40 wt% fiber composites (Fig. 5d). They also proposed that a rule of mixtures calculation can be effective in predicting the strength of these composites. Hinchcliffe et al. used continuous fiber strands of flax and jute to reinforce a PLA matrix[25] (Fig. 5c). This group observed enhanced 116%, 62%, 14%, and 10% for tensile strength, stiffness to weight, flexural specific strength, and rigidity to weight, respectively, as compared to PLA samples. Recently, Gupta et al. designed biofoams by using lignin and wheat straw (WS) as precursors. The team reports an ultimate compressive strength of lignin-50 wt% WS was ∼20.4 MPa after pyrolysis at 300 °C[26] (Fig. 5e-f). Based on these research efforts, the future of bioplastics looks promising in spite of the remaining challenges. ASTM D6400 is the standard for compostablebioplastics, althoughcom- posting can be done at home or in an industrial setting. For example, PLA is compostable in an industrial setting compared to chitin and PHA, which are compostable under home conditions. A common misconception is that all biodegradable polymers are compos- table under home conditions[20]. In order to develop better disposal practices for bioplastics, a public awareness campaign should be created to inform various stakeholders about disposal and composting from a circular economy perspective. Further research regarding precursors should be explored to lower the cost of bioplastics. On average, 998 million Mt of agricultural waste are generated every year. This waste could potentially be used as a precursor for manufacturing PHA by optimizing fermentation conditions[12]. Further, engineering of blended designs that focus on binary and ternary blends is recommended to increase the performance of bioplastics[23]. Finally, although natural fiber use has reached maturity in industry, it could further benefit from strict quality standards. ~AM&P For more information: Surojit Gupta, associate professor, University of North Dakota, Upson Hall II, Room 274, 243 Centennial Dr., Stop 8359, Grand Forks, ND 58202-8359, surojit.gupta@ und.edu. References 1. J. Zheng and S. Suh, Strategies to Reduce the Global Carbon Footprint of Plastics, Nat. Clim. Change, Vol 9, p 374-378, 2019. 2. E. Van Roijen and S. Miller, A Review of Bioplastics at End-of-Life: Linking Experimental Biodegradation Studies and Life Cycle Impact Assessments, Resour. Conserv. Recycl., Vol 181, 106236, 2022. 3. https://docs.european-bioplastics. org/publications/market_data/Report_ Bioplastics_Market_Data_2021_short_ version.pdf. 4. H.T. Sreenivas, N. Krishnamurthy, and G.R. Arpitha, A Comprehensive Review on Light Weight Kenaf Fiber for Automobiles, Int. J. Lightweight Mater. Manu., Vol 3, p 328-337, 2020. 5. O. Faruk, et al., Biocomposites Reinforced with Natural Fibers: 2000-2010, Prog. Polym. Sci., Vol 37, p 1552-1596, 2012. 6. M. Jawaid and H.P.S. Abdul Khalil, Cellulosic/Synthetic Fibre Reinforced Polymer Hybrid Composites: A Review, Carbohydr. Polym., Vol 86, p 1-18, 2011. 7. A. Bledzki, O. Faruk, and V. Sperber, Cars from Bio‐Fibres, Macromol. Mater. Eng., Vol 291, p 449-457, 2006. 8. V. Naik, M. Kumar, and V. Kaup, A Review on Natural Fiber Composite Material in Automotive Applications, Engineered Science, Vol 18, p 1-10, 2022. 9. M. Flieger, et al., Biodegradable plastics from renewable sources, Folia Microbiol., Vol 48, p 27-44, 2003. 10. N. Thummarungsan, et al., Influence of Graphene on Electromechanical Responses of Plasticized Poly (Lactic Acid), Polymer, Vol 138, p 169-179, 2018. (a) (b) (c) (d) (e) (f) Fig. 5 — Schematics of different bioplastic microstructures reinforced with: (a) particulates; (b) short fibers; (c) continuous fibers; (d) multilayered structures with fibers reinforcing the matrix in longitudinal and transverse directions; (e) porous; and (f) a porous network reinforced with fibers.

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