Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has positive biodegradable, non-toxic, sustainable, and compostable properties, making it attractive for use in packaging. However, the applications in flexible packaging are limited due to its brittleness and narrow processing temperature range [1]. To mitigate the brittleness of PHBV, a compostable polymer such as cellulose acetate (CA) can be used with a 2.45 degree of substitution to positively influence the toughness of PHBV [2]. Furthermore, based on the solubility parameters, PHBV and cellulose acetate are potentially miscible [3], [4].

In this research, PHBV was blended with CA to investigate the overall mechanical properties of the blend; however, CA requires plasticization in order to be melt compounded. Prior to processing, CA powder was plasticized with triethyl citrate (TEC) and rested at room temperature for 12 hrs. Subsequently, PHBV pellets were melt compounded with the plasticized CA (pCA) powder in a twin-screw extruder followed by injection moulding. Our study found 70/30 wt.% PHBV/pCA blend ratios had improved impact strength, exceeding virgin PHBV and pCA which is attributed to PHBV degradation from the high processing temperature. TEC plasticizer migrated during processing into the PHBV, partially plasticizing it, thus reducing its melt temperature and forming secondary crystallite structures in the form of a double melt peak from differential scanning calorimetry (DSC) study. Using CA as a filler in PHBV without TEC reduced the tensile and flexural strength, and had poor interfacial adhesion from scanning electron microscopy (SEM) study. The impact strength however, was improved at a 70/30 wt.% PHBV/CA blend ratio with 50% higher tensile modulus and strength, and flexural strength compared to PHBV/pCA 70/30 wt.% blends.

Acknowledgment

This research is financially supported by the Natural Sciences and Engineering Research Council (NSERC), Canada Discovery Grants (Project # 400320); the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) – University of Guelph, the Bioeconomy Industerial Uses Research Program Theme (Project # 030255); and the Ontario Ministry of Economic Development, Job Creation and Trade ORF-RE09-078 (Project #053970)

References

[1] K. Khosravi-Darani and D. Z. Bucci, “Application of Poly(hydroxyalkanoate) In Food Packaging: Improvements by Nanotechnology,” Chem. Biochem. Eng. Q., vol. 29, no. 2, pp. 275–285, 2015.

[2] R. M. Gardner, C. M. Buchanan, R. Komarek, D. Dorschel, C. Boggs, and A. W. White, “Compostability of cellulose acetate films,” J. Appl. Polym. Sci., vol. 52, no. 10, pp. 1477–1488, 1994.

[3] B. Wang, J. Chen, H. Peng, J. Gai, J. Kang, and Y. Cao, “Investigation on Changes in the Miscibility, Morphology, Rheology and Mechanical Behavior of Melt Processed Cellulose Acetate through Adding Polyethylene Glycol as a Plasticizer,” J. Macromol. Sci. Part B Phys., vol. 55, no. 9, pp. 894–907, 2016.

[4] J. S. Choi and W. H. Park, “Effect of biodegradable plasticizers on thermal and mechanical properties of poly(3-hydroxybutyrate),” Polym. Test., vol. 23, no. 4, pp. 455–460, 2004.