Poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV), a well-known biodegradable brittle polymer, was investigated with poly(butylene adipate-co-terephthalate) (PBAT) as a biobased toughener and various loadings of organically modified nanoclay as a reinforcement phase. This was conducted to determine the variation in mechanical, thermal and barrier properties after fabrication by two processes: (i) cast melt extrusion and (ii) compression moulding. The nanocomposite films were produced by combining PHBV/PBAT blend with 0.6, 1.2 and 1.8 wt% of nanoclay as shown in Figure 1(a). Improved oxygen and water vapour barrier properties were observed for the cast PHBV/PBAT nanocomposite films as compared to its compression moulded counterparts due to the uni-axial stretching of polymer chains. As a result, the melt casted nanocomposite films exhibited enhanced oxygen (~79%) (as shown in Figure 1b) and water vapor (~70%) permeabilities after adding nanoclay (1.2 wt%). This occurred because of the uniform dispersion of filler in the blend matrix as well as the strong adhesion between nanoclay and the blend matrix, which was confirmed by a rheological analysis. Another associated reason was the observed intercalation/exfoliation phenomena in nanoclay, which favorably occurred at the PHBV/PBAT interface, verified by a transmission electron microscopy (TEM). A further increment of clay content in polymer blends resulted in agglomeration problems. The cast PHBV/PBAT blend with 1.2 wt% nanoclay exhibited substantially enhanced (567.6%±0.1) elongation at break as compared to the blend matrix. This was caused by an improved stress transfer action, as compared with compressed films. Further, the formation of heterogeneous nucleation sites in both types of film were observed after adding nanoclay (1.8%) into the blend matrix.
The authors would like to thank the following for their financial support: Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)/University of Guelph-Bioeconomy for Industrial Uses Research Program (Project # 030054 and # 030255); the Natural Sciences and Engineering Research Council (NSERC), Canada Discovery Grants (Project # 400320); and the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) â University of Guelph, the Bioeconomy Industrial Uses Research Program Theme (Project # 030255); and the Ontario Ministry of Economic Development, Job Creation and Trade ORF-RE09-078 (Project #053970).