Effect of different biopolymers and polymers on the mechanical and permeation properties of extruded PHBV cast films

Abstract

The biopolymer poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) is a promising material for packaging applications but its high brittleness is challenging. To address this issue, PHBV was blended with nine different biopolymers and polymers in order to improve the processing and mechanical properties of the films. Those biopolymers were TPS, PBAT, a blend of PBAT 1 PLA, a blend of PBAT 1 PLA 1 filler, PCL and PBS, and the polymers TPU, PVAc, and EVA. The extruded cast films were analyzed in detail (melting temperature, crystallinity, mechanical properties, permeation properties, and surface topography). A decrease in crystallinity and Young's modulus and an increase in elongation at break and permeability were observed with increasing biopolymer/ polymer concentration. In PHBV-rich blends (70 wt % PHBV), the biopolymers/polymers PCL, PBAT, and TPU increased the elongation at break while only slightly increasing the permeability. Larger increases in the permeability were found for the films with PBS, PVAc, and EVA. The films of biopolymer/polymer-rich blends (with PBAT, TPU, and EVA) had significantly different properties than pure PHBV. A strong effect on the properties was measured assuming that at certain biopolymer/polymer concentrations the coherent PHBV network is disrupted. The interpretation of the permeation values by the Maxwell-Garnett theory confirms the assumption of a phase separation.

PHBV/TPU/cellulose compounds for compostable injection molded parts with improved thermal and mechanical performance

“…DSC results reveal that the addition of TPU to PHBV produces a slight decrease in both crystallinity and melting and crystallization temperatures of the blends in the composition range studied indicating that this component affects the crystallization process. These findings are in accordance with the previous works about PHBV/TPU blends reported in literature . Such behavior can be explained by the intermolecular interactions (i.e., dipole–dipole) between the phases in the liquid state, introducing some disorder in the system, which would be hampering the crystallization.…”

“…These findings are in accordance with the previous works about PHBV/TPU blends reported in literature. 15,17,25 Such behavior can be explained by the intermolecular interactions (i.e., dipoledipole) between the phases in the liquid state, introducing some disorder in the system, which would be hampering the crystallization. Once crystallization takes place, the TPU phase is excluded from the crystals, giving a final completely segregated morphology.…”

Extrusion Coating of Paper with Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)—Packaging Related Functional Properties

“…The reduction of tensile strength with an increasing PEG concentration is in accordance with the literature [23,27]. The tensile strength of pure PHBV (around 31 N/mm 2 ) is lower compared with the literature (36 N/mm 2 [34], 31.3 N/mm 2 [27], 23.5 to 28 N/mm 2 [27]). Choi determined a value of 15 N/mm 2 for PHBV blends with 20 wt.% TEC, for pure PHBV of 45 N/mm 2 .…”

“…Furthermore, we cannot explain the observed differences in post-processing crystallization behaviour. The crystallinity of pure PHBV was similar to the results of Jost [27], with lower values compared with another study with a value of 67% [34]. The difference can be explained by the different PHBV grade used.…”

“…This causes the formation of smaller spherulites and explains the higher flexibility of the blends compared with the pure polymer [22]. The crystallinity of pure PHBV was similar to the results of Jost [27], with lower values compared with another study with a value of 67% [34]. The difference can be explained by the different PHBV grade used.…”