Development and Characterization of Fully Renewable and Biodegradable Polyhydroxyalkanoate Blends with Improved Thermoformability

Abstract

Poly(3-hydroxybutyrate-co-3-valerate) (PHBV), being one of the most studied and commercially available polyhydroxyalkanoates (PHAs), presents an intrinsic brittleness and narrow processing window that currently hinders its use in several plastic applications. The aim of this study was to develop a biodegradable PHA-based blend by combining PHBV with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), another copolyester of the PHA family that shows a more ductile behavior. Blends of PHBV with 20% wt., 30% wt., and 40% wt. of PHBH were obtained by melt mixing, processed by cast extrusion in the form of films, and characterized in terms of their morphology, crystallization behavior, thermal stability, mechanical properties, and thermoformability. Full miscibility of both biopolymers was observed in the amorphous phase due to the presence of a single delta peak, ranging from 4.5 °C to 13.7 °C. Moreover, the incorporation of PHBH hindered the crystallization process of PHBV by decreasing the spherulite growth rate from 1.0 µm/min to 0.3 µm/min. However, for the entire composition range studied, the high brittleness of the resulting materials remained since the presence of PHBH did not prevent the PHBV crystalline phase from governing the mechanical behavior of the blend. Interestingly, the addition of PHBH greatly improved the thermoformability by widening the processing window of PHBV by 7 s, as a result of the increase in the melt strength of the blends even for the lowest PHBH content.

Progress in design and processing of polyhydroxyalkanoates (PHAs): Home compostable poly(3‐hydroxybutyrate‐co—3‐hydroxyhexanoate) (PHBHHx)/polybutylene succinate‐co‐adipate (PBSA) blend

“…In particular, from week 6 onwards, the samples start to lose weight markedly. This behavior is typical of PHA 48 . The amorphous fraction is preferred by microorganisms to be degraded first in the early stages, as the mobility of the chains facilitates the accessibility of their enzymes.…”

“…This behavior is typical of PHA. 48 The amorphous fraction is preferred by microorganisms to be degraded first in the early stages, as the mobility of the chains facilitates the accessibility of their enzymes. Despite different biodegradation rates, the final degree of biodegradation (indicated here as weight loss) achieved by all tested samples stabilized at around 4% during the test.…”

Electrospun Multilayered Films Based on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate), Copolyamide 1010/1014, and Electrosprayed Nanostructured Silica

“…The copolyamide that has been developed herein presents a melting point that is considerably lower than that reported for PA6/66, with values still slightly above 200 °C [ 31 ]. In food packaging applications, the low melting point of the PA1010/1014 allows the combination of this semi-crystalline gas barrier polymer with biopolymers such as PHBV, which was used in this study (with a melting point of 174 °C [ 32 ]).…”

Influence of Ulluco Starch Modified by Annealing on the Physicochemical Properties of Biodegradable Films

“…Data collection was carried out in the 2θ range of 3.5–70°, with a step size of 0.02035° (2θ) and a counting time of 0.8 s/step. Relative crystallinity was determined after deconvolution of peaks from diffractograms by the relationship between the crystalline peak area ( Ac ) and the total area ( At ) using Equation (1) [ 13 ]. Results were reported as the average of three measurements.…”