Volume Change during Creep and Micromechanical Deformation Processes in PLA–PBSA Binary Blends

Abstract

In this paper, creep measurements were carried out on poly(lactic acid) (PLA) and its blends with poly(butylene succinate-adipate) (PBSA) to investigate the specific micromechanical behavior of these materials, which are promising for replacing fossil-based plastics in several applications. Two different PBSA contents at 15 and 20 wt.% were investigated, and the binary blends were named 85-15 and 80-20, respectively. Measurements of the volume strain, using an optical extensometer, were carried out with a universal testing machine in creep configuration to determine, accompanied by SEM images, the deformation processes occurring in a biopolymeric blend. With the aim of correlating the creep and the dilatation variation, analytical models were applied for the first time in biopolymeric binary blends. By using an Eyring plot, a significant change in the curves was found, and it coincided with the onset of the cavitation/debonding mechanism. Furthermore, starting from the data of the pure PLA matrix, using the Eyring relationship, an apparent stress concentration factor was calculated for PLA-PBSA systems. From this study, it emerged that the introduction of PBSA particles causes an increment in the apparent stress intensity factor, and this can be ascribed to the lower adhesion between the two biopolymers. Furthermore, as also confirmed by SEM analysis, it was found that debonding was the main micromechanical mechanism responsible for the volume variation under creep configuration; it was found that debonding starts earlier (at a lower stress level) for the 85-15 blend.

Analysis of the Damage Mechanism around the Crack Tip for Two Rubber-Toughened PLA-Based Blends

“…Cavitation, in fact, arises at the crack tip, followed by void growth. If the voids are generated at the interface between the matrix and rubber particles [17], the mechanism is called debonding (Figure 1). Usually, high adhesion values contribute to the internal cavitation of the rubber particles, while low values contribute to the debonding mechanism.…”

Fully Biobased Reactive Extrusion of Biocomposites Based on PLA Blends and Hazelnut Shell Powders (HSP)

“…While the reactivity between ESO/DCA and its interaction with PLA matrix was demonstrated in literature [58], the evaluation of the reactivity between ESO/DCA and HSP was investigated in this paper. F12 and F15, the samples prepared with the HM200 and, respectively, with the highest amount of MA (or SA) with ESO were dissolved in chloroform, a good solvent for the matrix system but not for HSP [69].…”

“…In this work, both malic acid and succinic acid were investigated as possible dicarboxylic acids improving the reactivity of ESO. The selected matrix for the composite is the blend PLA/PBSA 60:40 [47], showing a good balance of stiffness and ductility [58].…”

A Brief Review of Poly (Butylene Succinate) (PBS) and Its Main Copolymers: Synthesis, Blends, Composites, Biodegradability, and Applications

“…Principally, PBS is used as a ductility enhancer for PLA; its main defect is the brittleness. A PBS copolymer with an adipate segment, PBSA, is also present in many works regarding the improvement of toughness for brittle matrices concerning the creep behavior [ 89 ].…”