Immiscible PHB/PBS and PHB/PBSA blends: morphology, phase composition and modelling of elastic modulus

Abstract

This paper reports the thermal, morphological and mechanical properties of environmentally friendly poly(3-hydroxybutyrate) (PHB)/poly(butylene succinate) (PBS) and PHB/poly[(butylene succinate)-co-(butylene adipate)] (PBSA) blends, prepared by melt mixing. The blends are known to be immiscible, as also confirmed by the thermodynamic analysis here presented. A detailed quantification of the crystalline and amorphous fractions was performed, in order to interpret the mechanical properties of the blends. As expected, the ductility increased with increasing PBS or PBSA amount, but in parallel the decrease in the elastic modulus appeared limited. Surprisingly, the elastic modulus was found properly described by the rule of mixtures in the whole composition range, thus attesting mechanical compatibility between the two blend components. This unusual behavior has been explained as due to co-continuous morphology, present in a wide composition range, but also at the same time as the result of shrinkage occurring during sequential crystallization of the two components, which can lead to physical adhesion between matrix and dispersed phase. For the first time, the elastic moduli of the crystalline and mobile amorphous fractions of PBS and PBSA and of the mobile amorphous fraction of PHB at ambient temperature have been estimated through a mechanical modelling approach.

Rheological and mechanical properties, heat resistance and hydrolytic degradation of poly(butylene succinate‐co‐adipate)/stereocomplex polylactide blends

“…Blending of PBSA with other biodegradable polymers to improve its comprehensive properties while still maintaining its biodegradability has gained interest. [21][22][23] Physical mixing of poly(lactic acid) (PLA), a biodegradable aliphatic polyester with good biocompatibility and high mechanical strength, improves the modulus and tensile strength of PBSA. [24][25][26][27] Ojijo et al 28 prepared a biodegradable PBSA/PLA binary blend by the melt-blending.…”

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

“…In terms of the elastic modulus evaluation, Righetti et al [ 61 ] studied the elastic moduli of the crystalline and mobile amorphous fractions of PBS through a mechanical modelling approach, isolating the two contributions.…”

Fabrication of poly(lactic acid), poly(butylene succinate), and poly(hydroxybutyrate) bio‐based and biodegradable blends for application in fused filament fabrication‐based 3D printing

“…A similar structure has been described by other researchers. 30,31,53 The compatibility of blends was further evaluated with FTIR spectroscopy. The FTIR spectra of S5B5, S7B3, S5L5, and S7L3 are shown in Figure 5.…”

“…Using PBS or similar copolymers has been shown to yield improvement in strength, elongation, and melt viscosity when blended with PLA and PHB. 16,21,[30][31][32][33] Bio-based and biodegradable polymer blends offer a range of benefits when used in FFF 3D printing. Given the tremendous interest in bio-based and biodegradable polymers as the main component to develop FFF filaments, in the present study, we undertake an in-depth investigation of formulations based on PBS in combination with PLA or PHA.…”

“…Therefore, adding PBS to PLA or PHA can enhance ductility, impact resistance, thermal processing, and other properties. Using PBS or similar copolymers has been shown to yield improvement in strength, elongation, and melt viscosity when blended with PLA and PHB 16,21,30–33 …”