Effect of ageing and annealing on the mechanical behaviour and biodegradability of a poly(3-hydroxybutyrate) and poly(ethylene- co -methyl-acrylate- co -glycidyl-methacrylate)blend: Mechanical behaviour of PHB/PEMAGMA blends

Characterization of Poly(3-hydroxybutyrate) (P3HB) from Alternative, Scalable (Waste) Feedstocks

Bioplastics hold significant promise in replacing conventional plastic materials, linked to various serious issues such as fossil resource consumption, microplastic formation, non-degradability, and limited end-of-life options. Among bioplastics, polyhydroxyalkanoates (PHA) emerge as an intriguing class, with poly(3-hydroxybutyrate) (P3HB) being the most utilized. The extensive application of P3HB encounters a challenge due to its high production costs, prompting the investigation of sustainable alternatives, including the utilization of waste and new production routes involving CO2 and CH4. This study provides a valuable comparison of two P3HBs synthesized through distinct routes: one via cyanobacteria (Synechocystis sp. PCC 6714) for photoautotrophic production and the other via methanotrophic bacteria (Methylocystis sp. GB 25) for chemoautotrophic growth. This research evaluates the thermal and mechanical properties, including the aging effect over 21 days, demonstrating that both P3HBs are comparable, exhibiting physical properties similar to standard P3HBs. The results highlight the promising potential of P3HBs obtained through alternative routes as biomaterials, thereby contributing to the transition toward more sustainable alternatives to fossil polymers.

Assessment of the structures contribution (crystalline and mesophases) and mechanical properties of polycaprolactone/pluronic blends

Films of biodegradable blends of polycaprolactone (PCL) and Pluronics F68 and F127 were manufactured by an industrial thermo-mechanical process to be applied as potential delivery systems. The effects of Pluronics on the structure (mesophase organization), and thermal and mechanical properties of polycaprolactone were investigated using differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), polarized optical microscopy (POM) and tensile mechanical tests. The addition of Pluronics affected the crystallization process by changing the relative amounts of crystalline, amorphous, and meso- (condis + plastic) phases. The melting transition and XRD profiles were deconvoluted to assess the individual contribution of the different crystal morphologies. Furthermore, it was found that the mechanical properties of the blends depended on the ratio and type of Pluronic. Thus, Pluronic F127 showed a larger mesophase content than its F68 counterpart with PCL and blends with enhanced ductility.

Improving Mechanical Properties for Extrusion-Based Additive Manufacturing of Poly(Lactic Acid) by Annealing and Blending with Poly(3-Hydroxybutyrate)

Based on differential scanning calorimetry (DSC), X-ray diffraction (XRD) analysis, polarizing microscope (POM), and scanning electron microscopy (SEM) analysis, strategies to close the gap on applying conventional processing optimizations for the field of 3D printing and to specifically increase the mechanical performance of extrusion-based additive manufacturing of poly(lactic acid) (PLA) filaments by annealing and/or blending with poly(3-hydroxybutyrate) (PHB) were reported. For filament printing at 210 °C, the PLA crystallinity increased significantly upon annealing. Specifically, for 2 h of annealing at 100 °C, the fracture surface became sufficiently coarse such that the PLA notched impact strength increased significantly (15 kJ m⁻²). The Vicat softening temperature (VST) increased to 160 °C, starting from an annealing time of 0.5 h. Similar increases in VST were obtained by blending with PHB (20 wt.%) at a lower printing temperature of 190 °C due to crystallization control. For the blend, the strain at break increased due to the presence of a second phase, with annealing only relevant for enhancing the modulus.

Recent advances in the development of biodegradable PHB-based toughening materials: Approaches, advantages and applications

Polyhydroxybutyrate (PHB) is a natural biodegradable polymer that is produced by many types of bacteria as an intracellular energy storage material. Due to its numerous advantages such as biodegradability, biocompatibility, availability and with physical properties comparable to petroleum-based thermoplastics, PHB is a potential substitute in biomedical and packaging fields. However, several physical drawbacks, such as high production cost, thermal instability, and poor mechanical properties, due to secondary crystallization and slow nucleation rate, limit its competition with traditional plastics in industrial and biomedical applications. Thereby, many attempts have been employed to improve the material performance of toughened PHB so as to achieve greater competitiveness and sustainability. In this review, the most recent developments of PHB-based toughening materials are discussed with respect to their approaches and strategies, which includes: drawing and thermal treatment, blending with materials from natural sources and synthetic polymers, as well as forming reinforced composites with natural fibers and inorganic fillers. The alternation of PHB chemical structure to form various types of functional copolymers with enhanced materials performance is also summarized. The expanded utilization of these newly developed sophisticated PHB materials as engineering materials and the biomedical significance in different domains are also addressed.

Confined PEO crystallisation in immiscible PEO/PLLA blends

PEO/PLLA blends are immiscible. PEO phase is confined into PLLA interlamellar and interspherulitic regions and a confined and fractional crystallisation of PEO occurs as the density of the PLLA crystalline phase increases.