Melt-spun polyhydroxyalkanoate monofilaments were successfully processed into woven and knitted textiles using industrial machinery, demonstrating their feasibility for textile applications. The filaments, composed of P(3HB)/P(3HB-co-4HB), exhibited an average tensile strength of ∼138 MPa and an elongation at break of ∼55%, with crystallinity of ∼30%. Cyclic loading of the filaments revealed pronounced hysteresis during the first cycle, which diminished in subsequent cycles. However, a relaxation time of 120 s was sufficient to reset the molecular conformational changes that occurred during the previous cycles. Furthermore, the incorporation of beta tricalcium phosphate (β-TCP) particles during melt spinning reduced tensile strength but improved thermal stability, enhancing processability. These findings highlight the potential of P(3HB)/P(3HB-co-4HB) monofilaments for sustainable textile applications requiring mechanical resilience and thermal robustness.

The textile industry faces an urgent need for sustainable alternatives to petroleum-derived fibers, with bio-based and biodegradable polymers emerging as promising candidates. In this work, we demonstrate the successful melt-spinning of polyhydroxyalkanoate (PHA) monofilaments, specifically P(3HB)/P(3HB-co-4HB), into woven and knitted textiles using standard industrial machinery. This is relevant, as PHA processing into textile-grade fibers has remained a major challenge due to its thermal sensitivity and mechanical limitations.

The resulting monofilaments exhibited tensile strengths of ~138 MPa and elongation at break of ~55%, with crystallinity around 30%. Mechanical testing under cyclic loading revealed pronounced hysteresis during the first cycle, which diminished in subsequent cycles; importantly, a short relaxation period of 120 s was sufficient to reset conformational changes, demonstrating recoverability under repeated stress. Beta tricalcium phosphate (ß-TCP) particles were incorporated during melt-spinning. While this reduced tensile strength, it significantly improved thermal stability, thereby expanding the processability window for melt spinning.

In this study, a bio-based resin containing glycerol, isosorbide, and 2,5-furan dicarboxylic acid was used to produce a glass fiber reinforced composite. The thermomechanical properties of the resin were examined through dynamic mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry, and were compared with those of commercially available unsaturated polyester resin and epoxy resin. Glass fiber composites were prepared using the synthesized bio-based resin, commercial unsaturated polyester resin, and commercial epoxy resin. Tensile tests, flexural tests, and aging tests were performed on all three types of composites and the results were compared. The findings suggest that the bio-based resin exhibits superior thermomechanical properties compared to the commercial resins. Bio-based resin demonstrates a high storage modulus of 4807 MPa and a loss modulus of 72 MPa at 25 ℃, along with a high glass transition temperature of 173 ℃. The flexural and tensile properties of the bio-based resin were better than that of the commercial resins. The composite produced from bio-based resin shows a flexural strength of 334 MPa and a tensile strength of 256 MPa. Aging results indicate that the synthesized bio-based resin was fairly stable at elevated temperatures. The outcome of this work shows that the bio-based glass fiber reinforced composite is a promising composite for high temperature applications. 

The influence of beta-tricalcium phosphate (ß-TCP) particles on the early cell attachment of MC3T3-E1 osteoblast precursor cells is investigated on a poly(3-hydroxybutyrate)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) polymer blend. MC3T3-E1 cells adhere to both polymer blends, with and without ß-TCP. In both cases, the cells show a typical cell morphology and focal adhesions on the polymer surface. The ß-TCP does not significantly improve the cell adhesion and hydrophilicity of the polymer films. Further, ß-TCP does not alter the degradation behavior of the poly(3-hydroxybutyrate)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blend when exposed to phosphate buffered saline solution for up to 70 days. However, the results confirm that the polyhydroxyalkanoate blends used in this study are non-cytotoxic and maintain structural integrity over time. These findings highlight the blend's promise for usage in long-term biomedical applications, particularly in bone tissue engineering, because of their stability in isotonic medium. 

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biobased and biodegradable polymer. This polymer is considered promising, but it is also rather expensive. The objective of this study was to compound PHBV with three different organic fillers considered waste: human hair waste (HHW), sawdust (SD) and chitin from shrimp shells. Thus, the cost of the biopolymer is reduced, and, at the same time, waste materials are valorised into something useful. The composites prepared were characterised by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile strength and scanning electron micrograph (SEM). Tests showed that chitin and HHW did not have a reinforcing effect on tensile strength while the SD increased the tensile strength at break to a certain degree. The biodegradation of the different composites was evaluated by a soil burial test for five months. The gravimetric test showed that neat PHBV was moderately degraded (about 5% weight loss) while reinforcing the polymer with organic waste clearly improved the biodegradation. The strongest biodegradation was achieved when the biopolymer was compounded with HHW (35% weight loss). The strong biodegradation of HHW was further demonstrated by characterisation by Fourier-transform infrared spectroscopy (FTIR) and solid-state nuclear magnetic resonance (NMR). Characterisation by SEM showed that the surfaces of the biodegraded samples were eroded.

We investigated the melt-spinning potential of a poly(3-hydroxybutyrate)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blend using a piston spinning machine with two different spinneret diameters (0.2 and 0.5 mm). Results from the differential scanning calorimetry, dynamic mechanical thermal analysis, and tensile testing showed distinct filament properties depending on the monofilaments’ cross-sectional area. Finer filaments possessed different melting behaviors compared to the coarser filaments and the neat polymer, indicating the formation of a different type of polymer crystal. Additionally, the mechanical properties of the finer filament (tensile strength: 21.5 MPa and elongation at break: 341%) differed markedly from the coarser filament (tensile strength: 11.7 MPa, elongation at break: 12.3%). The hydrolytic stability of the filaments was evaluated for 7 weeks in a phosphate-buffered saline solution and showed a considerably reduced elongation at break of the thinner filaments. Overall, the results indicate considerable potential for further filament improvements to facilitate textile processing.

Volatile fatty acids (VFAs) appear to be an economical carbon feedstock for the cost-effective production of polyhydroxyalkanoates (PHAs). The use of VFAs, however, could impose a drawback of substrate inhibition at high concentrations, resulting in low microbial PHA productivity in batch cultivations. In this regard, retaining high cell density using immersed membrane bioreactor (iMBR) in a (semi-) continuous process could enhance production yields. In this study, an iMBR with a flat-sheet membrane was applied for semi-continuous cultivation and recovery of Cupriavidus necator in a bench-scale bioreactor using VFAs as the sole carbon source. The cultivation was prolonged up to 128 h under an interval feed of 5 g/L VFAs at a dilution rate of 0.15 (d−1), yielding a maximum biomass and PHA production of 6.6 and 2.8 g/L, respectively. Potato liquor and apple pomace-based VFAs with a total concentration of 8.8 g/L were also successfully used in the iMBR, rendering the highest PHA content of 1.3 g/L after 128 h of cultivation. The PHAs obtained from both synthetic and real VFA effluents were affirmed to be poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a crystallinity degree of 23.8 and 9.6%, respectively. The application of iMBR could open an opportunity for semi-continuous production of PHA, increasing the feasibility of upscaling PHA production using waste-based VFAs. 

Hydroxyapatite (HA) has shown very promising results in hard tissue engineering because of its similarity to bone and hence the capability to promote osteogenic differentiation. While the bioactivity of HA is uncontested, there are still uncertainties about the most suitable hydroxyapatite particle shapes and sizes for textile scaffolds. This study investigates the influence of the shape and size of HA particles on as spun fibers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and HA, their mechanical and thermal properties as well as their influence on the fiber degradation in simulated blood matrix and their capability to mineralize in simulated body fluid. The key findings were that the different HA particles’ size does not affect the melting temperature and still maintains a thermal stability suitable for fiber production. Tensile testing revealed decreased mechanical properties for PHBV/HA as spun fibers, independently of the particle morphology. However, HA particles with 30 nm in width and 100 nm in length at 1 wt% HA loading achieved the highest tenacity and elongation at break amongst all composite fibers with HA. Besides, the Ca/P ratio of their mineralization in simulated body fluid is the closest to the one of mineralized human bone, indicating the most promising bioactivity results of all HA particles studied.

Unsaturated polyester resins, one of the most important thermosets, are invariably produced from oil-based monomers. Their application is limited in areas where high thermal stability is required due to their low Tg. Besides, these resins contain 30–40% hazardous styrene as a reactive solvent. Therefore, developing bio-based solventless unsaturated polyester resin with medium to high thermomechanical properties compared to petrochemical-based counterparts is important. In order to achieve this, a series of branched bio-based unsaturated polyester resins were synthesized using bulk polymerization method in two steps. In the first step, four different intermediates were prepared by reacting glycerol (as a core molecule) with either isosorbide (diol), 1,3-propanediol (diol), 2,5-furandicarboxylic acid (saturated diacid), or adipic acid (saturated diacid). In the second step, the branched intermediate was end capped with methacrylic anhydride to introduce reactive sites for cross-linking on the branch ends. The chemical structure of the resins was characterized by 13C-NMR. FT-IR confirmed the polycondensation reaction in the first step and the end functionalization of the resins with methacrylic anhydride in the second step. The effect of 2,5-furandicarboxylic acid and isosorbide on thermomechanical and thermal properties was investigated using dynamic mechanical analysis, differential scanning calorimetry, and thermo-gravimetric analysis. Results indicated that 2,5-furandicarboxylic acid based resins had superior thermomechanical properties compared to a commercial reference unsaturated polyester resin, making them promising resins for high-temperature composite applications. For example, the resin based on 2,5-furandicarboxylic acid and isosorbide and the resin based on 2,5-furandicarboxylic acid and 1,3-propanediol gave glass transition temperatures of 173 °C and 148 °C, respectively. Although the synthesized 2,5-furandicarboxylic acid based resins had higher viscosity (22.7 Pas) than conventional unsaturated polyester (0.4–0.5 Pas) at room temperature, preheated resins can be used for making high-temperature-tolerance fiber-reinforced composite. 

The superior biocompatibility and biodegradability of polyhydroxyalkanoates (PHAs) compared to man-made biopolymers such as polylactic acid promise huge potential in biomedical applications, especially tissue engineering (TE). Textile fiber-based TE scaffolds offer unique opportunities to imitate the anisotropic, hierarchical, or strain-stiffening properties of native tissues. A combination of PHAs' enhanced biocompatibility and fiber-based TE scaffolds could improve the performance of TE scaffolds. However, the PHAs' complex crystallization behavior and the resulting intricate spinning procedures remain a challenge. This review focuses on discussing the developments in PHA melt and wet spinning, their challenges, process parameters, and fiber characteristics while revealing the lack of an in-depth fiber characterization of wet-spun fibers compared to melt-spun filaments, leading to squandered potential in scaffold development. Additionally, the biomedical application of PHAs other than poly-4-hydroxybutyrate is hampered by a failure of polymer purity to meet the requirements for biomedical applications.