Delivering net-zero CO2 emissions by 2050 requires rapid, large-scale carbon sequestration. Global photosynthesis, driven by cyanobacteria, microalgae, and higher plants, captures CO2 and constitutes the dominant natural carbon sink (biomass). The built environment represents a second major sink. Large-scale microalgal cultivation and the integration of its bioproducts into building materials offers a pathway to capture and store CO2 in built infrastructure. Colourful sustainably produced biopolymers offer one such route for carbon sequestration. Although pigments have a minor direct contribution, their coloration potential can accelerate the adoption of C-containing materials to increase architectural carbon sequestration. Here, we blended (individually and in combination) a range of structurally different pigments; the carotenoids-lutein (yellow) and astaxanthin (red), a water-soluble chlorophyll derivative-sodium copper chlorophyllin (green), and a water-soluble protein (phycocyanin, blue) into two biopolymers, polyhydroxybutyrate-hydroxyhexanoate and polycaprolactone with melting points of 135 degrees C and 60 degrees C, respectively. Six blending processes were evaluated for homogeneous coloured biopolymer production. UV resistance of coloured biopolymers was evaluated and enhanced by the application of a UV-protective coating. The best of the coloured biopolymer samples were integrated into a small-scale curved architectural structure to gain insight into the use and performance of the translucent materials produced for exhibition.

The environmental impact of traditional petroleum-based plastics has driven the search for sustainable alternatives, with bio-based polyesters emerging as a promising solution. However, these polymers often suffer from insufficient mechanical properties, which limits their applications. To address this, self-reinforcement has been explored as an innovative approach to enhance the performance of bio-based polyesters. This review provides an overview of the recent advancements in self-reinforced bio-based polyesters, focusing on polymers such as poly(lactic acid) (PLA), polyhydroxyalkanoates (PHAs), and poly(butylene succinate) (PBS). Different self-reinforcement techniques, such as electrospinning, melt spinning, and hot compaction are explored for their effectiveness in enhancing tensile strength, modulus, and overall durability. The review also discusses the integration of these materials into applications ranging from packaging to biomedical devices, where biodegradability and mechanical performance are critical. Furthermore, the paper explores the prospects of self-reinforced bio-based polyesters, emphasizing the need for continued innovation in material design and processing techniques to overcome current limitations.

The pervasive accumulation of plastic waste in terrestrial and aquatic environments has become a critical environmental issue, largely due to the resistance of petroleum-derived polymers to microbial degradation. This persistence leads to the long-term generation of microplastics and widespread ecosystem contamination. As a response, biodegradable and bio-based materials such as polyhydroxyalkanoates (PHA) have emerged as promising sustainable alternatives. Among them, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) is a microbial polyester that exhibits excellent biodegradability, biocompatibility, and tunable mechanical properties. Owing to these characteristics, P(3HB-co-4HB) can be employed in a wide range of applications, from environmentally friendly packaging to biomedical devices. However, its processing has traditionally relied on toxic solvents such as chloroform. In this study, acetic acid is evaluated as a green alternative solvent for producing P(3HB-co-4HB) films and porous gels. Compared with chloroform, acetic acid caused moderate reductions in molecular weight (–12

Here we provide microscopic insight into the improved mechanical performance of biomass derived films of poly(lactic acid) (PLA) following melt blending with medium-density polyethylene (MDPE) and high-density polyethylene (HDPE). Laboratory based characterisations show that twin screw extrusion of the blend in the melt introduced elongated micron-scale phase-separated structures consisting of phase-separated semicrystalline PE with some degree of crystallographic orientation along the machine direction, and isotropic poorly ordered PLA. Characteristic regions of failure during uniaxial tensile deformation of films were identified using optical microscopy. The regions associated with failure. which appear as crazes and domains oriented orthogonally to the extension direction, are micron-scale in pure PLA but expand to millimetre-scale in the blended materials.. Polarised vibrational (infrared and Raman) microspectroscopy reveals specific molecular orientation of the PLA and PE chains in the failure regions. Spatially localised X-ray scattering provided information on electron density correlations from crystalline- (wide angle X-ray scattering, WAXS) and meso-scale domains (small angle X-ray scattering, SAXS) as well as orientational information on these domains. It was found from WAXS that the polymer chains in the brittle PLA films are not more ordered on the length-scale of chain packing following extension, but that ordered and oriented nm-scale domains are produced (fibrils). The phaseseparated PE structures are shown to play a role in the distribution of load in the blend during extension, inhibiting the formation of PLA fibrils. The synchrotron-based measurements reveal the differences in polymer organisation both in and away from the failure regions: the regions associated with failure show well-defined perturbations, whereas away from the failure the material does not display any resolvable perturbation from the bulk unstretched structure. These results indicate that the improved mechanical performance arises from a local redistribution of stresses in the brittle PLA by the PE phase in the craze region.

Incorporating lignin as an additive is a promising strategy to overcome the limitations of PLA-based composites. This study investigates the effects of adding esterified lignin from banana pseudostem and sugarcane bagasse into a PLA matrix. Composites were produced via melt-compounding followed by compression molding, using two lignin concentrations: 5 wt% and 10 wt%. Thermal analyses revealed a reduction of up to 14.4 degrees C in the glass transition temperature, particularly in samples containing modified lignin. Mechanical properties were also influenced by lignin addition, with the lowest tensile strength (approximately 10.76 MPa) observed in composites containing modified banana pseudostem lignin. However, elongation at break remained unchanged. All lignin-PLA composites exhibited enhanced hydrophobicity compared to neat PLA. Improved cohesion between unmodified sugarcane bagasse lignin and PLA resulted in lower surface roughness, while chemical modification led to more homogeneous banana lignin-based composites. Furthermore, all lignin-containing samples demonstrated a significant enhancement in antioxidant activity, reaching up to 84.9%. Lignin addition also provided complete UV-blocking efficiency, regardless of source, content, or chemical modification. These findings confirm that esterified lignin effectively enhances the performance of PLA, particularly in terms of hydrophobicity, antioxidant capacity, and UV-shielding properties, which is advantageous for non-load-bearing applications where functional performance is prioritized over mechanical reinforcement.

Bioplastics such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) offer biodegradability but remain brittle and thermally unstable, limiting broader application. Conventional biocomposites reinforced with fillers like wood and carbon can improve mechanical properties but suffer from poor fibre–matrix adhesion, inconsistent biodegradability and limited recyclability. Here we address this limitation by developing self-reinforced unidirectional laminates (UDLs) fabricated entirely from a single PHBV polymer. Continuous melt-spun fibres were drawn in two stages to induce chain orientation, increasing melting temperature by ~9 °C and tensile strength by ~77% relative to undrawn filaments (UDF). These fibres were then aligned and consolidated by selective hot compaction, where fibre skins softened and interdiffused while oriented crystalline cores remained intact. The resulting mono-material laminates exhibited sharpened and slightly elevated melting transitions, consistent with lamellar thickening and interfacial recrystallisation. Resultant Young’s modulus and tensile strength of the UDLs surpassed isotropic PHBV by ~46% and ~63%, respectively, with only modest loss in ductility. Nanoindentation mapping revealed a continuous stiffness gradient; high in fibre cores, intermediate in interphases and lower in recrystallised matrix regions, demonstrating efficient stress transfer across welded junctions. This scalable method delivers high-performance PHBV materials with full recyclability and biodegradability features, addressing processing limitations and enabling sustainable engineering and packaging applications.

Polyhydroxyalkanoates (PHA) are regarded as promising bio-based and biodegradable polymers for the development of sustainable products, and their presence in the plastics industry is steadily increasing. The study of their thermal transitions and properties as a function of thermal treatment is crucial from a processing perspective, as well as for the optimisation of material performance. This study investigates the effects of 3hydroxyvalerate (3HV) content (0, 8, 36, 48, 57, 60%.mol) and heat treatment on the thermal behaviour of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) using modulated differential scanning calorimetry (MDSC). Thermal stability, evaluated by gel permeation chromatography (GPC), showed that polyhydroxybutyrate (PHB) appears to have a lower thermal stability than PHBV with 8 mol.% 3HV but higher 3HV content tends to reduce stability, reflected by greater molecular weight loss with increasing heating temperature. Molecular weight decreased linearly for all samples. Self-nucleation enhanced crystallisation occurred during cooling, in most PHBV, even at high 3HV content. A melt memory effect persisted even above the melting of all the residual crystallites, and it promoted PHAs crystallisation. Once thermal history was fully erased, crystallisation temperature became independent of heat treatment, indicating that crystallisation kinetics depended more on thermal history than degradation. Melting temperature remained stable for some PHAs but decreased for others. It appears that thermal transitions, properties and their evolution with heating conditions are specific to each PHA. MDSC revealed complex melting behaviour involving reversing and non-reversing processes. Lower 3HV contents and fully released thermal history led to more significant structural rearrangements, including cold crystallisation and melting-recrystallisation during the heating scan. Self-nucleation process and cold crystallisation appear to promote the melting of formed crystallites through non-reversing mechanisms, whereas, with the removal of thermal history and increased thermal degradation promote the melting of crystallites via reversing mechanisms.

This study examines polyhydroxyalkanoate (PHA)-based biocomposites incorporating locally sourced, biomass-derived fillers as a sustainable alternative to conventional plastics. While environmentally advantageous, optimisation of their mechanical properties and processability remains challenging due to the complex interplay of factors influencing biocomposite behaviour. Various commercial PHA polymers with different types of comonomer and content, were compounded with Australian lignocellulosic biofillers, wood, macadamia, and walnut shells, characterised by distinct cellulose and lignin contents. Gel permeation chromatography assessed PHA molecular weight changes post-processing, indicating thermo-mechanical degradation as a function of biofillers. Differential scanning calorimetry revealed correlations between biofiller cellulose content and crystallisation behaviour, glass transition temperature, and crystal perfection, which aligned with tensile strength and elastic modulus trends. The degree of crystallinity in neat PHAs emerged as a key determinant of mechanical performance in biocomposites. Oscillatory rheometry revealed that neat poly(3-hydroxybutyrate-co-4-hydroxybutyrate) exhibited higher viscosity, while poly(3-hydroxybutyrate-co-hexanoate) showed lower viscosity, independent of comonomer content and molecular weight. Rheological analysis also showed viscosity correlated with biofiller cellulose content at low shear rates and with PHA molecular weight at higher shear rates. Overall, this work provides a comprehensive platform and guidance for the development of PHA-based biocomposites.

Polyhydroxyalkanoates (PHAs) are biodegradable bioplastics with strong environmental benefits, yet their inherent brittleness and high production cost limit their broader adoption. Blending PHAs with lignocellulosic biofillers offers a circular and cost-effective pathway but often compromises mechanical performance. This study investigates post-fabrication heat treatment, e.g. annealing (< 150 °C) and partial-melting (> 150 °C) conditions, as a scalable strategy to tailor the properties of PHAs such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), their blends with poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB), and their wood fibre biocomposites. Annealing improved ductility by enhancing the mobile amorphous fraction (MAF) and reducing the rigid amorphous fraction (RAF), while partial melting promoted crystal perfection but also induced thermal degradation, increasing RAF and material stiffness. Optimal mechanical performance was achieved after 30 min at 150 °C, with tensile strain at break increasing by 650

The increasing accumulation of polypropylene (PP) and polyethylene terephthalate (PET) wastes from medical applications necessitates recycling strategies that reduce reliance on virgin polymers and divert high purity plastics from disposal. This study evaluates the mechanical recyclability of PP and PET recovered from hospital waste by examining how increasing recyclate content affects material properties. DSC analysis showed stable thermal properties across blend ratios, indicating minimal thermal degradation. Mechanical properties were more sensitive to increased recyclate content. However, blends containing up to 30 wt% recyclate exhibited acceptable mechanical properties for non-critical applications. Integrating these findings into a circular economy framework highlights substantial environmental benefits. Incorporating 30 wt% mechanically recycled material yields estimated climate savings of ~0.45 tCO₂ eq/t for PP and ~0.7 tCO₂ eq/t for PET by avoiding virgin production emissions and preventing incineration. These results demonstrate that mechanically recycling selected medical plastics is technically feasible and environmentally impactful for healthcare systems.

This study aims to analyze the potential use of modified lignin-rich material isolated from banana pseudostem as a green additive in chitosan-based film. Organosolv pulping lignin-rich material was chemically-modified with maleic anhydride, and then added to chitosan-based casting film at 2 and 5 wt% concentrations. The results showed that the molecular weight of lignin increased after chemical modification from 1974 to 2162 g mol-1. The FTIR spectra also confirmed the chemical modification and showed CO stretching vibrations of carbonyl groups and a reduction in OH stretching vibrations present in aliphatic and phenolic structures. Although lignin has high thermal stability, no differences were observed after adding it to the chitosan matrix according to thermal analyses. However, lower tensile strength was identified with a reduction of up to 17.87 %. An increase of 10.06° in the water contact angle was observed after lignin incorporation, while water vapor permeability decreased by 14.4 % relative to the chitosan-based film. UV-blocking efficiency improved by up to 30.72 % and 50.30 % for films containing 2 wt% and 5 wt% lignin, respectively, compared to the control. All film samples showed an increased antioxidant capacity over 24 h, with maximum activity >34 %; however, no significant variation was attributed to the lignin addition. Overall, the results showed that the addition of esterified lignin at 5 wt% to chitosan-based film was the best formulation, improving mostly its UV-blocking capacity and hydrophobicity, which are valuable properties for industrial applications, such as food packaging.

Abstract Bioplastics and biocomposites are eco‐friendly alternatives to their petrochemical derived commodity material, but tend to have inferior mechanical and thermal properties. In this work, short‐fiber self‐reinforced bioplastic composites (SRBCs) have been developed that seek to overcome some of these shortcomings. The SRBCs leverage melt‐spun drawn poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) fibers with axially‐oriented crystalline structures that exhibit a ≈6.7 °C higher melt temperature than the same PHBV in isotropic form. This enables a controlled‐temperature compounding process that preserves the crystalline structure of the fibers without distortion and ensures uniform distribution within the matrix. The resultant composites display a ≈35% increase in ultimate tensile strength and a ≈55% increase in impact resistance compared to neat PHBV polymer. This monolithic‐type composite system, characterized by high interfacial compatibility and strong fiber‐matrix adhesion, also supports high‐value recycling while preserving its mechanical properties across multiple lifecycle uses. By focusing upon discontinuous short fiber reinforcement, this work provides unprecedented opportunities for scaling SRBCs through commodity application pathways such as injection molding, compression molding, and 3D printing.

Polyhydroxyalkanoates (PHAs) are biodegradable bioplastics with strong environmental benefits, yet their inherent brittleness and high production cost limit broader adoption. Blending PHAs with lignocellulosic biofillers offers a circular and cost-effective pathway but often compromises mechanical performance. This study investigates post-fabrication heat-treatment, e.g. annealing (< 150°C) and partial-melting (> 150°C) conditions, as a scalable strategy to tailor the properties of PHAs such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), their blends with poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB), and their wood fibre biocomposites. Annealing improved ductility by enhancing the mobile amorphous fraction (MAF) and reducing the rigid amorphous fraction (RAF), while partial melting promoted crystal perfection but induced thermal degradation, increasing RAF and material stiffness. Optimal mechanical performance was achieved after 30 min at 150°C, with tensile strain at break increasing by ~ 650% for neat PHAs and ~ 200% for wood/PHAs biocomposite variants. This was accompanied by a 20–30% reduction in modulus and ≤ 16% drop in tensile stress for the both materials. Notably, shrinkage above 175°C was significant in neat and blended PHAs but was strongly mitigated by wood biofillers. The results highlight post-fabrication heat treatment as a simple, effective method to enhance the mechanical behaviour and dimensional stability of PHAs-based materials for rigid packaging and other demanding applications.

Polyhydroxyalkanoates (PHAs) are environmentally friendly and biodegradable alternatives to petroleum-based plastics derived from bacteria, that decompose under ambient conditions. However, commonly used short chain length (SCL) PHAs, in particular, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), tend to be rigid and brittle inhibiting their wider usage. To address this, self-reinforced PHA monomaterial films, varying only by the comonomers in their backbone structure, were prepared using both electrospinning and electrospraying techniques. PHBV, a SCL-PHA, was electrospun as the highly crystalline fiber phase, while poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), a medium-chain-length (MCL) PHA, was electrosprayed as the flexible low crystalline matrix phase. The resulting self-reinforced PHA monomaterial films were annealed below the melting point of PHBV to improve fiber matrix adhesion and increase mechanical properties. These self-reinforced PHA monomaterial films were then characterized to assess their suitability for sustainable packaging and piezoelectric applications, showing promising results.

In this study, we explore an approach to enhance the mechanical performance of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by utilizing the self-reinforcing effect of β-phase-induced PHBV electrospun nanofiber mats. This involves electrospinning combined with low-temperature postspun vapor solvent interfiber welding. Scanning electron microscopy imaging confirmed fiber alignment, while XRD diffraction revealed the presence of both α and β crystalline phases under optimized electrospinning conditions. The resulting composite exhibited significant improvements in mechanical properties attributed to the formation of more perfectly structured α and β polymorphs and enhanced interfacial adhesion of electrospun nanofibers after vapor solvent treatment. This approach offers entirely recyclable and biodegradable materials, presenting the potential for a new family of sustainable bioplastics.

This research intends to create biodegradable packaging films using solution casting method. The films are composed of guar gum, carboxymethylcellulose, and blends of these materials with citric acid as a crosslinking agent. The concentration of citric acid ranges from 10 to 30% (w w-1). This study performs a curing treatment at 140 degrees C for 30 min on the dried films containing the crosslinking additive to promote the esterification between the polymeric matrix and the crosslinking agent. The thin films have a smooth, homogeneous, and transparent aspect. Although the crosslinking reaction - evidenced by FTIR spectra - does not affect the thickness of the material, it causes a slight color variation making the samples assume a yellowish shade. Moreover, the crosslinking process enhances the water resistance, decreases the crystallinity index, and improves the water vapor barrier and thermal resistance of the films. The SEM images reveal the excess of unreacted crosslinking agent accumulated on the samples; these particles work as a plasticizer, affecting the morphology of the films as well as their water resistance, crystallinity, and thermal resistance. The image outlines the methodology for producing guar gum and carboxymethylcellulose films crosslinked with. 10%, 20%, and 30% citric acid. It also displays the infrared spectra of both the neat and crosslinked films, highlighting the main characteristic bands of each polymer and their associations. image

Biochar samples derived from various agricultural wastes including corn cobs, corn straws, rice husks, and rice straws were investigated for potential use as ethylene absorbers to delay 'Gros Michel' banana ripening. The biochar samples were prepared using the pyrolysis method at 500 degrees C with a heating rate of 1 degrees C/min for 2 h and examined for their morphology, surface area, pore diameter, pore volume, functional groups, CHNS/O composition, elemental composition, and thermal properties. Each type of biochar had different elemental compositions and surface area. The largest surface area of 110.67 m2/g was found in rice husk biochar. The ethylene adsorption efficiency was determined in closed containers and low-density polyethylene (LDPE) bags containing 'Gros Michel' bananas treated with different biochar types. The rice husk biochar exhibited ethylene adsorption of 31.14 % in closed containers at 144 h and the low total color difference Delta E value of 22.30. Thus, rice husk biochar showed promise as an ethylene absorber to delay fruit ripening in packaging applications.

The design and manufacture of new biodegradable and bioderived polymeric materials has traditionally taken place through experimentation and material characterisation. However, cutting-edge computational methods now provide a less expensive and more efficient approach to innovative biopolymer design and scale-up. In particular, the holistic framework provided by Materials 4.0 combines multiscale simulations and computational modelling with theory and next-generation informatics (big data integration and artificial intelligence) to model biopolymer structures, understand their flow and processibility, and predict their properties. These computational methods are being utilised to model and forecast the properties of a wide variety of biopolymeric materials, including the large family of biodegradable polyesters along with lignocellulosics, polysaccharides, proteinaceous materials, natural rubber, and so on. Ranging from quantum- to macro-scale, computational modelling acts as a complement to traditional experimental techniques, probing molecular structure and intramolecular interactions as well as reaction mechanisms. This enables further kinetic modelling studies and molecular simulations. The research has been further expanded to include the use of machine learning approaches for material property optimisation in conjunction with expert knowledge and relevant experimental data. Aside from the modelling of structure-property relationships, computational modelling has also been used to predict the effect of biopolymer modifications and the influence of external factors such as the application of external fields or applied stress and the effects of moisture. In summary, there is a fast-developing library of computational modelling data for biopolymers, and the development of Materials 4.0 in this sector has enabled greater flexibility in design and processing options in advance of more expensive and time-consuming testing.

Improvements in the mechanical performance of biodegradable plastics are required to facilitate replacement of commodity plastics as part of a global push for the use of more sustainable materials. Reinforcing biodegradable plastics with fillers or fibres to create composite materials is an obvious choice for increasing mechanical properties but may affect recyclability and biodegradability. To avoid these issues, self-reinforced polymer composites (SRPCs), where the polymer matrix is reinforced with highly oriented films, fibres, or particles of the same polymer may be used. However, the use of biodegradable thermoplastics in SRPCs is currently limited to a few polymers, mostly focusing on poly(lactic acid) (PLA). Here, we have assessed the potential for a broader range of biodegradable thermoplastics to replace commercially available commodity-plastic-based SRPCs. This assessment was done using literature data for the oriented and isotropic bulk mechanical properties of commercially relevant biodegradable thermoplastics, along with properties for their SRPCs where available. It was found that despite polycaprolactone (PCL), poly(butylene succinate) (PBS), poly(butylene succinate adipate) (PBSA), and poly(butylene adipate terephthalate) (PBAT) not being suitable replacements for current commercially available SRPCs, they nonetheless exhibit increased modulus and strength after orientation. PLA, polyhydroxyalkanoates (PHAs), and poly(glycolic acid) (PGA) have more potential, with PGA being the most promising, although PLA and PHAs appear to offer potentially more sustainable alternatives to commercially available SRPCs and a wider range of end-of-life disposal options.

This study offers a novel approach that enables both the functionalization of degradable polymers and the modification of polymer properties during processing and use. Degradable polylactide was copolymerized with polyethylene glycol, with the aim to facilitate processing and blending by heating. Moreover, L,L- and D,D-lactide were employed for possible stereocomplexation, with the aim to enhance physical properties during use after processing. Additionally, gallic acid was introduced at both chain ends, which exhibited antioxidant properties as functionalization.