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The growing demand for sustainable materials has driven the exploration of natural fibers as eco-friendly alternatives to synthetic reinforcements for composites. This study investigates the potential of Posidonia oceanica, an abundant marine biomass, which is often driven to be stacked on the backshore and used so far for energy recovery and low-value applications, as a filler and possible reinforcement in cementitious and polymer composites. Most applications of Posidonia are concentrated in the Mediterranean area and focused on the construction industry. However, its introduction in polymer composites, especially as a source of cellulose or in combination with the use of bio-based matrices, can also be proposed. With this aim, the physical and chemical properties of Posidonia oceanica fibers need to be characterized, and their compatibility with various matrices needs to be evaluated. Experimental results demonstrate that Posidonia oceanica fibers, especially when treated with alkali and silane, or combining both treatments, can exhibit mechanical properties quite comparable to other natural fibers, namely to those obtained from grass species. As with any other type of waste, yet with more interest for its wide accumulation over the coastal line, the use of Posidonia oceanica in composites may contribute to reducing the environmental footprint of these materials, aligning with circular economy principles. This review highlights the dual benefits of utilizing marine biomass by advancing material sustainability while not being detrimental to coastal waste management. [ABSTRACT FROM AUTHOR]

Highlights This study presents a novel equation that obtains the intrinsic flexural modulus of a natural fiber from its microfibril angle (MFA) and its crystalline cellulose content, once having estimated both parameters from X‐ray diffraction (XRD). The percentage of crystalline cellulose was estimated as the content of cellulose times the crystallinity index. Moreover, the MFA of abaca strands was obtained through an equation relating MFA with the strain at break of the strands and by XRD azimuthal integration, obtaining similar results. Fully bio‐based composites, consisting of biopolyethylene reinforced with of abaca strands at 20 to 50 wt% contents, were tested to assess the impact of the natural fibers on the flexural modulus of the composites. The intrinsic flexural modulus was also evaluated by using three micromechanics models (Hirsh equation, Halpin and Tsai equation, and its modification by Nielsen). The values obtained from the application of the new equation, the micromechanics methods, and the literature showed satisfactory agreement. Evaluation of the flexural modulus of abaca strand reinforced bio‐polyethylene composites. Use of micromechanics models to obtain the intrinsic modulus of abaca strands. Formula that correlates the intrinsic flexural modulus of abaca to its crystalline cellulose content and microfibril angle. [ABSTRACT FROM AUTHOR]

In this study, olive pit agro-waste from the olive oil industry is valorized by incorporating it as an additive in a polyethylene terephthalate glycol (PETG) matrix to develop bio-based composite materials for large format additive manufacturing (LFAM). The olive pits were first ground into olive pit powder (OPP) and then functionalized by polymerizing poly(butylene adipate-co-terephthalate) PBAT on their surface, resulting in a hydrophobic, modified olive pit powder (MOPP) with enhanced compatibility with the PETG matrix. OPP and MOPP composites were compounded and 3D-printed via Fused Granular Fabrication (FGF) using 5, 10, and 15 wt.% concentrations. The PBAT coating increased the degradation temperature and specific heat capacity of the material, contributing to a lower melt viscosity during printing, as confirmed by MFR, MDSC, and TGA analyses. Tensile testing revealed that MOPP composites generally exhibited superior mechanical properties compared to OPP composites, likely due to the improved compatibility between PBAT on the MOPP surface and the PETG matrix. SEM analysis further validated these findings, showing a highly irregular and porous fracture surface in OPP composites, while MOPP composites displayed a smooth surface with well-integrated MOPP in the PETG matrix. [ABSTRACT FROM AUTHOR]

Applying coatings of paraffins and other synthetic waxes is a common approach to impart hydrophobic properties to fibres and thus control their surface characteristics. Replacing these fossil-based products with alternatives derived from renewable resources can contribute to humankind's transition to a sustainable bioeconomy. This study presents the coating of hemp fibres with waxes extracted from pine bark as an exemplar application. Two bio-based emulsifiers were used to prepare wax emulsions suitable for a dry blending process. The coatings on the fibres were characterised, quantified, and visualised using a combination of spectroscopic and microscopic techniques. Confocal fluorescence microscopy was an excellent tool to investigate the spatial distribution of the pine bark waxes on the fibre surfaces. While successful deposition was demonstrated for all tested formulations, coating homogeneity varied for different emulsifiers. Compounding the hemp fibres with a bio-based polyester resulted in the substantial improvement of the mechanical behaviour. However, the presence of a wax coating on the fibres did not lead to a significant change in mechanical properties compared to the controls with uncoated fibres. Optimising the composite chemistry or adjusting the processing conditions might improve the compatibility of the hemp fibres with the matrix material, resulting in enhanced mechanical performance. [ABSTRACT FROM AUTHOR]

Combining cellulose‐based components with functional materials is highly interesting in various research fields due to the improved strength and stiffness of the materials combined with their low weight. Herein, the mechanical properties of opal films are improved by incorporating cellulose fibers and microcrystalline cellulose. This is evidenced by the increase in tensile strength of 162.8% after adding 10 wt% of microcrystalline cellulose. For this purpose, core–shell particles with a rigid, crosslinked polystyrene core and a soft shell of poly(ethyl acrylate) and poly(ethyl acrylate‐co‐hydroxyethyl methacrylate) are synthesized via starved‐feed emulsion polymerization. The synthesized particles' well‐defined shape, morphology, and thermal properties are analyzed using transmission electron microscopy, scanning electron microscopy, and differential scanning calorimetry measurements. Free‐standing mechanochromic opal films with incorporated cellulose and structural colors are obtained after processing the core–shell particles with cellulose via extrusion and the melt‐shear organization technique. The homogeneous distribution of the cellulose within the composite material is investigated using fluorescent‐labeled cellulose. The opal film's angle‐dependent structural color is demonstrated using reflection spectroscopy. [ABSTRACT FROM AUTHOR]

Improving the sustainability and processability of shape memory composites is key to expanding their applications. This work introduces a novel bio-based shape memory composite resin with renewable cellulose nanocrystals, suitable for stereolithography (SLA) printing. We prepared epoxy soybean oil-based composites by incorporating Itaconic acid monomethyl ester (IAME) modified cellulose nanocrystals (CNCs-IAME) into IAME modified epoxy soybean oil (IESO). The CNCs-IAME/IESO composite resin, with a viscosity of 1.01–1.22 Pa•s, is ideal for SLA printing. Adding 0.75 wt% CNCs-IAME particles enhances mechanical properties, yielding a tensile strength of 19.54 MPa and elongation at a break of 34.03%. Demonstrated applications include flexible supports and temperature-responsive sensors. This innovative composite offers excellent sustainability and SLA-printability, showing great potential for new bio-based heat-activated shape memory materials.

This research paper focuses on the developments in 3D-printed composite material and its participation in the field of additive manufacturing of high-performance, custom-designed structures. Continuous fiber reinforced composites are widely used and possess desirable properties of light weight, high strength and high design freedom applicable in aerospace, automotive, healthcare and marine sectors. The paper brings into focus the many significant developments in methods of 3D printing and the use of continuous fiber-reinforced materials, topology optimization and multi-physics software for design and manufacturing. Using the results of simulation of manufacturing parameters including layer thickness, fiber orientation, and infill density, this paper reveals that small variations of parameters are critical for high mechanical property values. Also, the prospects of using composites based on 3D printing for various branches of industry are described; the popularity and need for such material increase. The research also discusses future prospects to the field including bio-based composites and application of smart materials and properties such as self-healing and real time monitoring innovations that would improve on the sustainability and efficiency of 3D printed composites. [ABSTRACT FROM AUTHOR]

This article presents the results of experimental measurements of the physical properties of new environmentally friendly bio-based composite building materials containing hemp shives bonded with a magnesium binder. Some of the tested materials contained an admixture of phase change material (PCM) of variable proportions in the binder to increase the heat capacity of building elements (walls), which can positively affect room temperature regulation. Densities and porosities are key parameters describing building materials, directly affecting mechanical, acoustic, and, most importantly, hygrothermal properties, including thermal conductivity, water vapor permeability, water absorptivity, and sorption curves. The experiment was carried out for ten different samples of bio-based building composites, differing in the bulk density obtained during the manufacturing process and in the PCM proportion. As part of the experiment, true density tests were conducted on a helium pycnometer. Then, the geometric densities of the tested materials (which may differ from the bulk density obtained during production) were measured using the Archimedes method, making it possible to obtain the total, closed, and open porosity values. Tests were also carried out for selected traditional building materials, such as red brick and autoclaved aerated concrete, to compare the results obtained. [ABSTRACT FROM AUTHOR]

Sustainability and the need for biodegradable composites are the two new buzzwords finding prominence in recent times. In this regard, there has been a significant increase in interest regarding natural fiber composites (NFCs) due to their potential to address environmental issues and contribution toward the development of sustainable materials. The aim of this extensive review is to thoroughly investigate the current research landscape, advancements, and applications of NFCs. The study covers a range of topics, including the various types of natural fibers commonly used, their processing techniques, reinforcement strategies, mechanical properties, morphological characteristics, biodegradability, and sustainability. It also explores their potential uses across different industries. Furthermore, this article examines the challenges and opportunities associated with NFCs, as well as their environmental impacts and economic viability. By conducting a detailed analysis of existing literature, this review aims to shed light on the advancements achieved so far and the future potential of NFCs as eco-friendly alternatives to conventional materials. Ultimately, it offers insights into how these materials can enhance sustainability in material engineering.

Combining cellulose‐based components with functional materials is highly interesting in various research fields due to the improved strength and stiffness of the materials combined with their low weight. Herein, the mechanical properties of opal films are improved by incorporating cellulose fibers and microcrystalline cellulose. This is evidenced by the increase in tensile strength of 162.8% after adding 10 wt% of microcrystalline cellulose. For this purpose, core–shell particles with a rigid, crosslinked polystyrene core and a soft shell of poly(ethyl acrylate) and poly(ethyl acrylate‐co‐hydroxyethyl methacrylate) are synthesized via starved‐feed emulsion polymerization. The synthesized particles’ well‐defined shape, morphology, and thermal properties are analyzed using transmission electron microscopy, scanning electron microscopy, and differential scanning calorimetry measurements. Free‐standing mechanochromic opal films with incorporated cellulose and structural colors are obtained after processing the core–shell particles with cellulose via extrusion and the melt‐shear organization technique. The homogeneous distribution of the cellulose within the composite material is investigated using fluorescent‐labeled cellulose. The opal film's angle‐dependent structural color is demonstrated using reflection spectroscopy.

The growing demand for sustainable materials has driven the exploration of natural fibers as eco-friendly alternatives to synthetic reinforcements for composites. This study investigates the potential of Posidonia oceanica, an abundant marine biomass, which is often driven to be stacked on the backshore and used so far for energy recovery and low-value applications, as a filler and possible reinforcement in cementitious and polymer composites. Most applications of Posidonia are concentrated in the Mediterranean area and focused on the construction industry. However, its introduction in polymer composites, especially as a source of cellulose or in combination with the use of bio-based matrices, can also be proposed. With this aim, the physical and chemical properties of Posidonia oceanica fibers need to be characterized, and their compatibility with various matrices needs to be evaluated. Experimental results demonstrate that Posidonia oceanica fibers, especially when treated with alkali and silane, or combining both treatments, can exhibit mechanical properties quite comparable to other natural fibers, namely to those obtained from grass species. As with any other type of waste, yet with more interest for its wide accumulation over the coastal line, the use of Posidonia oceanica in composites may contribute to reducing the environmental footprint of these materials, aligning with circular economy principles. This review highlights the dual benefits of utilizing marine biomass by advancing material sustainability while not being detrimental to coastal waste management.

This paper deals with the study of the evolution of the durability of short hemp fibres reinforced composites subjected to long-term ageing. The compounds were stored for ten years in atmospheric conditions (natural ageing) prior to the study. Therefore, two kinds of specimen are studied. First, the aged compounds were used to moulded tensile specimens. The residual mechanical behaviour of natural aged hemp/PP composites (natural aged specimens) were compared to properties obtained 10 years ago. This storage showed that the hemp is more sensitive to time degradation than PP and was confirmed by the initial degradation of compounds pointed out by ATG. Then, injected natural aged polypropylene reinforced with several hemp fibre weight fractions compounds were subjected to two different protocols in order to characterize their durability (aged specimens). The specimens were subjected to water immersion at ambient temperature and storage in a climatic chamber maintained at 40 °C with a relative humidity of 98%. The fracture surfaces were observed with SEM to identify the physical phenomena leading to the observed loss of mechanical properties. A weight water sorption of 14% with respect to hemp weight fraction was, for the first time, determined as a critical water sorption for which the reinforcement effect becomes negligible. The physical phenomenon responsible for this critical absorption was finally investigated with Infrared Spectroscopy, showing the occurring of a dissolution of the fibres.

Applying coatings of paraffins and other synthetic waxes is a common approach to impart hydrophobic properties to fibres and thus control their surface characteristics. Replacing these fossil-based products with alternatives derived from renewable resources can contribute to humankind’s transition to a sustainable bioeconomy. This study presents the coating of hemp fibres with waxes extracted from pine bark as an exemplar application. Two bio-based emulsifiers were used to prepare wax emulsions suitable for a dry blending process. The coatings on the fibres were characterised, quantified, and visualised using a combination of spectroscopic and microscopic techniques. Confocal fluorescence microscopy was an excellent tool to investigate the spatial distribution of the pine bark waxes on the fibre surfaces. While successful deposition was demonstrated for all tested formulations, coating homogeneity varied for different emulsifiers. Compounding the hemp fibres with a bio-based polyester resulted in the substantial improvement of the mechanical behaviour. However, the presence of a wax coating on the fibres did not lead to a significant change in mechanical properties compared to the controls with uncoated fibres. Optimising the composite chemistry or adjusting the processing conditions might improve the compatibility of the hemp fibres with the matrix material, resulting in enhanced mechanical performance.

The present research is aimed at examining the changes in tensile and compressive properties of natural fiber-reinforced composites (NFRC) exposed to various humidity conditions; this is due to the fact that moisture content (MC) in fibers is generally assumed to be detrimental to composite performance. It was found that once moisture is exposed, compressive strength and strain of specimens would be higher than those of tensile, whereas modulus of elasticity would be lower. Due to increasing moisture content, although elongation in all tests was enhanced, tensile and compressive strength declined by 15% and modulus of elasticity decreased by 20%. In addition, Poisson's ratio for both compressive and tensile properties was nearly identical (0.33) in distinct moisture content. A new understanding of moisture's effects on mechanical behavior is presented in this study by finding an optimum point for exposing moisture to increase compressive and tensile strength. [ABSTRACT FROM AUTHOR]

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Bio-based resins, obtained from renewable raw materials, are a more sustainable alternative to oil-based resins for fiber-reinforced polymer (FRP) composites. The incorporation of lignin in those resins has the potential to enhance their performance. This paper presents results of an experimental study about the effects of Lignoboost lignin incorporation on a partially bio-based vinyl ester (VE) resin. Two resins were prepared—without (reference) and with lignin addition (4% by weight) to its main chain—and their chemical, thermophysical, and mechanical properties were compared using Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and tensile and shear tests. Results suggest that the addition of lignin to the base resin resulted in a copolymer of increased heterogeneity and higher molecular weight, incorporating stiff and complex aromatic structures in the polymer chain. While requiring high-temperature curing, the VE–lignin copolymer presented improvements of 27% in tensile strength, 4% in shear strength, and increased glass transition temperature by about 8 °C, thus confirming the potential of this natural biopolymer for FRP composite applications. [ABSTRACT FROM AUTHOR]

Sub‐micro organosolv lignin (OBs) isolated from beechwood biomass, comprising of sub‐micro sized particles (570 nm) with low molecular weight and dispersity and relatively high total phenolic −OH content, is utilized for the production of bio‐based epoxy polymer composites. OBs lignin is incorporated into the glassy epoxy system based on diglycidyl ether of bisphenol A (DGEBA) and aliphatic polyoxypropylene α,ω‐diamine (Jeffamine D‐230), being utilized both as a curing agent, partially replacing D‐230, and as an additive, substituting part of both petroleum‐derived components. Up to 12 wt % replacement of D‐230 by OBs lignin is achieved, whereas approximately 17 wt % of OBs effectively replaces the conventional epoxy polymer. The incorporation of OBs lignin in the polymeric matrix is achieved without the use of any solvent or previous functionalization. Enhanced properties are obtained, with substantial increases in tensile strength, strain, stiffness, glass transition temperature, antioxidant activity, and resistance to solvents. [ABSTRACT FROM AUTHOR]

In this work, renewable composites were prepared by the association of a thermosetting resin synthesized via free-radical polymerization, using a mixture of tung oil, n-butyl methacrylate, and divinylbenzene, with silica-rich fillers, namely an algae biomass with high silica content, and a well-sorted sand. Furthermore, to investigate if the interaction between the non-polar resin and polar reinforcements could be improved, enhancing the materials' mechanical properties, itaconic anhydride, a bio-derived molecule obtained from itaconic acid, was introduced to the resin composition. Thermogravimetric analysis (TGA) suggested that the thermal stability of the composites was overall not changed with the addition of itaconic anhydride. The mechanical properties of the sand composites, however, did improve, as the storage modulus at room temperature, measured by dynamic mechanical analysis (DMA), almost doubled in the presence of itaconic anhydride. The glass transition temperatures of the materials increased by approximately 30 °C when sand was used as a reinforcement. Water absorption experiments validated an increase in the polarity of the unreinforced resin by the addition of itaconic anhydride to its formulation. The composites, however, did not exhibit a significant difference in polarity in the presence of itaconic anhydride. Finally, scanning electron microscopy (SEM), equipped with energy dispersive spectroscopy (EDS), demonstrated better matrix–filler adhesion in the presence of itaconic anhydride for high-silica algae composites. [ABSTRACT FROM AUTHOR]

Natural fiber-reinforced composites (NFRCs) are expected to find growing applications in near future, especially in Europe where stringent environmental codes are being legislated and public pressure for their enforcement is increasing. Study has shown that NFRCs are also gaining recognition among civil engineers as a viable alternative to traditional materials for use as concrete reinforcement in load-bearing structural members as in building frames and bridge decks. The present review strives to provide a brief overview of NFRCs, state-of-the-art developments in their manufacture, and examples of their structural applications. Another aspect of the review involves investigation of the challenges facing the use of fiber composite materials in civil engineering. These include the high manufacturing costs, difficulties associated with appraisal of its potential benefits, uncertainties about their properties, lack of understanding among civil engineers of the material and its service life, and the relatively small battery of standards developed for the composite industry. Finally, the study will conclude with the prospects of bio-composite applications and the emerging trends in novel bio-composites for future structural applications. [ABSTRACT FROM AUTHOR]

Research in bio-based composites is rapidly rising in terms of fundamental experiments and industry applications. Natural fibres are one of the common bio-based materials used in composites. Natural fibres have many advantages, including low cost, biodegradable, good thermal conductivity, and may also be used as an alternative to synthetic polymer composites. However, the hydrophilic characteristic of natural fibres can lead to poor interfacial adhesion between natural fibres reinforced and matrix phases, which can affect the properties of bio-based composites. To overcome this problem, the surface modification of natural fibres is required to improve the hydrophobic properties of the composite. A few studies revealed that silane improved the hydrophobicity, tensile strength and thermal stability of bio-based composites. The highest water contact angle of the treated bio-based composite was reported at 135°. Meanwhile, the tensile strength of silane-treated bio-based composite can increase up to 40%. The onset decomposition temperature of silanes treated with bio-based composite is 20 ° C higher compared to untreated bio-based composite. This article provides an insightful review of the surface treatment of bio-based composites via silane treatment on mechanical properties, thermal properties, water absorption, and water contact angle. [ABSTRACT FROM AUTHOR]

• Provide insight into the durability and suitability of mycelium and grass bio-based composites as green and sustainable insulation materials. • Eco-friendly and cost-effective AKD as a hydrophobic modification to effectively reduce hygric properties and improve thermal insulation capacity. • Both mycelium and grass bio-based composites with AKD modification significantly improved their resistance ability to mould growth. • Preferentially recommended using AKD-modified grass in distinct climates when applied as insulation components in assembly walls. • Providing the feasible guidance of accelerating bio-based composite practical application on insulation materials of sustainable building construction. Bio-based composites are increasingly used as thermal insulation materials in construction due to sustainability and low thermal conductivity. However, their high moisture absorption can negatively affect performance and mould growth risk, shortening product lifespan. This study introduces alkyl ketene dimer (AKD) as an eco-friendly and economical solution for the hydrophobic treatment of two bio-based composites, mycelium and grass, to enhance their durability. We compare the physicochemical properties, hygrothermal performance, and mould growth resistance of bio-based composites before and after hydrophobic modification while evaluating their durability in simulated building envelopes across different climates. Results showed that the modified bio-based composites were well-grafted with AKD. The water absorption of bio-based composites significantly decreased after modification, and the mould growth resistance capacity of modified composites was significantly improved. Moreover, hygrothermal simulations reveal that AKD modification effectively enhances their suitability under different climate profiles, particularly when modified grass composites are applied. [Display omitted] [ABSTRACT FROM AUTHOR]

Bio-based composites were developed from the epoxy derivatives of Lallemantia iberica oil and kraft lignin (ELALO and EpLnK), using UV radiation as a low energy consumption tool for the oxiranes reaction. To avoid the filler sedimentation or its inhomogeneous distribution in the oil matrix, different structure-directing agents (SDA) were employed: 1,3:2,4-dibenzylidene-D-sorbitol (DBS), 12-hydroxystearic acid (HSA) and sorbitan monostearate (Span 60). The SDA and EpLnK effect upon the ELALO-based formulations, their curing reaction and the performance of the resulting materials were investigated. Fourier-transform Infrared Spectrometry (FTIR) indicates different modes of molecular arrangement through H bonds for the initial ELALO-SDA or ELALO-SDA-EpLnK systems, also confirming the epoxy group's reaction through the cationic mechanism for the final composites. Gel fraction measurements validate the significant conversion of the epoxides for those materials containing SDAs or 1% EpLnK; an increased EpLnK amount (5%), with or without SDA addition, conduced to an inefficient polymerization process, with the UV radiation being partially absorbed by the filler. Thermo-gravimetric and dynamic-mechanical analyses (TGA and DMA) revealed good properties for the ELALO-based materials. By loading 1% EpLnK, the thermal stability was improved to with 10 °C (for Td3%) and the addition of each SDA differently influenced the Tg values but also gave differences in the glassy and rubbery states when the storage moduli were interrogated, depending on their chemical structures. Water affinity and morphological studies were also carried out. [ABSTRACT FROM AUTHOR]

This work concerns the waste management method of algae biomass wastes (ABW). For this purpose, we prepared bio-based thermoplastic polyurethane elastomer (bio-TPU) composites. Algae biomass wastes are derived from algal oil extraction of Chlorella vulgaris and from biomass of Enteromorpha and Zostera marina. ABWs were used in the bio-TPUs composites as a filler in the quantity of 1, 5, 10, and 15 wt.%. The bio-based composites were prepared via the in situ method. Polymer matrix was synthesized from a bio-based polyester polyol, diisocyanate mixture (composed of partially bio-based and synthetic diisocyanates), and bio-based 1,3 propanediol. In this study, the chemical structure, morphology, thermal and mechanical properties of prepared composites were investigated. Based on the conducted research, it was determined that the type and the content of algae waste influence the properties of the bio-based polyurethane matrix. In general, the addition of algae biomass wastes led to obtain materials characterized by good mechanical properties and noticeable positive ecological impact by increasing the total amount of green components in prepared bio-TPU-based composites from 68.7% to 73.54%. [ABSTRACT FROM AUTHOR]

Epoxy-based composites are designed for long-lasting applications, though their wide use is in contrast with their poor recyclability, which poses serious end-of-life issues. In order to reduce their environmental impact, precursors derived from fossil fuel based raw materials should be replaced with eco-friendly sources. This can be attained by using naturally derived epoxy matrices, or by finding a suitable solution for recycling at the end of life. In this paper, both strategies were analyzed, by replacing traditional monomers with epoxidized waste flour (EWF), an innovative bio-precursor derived from the organic waste stream, and a cleavable hardener, which allowed the recyclability of the matrix. The recyclable matrix was reinforced with recycled carbon fibers, derived from pyrolysis. DSC measurements were carried out in order to optimize the curing steps of the matrix, then flexural tests were performed in order to evaluate the mechanical response of the composite. A green recycling procedure was then investigated, which involved the use of non-toxic solvents and mild working conditions, and allowed recovery of the matrix while still preserving the properties of the carbon fibers. The components obtained after recycling were analyzed by FTIR analysis, which revealed the presence of the epoxy ring on the recycled waste flour. Hence, recycled waste flour was again used as a precursor and mixed with the cleavable hardener, thus, obtaining a closed-loop recycling. [ABSTRACT FROM AUTHOR]

Bio-based resins, obtained from renewable raw materials, are a more sustainable alternative to oil-based resins for fiber-reinforced polymer (FRP) composites. The incorporation of lignin in those resins has the potential to enhance their performance. This paper presents results of an experimental study about the effects of Lignoboost lignin incorporation on a partially bio-based vinyl ester (VE) resin. Two resins were prepared—without (reference) and with lignin addition (4% by weight) to its main chain—and their chemical, thermophysical, and mechanical properties were compared using Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and tensile and shear tests. Results suggest that the addition of lignin to the base resin resulted in a copolymer of increased heterogeneity and higher molecular weight, incorporating stiff and complex aromatic structures in the polymer chain. While requiring high-temperature curing, the VE–lignin copolymer presented improvements of 27% in tensile strength, 4% in shear strength, and increased glass transition temperature by about 8 °C, thus confirming the potential of this natural biopolymer for FRP composite applications.

Composites made of poly(l‐lactic acid) (PLLA) and β‐cyclodextrin/D‐limonene inclusion complex (CD‐Lim) are prepared to develop novel food packaging material with antibacterial properties. The composites are formulated with bio‐based materials that are also biodegradable. The addition of CD‐Lim to PLLA results in enhanced permeability and water uptake. Optical properties of PLLA/CD‐Lim composites also significantly vary compared to plain PLLA, with partial loss of transparency and gloss, but sizably increased barrier to UV light, which imparts protection from oxidation to lipid‐containing food. The mechanical properties of the composite films are also affected by composition. Most notably, PLLA films containing CD‐Lim display significant antibacterial and antifungal properties, proving their potential as active food packaging films. [ABSTRACT FROM AUTHOR]

The key to achieving high-performance plant fiber/polylactic acid (PLA) composites lies in solving the interfacial compatibility issue between the two components. However, current mainstream methods for interfacial modulation often come with energy consumption and environmental concerns. To address this, our study proposed the development of fully bio-based bamboo fiber (BF)/PLA composites based on the principles of non-toxicity, low carbon footprint, and environmental friendliness. In this study, we aimed to construct a molecular-scale multiphase crosslinking network structure in BF/PLA composites. To achieve this, we utilized cyclodextrins (CD) to induce a regularized alignment of PLA molecular chains and employed epoxidized soybean oil (ESO) ring opening reaction to form bonds connecting BF, CD, and PLA molecules. This approach ensured that the composite is fully bio-based while still exhibiting remarkable mechanical properties. The resulting BF/PLA@CD-ESO composites demonstrated impressive bending strength, reaching 108.65 MPa, which was 23.11 % higher than that of the BF/PLA composites. Moreover, the tensile strength reached 67.48 MPa, which was 39.06 % higher than that of BF/PLA composites. This study provides a convenient, green and sustainable method for preparing PLA-based composites. The resulting composites are expected to be used in disposable tableware, food packaging and environmentally friendly furniture. [Display omitted] • Raw materials are all bio-based, composites are green and environmentally friendly. • Molecular-scale interfacial engineering of multiphase crosslinking structure was constructed. • The composites have excellent mechanical properties and are at the leading edge of the study field. [ABSTRACT FROM AUTHOR]

Injection molded cellulose bio-based composites have been effectively manufactured using cellulose acetate (CA), environmentally friendly triethyl citrate (TEC) plasticizer, and cellulosic fibers. This study investigated the surface chemistry, the thermal stability, and the dielectric properties of CA biopolymer and its bio-based composites. DSC result of plasticized cellulose acetate (PCA) showed that the glass transition temperature decreased from 191°C to 101°C and the melting temperature from 224°C to about 140°C after plasticization, which improves the processing of the biopolymer Fourier Transform Infrared (FTIR) spectroscopy was used to determine the chemical properties of the raw materials and the bio-based composites. The results showed a good plasticization effect of TEC plasticizer by the presence of ester bonds at 1734 cm−1 in PCA spectra. Chemical interactions between hydroxyl groups of the different components were also observed in the 3200–3600 cm−1 region. Dielectric analysis at different frequencies of cellulose bio-based composites showed enhanced dielectric properties compared to pure PCA polymer. Composites with 50 wt% cellulose fibers had values of ε' and tan δ of about 4 and 0.13 at 1 MHz, respectively. These properties decreased as the frequency increased from 1 MHz to 3 GHz, reaching values of 2.8 and 0.04, respectively. The increase in temperature from the frozen state induced an increase in the dielectric properties and showed a relaxation process that shifted to higher temperatures at higher frequencies. [Display omitted] • Cellulose acetate was plasticized using triethyl citrate. • Cellulose enhanced the thermal and dielectric properties of biobased composites. • Dielectric properties increased with cellulose fiber content and temperature. • The dielectric constant has a linear relationship with cellulose content. • Cellulose composites can be used as high-temperature dielectric materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biodegradable PBAT-based composites were prepared by adding different biofillers coming from agro-food wastes. • 3D printed objects were successfully realized by selective laser sintering. • The specimens show increasing complexity structures and good level of dimensional definition. • The effect of the addition of the biofillers within the polymeric matrix was widely investigated. Nowadays, biodegradable polymeric materials can play a key role in many fields, including food packaging and biomedical. In the present work, composite powders based on PBAT matrix were prepared by mixing spherical particles obtained by emulsion solvent process with two different biofillers coming from food agro-wastes: a corn by-product and a filler derived from wine production. Sustainable PBAT-based composites were then successfully realized for the first time by means of selective laser sintering (SLS). This paper combines the use of natural fillers within a biodegradable matrix and 3D printing process. Fillers and composite powders were completely characterized as well as the PBAT-based composites obtained by SLS. The effect of biofillers within the PBAT matrix was investigated, by means of TGA, DSC, SEM, and DMA analyses. The bio-based composites obtained by SLS showed increased complex structures. Regarding the processability the printed samples are characterized by a good level of dimensional accuracy and porosity. Thus, biomedical field could benefit from the use of these kinds of fully biodegradable PBAT-based composites. [ABSTRACT FROM AUTHOR]

Crystalline bio-based composites exhibit discontinuous feeding and warpage of printed parts in traditional filament printing. Therefore, an additive manufacturing (AM) system based on micro-screw extrusion was designed, and wood flour/polyhydroxyalkanoates (WF/PHA) composites without additives were manufactured. The differential scanning calorimetry test showed that the crystallization temperature and melting temperature of the WF/PHA composites increased by 35.7 °C and 46.1 °C, respectively. The evaluation of the extrusion stability of the micro-screw extrusion system showed that the micro-screw speed had a greater influence on extrusion output than the printing temperature. The forming process under pressure and the WF/PHA blend prevented the warpage of printed samples. The tensile and flexural strengths of the WF/PHA composites reached 38.7 MPa and 77.3 MPa, respectively, and the modulus of the WF/PHA composites significantly improved with the increase in WF content. The rheological, thermal, and mechanical properties of the printed samples were used to determine the reason for the decrease in warpage. Finally, the test printing of thin and large-area sheets provides the conditions for the application of AM in fully bio-based composites.

In the present work, an attempt has been made to develop cow manure carbon-reinforced hybrid biophenol-based benzoxazine composites for antifouling coating applications. Bio-based benzoxazine with unsymmetrical molecular structure was synthesized using the mixture of a combination of cardanol and eugenol with diaminodiphenyl methane and paraformaldehyde, and the hybrid-benzoxazine obtained was characterized using different analytical techniques, viz., Fourier transform infrared, nuclear magnetic resonance and MALDI mass. Bio-based benzoxazine was further reinforced with varying weight percentages (1, 3 and 5 wt%) of biocarbon derived from cow manure to obtain hybrid composite coatings. The hybrid benzoxazine matrix and composites were studied for their thermal behaviour, contact angle (CA), morphology, corrosion-resistant behaviour and antifouling character to utilize them as coatings materials for different industrial applications. Results obtained from different studies inferred that the biocarbon-reinforced composites possess an enhanced value of glass transition temperature (249°C), high char yield (38.4%), improved CA (105.6°), higher efficiency of corrosion protection against mild steel surface (98%) and improved antimicrobial activity. [ABSTRACT FROM AUTHOR]

In this work TiO2 and highly inorganic ceramic clay were successfully immobilized into Bacterial Cellulose (BC), produced by Komagataeibacter xylinus K2G30 (UMCC 2756) strain, in different proportions. The morphology, structure, and mechanical properties of the composites, fabricated by wet mechanical mixing, were investigated through a multi-technique approach: density measurement, optical and electronic microscopy, FTIR spectroscopy, contact angle measurement and mechanical tensile testing, before and after aging, under UV light exposure. Results suggest completely different behavior by using TiO2 or Clay. In fact, porous fragile structures were obtained by employing Clay, whereas more compact and plastic-like specimen by using TiO2, due to different chemical bonding developed through H-bonding, as confirmed by FTIR. Enhanced tensile resistance at break was found for a content of TiO2 equal to 20 wt% and this result was not affected by aging, under UV light exposure. This study demonstrates how ceramic inorganic fillers for BC are able to act in completely different way, becoming of interests in different fields such as hydrophilic porous membranes for Clay and compact plastic-like film for textile industry with TiO2 addition. [ABSTRACT FROM AUTHOR]

Based on the knowledge that plant structures often have graded stiffness transitions between strengthening elements and the surrounding matrix, which result in good damping behaviour and high toughness of the plant structure, the fatigue behaviour of composites made from rayon fibre and polypropylene (PP) as a matrix could be enhanced by photochemical surface modification of the regenerated cellulose fibres. The surface modification was achieved by deposition of UV-polymerized organic thin layers using pentaerythritol triacrylate (PETA) as the monomer. It has been shown earlier that the photochemical modification yields a decrease in wettability of the highly hydrophilic and water adsorbing viscose fibres and an increase in their affinity towards non-polar substances, thus promoting fibre-matrix adhesion. The presented experiments proved that the distinguished mechanical properties of the deposited layer structure also mimic the graded transition and provide good damping and fatigue behaviour superior to either untreated rayon/PP or rayon/maleic anhydride-modified PP composites. [ABSTRACT FROM AUTHOR]

Purpose: While bio-based composites (bio-based plastics reinforced with natural fibers) have been discussed as potential sustainable alternatives to petroleum-based plastic composites, there are few quantitative environmental impact assessments of these materials. This work presents comparisons of petroleum-based and bio-based plastics as well as their composites to (1) assess environmental impacts from plastics and composite production and (2) determine which environmental impacts can be mitigated through production of bio-based composites, based on current manufacturing methods. Methods: Environmental impact assessments were performed to determine the burdens associated with cradle-to-gate production of bio-based and petroleum-based plastics and their composites with wood flour (i.e., sawdust) filler. The scope of this work incorporated emissions from thermoplastic and wood flour production as well as pelletization, molding, and transportation processes. Environmental impacts were assessed for several impact categories using the US Environmental Protection Agency's TRACI method. Using impacts quantified, as well as material property data from 36 sources in the literature, comparisons were drawn between composite types. Multiple functional units were used including a constant mass of material produced and two comparison methods normalizing environmental impacts by material properties. Uncertainty assessments were performed to determine environmental impact distributions for each plastic and wood fiber composite type. Results and discussion: The production of bio-based plastics and their composites led to lower environmental impacts than petroleum-based plastics and composites in several impact categories: global warming potential, fossil fuel depletion, and certain human health impacts. However, the production of bio-based plastics and their composites also resulted in some higher environmental impacts, such as eutrophication. Bio-based composites are capable of possessing similar or improved mechanical properties to their petroleum-based counterparts. As such, normalized environmental impacts to material properties indicated that bio-based composites could lead to desirable combined mechanical and environmental attributes for certain applications. Considering the differences between environmental impact categories and uncertainties in environmental impact assessments, selection of constituents cannot be based solely on material feedstock to mitigate environmental impacts in wood fiber composites. Conclusions: Findings indicate that both environmental impact assessments and mechanical properties should be considered concurrently to effectively distinguish the benefits of selecting petroleum-based or bio-based plastics. This work shows that depending on the intended application, the selection of a bio-based feedstock could either be beneficial for mitigating certain environmental impacts, have little effect on impacts, or increase environmental impacts. These findings reveal the importance of considering property alteration and multiple effects of utilizing these resources. [ABSTRACT FROM AUTHOR]

Unidirectional bamboo reinforced cardanol-based epoxy composites were prepared by a close mould method. Two morphologies of reinforcements were used in this research: bamboo fibres and bamboo strips. The present article investigates the influence of bamboo reinforcements on the thermal and mechanical properties of the bio based matrix. Differential Scanning Calorimetry analyses showed that the introduction of bamboo does not modify the physical properties of the matrix. DMA analyses in shear mode showed an improvement of the shear conservative modulus that reaches 1.7 ± 0.1 GPa. This value that is independent from the morphology of reinforcements, indicates the existence of physical interactions. The continuity of matter between bamboo strips or bamboo fibres and the matrix observed by SEM confirms this result. Nevertheless, in tensile mode, the improvement of the tensile conservative modulus is specific to the used morphology. Indeed, for bamboo strips composites, it is 7.7 ± 0.8 GPa, while for bamboo fibres composites, it reaches 9.6 ± 0.8 GPa. This result is explained by the optimisation of stress transfer thanks to the specific morphology of bamboo fibres. A significant increase is also observed for the rubbery modulus due to entanglements specific of bamboo reinforcement.

The aim of this paper was to investigate the effects of wood flour on the mechanical, morphological and thermal properties of poly (L-lactic acid) (PLA)-chitosan biopolymer composites produced by compression molding. The composites were characterized by a combination of mechanical properties, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The addition of chitosan to PLA matrix reduced the tensile strength from 57.1 MPa for pure PLA to 34.3 MPa for 5% chitosan and 11.5 MPa for 10% chitosan, and the flexure strength from 72.3 MPa for pure PLLA to 30.4 MPa for 5% chitosan and 24.6 MPa for 10% chitosan. The change trend in the young’s modulus was found to be similar as compare with the tensile strength. However, the flexure modulus generally increased with the addition of the chitosan as comparison with pure PLA. The mechanical properties of the PLA-chitosan blends with wood flour were found to be lower than theirs of the pure PLA. According to SEM images, some holes and small voids at various diameters on the fractured section of the all composites were seen. Tonset, T10%, T50%, T85% of the pure PLA decreased with the addition of both chitosan and wood flour. Thermal stability of the PLA-chitosan blends was determined to be better than the PLA-chitosan composites with wood flour.

The aim of this paper was to investigate the effects of wood flour on the mechanical, morphological and thermal properties of poly (L-lactic acid) (PLA)-chitosan biopolymer composites produced by compression molding. The composites were characterized by a combination of mechanical properties, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The addition of chitosan to PLA matrix reduced the tensile strength from 57,1 MPa for pure PLA to 34,3 MPa for 5% chitosan and 11,5 MPa for 10% chitosan, and the flexure strength from 72,3 MPa for pure PLLA to 30,4 MPa for 5% chitosan and 24,6 MPa for 10% chitosan. The change trend in the young's modulus was found to be similar as compare with the tensile strength. However, the flexure modulus generally increased with the addition of the chitosan as comparison with pure PLA. The mechanical properties of the PLA-chitosan blends with wood flour were found to be lower than theirs of the pure PLA. According to SEM images, some holes and small voids at various diameters on the fractured section of the all composites were seen. Tonset, T10%, T50%, T85% of the pure PLA decreased with the addition of both chitosan and wood flour. Thermal stability of the PLA-chitosan blends was determined to be better than the PLA-chitosan composites with wood flour. [ABSTRACT FROM AUTHOR]

This paper deals with the design, production and monitoring of a bio-composite footbridge with a span of 14 m across the river Dommel in the city of Eindhoven, the Netherlands. The specific bio-composite material that was used for this research is a Natural Fibre Reinforced Bio-Polymer (NFRBP). The goal of the research is to prove that NFRBP can be applied as a load-bearing structure in an outdoor environment. For this purpose, a multidisciplinary team of academic researchers from two universities and from the Centre of Expertise Biobased Economy, together with a manufacturer from the NFRBP industry, have developed a feasible design that could be produced in a short period of time and within a limited budget. The footbridge was designed, built and installed within less than one year. In the two years after the installation of the footbridge, the structural behaviour of the bridge was monitored by means of optical fibre glass strands, integrated within the structure, with the purpose of measuring deformations and change in elasticity that occur over time. [ABSTRACT FROM AUTHOR]

• Development of novel hemp shiv based composites with low thermal conductivity of 0.05 W/mK. • Enhanced vapour permeability and excellent moisture buffering value up to 3.6 g/m2 RH. • Pre-treatment of hemp shiv leads to high water resistance reducing water absorption by 123%. • The composites have low density (175–240 kg/m3) and show good mechanical performance. This study focuses on the development of advanced water resistant bio-based composites with enhanced hygrothermal performance for building applications. The highly porous structure of hemp shiv is responsible for low thermal conductivity and allows the material to adapt to varying humidity conditions providing comfortable indoor environment. However, the pore network and the hydrophilic nature of hemp shiv affects the compatibility and durability of the material in presence of excess moisture conditions. In this work, novel hemp shiv composites were prepared in a starch based or silica based matrix and characterised for their hygroscopic, thermal and mechanical properties. The hemp shiv based composites were resistant to water yet permeable to vapour and showed excellent moisture buffering capacity when compared to conventional hemp-lime composites. The composites prepared were light weight with low thermal conductivity values of 0.051–0.058 W/mK and showed good mechanical performance. Hemp shiv composites with superior hygrothermal characteristics have immense potential as robust thermal insulation building materials. [ABSTRACT FROM AUTHOR]

Highlights • Bundles of henequen strands as reinforcement in PP biocomposites. • Weibull scale factor of henequen strands for micromechanical analysis. • Micromechanics for the interface analysis. • Coupling factors and fiber orientation factors above the theoretical limit. Abstract The contribution of a reinforcement to the tensile strength of a composite can be evaluated by different micromechanics models. Nonetheless, one of the main difficulties is the evaluation of the intrinsic properties of the reinforcements. The literature shows experimental and model-based methodologies to estimate such intrinsic properties, and few are based on single fiber tensile test in combination with a Weibull analysis. This paper proposes using henequen strand to prepare polypropylene-based composites. Henequen fibers show a high cellulose content that allows obtaining strong interfaces when a coupling agent is added to the composite formulation. The novelty of this work is based on a simplified methodology to evaluate the intrinsic tensile strength of the reinforcements and its contribution to the tensile strength of the composite. A percentage of coupling agent that returns the highest tensile strength is identified with a strong interface. Then, typical values for a coupling factor and interfacial shear strength are used with a modified rule of mixtures and a modified Kelly and Tyson models to obtain the orientation factors. The prediction of composite behavior from fiber properties is necessary to anticipate the correlation between experimental and the back-calculated parameters. [ABSTRACT FROM AUTHOR]

Wheat straw is an abundant and cheap agricultural by-product. This research aims to produce an outperform-oriented strand board utilizing wheat straw for sustainable construction. The produced rectangular specimens via the compression molding process were tested in terms of mechanical, hygroscopic, morphological, and sound isolation performances. The results compared to the commercial (OSB) EN 300: 2006 standard showed excellent mechanical properties in wheat straw-based panels with a density of 0.60 g.cm−3, with a remarkable 44.61% increase in flexural strength and 42.2% improvement in Young's modulus over wood-based OSB. Taking into consideration the hygroscopic properties, wheat straw-based boards showed superior swelling resistance, with WS-OSB-0.45 leading the way with a 23% reduction compared to commercial OSB. Water absorption was inversely related to density, with WS-OSB-0.60 reducing water absorption by 8.9% compared to commercial OSB. The contact angle measurements showed that wheat straw-based panels (WS-OSB-0.60 at 106° and WS-OSB-0.45 at 100.4°) had more hydrophobic surfaces than commercial OSB (88.1°). The wheat straw-based OSB panels, especially WS-OSB-0.45, achieved remarkable sound reduction, with an overall sound reduction value of 35.2 dB, outperforming WS-OSB-0.6 (34.9 dB) and commercial OSB (34 dB). These results demonstrate the viability of using wheat straw residues as an environmentally friendly alternative to wood in the production of panels for building, furniture manufacturing, and equipment packaging applications. • As an eco-friendly alternative to wood, wheat straw residues can be used to produce panels. • Producing lightweight panels at different densities using wheat straw residues and polyurethane. • Hygroscopic and sound insulation properties of the panels were compared with those of wood-based OSB. • Wheat straw-based OSB was tested in two perpendicular directions for mechanical properties. • Wheat straw fibers are a viable alternative to wood in producing OSB without compromising performance. [ABSTRACT FROM AUTHOR]