This study explores the incorporation of renewable resources from Arundo donax into a polylactic acid matrix to enhance mechanical properties and sustainability. This approach uses lignocellulosic fillers from this fast-growing plant species to cut plastic waste and support a circular economy. Two types of fillers, stem fibres and shredded plant particles, were added to the PLA matrix, focusing on how they affect water interactions and material properties. Characterization tests, including rheology, TGA, DSC, WAXS, and DMTA, were conducted to assess the structure and performance of the composites. Results indicate that Arundo fillers minimally alters composite chemical structures, while rheological behaviour is significantly influenced by the filler type and loading. Thermal degradation varies slightly with filler content, ensuring stability for injection moulding. Mechanical performance is optimized with 10 % and 20 % filler content, enhancing stiffness and impact strength, while 40 % fibres leads to increased brittleness. The study highlights the impact of filler type on moisture absorption. Water saturation weakens tensile strength, but re-drying helps recover some properties, demonstrating PLA/Arundo composites’ resilience under moderate loads. This research emphasizes the complex interplay between filler characteristics, composite structure, and their effects on mechanical properties, crucial for evaluating the suitability of PLA composites in various applications.

Stabilizers play a crucial role in enhancing the durability of polymers, and recent interest in sustainable materials has accelerated the exploration of natural antioxidants as alternatives to traditional synthetic stabilizers. While antioxidants isolated from natural sources have already been integrated into polymers, the direct introduction of antioxidant-rich biomasses, like microalgae, offers a promising yet less explored approach. This study evaluates the effectiveness of microalgae biomass as a polyethylene (PE) stabilizer, using spirulina (washed and unwashed) and Tetraselmis striata. Antioxidant content was assessed through various extraction agents, revealing that water extracts of spirulina contained the highest polyphenol content (940.35 mg/100 g) and antioxidant activity. These biomasses were then integrated into a PE matrix at different loadings (0–30

Giant reed (Arundo donax), a plant species with potential for obtaining lignocellulosic fibres, was validated as reinforcement in thermoplastic composites with good processability, thermo-mechanical performance, and aesthetics. This study evaluates the impact of closed-loop recycling of high-density polyethylene (HDPE)-based composites with up to 40% of reed fillers: fibres and shredded plants, on their processing and application properties. Arundo fillers do not significantly impact the processing stability and performance of recycled composites and can improve some aspects. Minor chemical composition differences were observed, highlighting oxidation resistance. All formulations keep their viscous character and reduce the melt flow index slightly, benefiting reprocessing due to the absence of degradation-prone coupling agents. The composites remain thermally stable up to 230°C, with only slight weight loss at 160°C due to lignocellulosic filler degradation. Fillers lead to longer oxidation induction time compared to neat HDPE. Reprocessed moulded materials show higher stiffness and improved ultimate tensile and flexural strength, but lower impact resistance due to shorter filler length. Smaller fillers and improved matrix distribution also reduce water uptake. Fibrous fillers reduce the aspect ratio, making composites with shredded reed more similar to reed fibres, which are costlier to produce. Shortening of the reprocessed fibrous filler is associated with increased crystallinity in composite materials.

Different composites of polyethylene and two fillers (ignimbrite dust and Arundo donax fibers) were obtained by rotational molding. Both fillers were also combined among them to produce hybrid composites. The blends, prepared by dry-blending, were later rotomolded to determine the effect of such fillers into the tensile properties of the materials, before and after subjecting them to accelerated weathering on a UV chamber for up to 500 h. No significant differences are observed in the mechanical behavior of the different sample series, regardless their type or ratio of filler (5 or 10% by weight), due to the modifications only taking place on the sample surface and the rotomolded items having a thickness of nominally 4 mm. The carbonyl index was obtained from the FTIR spectra, determining an increase in this parameter with irradiation time. The samples with the Arundo fibers exhibit a lower carbonyl index, showing the potential stabilization effect of this lignocellulosic filler against UV, while the composites with the mineral powder tend to increase the oxidation of the samples when included at high loadings (10%).

The article explores the relevant environmental issues of hybrid composite materials, that are defined as those systems in which two reinforcing or filling materials are added to a matrix, or a reinforcement or filler is added to a blend of matrices. To that end, a systematic literature review of Life Cycle Assessments (LCAs) in the field was carried out by the authors according to the PRISMA model, given that LCA is internationally recognized to be a scientifically-based valid methodology for assessing and improving sustainability issues of products and services. Web of Science (WoS) and Scopus were used to perform the bibliographical search, those are globally recognized to be the most comprehensive databases of peer-reviewed journals and, so, to store the broadest range of scientific articles.The analysis of literature on the field of the lifecycle assessment (LCA) of hybrid materials have shown that this is a new path still to be explored. While LCA is widely used for the assessment of environmental properties of different materials and applications, to date only few papers apply this methodology to assess the lifecycle of hybrid materials.Results retrieved have been combined to obtain the core works assessed in this review, finding that currently the literature about the application of LCA methodologies for assessing the impacts of hybrid composites is very limited, with not many references found to date, and thus there is huge potential for future growing in this path.

Additive manufacturing (AM), or 3D printing, has revolutionized surgical guide fabrication in dentistry by enabling the creation of complex, customized parts. This study aims to evaluate and compare three predominant AM technologies for polymers—Material Extrusion (MEX), Vat Photopolymerization (VPP), and Powder Bed Fusion (PBF)—for producing surgical guides, focusing on desktop-level equipment. The analysis centers on key criteria: dimensional accuracy, manufacturing time, process complexity, and cost, both for single-set and multiple-set productions. The results reveal that while VPP and MEX technologies offer sufficient dimensional accuracy for clinical use, PBF technology falls short in this regard. In terms of cost and time, VPP proves to be the most efficient technology for manufacturing multiple sets of guides, a common scenario in dental clinics. However, MEX technology demonstrates its competitiveness, particularly in single-set, on-demand fabrication due to its fast-processing time and the potential for lower material costs with proper material selection. The study concludes that while VPP has been the traditional choice, advancements have made MEX a viable and practical option for a rapid and easy integration into smaller dental clinics.

The massive availability of biomass generated by the common giant reed (Arundo donax L.) motivates the search for its possible industrial use for the generation of high added-value products through implementing a biorefinery approach. The literature demonstrates the potential of common cane to obtain different high-value compounds, such as levulinic acid, oligosaccharides, fermentable sugars, highly digestible fiber for animal feed, polyphenols, and natural fibers for composite materials, among others. The data shows the upward trend in Europe toward the generation of new green industries, grouped under the biorefinery concept. Therefore, this review summarizes the current knowledge on the use of Arundo to produce materials, fibers, and chemicals. Major environmental concerns related to this plant are also reviewed. Special attention has been paid to the potential use of Arundo to produce chemicals using green chemistry approaches, as a way to contribute to and advance the achievement of Sustainable Development Goals. Recommendations for future research are also outlined.

This study verified the possibility of recycling polyethylene-based composites with up to 40% of lignocellulosic reinforcement after 5 cycles of compression molding, milling and extrusion. Two forms of filler from the same plant species, Arundo donax L., were studied, namely, fibers and shredded aerial parts of the plant. The properties of composites were assessed at each processing step, finding that the reprocessing affects to more extend the particulate filler than the fibrous one; the lower particle size resulted in lowered tensile properties. However, despite the fiber size reduction, as aspect ratio is not drastically diminished, the better dispersion of the fibers in the matrix counteracts the negative effects of their shorter size. Impact properties are improved with the recycling, possibly due to the increased homogeneity of the samples, which is also translated into a higher density (and lower porosity). The thermomechanical stability of the fiber composites is higher than for the shredded ones. The reduction in size of the fillers is reflected in the lowered viscosity obtained after the reprocessing. The fibers continue stiffening the matrix after the 5 reprocessing cycles, where the milled material acts more as a filler, reducing tensile properties, although showing a good flexural behavior.

This paper describes the effect of two different fillers derived from giant reed (Arundo donax L.), namely fibers and shredded aerial parts of the plant, on the thermal properties of polyethylene-based composites, as the analysis of dimensional stability of lignocellulose-based composites, and its relationship with their thermal diffusivity, has not yet been assessed in the literature. It has been found that the introduction of such materials resulted in a significant reduction of the coefficient of thermal expansion, particularly more important in the case of fibers, due to their higher aspect ratio; in particular, this coefficient is reduced to less than half for fibrous composites (from 1.6·10− 4 K− 1 to 6.1·10− 5 K− 1 or 3.5·10− 5 K− 1 for 20 and 40 Statement of Novelty Arundo donax L. is of great interest to biorefineries due to its fast growth and resistance to adverse environmental conditions. Most research on this plant species focuses on obtaining energy products or valuable chemicals, while very few are related to composite production, particularly on thermoplastic materials. The work found in the literature so far does not provide insights into the relationships between the types of filler (and their aspect ratio) and their thermal properties. Therefore, this work expands the knowledge on the thermal behavior of lignocellulose-polymer composites, supplementing the research, usually focused only on mechanical properties, in their characterization by correlative analysis of thermal influenced dimensional change with structure and thermal diffusivity. Determining the coefficient of thermal expansion (CTE) is a relevant parameter to assess the possibilities of using a material at high or low temperatures and evaluate the dimensional stability of a product during its service lifetime. On the other hand, thermal diffusivity brings together the capacity of a material to store thermal energy and distribute it throughout the material; that is, it relates heat capacity and thermal conductivity, which are also essential in using materials in market applications. Therefore, the work not only provides the results of thermal diffusivity and CTE of thermoplastic-reed composites but also correlates both parameters as a way to widen the range of application of plant-based composites in areas where dimensional stability (i.e., low thermal expansion) is required.

The wide range of applications and the numerous advantages of plastics have led to their excessive use, with subsequent damage to ecosystems. As an environmentally friendly alternative, biocomposites have gained much attention, and microalgae have become a potential source for their production. In this study, the use of washed and unwashed Spirulina in polyethylene-based composites has been evaluated as a way to prevent the thermooxidation of polyethylene, while at the same time, reducing the amount of virgin plastic used. Biocomposites were produced by rotomolding, testing different biomass contents and determining their mechanical and thermal performances as well as their water uptake level. Composites with up to 15% of biomass (by weight), a particularly high ratio for rotomolding, were satisfactorily produced. Using 5% of both biomasses did not significantly modify the behavior when compared with the neat PE samples’ properties. For higher loadings, the use of non-washed biomass allowed us to obtain better properties, with added benefits related to using an unwashed biomass (less water consumption, lower costs and fewer environmental impacts). On the other hand, this study showed a promising beneficial effect on the thermooxidative resistance of composites, as the oxidation induction times were notably increased with biomass addition.

Substituting petrochemical plastics with biobased plastics from natural feedstock offers an environmentally friendly alternative to reduce the carbon footprint. Proteins are promising biopolymers that can be transformed into plastics and sourced from various types of biomass, such as microalgae. Microalgae, particularly spirulina, is considered an excellent renewable resource for bioplastic production due to its high protein content. This study focuses on the characterization of spirulina-polyethylene (PE) composites molded by compression molding technology. Both washed (for salt removal), and unwashed biomass were used in order to explore a potentially more sustainable and cost-effective option. Various loadings of both biomass types (5 %- 30 % by weight) were investigated, and the mechanical (tensile, flexural, and impact resistance) as well as thermal properties (thermogravimetric analysis and differential scanning calorimetry) of the resulting composites were determined. The mechanical properties remained nearly unchanged compared to neat PE when the biomass content was kept under 10 wt.% for both the washed and unwashed biomass. At higher biomass loadings, a reduction in mechanical performance was observed; however, the molded parts maintained good aesthetics and acceptable properties. Despite the predictable adverse changes in thermal behavior, the processability of the materials was not affected. Differential scanning calorimetry indicated that total plasticization of the biomass protein was not achieved during the molding process. Additionally, no significant differences were found between the washed and unwashed biomass, suggesting that using unwashed biomass could be more economically and environmentally beneficial.

The possibility of rotomolding polypropylene (PP) composites with high loadings of a silica-based dust of ignimbrite, a byproduct of volcanic stone extraction is demonstrated. This study aims to establish the properties of composites with various ratios of mineral dust as a filler in PP matrices at loadings from 5 to 30 wt%, ultimately transforming mining residues into a valuable resource for composite production and creating a value chain around the traditional mining industry. Once the composites were obtained, they were subjected to several characterization techniques to comprehensively assess their mechanical and thermal properties. In general, a high percentage of ignimbrite powder has resulted in a reduction in the mechanical properties of neat PP, although no significant changes were observed for composites at lower loadings. Furthermore, the incorporation of this mineral material modified the thermal properties of the PP, enhancing its thermal stability. The blending of the matrix and filler resulted in a reduction in both the melting crystallization temperatures for highly-filled composites. Rotomolded items with good aesthetics, with stone-like appearance, were obtained without any modification on the mineral dust or even without any melt compounding, therefore not increasing the energy consumption during the composites production.Highlights Composites production is a suitable strategy for valorization of mineral residues. Welded ignimbrite residual dust has been used for the first time in composites. Mineral dust has been successfully used in composites obtained by rotomolding. Polypropylene with up to 30% of the stone dust can be processed. Good aesthetics and mechanical features can be obtained with mineral wastes.

Giant reed (Arundo donax L.) is a plant species with a high growth rate and low requirements, which makes it particularly interesting for the production of different bioproducts, including natural fibers. This work assesses the use of fibers obtained from reed culms as reinforcement for a high-density polyethylene (HDPE) matrix. Two different lignocellulosic materials were used: i) shredded culms and ii) fibers obtained by culms processing, which have not been reported yet in literature as fillers for thermoplastic materials. A good stress transfer for the fibrous composites was observed, with significant increases in mechanical properties; composites with 20% fiber provided a tensile elastic modulus of almost 1900 MPa (78% increase versus neat HDPE) and a flexural one of 1500 MPa (100% increase), with an improvement of 15% in impact strength. On the other hand, composites with 20% shredded biomass increased by 50% the tensile elastic modulus (reaching 1560 MPa) and the flexural one (up to 1500 MPa), without significant changes in impact strength. The type of filler is more than its ratio; composites containing fibers resulted in a higher performance than the ones with shredded materials due to the higher aspect ratio of fibers.

Novel bio-based low-density polyethylene (LDPE) composites have been manufactured using different Canadian goldenrod (CG) invasive plant parts. Fragmented and ground blossoms (CGB) and mixed leaves and stems (CGSL) were used as fillers introduced by melt mixing into an LDPE matrix at various concentrations (2, 5, 10, 20, 40 wt %). Moreover, the influence of a series of modified fillers based on stems and leaves saturated with an extract made of blossoms (CGSL+E) on LDPE has been verified. The oxidation resistance of composites was enhanced based on the oxidation induction time (OIT) assessment, which increased from 0.5 min for LDPE to 178 min (CGB), 231 min (CGSL), and 140 min (CGSL+E). All composite series formed by compression molding were exposed to UV-light radiation using Xenon lamps and subjected to spectroscopic (FTIR) analysis, color assessment, and mechanical testing. LDPE/CGSL+E composites demonstrated the most favorable mechanical properties after UV-light exposure. In their case, an increase in Young modulus of 360 MPa was observed for the 40 wt % sample (PE similar to 180 MPa) and an acceptable decrease in tensile strength of 6.5 MPa compared to the reference LDPE of 9.8 MPa. The study consists of a screening for future research on the use and simultaneous valorization of the invasive plant into functional composite fillers with increased oxidation resistance.

Rotational molding advantages include the production of a hollow part with no welding lines, either of small or big sizes, with no internal stresses and good surface details. However, the process is limited by the long cycle times, and its related high energy consumption. Different strategies can be followed to reduce such energy use. This work assesses the use of pressure inside the molds during the densification and cooling stages, finding reductions in overall cycle time of approximately 20%, because of the reduction in the heating time required but also to the increased cooling rate. The influence of such an approach on the production of composites with reed fibers has also been assessed, finding a similar trend towards cycle time reductions. The rotomolded samples’ thermomechanical and rheological behavior were determined, finding that viscosity was not affected due to the incorporation of air during the moldings; besides, the homogeneity of the composites increased due to the mold pressurization. The parts obtained show good aesthetics and good thermomechanical behavior along the entire temperature range studied, and particularly for 10% composites; higher fiber ratios should be prepared via melt compounding. Therefore, the mold pressurization allows us to reduce both oven and cooling times, which can be translated into an increase in productivity and a decrease in energy consumption, which are undeniably related to the increase in the products’ sustainability and cost.

The massive biomass availability generated by the common giant reed (Arundo donax L.) motivates the research for its possible industrial use for high-added-value products through a biorefinery approach. The literature demonstrates the potential of common cane to obtain different high-value compounds, such as levulinic acid, oligosaccharides, fermentable sugars, highly digestible fiber for animal feed, polyphenols, and natural fibers for composite materials, among others. Arundo can also provide valuable lignocellulosic fibers with an application as composite reinforcement, which is the aim of this review. The work is split into different sections: fiber obtaining, mainly done by mechanical procedures, fiber characterization (composition, thermal degradation, "mechanical properties", and crystallinity), and properties of composites with reed fiber. Most authors refer to producing board panels with insulating properties, followed by introducing reed fibers or ground materials in thermoset resins. Few papers focus on the production of thermoplastic composites with Arundo, which shows the opportunity for deepening research in this area. PRISMA flowchart has been followed to perform the literature review. Different sources have been used, and retrieved results have been combined to obtain the core studies assessed in this review, evaluating the options of using Arundo fibers to obtain polymer composites.

The range of materials suitable for rotational molding is not as wide as for other polymer processing technologies. An option to reduce the carbon footprint of such materials is to introduce natural fibers, such as abaca. In this work, different loadings of abaca fibers (5 to 20 % by weight) were molded using one, two and three-layer constructions. A comparison of the mechanical behavior (tensile, flexural, and impact properties) with the fiber content, considering the method of obtaining the composite (1, 2 or 3 layers) was performed. The thermomechanical behavior of the matrix was not affected due to the introduction of the fibers; apart from a reduction in the storage modulus, especially at low temperature, the curves have a similar profile. In general terms, the tensile and flexural strength were not affected by the incorporation of the fibers, that is, the composites exhibit similar behavior to neat polyethylene. Significant improvements in the tensile modulus were obtained for the parts manufactured with 2 layers, with 10 wt.% fiber in the internal one. As expected, the impact strength was reduced for all the composites, although the layer of PE on the inner side that coats the fibers counteracts this reduction to a certain extent. An increase in the heating time was observed for all the composites made in different layers; although the incorporation of fibers slightly modifies the course of the curve, the heating time is only significantly increased for loadings over 10%. The higher energy consumption needed to obtain the part in the different layers would only then be justified by an increase in the composite properties, which is not the case of the parts obtained in this work.

The incorporation of materials different from the polymer within the rotational molding process usually results in lowered mechanical properties, where impact strength is of particular concern. In order to overcome this issue, multilayer structures of virgin polyethylene (PE) and banana fiber composites were prepared to determine the impact of the different layers on the performance of the final part. Cycle time has been studied to identify the influence of the addition of fibers in the process. The tensile, flexural and impact properties have been analyzed, finding improvements in Young’s modulus of up to 13%, although at the expense of significant decreases in impact strength. A reduction in the fiber size due to the pulverization process was observed, which affected the rheological and mechanical behavior of the composite. The beneficial effects of working in multiple layers have been demonstrated in this work, where composites with up to 5% of banana fiber have been produced in two-layer structures. Finally, the need to add neat polyethylene in the external layer is also highlighted as a way to counteract the reductions in mechanical properties, particularly for flexural elastic modulus and tensile strength, and this also helps with the drop in impact behavior to a lower extent.

This work describes an extraction method for giant reed fibers from stems and leaves based on chemical soaking and crushing through a rolling mill. Obtained fibers, together with the shredded plant (stems + leaves), are characterized in terms of chemical composition, thermal stability, morphology, and crystallinity. Mechanical properties of fibers have also been assessed (single fiber tensile tests). The results show that the proposed method allows obtaining fibers with higher cellulose content (near 70%), good thermal stability (10% weight loss over 270°C), higher density, and better mechanical properties than other Arundo fibers previously reported in the literature. Fibers from leaves are thinner and show higher crystallinity than those from stems (72 μm vs. 157 μm, 73% vs. 67% crystallinity, respectively), although mechanical properties are similar for both (around 900 MPa for tensile strength and over 45 GPa for elastic modulus). Analysis of the microstructure shows that fibers consist of microfiber bundles, and the removal of a thin layer of non-cellulosic nature is clear; fibers provide a rougher, cleaner surface than shredded raw material.