Search Results (31)

Transient extrusion defects are a fundamental process control challenge in fused granular fabrication (FGF), arising from the finite melt pressurization time of screw-driven extruders at each start–stop event. This study presents an integrated experimental and analytical framework for the characterization and open-loop feedforward compensation of these transient dynamics, demonstrated on two composite thermoplastic feedstocks: a recycled random polypropylene (RPP1) and a 20 wt% wood-fiber-reinforced polypropylene composite (WFPP). Unlike prior filament- or single-material feedforward strategies, this framework derives and statistically validates material-specific compensation parameters across two rheologically distinct feedstocks. Single-layer road experiments were conducted on a custom instrumented FGF platform across a 2³⁻¹ half-fraction factorial design varying melt temperature, print acceleration, and nozzle diameter, with screw speed stepped among 20, 40, and 80 RPM to excite transient states; deposited road geometry was digitized and spatially registered to the synchronized process signals. Main-effects regression confirmed that nozzle diameter is the dominant predictor of mean road width, while screw velocity exerts a significant negative effect attributable to speed-dependent backflow. Prediction-error minimization on the pooled multi-experiment dataset yielded a parsimonious first-order transfer function, G(s) = 0.990/(1 + 1.909s), whose time constant is physically attributed to melt compressibility in the barrel volume upstream of the nozzle restriction. This model was embedded in a G-code post-processor implementing two sequential corrections: a material-specific steady-state slip gain and a discrete linear-advance term parameterized by the identified time constant. For RPP1 at the nominal gain, the print latency interquartile range decreased from 5–20 mm to 2–8 mm without degrading steady-state dimensional accuracy; the combination of nominal gain with active retraction further reduced latency to near-zero. Analysis of covariance (ANCOVA) confirmed that optimal feedforward gains are statistically material-dependent across all three quality metrics (p < 0.05), providing statistical justification for material-specific compensator parameterization. The results establish a practical, hardware-agnostic route to reduce transient deposition defects in pellet-based additive manufacturing, extensible to additional feedstocks. Full article

Infectious prion adsorption on metal, minerals, wood, and plastic is well documented, raising the specter of food safety hazards for meat packing workers, sport hunters, and consumers. We previously demonstrated that sodium hypochlorite, and to a lesser extent, potassium peroxymonosulfate, and hypochlorous acid can decontaminate prion-contaminated nonporous surfaces. However, the extent to which chemical aging of surfaces affects subsequent recoverable prion seeding activity is unknown. In this study, we investigated the potential for four chemical decontaminants known for their anti-prion activity (sodium hypochlorite [bleach], hypochlorous acid [Briotech], potassium peroxymonosulfate [Virkon-S], and Wex-Cide-128) to alter the surfaces of steel knives and the subsequent prion decontamination efficacy of each. We found that hypochlorous acid, sodium hypochlorite, and potassium peroxymonosulfate corrode the surfaces of steel knives, resulting in significant physical alterations. Knives exposed to hypochlorous acid exhibited the most substantial corrosion (rust), which is consistent with its oxidizing effects. Oxidation of the knife surface was corroborated by complementary energy-dispersive X-ray spectroscopy data trends. Scanning electron microscopy data indicate corrosion is apparent after minimal exposure to oxidizing agents. Finally, we used the real-time quaking-induced conversion assay on swabs collected from chemically aged knife surfaces to evaluate recoverable surface-associated CWD-prion seeding activity detected by RT-QuIC after prion exposure and decontamination. Our results indicate decreased recoverable prion seeding activity from knife surfaces aged with 40% bleach. We also observed some recoverable seeding activity post-decontamination on knives chemically aged with 10% bleach and Wex-Cide-128, but largely similar efficacy to prior studies. This implies that existing chemical prion decontaminants are likely effective after repeated use on steel surfaces. Full article

The increasing use of pressure-sensitive labels (PSLs), driven by growth in the packaging sector, raises concerns regarding material consumption and end-of-life management under evolving European packaging regulations. This study investigates the biodegradation potential of sustainable PSL facestocks produced from 15% agro-industrial by-products, 40% post-consumer recycled fibers, and 45% virgin wood pulp. Their biodegradation behavior was compared with bio-based polyethylene (PE) facestocks using laboratory-scale aerobic soil burial tests conducted for up to 28 days. Biodegradation was assessed through weight loss measurements, visual evaluation, Fourier transform infrared (FTIR) spectroscopy, and fluorescence analysis. Fiber-based facestocks exhibited significant degradation, reaching approximately 50–55% weight loss after 28 days, accompanied by structural changes in the cellulose matrix and reduced fluorescence intensity. In contrast, bio-based polyethylene facestocks showed negligible weight loss and only minor spectroscopic changes, indicating high stability under the tested conditions. The results demonstrate that fiber-based samples derived from agro-industrial and recycled sources possess substantially higher biodegradation potential than bio-based polymeric alternatives. These findings support the use of fiber-based PSL facestocks in applications requiring improved environmental compatibility. Full article

The development of composite materials based on post-consumer polymers and agricultural residues is a pragmatic valorization approach that extends the lifetime of materials. This research aimed to analyze the selected physical and mechanical properties of post-consumer-polyethylene-based composites with lignocellulosic fillers. This study explores the ‘ready-to-use’ valorization of untreated oilseed pomaces. The polyethylene ratio was set at 30% and 40%. Wood particles were substituted with oilseed pomace from nigella, rapeseed and evening primrose. The content of the pomace replacing wood particles was 30%, 65% and 100%. The composites made of post-consumer polyethylene and wood particles were used as a reference. The manufacturing process utilized a hybrid approach, combining extrusion with flat pressing. Increasing pomace content generally reduced the modulus of rupture and modulus of elasticity. Surface roughness decreased with higher pomace addition, except for the 30% rapeseed content for the lower polyethylene ratio, i.e., 30%, which showed unusually high roughness. Higher pomace content improved surface wettability, particularly for nigella-based composites. Water absorption and thickness swelling after 2 h and 24 h of soaking were highest at 30% pomace content and decreased with increasing substitution levels. Evening primrose composites consistently exhibited the lowest water uptake and swelling. Full article

This study quantifies the mechanical behavior of 10–15 mm thick WPC boards compression-molded from post-consumer bottle-cap polyolefins (PP/HDPE, 70/30 wt%) and pine sawdust (0, 10, 20 wt%). Flexural and tensile strength/modulus are determined and application-oriented acceptability assessed for non-structural temporary concrete formwork under ASTM bending and tension protocols. Mechanical performance was evaluated using three-point and four-point bending tests, as well as axial tension. Flexural strengths averaged 17.31, 16.38, and 8.71 MPa for 0, 10, and 20 wt% sawdust (three-points), and 15.23, 13.18, and 9.20 MPa (four-points), with flexural moduli as high as 1.60 GPa (four-points). Tensile strengths averaged 3.60, 3.79, and 3.44 MPa, with tensile elastic moduli of 0.10, 0.33, and 0.36 GPa, respectively. Stress–strain curves showed a nonlinear elastic-brittle response without a defined yield point, followed by fracture, consistent with porous, non-compatibilized WPCs. Variability increased with the sawdust content, reflecting the distribution of filler and matrix-fiber adhesion. Although the properties are inferior to those of conventional building materials, the results are within the application-oriented ranges for non-structural temporary formwork (as established by the reported ASTM tests). UV durability associated with carbon black-pigmented caps is presented as a literature-supported hypothesis for future accelerated aging, rather than as a measured outcome. Overall, the findings demonstrate a circular-economy pathway that converts post-consumer plastics and sawmill waste into WPC panels for sustainable construction. Full article

This paper reviews various emerging alternative SCMs derived from minerals and biomass sources, industrial byproducts, and underutilized waste streams. The paper compiles and evaluates physicochemical properties, reaction mechanisms in cementitious systems, resource availability, supply chain dynamics, technology readiness, the impact on concrete performance, and environmental and cost factors for each candidate SCM. Specifically, the review examines wood ash from bioenergy plants, volcanic and sedimentary natural pozzolans, and construction and demolition waste. This includes recycled concrete fines, asphalt plants’ rock dust (baghouse fines), aggregate production fines, and post-consumer waste, particularly municipal solid waste incinerator ash and wastewater sludge ash. Additionally, the paper explores innovative additives such as cellulose and chitin nanomaterials and calcium–silicate–hydrate nanoseeds to address challenges of slower strength development and rheological changes. The key contribution of this review is a multifactor framework for assessing alternative SCMs, emphasizing availability, supply chain, market readiness, and environmental performance, combined with an engineering performance review. Full article

Acid hydrolysis can be more efficient than water hydrolysis, particularly in breaking down cured adhesives found in waste panels within a shorter reaction time, which could benefit large-scale industrial processes. This study evaluates the effects of various acid hydrolysis conditions on the thermal, physical, and chemical properties of recycled particles intended for particleboard production. Particleboards were recycled using oxalic acid and ammonium chloride at different concentrations and reaction times at 122 °C. The thermal stability of the particles was determined by thermogravimetric analysis. Particle size distribution, particle morphology, nitrogen content, pH and acid/base buffer capacity were analyzed. The effect of the recycled particles on the urea-formaldehyde (UF) curing was assessed using differential scanning calorimetry and the gel time method. The recycled particles exhibited a higher thermal degradation beyond 200 °C, indicating their thermal stability for manufacturing new panels. The acid treatments did not damage the anatomical structure of the particles, preserving the prosenchymatous elements. The nitrogen content of recycled particles decreased by up to 90% when oxalic acid was used, compared to raw board particles. Recycled particles exhibited a lower pH, with a maximum reduction of 44%. They also showed a decreased acid buffer capacity and an increased base buffer capacity compared to raw board particles. This effect was particularly pronounced in treatments that included ammonium chloride. The recycled particles did not significantly affect the peak polymerization temperature of the UF adhesive. However, some treatments affected the gel time of the adhesive, particularly those using 30% ammonium chloride. The results indicate that particleboards can be effectively recycled through acid hydrolysis, mainly with oxalic acid, which provides better results than hydrolysis using water alone. Oxalic acid showed increased selectivity in eliminating the cured UF adhesive, resulting in recycled particles suitable for manufacturing new panels. Full article

This study investigates the properties of composites produced using post-consumer polypropylene (PP) reinforced with lignocellulosic fillers from Nigella sativa (black cumin) and rapeseed pomace. Using agri-food by-products like pomace supports waste management efforts and reduces the demand for wood in wood–plastic composites. The composite production method combined extrusion and hot flat pressing. Mechanical tests showed a decrease in the tested parameters. Compared to the control variant, the MOE decreased by 26.4% (PP_R variant) and 46.9% (PP_N variant), and the MOR value decreased by 78.7% (PP_N) and 55.1% (PP_R). No significant differences in surface roughness parameters were observed. The composite with nigella particles demonstrated increased wettability. TGA tests showed reduced thermal stability compared to PP and differences between composite variants. The composites exhibited susceptibility to fungal overgrowth, which suggests potential biodegradability. The composites demonstrated complete overgrowth by inoculated fungi, reaching 100% coverage, while samples from PP known to be resistant to biological factors remained unaffected. Although the mechanical properties of the composites were degraded, the use of lignocellulosic fillers offers undeniable advantages, such as waste management of lignocellulosic and polypropylene byproducts, reduced wood demand, and the potential biodegradability of the obtained composites. However, there is a need for further optimization of manufacturing processes and material composition to enhance the material performance. Full article

The increasing complexity and production volume of glass-fiber-reinforced polymers (GFRP) present significant recycling challenges. This paper explores a potential use for mechanically recycled GFRP by blending it with high-density polyethylene (HDPE). This composite could be applied in products such as terrace boards, pipes, or fence posts, or as a substitute filler for wood flour and chalk. Recycled GFRP from post-consumer bus bumpers were ground and then combined with recycled HDPE in a twin-screw extruder at concentrations of 10, 20, 30, and 40 wt%. The study examined the mechanical and structural properties of the resulting composites, including the effects of aging and re-extrusion. The modulus of elasticity increased from 0.878 GPa for pure rHDPE to 1.806 GPa for composites with 40 wt% recycled GFRP, while the tensile strength ranged from 36.5 MPa to 28.7 MPa. Additionally, the porosity increased linearly from 2.65% to 7.44% for composites with 10 wt% and 40 wt% recycled GFRP, respectively. Aging and re-extrusion improved the mechanical properties, with the tensile strength of the 40 wt% GFRP composite reaching 34.1 MPa, attributed to a reduction in porosity by nearly half, reaching 3.43%. Full article

In an attempt to make a first step toward monitoring the sustainability of wood as (one of) the main element(s) of the EU biomass supply, a novel approach combining a physical accounting model with a material flow–life cycle assessment approach was used to trace the locations of origin of the wood and the associated sustainability impacts. Applying this approach to EU trade data from 2018, we found that around one-third of the wood fiber input in finished paper products consumed in the EU was imported. The main countries of origin were Brazil, the United States and Uruguay. We used Uruguay as a case study of an important country that provides wood pulp to assess the associated sustainability impacts. The results reveal synergies and trade-offs between employment, value added and environmental impacts. We highlight the need to analyze sustainability impacts in different dimensions of sustainability and consider not only territorial impacts in isolation but also from a global perspective in order to have a more holistic overview. Future extensions of the approach could include the coverage of other commodities, additional impacts along the global supply chain (e.g., post-use) and additional sustainability indicators. Full article

This article outlines the design and performance of a flue gas condensation system integrated with a biomass combustion plant. The system comprises a biomass plant fuelled by wood chips, generating flue gases. These gases are condensed via a double heat exchanger set-up, extracting water and heat to reduce concentrations of CO, CO₂, and NO_x while releasing gases at a temperature close to ambient temperature. The 100 kW biomass plant operates steadily, consuming 50 kg of wood chips per hour with fuel energy of 18.98 MJ/kg. Post combustion, the gases exit at 430 °C and undergo two-stage cooling. In the first stage, gases are cooled in a high-temperature tube heat exchanger, transferring heat to air. They then enter the second stage, a flue gas/water heat exchanger, recovering sensible and latent thermal energy, which leads to water condensation. Flue gas is discharged at approximately 33 °C. Throughout, parameters like the flue gas temperatures, mass flow, fuel consumption, heat carrier temperatures, and water condensation rates were monitored. The test results show that the system can condense water from flue gas at 75 g/min at 22 °C while reducing pollutant emissions by approximately 20% for CO₂, 19% for CO, 30% for NO, and 26% for NOx. Full article

The circular economy forces societies to take actions aimed at giving post-consumer products a “second life”. As we know, wood is perfect for this. Moreover, reusing wood helps keep carbon in circulation, thus limiting its emissions into the atmosphere. It turns out that extensive research on determining the durability of wood is very useful and valuable for one more reason. Well, they can be used to create a model to determine the usefulness of wood, which has only apparently lost its utility value during many years of exposure to external factors. The research subject was samples of wood impregnated with protection agents and modified, originating from many years of field tests. The aim of the research was to correlate the results of wood durability determined after a period of exposure in open space with the results of determining the potential usefulness of such wood. On this basis, a model for determining the value of post-consumer wood was created. As a main result of post-consumer wood analysis, the high durabilities against C. puteana with mass loss below 3% were noticed for acetylated, furfurylated, and CCA-treated wood. Moreover, high color stabilities (ΔE < 10) were observed for thermowood and furfurylated wood. Full article

This systematic review study adopted the PRISMA methodology to investigate recent research on wood-plastic composites (WPC) utilizing post-consumer plastics in the construction industry. Initially, 3111 articles were selected from academic databases using keywords such as “wood and plastic composites”, “WPC”, “polymer”, “recycled”, “waste”, “construction”, and “sustainability.” After stringent exclusion criteria, 15 relevant studies on plastic waste composites were identified. These studies often employ post-consumer plastics like polypropylene and high-density polyethylene, along with plant-based fillers, aiming to enhance mechanical properties and reduce reliance on virgin materials. Analysis of these studies revealed that the optimal plastic composition in the composites ranged from 40% to 45% wood and from 50% to 60% plastic, with the extrusion process being the most employed for shaping. Specific factors, such as the use of compatibilizers and the particle size of raw materials, were identified as significant influencers on composite strength. These materials exhibited high thermal stability, rendering them suitable for construction applications exposed to high temperatures. The diversity of plastic waste explored in the studies underscores the potential to tailor thermal properties to specific application demands. These composites facilitate closed-loop plastic recycling, enabling their reintegration into the production chain and offering opportunities for lightweight, durable, and high-performance products in the construction industry. However, beyond the factors examined in the studies, a meticulous assessment of the fire resistance, weather resistance, ultraviolet resistance, moisture absorption, dimensional stability, degradation, long-term durability, impact strength, recyclability, and cost-effectiveness of the material is crucial. Thoughtful consideration of these factors is essential to achieving a comprehensive understanding of the potential and limitations of recycled plastic composites in promoting energy efficiency and sustainability in the construction industry. Full article

Wood-plastic composites (WPCs) have shown exceptional promise as a building material, especially for outdoor uses. Using renewable wood fiber as the reinforcing filler in WPCs increases the material’s environmental sustainability. While virgin commodity thermoplastics are primarily used in these composites, using post-consumer plastic further contributes to their sustainability. While they are beginning to be used in the Gulf countries, information on their performance, especially durability under harsh desert climates, is sparse. The present investigation on WPCs is based on the two most popularly used thermoplastics in WPCs, virgin high-density polyethylene (HDPE) and polypropylene (PP), with the wood content varying between 0 and 36 wt. %. These were prepared with melt processing from a masterbatch and characterized primarily using thermal methods and tensile properties of their injection molded test pieces. Variations in tensile properties, especially the tensile modulus (MPa), the tensile strength (MPa), and the ultimate extensibility (%) of the composite samples were investigated to determine an optimal wood-fiber loading. For either polymer type, exceeding 27 weight percent of wood fiber resulted in unacceptably low ultimate extensibility of the material. Full article

The exploitation of natural fibers to reinforce polymers is a promising practice. Thus, biocomposites have gained increased attention in automotive, construction, and agricultural sectors, among others. The present work reports the reinforcement of recycled high-density polyethylene (r-HDPE) with hemp fibers to afford composite materials as sustainable analogues to conventional wood/plastic composite (WPC) products. HDPE bottles (postconsumer waste) were used as r-HDPE and further reinforced by the addition of hemp fibers. For the synthetic part, thirteen composite materials with different filler concentrations (10–75% wt. in hemp fibers) using either Joncryl or polyethylene-grafted maleic anhydride (PE-g-MA) as compatibilizers were prepared via melt mixing. Materials with good integrity were obtained with a fiber load as high as 75% wt. The structural, thermal, mechanical, and antioxidant properties of the r-HDPE/hemp composites were evaluated using multiple complementary characterization techniques. Stereoscopic microscope images demonstrated the satisfactory dispersion of the hemp fibers into the polymeric matrix, while scanning electron microscopy microphotographs revealed an improved adhesion between the filler and the polymeric matrix in the presence of compatibilizers. The incorporation of hemp fibers contributed to the improvement of the elastic modulus of the composites (almost up to threefold increase). The results showed that as the hemp fiber content increased, the antioxidant properties as well as the degradability of the composites increased. It is noteworthy that composites containing 75% wt. hemp fibers neutralized 80% of 2,2-diphenyil-1-picrylhydrazyl radicals within 45 min (DPPH assay). In conclusion, the present research work demonstrates that thermally recycled HDPE reinforced with biomass fibers received from agricultural waste is a valid alternative for the preparation of commodity products with an eco-friendly character compared to conventional wood/plastic composites. Full article