The appeal of the approach lies in its double valorization strategy. Juncus Acutus is a fast-growing biomass resource that requires little agricultural input, while expanded polystyrene is a notoriously persistent plastic waste that is difficult to recycle economically. By dissolving recycled EPS and using it as a binder for JA fibers, the team effectively locks polymeric waste into a useful product rather than sending it to landfill or incineration. The researchers prepared three composites with fiber-to-EPS ratios of 70:30, 60:40, and 50:50 by weight, designated JA70, JA60, and JA50 respectively, and measured their density, thermal properties, and compressive strength in the laboratory.

The experimental results reveal a clear trend with increasing fiber content. Raising the JA fraction from 50 to 70 percent reduced the bulk density of the composites from 371.6 to 289.9 kilograms per cubic meter, a drop of roughly 22 percent. Thermal conductivity fell in parallel, from 0.117 to 0.096 watts per meter-kelvin, meaning the fiber-rich panels conduct less heat and insulate better. Thermal diffusivity, which describes how quickly heat propagates through a material, decreased by approximately 15 percent across the same range, while specific heat capacity increased by about 10 percent. Together, these changes indicate that fiber-rich composites store more thermal energy per unit mass and release it more slowly, a combination that improves thermal inertia and helps regulate indoor temperatures.

Mechanical performance moved in the opposite direction, as expected for a polymer-bonded fiber composite. Compressive strength declined as the proportion of EPS binder decreased, since the polymer matrix is what holds the fibrous network together under load. Nevertheless, the JA70 formulation still reached 0.16 megapascals, which the authors describe as adequate mechanical integrity for handling and for use in non-structural insulation applications. The JA70 blend also provided the most favorable balance between thermal and mechanical properties among the three formulations tested, making it the leading candidate for practical development.

To quantify the environmental benefits, the team conducted a cradle-to-gate life-cycle assessment covering raw material acquisition through manufacturing. The global warming potential of the JA70 composite was estimated at 1.1 kilograms of CO2-equivalent per kilogram of material. While this figure is not zero, the authors note that it reflects the impacts of the recycled polymer content and the processing route, and they highlight that further work is needed to address solvent-related impacts associated with dissolving the EPS. The assessment demonstrates the potential of the composites as lower-impact insulation materials while also identifying specific environmental hotspots that future optimization should target.

The numerical analysis adds a dynamic dimension to the static laboratory measurements. Using the experimentally derived thermal properties as inputs, the researchers performed transient simulations under representative climatic conditions to model how the composites behave in real building walls over time. The simulations showed that the fiber-rich panels demonstrate improved thermal inertia and indoor temperature regulation compared with the other formulations. In practical terms, this means buildings insulated with the JA70 composite would heat up and cool down more slowly, smoothing indoor temperature swings and potentially reducing the energy demand for heating and cooling in hot climates.

The choice of Juncus Acutus as the fiber source is significant for the regional context. The plant is abundant in the Mediterranean basin and has previously been investigated as a reinforcement for unfired clay bricks, but this study is among the first to combine it with recycled polystyrene specifically for insulation panels. Using locally available biomass reduces transport emissions and supports rural economies, while the recycled EPS content diverts a problematic plastic waste stream from landfill. The authors frame the work as a response to the growing demand for lower-impact building insulation materials, a sector where conventional products such as virgin polystyrene and mineral wool carry substantial embodied carbon.

Despite the promising results, the study is candid about its limitations. The authors highlight the need to further address solvent-related impacts, moisture resistance, fire performance, and long-term durability before practical building application. The solvent used to dissolve the recycled EPS is an environmental concern that the life-cycle assessment identifies as a hotspot, and the hygrothermal and fire behaviour of the composites remain to be fully characterized. Long-term durability under real building conditions, including exposure to moisture, temperature cycling, and biological attack, is another area that requires investigation before the material can be deployed at scale.

The research was supported by the PhD-ASsociate Scholarship program funded by the CNRST, Morocco, and was conducted at the Mechanics and Energy Laboratory of Mohammed First University in Oujda. The team, led by Jinane Mejdoubi, included Othmane Horma, Boutahar Laaouar, Ahmed Mezrhab, and Mohammed Amine Moussaoui. Their work contributes to a growing body of research on bio-based insulation composites, a field where researchers worldwide are exploring fibers from hemp, date palm, wheat straw, eucalyptus bark, and other biomass sources as alternatives to conventional insulation products.

The study demonstrates that combining Juncus Acutus fibers with recycled expanded polystyrene can produce insulation composites with competitive thermal performance, adequate mechanical integrity for non-structural applications, and a quantifiable lower-impact profile compared with conventional alternatives. The 70 percent fiber blend emerges as the leading formulation, offering the lowest thermal conductivity, the highest specific heat capacity, and improved thermal inertia in transient simulations. While challenges related to solvents, moisture, fire, and durability remain, the research provides a technical foundation for developing lower-impact insulation materials that valorize both biomass and polymeric waste streams simultaneously.

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Subject of Research: Juncus Acutus fiber–recycled expanded polystyrene composites for lower-impact insulation: experimental characterization and numerical thermal analysis

Article Title: Juncus Acutus fiber–recycled expanded polystyrene composites for lower-impact insulation: experimental characterization and numerical thermal analysis

Article References: Mejdoubi, J., Horma, O., Laaouar, B., Mezrhab, A., & Moussaoui, M. A. (2026). Juncus Acutus fiber–recycled expanded polystyrene composites for lower-impact insulation: experimental characterization and numerical thermal analysis. Environmental Science and Pollution Research. https://doi.org/10.1007/s11356-026-38313-7

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38313-7

Keywords: Juncus, Acutus, fiber, recycled, expanded, polystyrene, composites, lower-impact, insulation, experimental, characterization, numerical

The motivation for the work is grounded in one of the largest waste streams on the planet. The global textile sector generates more than 92 million tons of waste annually, and denim, composed primarily of cotton cellulose fibers, makes up a significant share of both post-consumer and post-industrial textile refuse. While recycling initiatives have improved diversion rates in recent years, a substantial fraction of this material is still landfilled, contributing to soil contamination, groundwater pollution, and greenhouse gas emissions. Recycling textile waste is technically difficult because fabrics are heterogeneous, often blended, and laced with chemical additives from processing. Yet embedding waste textile fibers into polymer matrices has emerged as a promising strategy to transform low-value waste into functional materials for structural, thermal, and acoustic applications.

Denim has particular appeal as a reinforcement. Its woven structure, high fiber content, and residual mechanical integrity allow recycled denim composites to achieve competitive performance compared with some conventional glass-fiber-reinforced systems, while offering clear sustainability advantages. Jute, meanwhile, is one of the most widely available and cost-effective natural fibers in the world, prized for its favorable stiffness and tensile strength among bast fibers. Hybridizing the two waste streams seemed like an obvious win. But there was a catch the researchers deliberately chose to confront: untreated jute fibers carry a surface burden of waxes, lignin, hemicellulose, and pectins that inhibit effective wetting and bonding with hydrophobic epoxy matrices. Chemical treatments such as alkali treatment, silane coupling, and acetylation can fix this problem, but they add cost, processing complexity, and chemical usage that erode the environmental logic of natural fiber composites in the first place.

The experimental design was elegantly simple. The team fabricated two laminates by hand lay-up, each containing identical amounts of epoxy resin, hardener, and recycled denim. The denim, a heavyweight 3/1 twill cotton fabric with an areal density of 300 to 400 grams per square meter, came from pre-consumer offcuts at jeans factories and was used as received, without washing or treatment. The jute, by contrast, was recovered from used and deteriorated jute bags, washed, solar-dried for two hours, and cut into short fibers roughly five to ten millimeters long. Five denim layers were stacked in each mold; in the hybrid version, 5.80 grams of untreated jute, about 1.7 percent of the laminate by weight, was first mixed into the epoxy resin and brushed between the denim plies. The laminates were compressed under a 30-kilogram load, cured for 72 hours at ambient conditions, and post-cured at 60 degrees Celsius for one hour, yielding final thicknesses of approximately 4.1 millimeters.

The mechanical results tell a story of good intentions colliding with interfacial chemistry. In tensile testing according to ASTM D3039, the denim-only composite achieved an ultimate tensile strength of 31.4 plus or minus 0.2 megapascals at a strain of 10.5 percent, exhibiting continuous strain hardening as the woven cotton yarns progressively straightened and reoriented under load. The jute-containing hybrid plateaued at just 25.2 plus or minus 0.3 megapascals, fracturing at less than half the strain. That represents a 19.5 percent reduction in strength and a 59 percent reduction in strain at maximum stress. The energy penalty was even more dramatic: numerical integration of the stress-strain curves showed the denim composite absorbed 2.69 megajoules per cubic meter up to peak stress, while the hybrid managed only 0.80, a roughly 70 percent loss in tensile energy absorption. Initial stiffness, by contrast, was nearly identical between the two materials, at around 1.3 gigapascals, indicating the jute only revealed its destructive influence once significant deformation began.

Flexural and impact testing confirmed the same pattern. In three-point bending, flexural strength fell from 67.8 plus or minus 3.4 megapascals for the denim composite to 55.5 plus or minus 4.6 megapascals for the hybrid, an 18 percent drop, while flexural modulus declined 13 percent, from 2,843 to 2,482 megapascals. Unnotched Charpy impact tests told the most sobering story: impact strength plummeted 33 percent, from 8.30 to 5.60 kilojoules per square meter. Poor adhesion between the untreated jute and the epoxy creates weak zones that act as stress concentrators under sudden loading, facilitating crack initiation, fiber pull-out, and premature fracture. The researchers note that in bending, the compressive half of the section and the denim layup partially mask the weak interface, whereas in pure tension the poorly bonded jute phase governs failure, which explains why the energy loss was so much larger in tensile loading.

Scanning electron microscopy of the fractured surfaces provided direct, visually compelling evidence for the mechanism. The denim-epoxy composite showed fibers well embedded in the matrix with good interfacial interaction, with matrix residue clinging to the cotton yarns and indicating effective load transfer. The hybrid composite told a different story: inadequate fiber wetting, extensive fiber pull-out, microvoids, and clean jute fiber surfaces with visible gaps at the interface, the microscopic fingerprints of debonding at low stress. The pulled-out jute appeared as split technical-fiber bundles, a phenomenon known as fibrillation, in which failure proceeds by separating elementary fibers held together by a pectin- and lignin-rich middle lamella rather than by fracturing the fiber itself. Because bundle splitting and pull-out dissipate little energy, these morphological features explain the early plateau in the tensile curves, the severe loss of energy absorption, and the depressed impact resistance of the hybrid material.

Interestingly, the thermal and moisture results were not uniformly negative for the jute hybrid. Thermogravimetric analysis showed both composites exhibited comparable degradation profiles, with the principal mass-loss region between 300 and 450 degrees Celsius and maximum decomposition rates at approximately 365 degrees Celsius for both. Differential scanning calorimetry revealed a main endothermic decomposition peak at 388.1 degrees Celsius for the denim composite and a slightly lower peak at 381.3 degrees Celsius for the hybrid, consistent with the earlier onset of hemicellulose decomposition in the jute phase. Notably, the hybrid retained 8.3 percent char residue at 600 degrees Celsius, while the denim-only composite was almost fully volatilized. Even more surprising, the hybrid absorbed less water, 5.60 percent versus 6.39 percent, and took longer to saturate, 384 hours versus 288 hours. The researchers attribute this to the jute-filled resin occupying the inter-yarn channels that otherwise act as wicking pathways in the denim-only laminate, rather than to the jute surface chemistry itself.

The practical upshot is a clear engineering directive rather than a dead end. The denim-epoxy composite, with its balanced property set, is well suited for low-to-moderate load-bearing, non-safety-critical applications such as furniture panels, interior partitions, automotive trim, packaging inserts, and equipment casings. The jute hybrid, with lower strength but slower water uptake and reduced porosity, may find a niche in indoor panels for humid environments where mechanical demands are modest. But the study’s most important contribution may be its cautionary message for the green materials movement: untreated jute fibers behaved as defect sites rather than reinforcements, and the literature the authors compiled shows that alkali, silane, or acetylation treatments can substantially improve jute-epoxy performance. Until surface treatment is incorporated, the authors conclude, the promise of denim-jute hybrid composites will remain unfulfilled, a reminder that in sustainable materials engineering, chemistry at the interface matters as much as the sustainability of the supply chain.

Subject of Research: The effect of untreated jute fiber incorporation on the mechanical, thermal, and hygroscopic properties of recycled denim-epoxy hybrid composites

Article Title: Effect of untreated jute fiber incorporation on the properties of recycled denim–epoxy hybrid composites

Article References: Hossen, R., Apu, M. U., Neha, T. R., Ahasan, E., Islam, M. R., & Mim, J. J. (2026). Effect of untreated jute fiber incorporation on the properties of recycled denim–epoxy hybrid composites. Results in Engineering, 32, Article 112828. https://doi.org/10.1016/j.rineng.2026.112828

Image Credits: AI Generated

DOI: 10.1016/j.rineng.2026.112828

Keywords: Effect, untreated, jute, fiber, incorporation, properties, recycled, denim, epoxy, hybrid, composites, scientific research