The effects of surface pretreatment (water and alkali) and modification with silane on moisture sorption, water resistance, and reaction to fire of hemp fiber reinforced polylactic acid (PLA) ...composites at two fiber loading contents (30 and 50 wt.%) are investigated in this work. Moisture adsorption was evaluated at 30, 50, 75 and 95% relative humidity, and water resistance was determined after a 28-day immersion period. The cone calorimetry technique was used to investigate response to fire. The fiber surface treatment resulted in the removal of cell wall components, which increased fiber individualization and homogeneity as shown in scanning microscopic pictures of the composite cross-section. Although the improved fiber/matrix bonding increased the composite’s water resistance, the different fiber treatments generated equal moisture adsorption results for the 30 wt.% reinforced composites. Overall, increasing the fiber amount from 30 to 50 wt.% increased the composite sensitivity to moisture/water, mainly due to the availability of more hydroxyl groups and to the development of a higher pore volume, but fire protection improved due to a reduction in the rate of thermal degradation induced by the reduced PLA content. The new Oswin’s model predicted the composite adsorption isotherm well. The 30 wt.% alkali and silane treated hemp fiber composite had the lowest overall adsorption (9%) while the 50 wt.% variant produced the highest ignition temperature (181 ± 18 °C).
Frost-retted hemp fibers were investigated to assess their suitability for composite applications. Chemical analysis of frost-retted hemp fibers highlighted a high amount of solubles (pectins) at the ...fibers surface and a low lignin content in the fibers that was attributed to an unfavorable synthesis of lignin in the cell wall due to the particularly cold temperature during hemp growth in the Nordic countries. The fibers tensile properties were considered at two different scales and the performances of hemp/PLA composites were assessed. Recommendations were provided for the use of frost-retted hemp fibers in the reinforcement of thermoplastic composites.
This article investigates the effects of combining a novel protic ionic liquid-based fire retardant (FR) with alkalized hemp fiber. A pivotal importance of this study refers to the hydrophilic ...properties and limits regarding poor thermal resistance of green composites where standard guidelines for fire risks are crucial. Although it is well-studied that alkalization is essential for green composite’s moisture and mechanical durability, research on the flammability of such a combined treatment for natural fiber-reinforced biopolymer composites is lacking. The alkaline treatment used in the current study follows a process already studied as optimal, particularly for the selected hemp fiber. The fire performance was examined using a bench scale approach based on self and piloted ignition from cone calorimeter tests. The result from the Fourier-transform infrared analysis of the hemp fiber confirms phosphorylation following the fire-retardant treatment, which was visible from the morphological examination with scanning electron microscope. The presence of FR in the composites led to impactful moisture sorption. However, the FR composites demonstrated an enhanced response to fire, indicating potential use as a Class B standard for building construction, and hazard level 3 (HL3) classification as an interior material in vehicles, provided the problem of high emission of smoke is mitigated.
This research investigates an effective alkali (NaOH) treatment and fire-retardant coating to produce biocomposites from frost-retted hemp fiber and PLA. The fiber surface treatment with various NaOH ...concentrations was investigated throughout a range of soaking times. The results show that the extracted non-cellulosic fiber content increases with treatment duration and NaOH concentration, while the fraction of targeted components removed remains nearly unchanged after soaking for 1, 2, and 4 h with a 5 wt.% NaOH solution. At the composite level, the treatment with 5 wt.% NaOH solution for 1 h emerged as the most efficient, with tensile strength, Young's modulus, flexural strength, and flexural modulus of 89.6 MPa, 9.1 GPa, 121.6 MPa, and 9.6 GPa, respectively, using 30 wt.% fibrous reinforcement. The fire performance of the examined batches of biocomposites improved significantly with the novel fire-retardant (Palonot F1) coating. However, the tensile strength notably decreased, while the flexural properties showed only a slight reduction. In most cases, the biocomposites with the alkali-treated hemp fiber had delayed ignition during the 5 min exposure to the cone heater. The findings in this work contribute to studies that will be required to give design guidelines for sustainable building options.
This study investigated the effect of hemp fiber pretreatments (water and sodium hydroxide) combined with silane treatment, first on the fiber properties (microscale) and then on polylactide (PLA) ...composite properties (macroscale). At the microscale, Fourier transform infrared, thermogravimetric analysis, and scanning electron microscopy investigations highlighted structural alterations in the fibers, with the removal of targeted components and rearrangement in the cell wall. These structural changes influenced unitary fiber properties. At the macroscale, both pretreatments increased the composites' tensile properties, despite their negative impact on fiber performance. Additionally, silane treatment improved composite performance thanks to higher performance of the fibers themselves and improved fiber compatibility with the PLA matrix brought on by the silane couplings. PLA composites reinforced by 30 wt.% alkali and silane treated hemp fibers exhibited the highest tensile strength (62 MPa), flexural strength (113 MPa), and Young's modulus (7.6 GPa). Overall, the paper demonstrates the applicability of locally grown, frost-retted hemp fibers for the development of bio-based composites with low density (1.13 to 1.23 g cm
).
Birch (Betula pendula Roth) is the primary wood used for plywood manufacturing in the Baltic and Nordic regions. Birch plywood is a valuable material with superior properties to solid wood, but its ...poor flammability limits its use in building construction and transportation. Several fire-retardant impregnated spruce and birch plywood solutions are available on the market, the majority of which are based on the concept of fire-retardant pressure impregnated veneers or soaked plywood. Hence, the demand for fire-resistant plywood is increasing worldwide. However, for the plywood industry, it is crucial that any fire protection enhancement process does not significantly disrupt the current production setup. This study investigates the effect of face veneer thickness (FVT) and fire retardant (FR) concentration on the fire performance of birch plywood. The FR treatment was applied by roller coating with the main and diluted (70 %) concentrations of a new protic ionic liquid, FR. Three FVTs were evaluated: 1.0 mm, 1.5 mm and 2.6 mm. The cone heater test demonstrated that the 70 % diluted FR did not provide adequate fire protection, while the plywood batches with 2.6 mm FVT provided a better reaction to fire. Conversely, the SBI test revealed that the 1.5 mm plywood meets the EUROCLASS B requirement for building applications, mainly because of the 2.6 mm FVT's 3 % higher total heat release compared to the EUROCLASS requirement. This outcome suggests magnified non-uniformity in large samples, particularly insufficient coverage of FR despite deep penetration with 2.6 mm FVT. Given the current plywood industry practices, roller coating with the main concentration of the protic ionic liquid FR and a 1.5 mm FVT is a feasible method to improve the fire performance of birch plywood for construction applications.
•Unreserved plywood use in the construction sector demands certain fire performance.•Face veneer thickness is critical parameter for plywood fire retardant treatment.•Optimizing fire retardant spread rate is key for diverse veneer thicknesses.•Plywood with standard 1.5 mm veneer can achieve EUROCLASS B fire rating.•Fire retardant treatment effectiveness hinges more on concentration than penetration.
"Net zero whole life carbon" is an ambitious climate target that refers to neutralizing and offsetting the entire LCA-based carbon footprint of a building, including both operational and embodied ...greenhouse gas emissions. Especially in the Northern climate, viable building envelope structures must, therefore, provide good thermal insulation and low embodied emissions. Carbon offset is typically based on excess on-site renewable energy or purchased carbon offsets disconnected from the building and the site. Viable strategies for carbon neutrality start by minimizing material-related and energy-related CO2e emissions. As a result, new kinds of building envelope structures have been recently introduced in the academic literature and experimental building projects.
Traditional construction materials, such as timber and clay, have been sourced locally and processed manually, providing good results for the embodied emissions in life cycle assessment. Recent studies on clay-based construction materials have concluded that more research on clay as a construction material is needed, in particular considering its environmental performance.
One specific concern in the Northern climate is that the weather conditions limit clay construction outdoors and prevent industrial-scale application of these solutions. The methods of prefabrication can address these issues.
This study introduces the critical technical and environmental properties of a new prefabricated wall element based on a combination of light timber frame and light clay. In a hybrid light clay-timber structure, a mixture of clay and hemp shives is cast between the timber studs. On the one hand, the novelty of this wall structure is the prefabrication that enables industrial applications and upscaling without the limitations of weather conditions. On the other hand, the study assesses the climate impact of a light clay-timber wall element : cradle-to-gate emissions, thermal insulation, and the climate benefits outside the system boundary (carbon handprint) reported in the D-module of the LCA framework.
The study also shows that natural materials require a different approach than synthetic materials from industrial processes. There may be variations in the properties of hemp and clay, especially when local sourcing is prioritized for better environmental performance. Moreover, the mixing and installation processes have a significant impact on the final properties and the performance. We show that constructing a light clay wall is a knowledge-intensive process that may result in very different technical properties.
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