Search Results (6)

This paper introduced a simple, efficient method to prepare mechanically strong lignin-based foams (lignofoams) with open-cell structures using a facile baking technique. The self-expansion of lignin occurred without any additional chemical blowing agents, foaming agents, plasticizers, or lubricants. During heating, kraft lignin softened, and the internal water, either initially adsorbed or generated in situ through the dehydration of hydroxyl groups, acted as a natural blowing agent for foaming a porous foam structure. Incorporating a small amount of polypropylene (PP) enhanced mechanical properties by coating the inner walls of open cells. The porous, softened composite was then cooled to room temperature and solidified into the self-expanded lignofoam. The resulting lignofoams exhibited tunable densities ranging from 0.21 to 0.49 g/cm³ and a maximum compressive strength of 3.6 MPa. The lignofoam also showed excellent thermal insulation properties with low thermal conductive coefficients (0.057–0.098 W/mK). These features highlight the great potential of lignofoam for a bio-based thermal insulation material for construction applications. Full article

The construction sector plays a key role in climate change due to its high energy consumption and greenhouse gas emissions. Developing environmentally friendly building materials with low environmental impact is essential to improving energy efficiency. Insulation derived from agricultural waste is particularly promising due to its low ecological footprint, responsible resources use, and potential for integration into various construction systems. This study evaluates the potential of rice husk fiber as a thermal insulating material applied through the blowing technique in the Skylark 250 modular system. Rice husk fiber was morphologically and thermally characterized using scanning electron microscopy (SEM), while its thermal behavior was analyzed by thermogravimetric analysis (TGA) alongside a fire behavior assessment. Additionally, energy simulations were conducted to compare the thermal performance of rice husk fiber with other insulating materials when integrated into a building’s thermal envelope. The results showed an average thermal conductivity of 0.040 W/mK, a U-value of 0.17 W/m²K, and a heating demand of 9.56 kWh/m²-year when applied to the modular system. The material also exhibited good fire resistance, with a smoldering velocity of 3.40 mm/min. These findings highlight rice husk fiber’s potential as a sustainable insulation material for modular construction, contributing to energy efficiency and climate change mitigation. Full article

Water is the most environmentally friendly solvent; however, conventional solution spinning using water as a solvent is challenging due to its low evaporation rate. We developed a double-pronged solution blow spinning (DP-SBS) system. This spinning technique significantly enhances solvent evaporation, and the designed structure (double-pronged) avoids the common problem of needle clogging caused by heating. DP-SBS enables high-yield production of water-soluble polymer nanofibers, with a production rate of up to 5.94 g/h, which far exceeds what can be achieved with traditional electrospinning or solution blow spinning. This method is also highly efficient for producing non-water-soluble polymer nanofibers, achieving a production rate of up to 7.91 g/h, the highest reported value to date. Additionally, this approach can be used to produce not only common two-dimensional fiber membranes but also fiber sponges in a single step using the double-pronged airflow system. For the first time, chitosan nanofiber sponges were successfully produced and demonstrated to have excellent hemostatic properties in medical hemostasis. This method can also be extended to the production of other 3D nanomaterials, such as mullite nanofiber sponges, which exhibit outstanding thermal insulation performance at high temperatures. Full article

Various polyurethane foams (i.e., rigid, flexible, and spray polyurethane foams) offer diverse applications due to their unique properties, including thermal insulation, cushioning, and seamless gap filling. These foams provide solutions across industries such as construction, automotive, and refrigeration. However, the foaming process presents several challenges that may result in various defects in the final products. This work provides innovative predictive techniques for polyurethane foam expansion and applications in advanced manufacturing processes. The foaming height of the third polyurethane foaming agent (PU-3) closely aligned with the experimentally measured values. The relationship between foaming height and time is influenced by the type and concentration of catalysts, as well as the blowing agents used. However, simulations using Moldex 3D Version 2024 revealed a nonlinear relationship between foaming height and time, characterized by three distinct foaming rates. Zone B demonstrated the highest foaming rate, followed by Zone C, while Zone A showed the lowest rate. The foaming height and rate were significantly influenced by the foaming angle, with smaller angles enhancing both parameters. At a mold temperature of 30 °C and with an expansion coefficient of 35, the predicted foaming height of the polyurethane agent achieved an average accuracy of approximately 96% across four foaming angles. Based on these experimental findings, this study introduces three mechanisms involved in the foaming process of polyurethane foam components. Full article

The demand for renewable resources in building construction is increasing, and wheat straw is an excellent option due to its superior environmental performance compared to traditional insulation materials. However, the hygrothermal properties of chopped wheat straw insulation have remained largely unexplored. At the moment, blown-in straw is only blown in vertically, although horizontal blowing would be more efficient depending on the situation. This study investigates the effect of different blowing techniques on the thermal properties of chopped wheat straw insulation, focusing on the difference between vertical and horizontal blowing techniques. In-situ-measured thermal conductivities were compared with design values used in energy balances. In addition, the long-term hygrothermal behavior of chopped wheat straw insulation treated with flame retardants was investigated. The methodology included heat flow plate measurements, needle probe measurements and laboratory measurements using the hot plate method. The results show that there is no significant difference in thermal performance between the blowing techniques. The measured thermal conductivities were lower than expected, challenging the current general normative moisture surcharge on the thermal conductivity of natural fiber insulation. The addition of the flame retardant had no noticeable effect on the hygrothermal properties of the chopped straw. Chopped wheat straw can be regarded as a highly ecological insulation material with great potential for the future. Full article

Houses in the operational stage consume around 40% of the world’s energy, and most of it is consumed by air conditioning. This generates several problems, especially in cities, where biomass combustion is the most widely used form of heating. For this reason, environmental regulation works in parallel with energy efficiency, where efficient and low-impact thermal insulating materials are key to reduce the energy demand and fuel consumption to generate comfort in dwellings. This work considers the valorization of wheat straw from the Araucanía region of Chile, to develop a prototype for a thermal insulating material applied through the blowing technique. The results show the insulation potential of the fiber, which, in post-chopping conditions and at an average density of 80 [kg/m³], has thermal conductivity of 0.034 [W/mK]. This value is much better than that of glass wool and other inorganic materials sold in the Chilean market. In addition, the developed material can be incorporated into partitions using the blowing technique, improving the execution time for the thermal insulation section. Finally, it is indicated that a good option to install a processing plant is in the central valley of the region, specifically in the communes of Victoria and Perquenco. Full article