Search Results (71)

In this study, we tested a flexible polyurethane (PU) foam, synthesized from bio-based components, for the removal of petroleum-derived fuels from water samples. The PU was synthesized via the prepolymer method through the reaction of PEG 400 with L-lysine ethyl ester diisocyanate (L-LDI), followed by chain extension with 2,5-bis(hydroxymethyl)furan (BHMF), a renewable platform molecule derived from carbohydrates. Freshwater and seawater samples were artificially contaminated with commercial diesel, gasoline, and kerosene. Batch adsorption experiments revealed that the total sorption capacity (S, g/g) of the PU was slightly higher for diesel in both water types, with values of 67 g/g in freshwater and 70 g/g in seawater. Sorption kinetic analysis indicated that the process follows a pseudo-second-order kinetic model, suggesting strong chemical interactions. Equilibrium data were fitted using Langmuir and Freundlich isotherm models, with the best fit achieved by the Langmuir model, supporting a monolayer adsorption mechanism on homogeneous surfaces. The PU foam can be regenerated up to 50 times by centrifugation, maintaining excellent performance. This study demonstrates a promising application of this sustainable and bio-based polyurethane foam for environmental remediation. Full article

This review examines the chemical functionalization of Camelina, hemp, and rapeseed oils for the development of sustainable bio-based resins. Key strategies, including epoxidation, acrylation, and click chemistry, are discussed in the context of tailoring molecular structure to enhance reactivity, compatibility, and material performance. Particular emphasis is placed on overcoming the inherent limitations of vegetable oil structures to enable their integration into high-performance polymer systems. The agricultural sustainability and environmental advantages of these feedstocks are also highlighted alongside the technical challenges associated with their chemical modification. Functionalized oils derived from Camelina, hemp, and rapeseed have been successfully applied in various resin systems, including protective coatings, pressure-sensitive adhesives, UV-curable oligomers, and polyurethane foams. These advances demonstrate their growing potential as renewable alternatives to petroleum-based polymers and underline the critical role of structure–property relationships in designing next-generation sustainable materials. Ultimately, the objective of this review is to distill the most effective functionalization pathways and design principles, thereby illustrating how Camelina, hemp, and rapeseed oils could serve as viable substitutes for petrochemical resins in future industrial applications. Full article

Polyurethanes (PUs) are extremely versatile materials used across different industries. Traditionally, they are synthesized by reacting polyols and isocyanates, both of which are petroleum-derived reagents. In response to the demand for more eco-friendly materials, research has increasingly focused on developing new routes for PU synthesis using renewable feedstocks. While substituting isocyanates remains a greater challenge, replacing fossil-based polyols with bio-based alternatives is now a promising strategy. This review explores the main natural sources and their transformations into bio-polyols, the incorporation of bio-fillers into PU formulations, and the production of non-isocyanate polyurethanes (NIPUs). Additionally, the study summarizes the growing body of research that has reported successful outcomes using bio-polyols in PU foams for distinct applications. Full article

Flexible polyurethane foams are a diverse class of materials encompassing furniture, packaging, automotive, and many other industrial and domestic applications. Polyurethane foams are synthesized by the addition of polyols and isocyanates; however, the petroleum origin and toxic nature of isocyanates have driven many to look for more sustainable routes to production. Renewable fillers have emerged as a biobased resource to decrease the carbon footprint of this widely used polymeric material. In this study, soy hulls, as mass-produced, industrial by-products of soybean production, were used to create a biochar beneficial in the synthesis of flexible polyurethane foam composites. The addition of soy hull biochar was found to maintain the compression properties of foams at a decreasing isocyanate index, reducing the amount of isocyanates needed for production. In addition, the addition of biochar decreased the flammability of foams, important for many applications where consumer safety is important. The results point to the ability to create safer, more sustainable, and even more cost-effective polyurethane foams through the reduction in isocyanate use while maintaining the properties of this important class of polymers. Full article

The key challenge in polymer science is developing sustainable synthesis methods using renewable feedstocks. This study explores plant-derived diarylheptanoids with various structures as the building blocks for polyurethane (PU) materials. Diarylheptanoid glucosides isolated from black alder (Alnus glutinosa) bark were hydrolyzed and fractionated to remove sugar moieties. The resulting diarylheptanoids, along with unhydrolyzed analogues and curcumin, were used as biomass-based polyols to synthesize model PU films. Incorporating diarylheptanoids enhanced the mechanical strength and reduced the flexibility of PU due to increased crosslinking, with effects proportional to the OH functionality of the biomass-based polyols. Weight loss, FTIR, and Py-GC-MS/FID analyses revealed that the catechol moieties and the glucosidic bonds are biodegradable structural subunits of diarylheptanoids incorporated into PU films. Rigid polyurethane foams (PURs) incorporating high-OH-functionality diarylheptanoid glucosides such as oregonin demonstrated significantly higher compression strength and less weight loss during non-isothermal thermal analysis in air compared to those of commercial polyol-based foams. A cone calorimeter test showed that the PUR foam with diarylheptanoid derivatives had a lower degradation rate, a longer flame-burning time, 30% less heat emission, and 25% less smoke, indicating improved flame retardancy. Adding 1–2% oregonin-enriched black alder bark extracts to commercial Elastopir 1132/509/0 PUR foam significantly improved its resistance to thermal oxidative aging, outperforming the commercial antioxidant Irganox. Full article

Rigid polyurethane foam (RPUF) is a widely utilized thermosetting polymer across various industrial applications, valued for its exceptional properties. However, the demand for sustainable alternatives to petroleum-based polymers has grown increasingly urgent due to rising environmental concerns. Despite its widespread use, RPUF faces challenges such as inadequate mechanical strength, limited thermal stability, and high flammability, all of which are crucial considerations in commercial and household applications. Globally, ongoing efforts are focused on developing innovative technologies that convert renewable sources into new monomers and polymers, some of which could serve as alternatives to traditional RPUFs. Several approaches have been explored to improve the thermal stability, mechanical strength, and flame retardancy of RPUFs, including the modification of bio-based polyols and the incorporation of performance-enhancing fillers. This review emphasizes recent advances in RPUFs derived from natural resources, focusing on their preparation, characterization, and properties, and strategies to enhance the mechanical strength and flame safety of bio-based RPUFs. Additionally, it explores the applications of RPUF materials across various fields, addressing the challenges and potential developments in packaging, household items, construction, and automotive applications. Full article

The use of black alder (BA) bark biomass in rigid polyurethane (PUR) foam compositions was the main task of investigation. Extractive compounds isolated from the bark through hot water extraction were used as precursors for bio-polyol synthesis via acid-free liquefaction with the polyether polyol Lupranol 3300 and through oxypropylation with propylene carbonate. The OH functionality and composition of the polyols were analyzed via wet chemistry and FTIR spectroscopy. The solid remaining after the isolation of extractive compounds was also utilized as a natural filler in PUR foams. The effects of replacing commercial polyols with bio-polyols on the foam rising rate and their mechanical properties, morphology, thermal conductivity, and thermal degradation characteristics were examined. The oxypropylated extractive-based PUR compositions demonstrated the most favorable balance between the biomass content and material properties. At an apparent density of 40 kg/m³, the compressive strength of the produced foams was enhanced by 1.4–1.5 times, while the maximum thermal degradation rate in air decreased by 3.8–6.5 times compared to reference materials without adversely affecting the foam morphology. The composition based on liquefied extractives showed lower performance but still improved properties relative to the reference foams. Introducing 3.7–14% of extracted bark into the foam compositions increased the biomass content to 22–24%, although this led to a decrease in the compressive strength and thermal stability. It was shown that partially substituting fossil-derived components with renewable bark biomass in the composition of PUR foams allows for materials with characteristics similar or better to petrochemical-based materials to be obtained. Therefore, the results presented can be considered a contribution to addressing environmental problems and promoting the development of a sustainable economy. Full article

Within the range of composite laminates for structural applications, sandwich laminates are a special category intended for applications characterized by high flexural stresses. As it is well known from the technical literature, structural sandwich laminates have a simple configuration consisting of two skins of very strong material, to which the flexural strength is delegated, between which an inner layer (core) of light material with sufficient shear strength is interposed. As an example, a sandwich configuration widely used in civil, naval, and mechanical engineering is that obtained with fiberglass skins and a core of various materials, such as polyurethane foam or another lightweight material, depending on the application. Increasingly stringent regulations aimed at protecting the environment by reducing harmful emissions of carbon dioxide and carbon monoxide have directed recent research towards the development of new composites and new sandwiches characterized by low environmental impact. Among the various green composite solutions proposed in the literature, a very promising category is that of high-performance biocomposites, which use bio-based matrices reinforced by fiber reinforcements. This approach can also be used to develop green sandwiches for structural applications, consisting of biocomposite skins and cores made by low-environmental impact or renewable materials. In order to make a contribution to this field, a structural sandwich consisting of high-performance sisal–epoxy biocomposite skins and an innovative renewable core made of balsa wood laminates with appropriate lay-ups has been developed and then properly characterized in this work. Through a systematic theoretical–experimental analysis of three distinct core configurations, the unidirectional natural core, the cross-ply type, and the angle-ply type, it has been shown how the use of natural balsa gives rise to inefficient sandwiches, whereas performance optimization is fully achieved by considering the angle-ply core type [±45/90]. Finally, the subsequent comparison with literature data of similar sandwiches has shown how the optimal configuration proposed can be advantageously used to replace synthetic glass–resin sandwiches widely used in various industrial sectors (mechanical engineering, shipbuilding, etc.) and in civil engineering. Full article

The growing demand for viscoelastic polyurethane foams creates a need for new sustainable raw materials that support cost-effective production while maintaining the desired material performance and fire safety standards. In this regard, our study aimed to develop viscoelastic polyurethane foam composites with reduced flammability and a high proportion of renewable raw materials. To achieve this, blackcurrant pomace, expandable graphite and a third-generation blowing agent were introduced to a viscoelastic polyurethane foam composition containing a reactive flame retardant in the formulation. The effects of the incorporated additives on the foaming process, flammability, chemical structure, cellular structure, thermal properties and physico-mechanical properties of the composites were determined. The results showed that the viscoelastic foam composite containing 30 php of blackcurrant pomace and 15 php of expandable graphite had a pHRRmax 52% lower than that of the reference material. The additional use of a blowing agent enhanced the flame-retardant effect of the materials, resulting in a 67% reduction in pHRRmax of the composite compared to the reference material. Moreover, the developed biocomposites exhibited promising limiting oxygen index values of 26–28%, compared to the 21% shown for the reference sample. Consequently, the best-performing biocomposites achieved the V-0 flammability rating according to the UL-94 standard. This study’s results indicate the composites’ high application potential due to their reduced flammability and the materials’ desirable physical and mechanical properties. Full article

Polyurethane (PU) foams are cellular polymeric materials that have attracted much attention across various industries because of their versatile properties and potential for multifunctional applications. PU foams are involved in many innovations, especially in multi-functional and high-performance applications. Special attention is given to developing tailored PU foams for specific application needs. These foams have various applications including flame retardancy, sound absorption, radar absorption, EMI shielding, shape memory, and biomedical applications. The increasing demand for materials that can perform multiple functions while maintaining or enhancing their core properties has made PU foams a focal point of interest for engineers and researchers. This paper examines the challenges faced by the PU foam industry, particularly in developing multifunctional products, as well as the strategies for improving sustainability, such as producing PU foams from renewable resources and recycling existing materials. Full article

The European Climate Law mandates a 55% reduction in CO₂ emissions by 2030, intending to achieve climate neutrality by 2050. To meet these targets, there is a strong focus on reducing energy consumption in buildings, particularly for heating and cooling, which are the primary drivers of energy use and greenhouse gas emissions. As a result, the demand for energy-efficient and sustainable buildings is increasing, and thermal insulation plays a crucial role in minimizing energy consumption for both winter heating and summer cooling. This review explores the historical development of thermal insulation materials, beginning with natural options such as straw, wool, and clay, progressing to materials like cork, asbestos, and mineral wool, and culminating in synthetic insulators such as fiberglass and polystyrene. The review also examines innovative materials like polyurethane foam, vacuum insulation panels, and cement foams enhanced with phase change materials. Additionally, it highlights the renewed interest in environmentally friendly materials like cellulose, hemp, and sheep wool. The current challenges in developing sustainable, high-performance building solutions are discussed, including the implementation of the 6R principles for insulating materials. Finally, the review not only traces the historical evolution of insulation materials but also provides various classifications and summarizes emerging aspects in the field. Full article

Polyurethanes (PUs) are one of the most versatile polymeric materials, making them suitable for a wide range of applications. Currently, petroleum is still the main source of polyols and isocyanates, the two primary feedstocks used in the PU industry. However, due to future petroleum price uncertainties and the need for eco-friendly alternatives, recent efforts have focused on replacing petrol-based polyols and isocyanates with counterparts derived from renewable resources. In this study, waste cooking oil was used as feedstock to obtain polyols (POs) for new sustainable polyurethane foams (PUFs). POs with various hydroxyl numbers were synthesized through epoxidation followed by oxirane ring opening with diethylene glycol. By adjusting reagent amounts (acetic acid and H₂O₂), epoxidized oils (EOs) with different epoxidation degrees (50–90%) and, consequently, POs with different OH numbers (200–300 mg KOH/g) were obtained. Sustainable PUFs with high bio-based content were produced by mixing the bio-based POs with a commercial partially bio-based aliphatic isocyanate and using water as the blowing agent in the presence of a gelling catalyst and additives. Various water (4, 8, 15 php) and gelling catalyst (0, 1, 2 php) amounts were tested to assess their effect on foam properties. PUFs were also prepared using EOs instead of POs to investigate the potential use of EOs directly in PUF production. Characterization included morphological, chemical, physical, thermal, and mechanical analyses. The rigid PUFs exhibited high density (150–300 kg/m³) and stability up to 200 °C. The combined use of bio-based polyols with partially bio-based isocyanate and water enabled PUFs with a bio-based content of up to 77 wt.%. EOs demonstrated potential in PUF production by bypassing the second synthesis step, enhancing sustainability, and significantly reducing energy and costs; however, PUF formulations with EOs require optimization due to lower epoxy ring reactivity. Full article

Cryogenics is the science and technology of very low temperatures, typically below 120 K. The most common applications are liquified natural gas carriers, ground-based tanks, and propellant tanks for space launchers. A crucial aspect of cryogenic technology is effective insulation to minimise boil-off from storage tanks and prevent frost build-up. Rigid closed-cell foams are prominent in various applications, including cryogenic insulation, due to their balance between thermal and mechanical properties. Polyurethane (PU) foam is widely used for internal insulation in cryogenic tanks, providing durability under thermal shocks and operational loads. External insulation, used in liquified natural gas carriers and ground-based tanks, generally demands less compressive strength and can utilise lower-density foams. The evolution of cryogenic insulation materials has seen the incorporation of environmentally friendly blowing agents and bio-based polyols to enhance sustainability. Fourth-generation physical blowing agents, such as HFO-1233zd(E) and HFO-1336mzz(Z), offer low global warming potential and improved thermal conductivity. Additionally, bio-based polyols from renewable resources like different natural oils and recycled polyethylene terephthalate (PET) are being integrated into rigid PU foams, showing promising properties for cryogenic applications. Research continues to optimise these materials for better mechanical performance and environmental impact. Full article

Polyurethanes (PU) have drawn great attention due to their excellent mechanical properties and self-healing and recyclable abilities. Lignin is a natural and renewable raw material in nature, composed of a large number of hydroxyl groups, and has a great potential to replace petroleum polyols in PU synthesis. This review summarizes the recent advances in modification methods such as the liquefaction, alkylation, and demethylation of lignin, and a systematic analysis of how to improve the reactivity and monomer substitution of lignin during polyurethane synthesis for the green manufacturing of high-performance polyurethanes was conducted. Polyurethane can be used in the form of films, foams, and elastomers instead of conventional materials as a dielectric or substrate material to improve the reliability and durability of flexible sensors; this review summarizes the green synthesis of polyurethanes and their applications in flexible electronics, which are expected to provide inspiration for the wearable electronics sector. Full article

The utilization of polyols derived from renewable sources presents an opportunity to enhance the sustainability of rigid polyurethane (PUR) foams, thereby contributing to the advancement of a circular bioeconomy. This study explores the development of PUR rigid foams exclusively using polyols sourced from second-generation renewable biomass feedstocks, specifically depolymerized birch bark suberin (suberinic acids) and tall oil fatty acids. The polyols achieved a total renewable material content as high as 74%, with a suberinic acid content of 37%. Response surface modeling was employed to determine the optimal bio-polyol, blowing agents, and catalyst content, hence, optimizing the bio-based foam formulations. In addition, response surface modeling was applied to rigid PUR foam formulations based on commercially available petroleum-based polyols for comparison. The results, including apparent density (~40–44 kg/m³), closed cell content (~95%), compression strength (>0.2 MPa, parallel to the foaming direction), and thermal conductivity (~0.019 W/(m·K)), demonstrated that the suberinic acids-based rigid PUR foam exhibited competitive qualities in comparison to petroleum-based polyols. Remarkably, the bio-based rigid PUR foams comprised up to 29% renewable materials. These findings highlight the potential of suberinic acid-tall oil polyols as effective candidates for developing rigid PUR foams, offering promising solutions for sustainable insulation applications. Full article