Search Results (54)

In this work, rigid polyurethane materials were synthesized via a one-step polymerization method using isocyanate (MDI) and polyether polyol (4110S) as the main raw materials, with 1, 4-butanediol (BDO), 1, 6-hexanediol (HDO), diethylene glycol (DEG), and dipropylene glycol (DPG) as chain extenders. The influence of chain extender structure on the mechanical properties of rigid polyurethane was systematically investigated. The results indicate that when BDO was employed as a chain extender, the polyurethane exhibited the most uniform pore size distribution and the best mechanical properties. It was found that hydrogen bonding plays a dual role: on the one hand, it promotes microphase separation between soft and hard segments; on the other hand, it extends the molecular chains’ length, which hinders segment separation and consequently constrains its mechanical properties. Further analysis reveals that the influence of molecular chain length on mechanical properties outweighs that of polarity. Full article

Epoxy resins often require toughening to broaden their engineering applications, such as in durable concrete repair. This study addresses this need by developing high-performance polyurethane/epoxy (PU/EP) interpenetrating polymer networks (IPNs). The composites were synthesized via prepolymer and stepwise methods using polyether polyol (PPG-1000), isocyanate (MDI-50), and E51 epoxy. At an optimal PU prepolymer content of 15 wt%, the polyether-based IPNs achieved a balanced mechanical profile (tensile strength: 59.90 MPa; elongation at break: 6.46%; compressive strength: 69.99 MPa). Further tuning of the soft segment by introducing polyester polyol (PS-2412) yielded superior performance at a PS-2412/PPG-1000 ratio of 30/70. This formulation increased tensile and compressive strengths by 11.4% and 6.07% (to 66.74 MPa and 74.24 MPa), and dry and wet bond strengths by 12.1% and 36.3% (to 5.68 MPa and 4.62 MPa), respectively. The enhancement is attributed to the increased crosslinking density and more uniform network structure imparted by PS-2412, which improves stress distribution and interfacial adhesion. This work provides an effective soft-segment design strategy for fabricating toughened epoxy composites with robust mechanical and adhesive properties. Full article

Systemic anticancer therapy causes a number of side effects; therefore, local drug release devices may play an important role in this area. In this study, we developed polyurethane-dendrimer foams containing different amounts of third-generation poly (amidoamine) dendrimers (PAMAM G3) to evaluate their ability to encapsulate and release the model anticancer drug doxorubicin (DOX), as well as their biocompatibility and effectiveness against normal and cancer cells in vitro. PU–PAMAM foams containing 10–50 wt% PAMAM G3 were prepared using glycerin-based polyether polyol and castor oil as co-components. Structural and rheological analyses revealed that foams containing up to 20 wt% PAMAM G3 exhibited a well-developed porous structure, while higher dendrimer loadings (≥30 wt%) led to irregular cell shapes, pore coalescence, and thinning of cell walls, and indicated a gradual loss of structural integrity. Rheological creep–recovery measurements confirmed the structural findings: moderate PAMAM G3 incorporation (≤20 wt%) increased both the instantaneous and delayed elastic modulus (E₁ ≈ 130–140 kPa; E₂ ≈ 80 kPa) and enhanced elastic recovery, reflecting improved cross-link density and foam stability. Higher dendrimer contents (30–50 wt%) caused a decline in these parameters and higher viscoelastic compliance, indicating a softer, less stable structure. The DOX loading capacity and encapsulation efficiency increased with PAMAM G3 content, reaching maximum values of 35% and 51% for 30–40 wt% PAMAM G3, respectively. However, the most sustained DOX release profiles were observed for matrices containing 20 wt% PAMAM G3. Analysis of cumulative release and kinetic modeling revealed a transition from diffusion-controlled release at low PAMAM contents to burst-dominated release at higher dendrimer loadings. Importantly, matrices containing 10–20 wt% PAMAM G3 also indicated selective anticancer action against squamous cell carcinoma (SCC-15) compared to non-cancerous human keratinocytes (HaCaT). Moreover, the DOX they released effectively destroyed cancer cells. Overall, PU–PAMAM foams containing 10–20 wt% PAMAM G3 provide the most balanced combination of structural stability, controlled drug release, and cytocompatibility. These materials therefore represent a promising platform as passive carriers in drug delivery systems (DDSs), such as local implants, anticancer patches, or bioactive wound dressings. Full article

This study explores the potential of pine bark—a highly accessible and underexploited by-product of forestry and food processing—as a renewable raw material for rigid polyurethane (PUR) foam production. Under optimal extraction conditions, water-soluble extractives rich in carbohydrates were isolated from biomass with a yield of 25% and subsequently condensed with propylene carbonate (PC) to produce bio-based polyols. The polyols synthesized at a PC/OH molar ratio ranging from 1 to 5 were incorporated into rigid PUR foam formulations as substitutes for commercial polyether polyols. The foams containing bio-polyols synthesized at a PC/OH ratio of 3 demonstrated the highest compressive strength and thermal insulation performance, exceeding those of the reference material by 30% and 9%, respectively, and exhibited enhanced thermo-oxidative stability. Incorporation of extracted bark up to 10 wt% as a filler in the PUR matrix led to a decrease in mechanical properties to the level of the reference foam and a 19% reduction in thermal insulation capacity, without affecting the closed-cell content. Cone calorimetry revealed that both filled and unfilled bio-polyol-based PUR foams exhibited lower degradation rate, heat release rate, and total smoke release compared with the reference material, indicating reduced flammability and a lower tendency toward fire propagation. Full article

A biodegradable, lightweight substrate for facility-based stereoscopic planting was developed via a one-step polyurethane foaming process. The substrate was synthesized by incorporating a biomass mixture of bamboo charcoal and cassava flour into a polyurethane foam matrix. This study investigated the effects of varying the content ratios of polyether polyol, isocyanate, bamboo charcoal powder, and cassava flour on the structural and functional properties of the composite foam. Results indicated that the biomass blend significantly influenced the foam’s physicochemical properties, water retention capacity, hardness, and elasticity. Specifically, bamboo charcoal powder enhanced the porosity and degradation rate of the foam, whereas the swelling of cassava flour upon water absorption improved the matrix’s resilience and cohesion. A polyether polyol/isocyanate ratio of 4:1 yielded a substrate with superior physicochemical properties, water retention capacity, germination rate, seedling index, and plant dry weight. Subsequently, the optimal overall performance was achieved at a biomass/polyol–isocyanate ratio of 1:3. This optimal formulation exhibited a degradation rate of 6.24 ± 0.94%, porosity of 66.07 ± 1.10%, and water retention capacity of 86.03 ± 1.59%. Consequently, it also produced the highest seed germination rate (84 ± 5.16%), seedling index (12.49 ± 1.94), and mature plant dry weight (4.00 ± 0.51 g). Microscopic analysis confirmed that the biomass addition refined the substrate’s pore structure, leading to greater uniformity and stability of the internal pores. This enhancement reduced the foam’s susceptibility to collapse and improved its elasticity and cohesion, thereby making it more amenable to mechanized handling and planting operations. Full article

A series of polyether and poly(ether carbonate) polyols have been synthesized via Zn(II)-Co(III) double metal cyanide (DMC)-catalyzed ring-opening (co)polymerization of various epoxides, such as propylene oxide, 1,2-epoxybutane, epichlorohydrin, styrene oxide, and glycidol, with and without CO₂. The resulting polyether polyols exhibit linear and branched architectures (degrees of branching, DB = 0.27), high catalytic activities with turnover frequencies up to 461 min⁻¹, narrow dispersities (1.15–1.25), and low levels of unsaturation (0.004 meq g⁻¹). The DMC catalysts also enable the efficient synthesis of poly(propylene carbonate) polyol with carbonate contents up to 40% and yields reaching 63%. Additionally, branched poly(ether carbonate) polyols with tunable DB values (0.14–0.21), yields up to 70%, and carbonate contents up to 33% are synthesized via CO₂ fixation to glycidol. The synthesized polyols hold strong potential for industrial applications in polyurethanes and other advanced materials, offering versatile performance for use in coatings, adhesives, sealants, and elastomers. Overall, this study highlights the effectiveness of DMC catalysts in producing high-performance polyols, contributing to the development of sustainable materials with precise architectural control. Full article

Alkali-activated materials have gained increasing popularity in the field of soil barrier materials due to their high strength and low environmental impact. However, barrier materials made from alkali-activated materials still suffer from long setting times and poor barrier performance in acidic, alkaline, and saline environments, which hinders the sustainable development of green alkali-activated materials. Herein, coconut shell biochar, sodium silicate-based adhesives, and polyether polyol/polypropylene polymers were used for multi-stage material modification. The modified materials were evaluated for barrier performance, rapid formation, and resistance to acidic, alkaline, and saline environments, using metrics such as compressive strength, permeability, mass loss, and VOC diffusion efficiency. The results indicated that adhesive modification reduced the material’s setting time from 72 to 12 h. Polymer modification improved resistance to corrosion by 15–20%. The biochar-containing multi-stage modified materials achieved VOC diffusion barrier efficiency of over 99% in both normal and corrosive conditions. These improvements are attributed to the adhesive accelerating calcium silicate hydration and forming strength-enhancing compounds, the polymer providing corrosion resistance, and biochar enhancing the volatile organic compounds (VOC) barrier properties. The combined modification yielded a highly effective multi-stage green barrier material suitable for rapid barrier formation and corrosion protection. These findings contribute to evaluating multi-level modified barrier materials’ effectiveness and potential benefits in this field and provide new insights for the development of modified, green, and efficient alkali-activated barrier materials, promoting the green and sustainable development of soil pollution control technologies. Full article

The growing production of polyurethane foam (PUF) and increasing global PUF waste generation urges the development of a circular economy strategy to promote the recovery of its raw materials, namely polyether polyols, in a sustainable and economically feasible way. This work assesses the promising microwave-assisted PUF aminolysis technology from three different perspectives: (a) evaluating the experimental feasibility and characteristics of the recycled products; (b) modeling an industrially relevant holistic process based on experimental findings to assess energy requirements and c) comparing the environmental impacts ascribed to the production of virgin vs. recycled polyols. The most relevant findings are as follows: (1) the recycled polyols out of MW-aminolysis are indistinguishable from virgin polyols; (2) the potential energy consumption of the overall process (including post-processing steps) for a continuous PUF depolymerization process with a 14.8 kg/h RP production capacity is as low as 1.9 kWh/kg RP and (3) recycled polyols have a substantially lower environmental footprint than virgin polyols in all selected impact categories, ranging from a reduction in CO₂ emissions (38% decrease) to water consumption (74% decrease). These results and analyses pave the way for enhancing material circularity in the PU sector. Full article

In this study, isosorbide (ISB), a bio-based compound derived from the dehydration of D-sorbitol, was used as a sustainable resource to produce various types of rigid polyurethane foams (RPUFs). Featuring a rigid bicyclic structure and two hydroxyl groups, ISB was solubilized in polyether polyol at concentrations up to 10 wt% for RPUF production. ISB-based RPUFs exhibited smaller and more uniform cell sizes, along with a 4% increase in closed-cell content, resulting in improved thermal insulation with a 4.69% reduction in thermal conductivity. Additionally, the compressive strength increased by up to 31%, enhancing the material’s durability. The compatibility of ISB with conventional raw materials and its unique structure contributed to these improvements. The reversible urethane bond formation of ISB was also observed, influencing cell structure during foaming. These results indicate that ISB can effectively improve both the thermal insulation properties and material durability under compression of RPUFs, making it a promising material for sustainable 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

In this paper, we investigated the efficient metal-free phosphorus–nitrogen (PN) catalyst and used the PN catalyst to degrade waste PU with two-component binary mixed alcohols as the alcohol solvent. We examined the effects of reaction temperature, time, and other factors on the hydroxyl value and viscosity of the degradation products; focused on the changing rules of the hydroxyl value, viscosity, and molecular weight of polyols recovered from degradation products with different dosages of the metal-free PN catalyst; and determined the optimal experimental conditions of reaction temperature 180 °C, reaction time 3 h, and PN dosage 0.08%. The optimal experimental conditions were 180 °C, 3 h reaction time, and 0.08% PN dosage, the obtained polyol viscosity was 3716 mPa·s, the hydroxyl value was 409.2 mgKOH/g, and the number average molecular weight was 2616. The FTIR, ¹H, NMR, and other tests showed that the waste urethanes were degraded into oligomers successfully, the recycled polyether polyols were obtained, and a series of recycled polyurethanes with different substitution ratios were then prepared. A series of recycled polyurethane materials with different substitution rates were then prepared and characterized by FTIR, SEM, compression strength, and thermal conductivity tests, which showed that the recycled polyurethane foams had good physical properties such as compression strength and apparent density, and the SEM test at a 20% substitution rate showed that the recycled polyol helped to improve the structure of the blisters. Full article

Polyurethane materials, widely used in indoor environments, occasionally exhibit unpleasant odors. An important source of polyurethane odorants is polyether polyols. Previous studies identified odorous 2-ethyldimethyl-1,3,6-trioxocanes in polyurethane materials and polyols but did not investigate the odor activity of the individual isomers. In the present work, an isomer mixture of the precursor dipropylene glycol was fractionated through preparative high-performance liquid chromatography. After the conversion to the corresponding trioxocanes, gas chromatography-olfactometry analyses revealed that just one positional isomer, namely 2-ethyl-4,7-dimethyl-1,3,6-trioxocane, was odor active. Moreover, we observed clear differences in the odor threshold concentrations among its stereoisomers. Only two out of eight isomers displayed an odor, both with an earthy smell and one being approximately 60 times more potent than the other. These insights contribute to a better understanding of polyurethane odor on a molecular level and provide a basis for effective odor control. Full article

In this study, a new environmentally friendly and efficient method for recycling and reusing waste polyurethane sheets is proposed. SiO₂ aerogel was prepared using the sol–gel method, and mullite whiskers were introduced to enhance its toughness. The whisker-toughened aerogel was used in the degradation of waste polyurethane to produce modified recycled polyol, which was subsequently used to prepare recycled polyurethane foam insulation material. Following a series of tests, including Fourier-transform infrared spectroscopy, apparent density, viscosity, heat loss, and thermal conductivity, the results showed that when the aerogel with wt% = 0.9% mullite whiskers and 0.06 g of whisker-toughened aerogel were added, the viscosity was close to that of polyether polyol 4110. The optimal compressive strength of the resulting composite blister structure reached 817.93 MPa, with a thermal conductivity of 0.0228 W·(m·K)⁻¹, demonstrating good thermal stability. These results indicate that the whisker-toughened aerogel effectively reduces the viscosity of the degraded materials and significantly improves the mechanical properties and thermal stability of the regenerated polyurethane thermal insulation materials. This research provides new ideas and new methods for waste polyurethane recycling and offers a new perspective for the research and development of thermal insulation materials. Full article

This study aimed to enhance the initial adhesion performance of reactive polyurethane hot-melt adhesives by using a bio-based polycarbonate polyol instead of traditional polyester or polyether polyols and by incorporating thermoplastic polyurethane (TPU) in varied proportions. Adhesives synthesized from bio-based polycarbonate polyols and polypropylene glycol with MDI as the isocyanate were characterized chemically, thermally, and mechanically (FTIR, DSC, plate–plate rheology, DMA, and T-peel strength test). Adding 10–15 wt.% TPU significantly improved green strength and initial adhesion at room temperature and after accelerated cooling. The bio-based polycarbonate polyol promotes superior flexibility at low temperatures compared to fossil-derived alternatives, aligning with sustainability objectives. The results showed that 10 wt.% TPU maximized green strength without compromising flexibility, whereas 15 wt.% TPU, though enhancing adhesion, reduced flexibility due to increased crystallinity. T-peel tests on footwear materials indicated that all the adhesives exceeded the EN 15307:2015 requirements, with the highest peel strength achieved after curing. These findings highlight the benefit of bio-based polycarbonate polyols and TPUs in achieving strong, flexible, and eco-friendly adhesives suitable for demanding applications. Full article

With the increasing drilling depth of mines, the cross-complexity of fissures in the rock body, and the frequent occurrence of sudden water surges, polymer slurry, with its advantages of good permeability and strong water plugging, is increasingly used in mine grouting projects. Additional research is needed in order to further improve the grouting performance of polymer slurry, ensure the safety of mining operations, and reduce the grouting cost. In this paper, a polymer composite grouting material was prepared with diphenyl methyl diisocyanate, polyether polyol, and fly ash, as the main raw materials, with coupling agent and catalyst as auxiliary reagents. The performance of the composite grouting material in terms of mechanical properties, thermal stability, hydrophobicity, and bonding was explored. This study’s findings indicated that incorporating fly ash led to notable enhancements in the thermal stability and water resistance of the polymer slurry. Furthermore, the introduction of fly ash notably raised the starting degradation temperature of the polymer, boosted the water contact angle of the composite material, and reduced the density and reaction temperature of the composite material. In addition, the catalyst and coupling agent as auxiliary reagents affected the polymers in terms of mechanical properties; in this paper, dibutyltin dilaurate was used as the catalyst, and organosilanes were used as the coupling agent. The catalyst successfully sped up the polymer’s gel time, however, an excessive quantity of catalyst compromised the polymer’s mechanical characteristics. The addition of organosilanes has a positive effect on the dynamic mechanical properties of the composites, fracture toughness, compression, bending, and bond strength. The research can offer a theoretical direction for creating polymer mixtures in mine grouting projects. Full article