Two polyurethane polyaniline nanocomposites have been synthesized using two in situ polymerization routes of dried and wet bases to valorize the polyurethane waste. The physical and chemical properties of polyurethane-based nanocomposites were compared using SEM, XRD, FTIR, and Zeta potential. SEM images showed that the average particle size of the dried-based composite was 56 nm, while the wet-based composite had an average size of 75 nm. The separation efficiency for methylene blue (MB) and Congo red (CR) dyes was evaluated against free polyurethane foam waste. It was evident that pure polyurethane (PPU) achieved only 4.79% and 16.71% removal for MB and CR, respectively. These dye decontamination efficiencies were enhanced after nano polyaniline decoration of polyurethane foam either through dried base polymerization (DPUP) or wet base polymerization (WPUP). WPUP composite records 11.23% and 85.99% for MB and CR removal, respectively, improved to 26.69% and 90.07% removal using DPUP composite for the respective dyes. The adsorption kinetics, isotherms, and thermodynamics were investigated. The experimental results revealed the pseudo-second-order kinetic model as the most accurately described kinetics model for both CR and MB adsorption. The Langmuir model provided the best fit for the data, with maximum adsorption capacities of 110.98 mg/g for CR and 26.86 mg/g for MB, with corresponding R-squared values of 0.9974 and 0.9608, respectively. Regeneration and reusability studies of PPU, WPUP, and DPUP showed effective reusability, with DPUP displaying the highest adsorption capacity. These results aid in creating eco-friendly and cost-efficient adsorbents for dye removal in environmental sanitation.

This study investigates the incorporation of algae-based activated carbon into polyurethane foam to improve a biocomposite for gasoil sorption. The biocomposites were thoroughly analyzed using various techniques to examine the properties of both the blank foam and the algae activated carbon foam with a carbon content of 4.41 mass% and particle diameter of 500 µm. These techniques included Scanning Electron Microscopy (SEM), thermogravimetric analysis (TGA), and density analysis. The TGA analysis revealed that the biocomposites had an impact on the onset temperature (Tonset) of the foams. Higher concentrations of the biocomposites resulted in a decrease in Tonset from approximately 310 °C in the blank foam (PUF0) to 300 °C in the composite (PUF3B). The final residue percentage also decreased from around 20% in PUF0 to 10% in PUF3B. Density analysis showed that the apparent density of the foam increased from 0.016 g/cm3 in the blank foam to 0.020 g/cm3 in the biocomposite (PUF3B), while the real density slightly decreased from 0.092 g/cm3 to 0.076 g/cm3, indicating a reduction in overall porosity from 82.5% to 74.4%. All foams that were modified showed an increase in their ability to absorb gasoil in a PUF/gasoil/water system. The optimized biocomposite (PUF1B), with 1.14 mass% of 500 µm algae carbon, displayed the highest sorption capacity, starting at approximately 50 g/g at 1.5 h and increasing to 53 g/g over 72 h. The analysis of adsorption kinetics revealed that by utilizing adsorption isotherms, particularly the Langmuir isotherm, a more accurate fit to the data was achieved. This allowed for the prediction of the maximum gasoil adsorption capacity. This study aims to further develop, analyze, and utilize biocomposites made from algae-based activated carbon and polyurethane. These materials offer a sustainable and environmentally friendly approach to cleaning up oil spills.

Polyurethane foams are materials characterized by low density and thermal conductivity and can therefore be used as thermal insulation materials. They are synthesized from toxic and environmentally unfriendly petrochemicals called isocyanates and polyols, which react with each other to form a urethane group via the displacement of the movable hydrogen atom of the -OH group of the alcohol to the nitrogen atom of the isocyanate group. The following work describes the synthesis of polyurethane foams, focusing on using environmentally friendly materials, such as polyols derived from plant sources or modifiers, to strengthen the foam interface derived from plant precipitation containing cellulose derived from paper waste. The polyurethane foam industry is looking for new sources of materials to replace the currently used petrochemical products. The solutions described are proving to be an innovative and promising area capable of changing the face of current PU foam synthesis.

In this study, the crashworthiness behavior and energy absorption capacity of composite tubes under lateral indentation by steel rods aligned parallel to the specimen axis are investigated using experimental methods. Key parameters such as tube diameter, length, wall thickness, and indenter diameter are systematically examined and compared. Additionally, the influence of polyurethane foam fillers on damage modes and energy absorption capacity is rigorously analyzed. Contrary to conventional findings, smaller diameter specimens filled with foam demonstrate superior energy absorption compared to their larger counterparts, primarily due to enhanced compression of the foam volume. Experimental results reveal a complex interplay of damage mechanisms in composite specimens, including matrix cracking, fiber breakage, foam crushing, foam densification, foam fracture, and debonding of composite layers, all contributing to enhanced energy absorption. Increased tube thickness, length, and indenter diameter, alongside decreased tube diameter, are correlated with higher contact forces and improved energy absorption. Smoother shell fractures are promoted, and overall energy absorption capabilities are enhanced by the presence of foam fillers. This investigation provides valuable insights into the structural response and crashworthiness of composite tubes, which is essential for optimizing their design across various engineering applications.

Although bamboo is widely distributed in Japan, its applications are very limited due to its poor combustion efficiency for fuel. In recent years, the expansion of abandoned bamboo forests has become a social issue. In this research, the possibility of a liquefaction process with fast and efficient liquefaction conditions using moso bamboo as raw material was examined. Adding 20 wt% ethylene carbonates to the conventional polyethylene glycol/glycerol mixed solvent system, the liquefaction time was successfully shortened from 120 to 60 min. At the same time, the amount of sulfuric acid used as a catalyst was reduced from 3 wt% to 2 wt%. Furthermore, polyurethane foam was prepared from the liquefied product under these conditions, and its physical properties were evaluated. In addition, the filler effects of rice husk biochar and moso bamboo fine meals for the polyurethane foams were characterized by using scanning electron microscopy (SEM) and thermogravimetry and differential thermal analysis (TG-DTA), and the water absorption and physical density were measured. As a result, the water absorption rate of bamboo fine meal-added foam and the thermal stability of rice husk biochar-added foam were improved. These results suggested that moso bamboo meals were made more hydrophilic, and the carbon content of rice husk biochar was increased.

Microalgal-bacterial consortia (MBC) and microalgal consortia (MC) were cultivated with primary and final treated wastewaters, respectively, using a fluidised carrier. This study determines the main factors and operations required for flocculating suspended MBC (SMBC) and MC (SMC) in cultures. The flocculated SMBC and SMC with good settleability require the detachment of thickened MBC or MC on the carrier and suppressed SMBC and SMC formation by the original MBC and MC grown in the culture. Flocculation was achieved by controlling the carrier and culture replacements. A carrier replacement ratio of 0.04 d-1 and a culture replacement ratio of 0.95 d-1 minimised the dissolved organic carbon (15.3 mg-C/L) and SMBC residue (7.3 mg/L). Thus, treating primary treated wastewater with MBC formed using fluidised carriers is a promising strategy, enabling the use of whole cells in MBC for renewable energy production.

The ability of right-angled synchronous fluorescence spectroscopy (SFS) was explored to analyse the bacterial load in water treated with green synthesized silver nanoparticles (AgNPs) coated polyurethane foam (PUF). Gram negative (Escherichia coli, Pseudomonas aeruginosa) and Gram positive (Staphylococcus aureus) bacteria cultured in nutrient broth were diluted in autoclaved water containing NPs-coated PUF. The survival rate of S. aureus and E. coli lowered after ten minutes as compared to P. aeruginosa; however, after thirty minutes, the percentage viability dropped and recorded as 3.4%, 0.9%, and 0.1% for E. coli, P. aeruginosa and S. aureus respectively in the treated suspensions. No spectral change was observed in the fluorescence emission from the positive control and treated bacterial suspension owing to the masking effect of the emission from nutrient broth. In parallel, SF spectra recorded for directly picked bacterial colony dissolved in water showed remarkable drop in tryptophan emission after treatment with NPs-coated PUF. The SF data changes were assisted by hierarchical cluster analysis, which also made it possible to distinguish between positive control and treated bacterial suspensions. SFS has shown to be a reliable substitute for the culture plate approach for the quick identification of bacterial contamination in water.

The concept of sustainable development has led to a growing research interest in bio-based flame-retardant polyurethane foams. These foams offer environmentally friendly, sustainable, and flame-retardant raw materials for the construction, automotive, and furniture industries. The 15 wt% soybean oil-based polyol rigid polyurethane foams (RPUF-S3A20B system) were modified with 20 wt% ammonium polyphosphate (APP) and homemade magnesium borate hydroxide (MgBO2(OH)). Thermogravimetric analysis, pyrolysis kinetic analysis, limiting oxygen index (LOI) test, cone calorimetry (CONE), morphological analysis, and smoke density (Ds) were employed to investigate the impact of MgBO2(OH) on the thermal stability and flame-retardant properties of the RPUF-S3A20B system. The results indicated that RPUF-S3A20B12.5 with 12.5 wt% MgBO2(OH) had better thermal stability and higher activation energy. In addition, its LOI was increased by 3.1% compared to RPUF-S3A20 without MgBO2(OH). The peak heat release rate (PHRR) and total heat release rate (THR) of RPUF-S3A20B12.5 at a radiant flux of 25 kW/m2 were reduced by 45.8% and 35.0% compared with RPUF-S3A20. RPUF-S3A20B12.5 demonstrated the lowest smoke density (17.4 and 17.5) and highest light transmission (73.9% and 73.7%) in both flameless and flame conditions, indicating superior flame-retardant and smoke-suppression properties. These findings offered valuable insights for further research on synergistic flame-retardant systems in bio-based polyurethane foams.

Biomass has been widely used due to its environmental friendliness, sustainability, and low toxicity. In this study, aminophosphorylated cellulose (PNC), a biomass flame retardant containing phosphorus and nitrogen, was synthesized by esterification from cellulose and introduced into polyurethane to prepare flame-retardant rigid polyurethane foam. The combustion properties of the PU and PU/PNC composites were studied using the limiting oxygen index (LOI), UL-94, and cone calorimeter (CCT) methods. The thermal degradation behavior of the PU and PU/PNC composites was analyzed by thermogravimetric analysis (TGA) and thermogravimetric infrared spectroscopy (TG-IR). The char layer after combustion was characterized using SEM, Raman, and XPS. The experimental results showed that the introduction of PNC significantly improved the flame-retardant effect and safety of PU/PNC composites. Adding 15 wt% PNC to PU resulted in a vertical burning grade of V-0 and a limiting oxygen index of 23.5%. Compared to the pure sample, the residual char content of PU/PNC15 in a nitrogen atmosphere increased by 181%, and the total heat release (THR) decreased by 56.3%. A Raman analysis of the char layer after CCT combustion revealed that the ID/IG ratio of PU/PNC15 decreased from 4.11 to 3.61, indicating that the flame retardant could increase the stability of the char layer. The TG-IR results showed that PNC diluted the concentration of O2 and combustible gases by releasing inert gases such as CO2. These findings suggest that the developed PU/PNC composites have significant potential for real-world applications, particularly in industries requiring enhanced fire safety, such as construction, transportation, and electronics. The use of PNC provides an eco-friendly alternative to traditional flame retardants. This research paves the way for the development of safer, more sustainable, and environmentally friendly fire-resistant materials for a wide range of applications.

In recent years, there has been an increasing interest in producing new materials that use renewable resources and halogen-free flame retardants with nonleaching properties. This research focuses on designing and synthesizing phosphorus-nitrogen-based biopolyols for use in polyurethane (PU) foam production. Polyol (ESBO-DYM) with dual functionalities, renewability, and nonflammability is synthesized through the epoxy ring-opening reaction of epoxidized soybean oil with phosphorus and nitrogen-containing tetraol products (DYM). The mechanical and flame retardant properties of PU foams with the addition of an ESBO-DYM were investigated. Increasing the amount of phosphorus in the PU foams increased the thermal stability properties. Using 100% ESBO-DYM as a polyol in the foam formulation increased the limiting oxygen index (LOI) value to 22.9% and resulted in the highest char yield according to the thermal gravimetric analysis (17% at 600 °C). Additionally, the introduction of ESBO-DYM polyol into the formulation resulted in a decrease in the compression strength of the foams. The foam density decreased as the amount of ESBO-DYM polyol in the formulation increased. The foam with the highest amount of ESBO-DYM had a foam density of 29.1 kg/m3. The morphology of the foams was characterized using a scanning electron microscope (SEM). As a result of this study, flame retardant polyurethane foams were formulated using a renewable source, polyol, along with commercial compounds.