The aim of this study is the development of a polyurethane (PU) wood surface coating formulated from a niger polyesteramide polyol derived from niger seed oil (NSO). The synthesis procedure began with the preparation of long-chain fatty diethanolamide through the amidation of niger seed oil, followed by esterification with isophthalic acid to obtain hydroxyl-functional polyesteramide polyols. Structural confirmation of the fatty amide and final bio-polyol was achieved using ATR-FTIR and 1H NMR spectroscopy, which verified the successful incorporation of both amide and ester groups. Subsequently, PU coatings were formulated using the synthesized polyol, which was reacted with two aliphatic/aromatic isocyanate systems, hexamethylene diisocyanate biuret (HDI) and methylene diphenyl diisocyanate (MDI), to produce bio-based polyurethanes. When applied to wood panel substrates, the coatings exhibited high gloss, strong adhesion, and notable resistance to chemical exposure. Additionally, the films demonstrated self-cleaning behavior and inhibited bacterial growth, which enhances their functional advantages for wood protection. Thermogravimetric analysis revealed good thermal stability up to 300 °C for both the coatings. And scanning electron microscopy confirmed that the coating had a homogeneous and defect-free structure. These results suggest that NSO-based niger polyesteramide polyol could serve as a renewable source for high-performance polyurethane wood coatings.

In this study, the properties of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends were analyzed according to the PBS content during the manufacture of the blend. However, the inherent immiscibility between PLA and PBS often leads to phase separation and limited mechanical performance, particularly in melt-spun fiber applications, which restrict their practical use. To increase the miscibility of the PLA/PBS blend, methylene diphenyl diisocyanate (MDI) was added up to 0.8 wt.%, and the characteristics were analyzed via thermogravimetric analysis, differential scanning calorimetry, viscosity measurements, dynamic mechanical analysis, and Fourier-transform infrared spectroscopy. As the PBS content in the blend increased, the thermal stability, viscosity, elastic properties, and glass transition temperature decreased. In contrast, as the MDI content in the PLA/PBS blend increased, the thermal stability, viscosity, elastic properties, and glass transition temperature increased. The results revealed that the miscibility of the PLA/PBS blend increased as the MDI content in the blend increased. Additionally, the tensile strength and elongation of the PLA/PBS blend fibers manufactured through melt spinning were analyzed. While the tensile strength decreased as the PBS content increased, the tensile strength and elongation considerably improved as the MDI content in the blend increased. Specifically, the tensile strength of the PLA/PBS blend fibers increased from 2.55 to 2.99 gf/de, corresponding to an improvement of approximately 17%, while the elongation at break increased from 22.48% to 41.64%, representing an enhancement of approximately 85% with increasing MDI content.

Conventional particleboards often exhibit limited mechanical strength, which restricts their use in load-bearing and high-performance applications; reinforcing these boards with carbon fibers offers a potential solution to overcome these limitations. This study investigated the effect of carbon fiber (CF) content on the mechanical performance of single-layer particleboards bonded with polymeric methylene diphenyl diisocyanate (pMDI) adhesive. Carbon fibers were examined as a reinforcement to improve the mechanical properties of particleboards. Experimental boards were produced with 0, 10, 20, 30, 40, and 50% CF (based on the oven-dry mass of wood particles). The analysis included density profile distribution, modulus of rupture (MOR), modulus of elasticity (MOE), and screw withdrawal resistance (SWR). The results showed that mechanical performance improved only at lower CF contents. The most pronounced effect was observed at 10% CF, where MOR increased from 15.2 MPa (control) to 19.2 MPa, and MOE increased from 2.45 GPa to 2.91 GPa. Higher CF additions (≥20%) did not yield further improvements, and at elevated levels (≥30%), bending performance decreased (MOR dropped to 14.1–13.5 MPa) due to poor fiber dispersion and weakened interfacial bonding between fibers and wood particles. Screw withdrawal resistance increased gradually with CF content, from 156 N in the control boards to 182 N at 50% CF, although the improvement was limited by adhesion quality and mat heterogeneity. Overall, the study demonstrates that small CF additions can enhance selected mechanical properties of particleboards, whereas higher loadings negatively affect performance due to microstructural incompatibilities.

Diisocyanates are potent sensitizers extensively used in polyurethane-based materials, with numerous case reports linking them to allergic contact dermatitis (ACD). Recent extractables studies have detected residual diisocyanates in medical devices such as wound dressings. However, these assessments typically rely on non-physiological extraction methods, limiting their relevance to actual skin exposure conditions. This study aimed to develop and validate a physiologically relevant method for quantifying residual 4,4'-diphenylmethane diisocyanates (MDI), dicyclohexylmethane-4,4-diisocyanates (DMDI), hexamethylene diisocyanates (HDI), toluene diisocyanates (2,4- and 2,6-TDI) and isophorone diisocyanates (IPDI) leaching from wound dressings, and subsequently assess their risk of sensitisation induction and ACD elicitation. Diisocyanate standards were stabilised as di-lysine adducts in an artificial sweat solution, simulating skin exposure. An optimised LC-MS/MS method was used for quantification. The method was validated across a wide concentration range and subsequently applied to 36 commercial wound dressings. Exposure levels were evaluated against toxicological thresholds for quantitative risk assessments. The method proved reliable for all target diisocyanates (except IPDI) at concentrations ≥ 15 ppb. Analysis of the samples revealed that 44% contained quantifiable levels of residual diisocyanates. Notably, over 50% of the HDI-positive and 20% of MDI-positive samples exceeded the acceptable exposure level (AEL) for sensitisation induction. Moreover, all samples exceeding the AEL fell above the acceptable non-eliciting area dose for contact dermatitis (ANEAD). We developed and validated a physiologically relevant method to quantify diisocyanate residues leaching from wound dressings, demonstrating that HDI, in particular, poses a significant risk for sensitisation induction and can elicit ACD in individuals who are already sensitised.

Summary Lost circulation is a critical technical challenge in the process of drilling. Lost circulation materials (LCMs) with self-healing properties offer an effective method for lost circulation control by forming an integrated plugging layer within fractures. The phase-locking effect enables the confinement of dynamic bonds within the hard segment phase of self-healing polyurethane (PU), thereby restricting their kinetic exchange and controlling the self-healing properties of the material. In this work, a PU elastomer (HS-PU) with heat resistance and self-healing properties was prepared by using hydroxyl-terminated polybutadiene (HTPB) as the soft segment and 4,4'-diphenylmethane diisocyanate (MDI) as the hard segment and introducing dynamic disulfide bonds. HS-PU was systematically characterized by Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), and thermogravimetric analysis. HS-PU exhibited excellent water resistance, and the retention rate of the tensile strength was as high as 91.3% after soaking in water for 36 hours. Besides, HS-PU has good heat resistance and can achieve self-healing in the range of 110–150°C, and the self-healing rate increases with increasing temperature. The pressure-bearing capacity of HS-PU at 130 and 150°C is 4 and 3.5 MPa, respectively, and the capacity can reach 13 MPa after the addition of bridge-plugging materials. Moreover, HS-PU still has excellent pressure-bearing performance in water-based muds (WBMs). This work provides a new approach for controlling lost circulation in complex formations at the field and developing heat-resistant self-healing LCM, holding significant practical importance for ensuring safe and efficient drilling operations.

New insights into value-added application of phosphogypsum in asphalt mixture through chemical stabilization of polymeric methylene diphenyl diisocyanate

The acceptable impact of leachate methylenediphenyl diisocyanate and methylenediphenyl diamine in polyethersulfone membrane dialyzers on long-term dialysis patients

Synthesis of methyl diphenylmethane dicarbamate by methyl phenylcarbamate condensation catalyzed by NKC-9: non-phosgene preparation of key precursors for diphenylmethane diisocyanate

ABSTRACT Understanding polyurethane (PUR) decomposition is essential to promote the chemical recycling of plastic waste via pyrolysis. In this study, four representative polyurethanes were pyrolyzed in a lab‐scale batch pyrolysis system to investigate their thermal decomposition characteristics. The solid, condensate and gas yields and the chemical composition of the product phases strongly depend on the structural PUR configuration and the pyrolysis temperature. In all cases, the condensate is the dominant product phase, exhibiting a broad compound spectrum, attributable to the urethane bond scission and the polyol backbone disintegration. The polyurethane monomer methylene diphenyl diisocyanate (MDI) is not detected. Up to 15 mass‐% of the PUR is converted to the PUR monomer precursors 4,4′‐methylenedianiline (MDA) and aniline. Secondary reactions, including MDI derivatization, are plausible. CO 2 is the main gaseous compound, accompanied by short‐chain hydrocarbons and oxygenated compounds. Nitrogen retention in the solid phase indicates urethane bond involvement, while oxygen mainly migrates to the condensate and gas. This study provides in‐depth information on PUR pyrolysis characteristics, laying the foundation for the development of circular PUR waste‐to‐chemical processes. Potentials and challenges for chemical recycling are highlighted. The necessity of further research on PUR co‐pyrolysis, adequate compound separation, and product upgrading is emphasized.

ABSTRACT Self‐stratifying polymer systems are of great interest for coatings, as such systems reduce the time, cost, and environmental impact associated with the application of multilayered coatings by providing several layers in a single coating step. We have developed an understanding of self‐stratification in polyurethane systems that occurs when hydrophobic and hydrophilic polyols containing ethylene oxide, propylene oxide, and butylene oxide mers and prepolymers containing toluene diisocyanate and methylene diphenyl diisocyanate are mixed and cured. When these components are mixed in appropriate proportions, self‐stratification occurs where the hydrophobic component migrates to the air interface and the hydrophilic component to the substrate interface, with a thin hydrophobic layer present at the substrate walls when the substrate is hydrophobic. Self‐stratification requires less than 60 min, significantly less than the time required for the storage modulus to crossover the loss modulus (∼5 h). SIMS, XPS, and confocal Raman show that the stratification process at the air and substrate interfaces is dependent on interfacial surface energies, with the thickness and composition of the up to 10 µm thick interfacial region at the substrate controlled by the substrate surface energy. Self‐stratification is observed in both the bulk and thicknesses conventionally associated with coatings (10s of µm).

A malignant leakage presents a significant challenge in drilling engineering, particularly within carbonate formations, where such a leakage is frequently encountered. Currently, there is no effective solution to this problem. In this study, a water-reactive polyurethane sealing agent was developed using multifunctional polypropylene glycol and 1,4-butanediol (BDO) as soft segments, diphenylmethane diisocyanate (MDI) as the hard segment, and a composite catalyst consisting of N, N-dimethyl cyclohexylamine (PC-8) and dibutyltin dilaurate (T-12). The material reacts rapidly with water to form a high-strength gel, with the reaction time being controllable. Through experimental optimization, it was determined that the BDO mass fraction was 1%, and the molar ratio of isocyanate group to hydroxyl group was 1.8. Additionally, the gelation time can be controlled by adjusting the mass fraction of the composite catalyst. Experimental results from sand-bed and fracture-plate tests indicated that the material could withstand pressures exceeding 3 MPa at 93 °C and exhibited resistance to saturated NaCl and CaCl2 environments. The plugging mechanism was investigated using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier-transform infrared (FTIR) spectroscopy. The results demonstrated that the agent formed a compact, micron-scale porous structure upon reacting with water, exhibiting excellent thermal stability and dual plugging performance through both physical and chemical mechanisms. Due to its water-reactive characteristics, a multi-stage injection process was adopted for field application design. This material shows promising potential for mitigating large-fracture-type malignant leakages in drilling operations.

Radar absorbing materials (RAMs) have become increasingly important in modern stealth technologies due to the growing need to minimize radar signatures. However, most RAMs suffer from high weight and limited structural flexibility, which restrict their practical use in lightweight and conformal applications. Therefore, developing lightweight and structurally adaptable absorbers has become a critical research priority, and this study addresses this need by evaluating the effects of polyurethane foam (PUF) density and morphology on their electromagnetic absorption performance. PUF composites with different matrix densities (30, 80, and 120 kg/m 3 ) were prepared by incorporating nickel-coated carbon fillers at varying loadings. In addition, to examine the effect of filler localization, additional samples with identical composition were fabricated using three preparation strategies, introducing the filler into the polyol phase, the isocyanate phase, or equally dividing it between both. These approaches resulted in distinct filler distributions, allowing the evaluation of how spatial arrangement influences electromagnetic behavior. As expected, increasing foam density progressively enhanced absorption performance, with notable attenuation observed only at densities of 80 kg/m 3 and above. A well-balanced cellular morphology was obtained by equally dividing the filler between both phases, resulting in homogeneous localization across both cell interiors and walls. This strategy facilitated more regular foam formation compared to polymeric methylene diphenyl diisocyanate ( pMDI ) based dispersion and offered comparable absorption performance, while clearly outperforming the polyol-only method in efficiency and thickness. As a key outcome, a PUF with an experimental density of 0.553 g/cm 3 achieved a minimum reflection loss ( RL min ) of −41.80 dB at 4.3 cm thickness, while maintaining Reflection Loss ( RL ) values below −10 dB across the entire X-band. Overall, the results demonstrate that both foam density and filler localization serve as effective design parameters to tune dielectric behavior and optimize absorption in lightweight polyurethane-based RAMs.

ABSTRACT There is a necessity to develop products using natural fibers instead of those derived from fossil fuels. In former years, insulation board products were based commonly on nonrenewable sources like glass and rock. Nowadays, the trend in insulation boards is turning to lignocellulosic-based fiber. However, the binder nature is still an issue, being polymeric diphenylmethane diisocyanate, a nonrenewable origin one, the most common in pressure-resistant insulation boards. To address this, wood-based insulation boards were created using an adhesive derived from isolated-canola protein, a naturally-based binder. Wood-fiber-based insulation boards were produced by hot press with densities of 100 kg.m−3, 115 kg.m−3, 130 kg.m−3 and 160 kg.m−3 and binder proportions of 10% and 12%. They were compared with wood-based boards bonded with 4% pMDI, as is common in similar commercial wood-fiber insulation boards. The results report that as density increases, compression and internal bonding strength values also rise, irrespective of the binder type. The thermal conductivity values demonstrated that produced boards can be classified as insulation materials, with density having a direct influence on thermal conductivity. The findings confirmed that it is feasible to produce wood-based insulation boards using a canola-based binder with sodium nitrite as a crosslinker.

ABSTRACT Given the defects existing in traditional additive flame retardants, it is of great research significance to endow polyurethane (PU) with intrinsic flame retardancy through molecular structure design. The polyester polyol (PAHI) is first synthesized by esterification with 1, 6‐adipic acid, 1, 6‐hexanediol, and itaconic acid, and then the itaconic acid reacts with 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) to form a polyester polyol (PAHI‐DOPO). The PAHI‐DOPO monomer is used as part of PU flexible section to be cured with diphenylmethane diisocyanate (MDI) to obtain PU with an increased LOI value of 30.4% and flame‐retardant grades reaching the V‐0 level. Moreover, a small amount of PAHI‐DOPO can significantly enhance the mechanical properties of PU, resulting in a strength increase from 15.1 to 18.2 MPa and an improvement in toughness from 753% to 815%. Compared with direct addition of equal amount of DOPO as flame retardant, the transparency and mechanical properties of PU are significantly improved. Interestingly, the intrinsic flame‐retardant approach effectively avoids the sharp decrease in mechanical properties that occurs when the flame retardant migrates from the samples upon immersion in water. Thus, this synthetic flame‐retardant polyester polyol offers an efficient, durable, and environmentally friendly approach to enhancing the flame‐retardancy of PU.

In the present work, novel thermoresponsive hydrogels were developed from renewable resources, and the influence of bacterial cellulose molar ratio on their chemical structure, thermal properties, swelling behavior, morphology, and biocompatibility was systematically investigated. The hydrogels were fabricated using castor oil, 4,4'-diphenylmethane diisocyanate, bacterial cellulose, N-isopropylacrylamide, and N,N'-Methylenebisacrylamide. Structural and physicochemical characterizations were performed by Fourier-transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, and thermogravimetric analysis. The highest equilibrated swelling degree was achieved as 592.6% at the maximum bacterial cellulose content. SEM images revealed that the formation of spongy architecture is caused by the increase in the bacterial cellulose content. In vitro biocompatibility studies revealed that the hydrogel with the highest bacterial cellulose content exhibited the greatest cytocompatibility, with an IC50 value of 11.16 mg/ml. Overall, the findings demonstrate the successful fabrication of a novel bio-based thermoresponsive hydrogel through an eco-friendly approach, highlighting its potential for diverse biomedical applications.

ABSTRACT This study investigated the structure – property relationships of particleboards incorporating macadamia nutshell (MNS) and evaluated its feasibility as a sustainable raw material in compliance with GB/T 4897–2015 Type P2 requirements. MNS, an agricultural byproduct rich in hemicellulose (39.8%) and lignin (32.0%) but low in cellulose (23.7%), was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and chemical analysis. Particleboards were fabricated with 0–100% MNS in the core layer using polymeric 4,4′-diphenylmethane diisocyanate at 180 °C and 3 MPa for 7 min. Physical and mechanical properties, including density profile, thickness swelling, internal bond strength, modulus of rupture, modulus of elasticity, and screw withdrawal resistance, were evaluated following GB/T 17657-2022. Increasing MNS content reduced mechanical performance due to its rigid morphology and weak interfacial bonding, while excessive substitution (≥ 75%) resulted in void formation, irregular density profiles, and significant property deterioration. Nevertheless, up to 25% substitution satisfied Type P2 requirements for strength and screw-holding capacity, while also enhancing water resistance, which was attributed to the hydrophobic nature of lignin. These findings highlight the potential of MNS utilization as a bio-based filler for eco-friendly particleboard production, supporting value-added utilization of agricultural residues in interior and non-load-bearing applications.

The current research was conducted to study the use ofwaste materialsto isolate lignin, which was further used to prepare polyurethanehot-melt adhesives. To enhance the reactivity of lignin, its hydroxylcontent was increased by hydroxymethylation, and then it was polymerizedwith 4,4′-methylenediphenyl diisocyanate (MDI), polyethyleneglycol (PEG), and 1,4-butanediol (BDO) to prepare polyurethane hot-meltadhesives. SiO2 nanoparticles were added to provide mechanicalstrength to the final polymer. The structure of the final polymerwas confirmed by FT-IR spectroscopy. Morphological behaviors wereanalyzed by using SEM and XRD. Thermomechanical characteristics werestudied by using thermogravimetric analysis (TGA\\DSC). Finally, theadhesion properties were analyzed by using melting viscosity, softeningtemperature, and a T-peel strength test. The absence of the -NCO peakof monomers in the FT-IR spectra confirmed the completion of the reaction.The gradual decrease in thermal transition and increasing crystallinityin the DSC\\TGA thermograms represent its stable thermal behavior.SEM and XRD show that the prepared hot-melt polyurethane adhesiveshave distinct crystallinity and peaks. Melting viscosity, softeningtemperature, and T-peel strength test exhibit the strong adhesivebehaviors of the prepared biobased polymers in different time intervalsunder stress and heating conditions. HMPUA-4 with optimum values oflignin and SiO2 nanoparticles is considered to be the bestproduct due to its high adhesive properties and sustainability. Lignin’sstrong antibacterial activity is also evidence that a promising polymericadhesive was prepared that can be used in various fields.

This study investigates the effects of different processing methods on the chemical composition of thermoplastic polyurethanes, focusing on isocyanates and extractable oligomers. Using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and gas chromatography/mass spectrometry (GC/MS), seven commercially available thermoplastic polyurethane samples are analyzed as unprocessed granulate, injection‐molded, and 3D‐printed parts. Diffuse reflectance infrared Fourier transform spectroscopy analysis enables direct identification and quantification of isocyanates. In two polyester‐based materials, substantial isocyanate contents were detected after processing. In both cases, the concentrations exceeded the w = 0.1 % threshold defined by REACH Regulation (EU) 2020/1149 for monomeric diisocyanates, thereby underscoring the regulatory significance of processing‐induced changes. Gas chromatography/mass spectrometry analysis complements these results by indirectly but quantitatively detecting the formation of oligomers during processing via methylene diphenyl diisocyanate. The highest isocyanate content determined was w = 1.16 % in an injection‐molded sample. The comparison of both methods shows their complementary significance in isocyanate detection. The study highlights the importance of choosing the correct processing parameters and analytical techniques to ensure thermoplastic polyurethane integrity and reduce undesirable changes in material composition.

Optimization of green development for methylene diphenyl diisocyanate industry based on synergistic benefit

The energy and resource efficient operation of continuously operated large-scale chemical plants is an important factor in the transition towards a sustainable and green process industry. In this work, the operation of the heat exchangers in the diphenylmethane diisocyanate (MDI) process is optimized to reduce fouling and thereby increase their energy efficiency. Real-time optimization (RTO) using Modifier Adaptation With Quadratic Approximation (MAWQA) is applied to cope with plant–model mismatch. It is combined with distributed estimation of the modifiers while retaining a centralized optimization to ensure rapid convergence. It reduces the data points needed for their computation and enables application to large-scale processes. The plant model that is used in the optimization is a surrogate of an available detailed flow-sheet simulator model. The algorithm is demonstrated first for a small problem and then applied to the operator training simulator (OTS) of the MDI process in several operation scenarios. Compared to previous work, the algorithm converges to the optimal operating conditions in fewer iterations.