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Polyurethanes (PUs) are widely utilized in various industries due to their versatile properties. Traditionally, these polymers are synthesized using petrochemical-based polyols, which pose environmental concerns. To address this issue, there is a growing trend towards the use of bioresources in polymer manufacturing. This study explores the synthesis of a Schiff base diol derived from ethylene diamine (EDA) and vanillin, which can be obtained by depolymerization of lignin. Additionally, a soybean oil-based polyol (SOP) was employed as a sustainable alternative to traditional petroleum-based polyols. The synthesized Schiff base diol and SOP were used to prepare PU films, incorporating both aromatic and aliphatic diisocyanates which are methylene diphenyl diisocyanate (MDI) and hexamethylene diisocyanate (HDI), respectively. The primary objective was to investigate the impact of the aromatic and aliphatic nature of the isocyanates on the properties of the resultant PU films. The thermal stability and mechanical properties of the PU films were evaluated and compared. The results demonstrate that the bio-based PU films exhibit good thermal stability. However, contrary to expectations, the mechanical strength decreased with an increasing amount of Schiff base diol, while the elongation percentage increased. A flammability test was also performed to assess flame retardancy, and an unexpected trend was observed in HDI-containing PU films, which is discussed in detail in the manuscript. The study highlights the potential of using bioresources, such as vanillin and soybean oil, to produce sustainable and thermally stable PUs, paving the way for more environmentally friendly applications in the polymeric industry and beyond. [ABSTRACT FROM AUTHOR]

The activated carbon (AC) has been widely used in the field of electromagnetic protection because of its porous, hollow microstructure and excellent electrical conductivity. In this paper, AC was prepared through KOH activation process. The ACs/polyimide foam (PIF) composite was prepared in situ during the synthesis of PI and the ACs. In this paper, AC was prepared using the potassium hydroxide (KOH) activation process. The AC/PIF composites were prepared by mixing ACs and pyromellitic dianhydride (PMDA) with methylene diphenyl diisocyanate (MDI). The pore structure and surface morphology of the ACs were observed using nitrogen adsorption–desorption isotherms and scanning electron microscopy (SEM). After KOH activation with KOH, the surface area and total pore volume of ACs significantly increased by 79.31% and 0.9539 cm3/g, respectively, mainly were the microporous structure. X‐ray photoelectron spectroscopy (XPS) results confirmed an increase in the oxygen content of ACs after KOH activation, indicating an increase in the relative hydroxyl content on the surface. The SEM resulting of the ACs/PIF composite has a well‐developed open cell structure. Thermal gravimetric analysis (TGA) revealed that ACs significantly improved the thermal stability of the ACs/PIF composite. The compressive strength of the ACs/PIF‐3 increased from 518 to 834 KPa, significantly enhancing its mechanical properties. Simultaneously, the microwave absorption performance can be controlled and regulated by optimizing the impedance gradient of the skeleton. Results showed that when ACs constituted 8 wt% of the PIF, the real permittivity (ɛ′) and imaginary permittivity (ɛ″) of ACs‐PIF‐5 were approximately 2.03 and 0.025, respectively. [ABSTRACT FROM AUTHOR]

This study explored the feasibility of Waste Cooking Oil (WCO)‐based Bio‐Polyurethane (Bio‐PU) as an eco‐friendly alternative to petroleum‐derived polyols in plywood adhesives. The objective is to evaluate the impact of varied WCO concentrations and methylene diphenyl diisocyanate (MDI) levels on Bio‐PU and plywood performance. The Bio‐PU's characteristics, rheology, and functional groups are studied. Plywood made from three layers of 100 mm x 100 mm × 2 mm rubberwood (Hevea brasiliensis) veneer is bonded with Bio‐PU using a dual spread approach at 180 g.m−2, hot pressed at 120 °C and 1 MPa for 4 min. The laboratory‐fabricated plywood is tested for physical, mechanical, and adhesive properties. Results showed that Bio‐PU exhibited unique adhesive characteristics, with excellent adhesive strength, despite a slight decrease with higher WCO concentrations. WCO insertion do not compromise delamination resistance. FTIR analysis confirmed successful polyurethane chain synthesis. This research highlighted the potential of WCO‐based Bio‐PU's as a sustainable, high‐performance plywood adhesive. [ABSTRACT FROM AUTHOR]

In this research, the synthesis and characterization of a shape memory–assisted self‐healing polyurethane (SHSMPU) coating based on strong quadrupole hydrogen bonding interaction have been investigated. The coating was fabricated with an acrylic polyol, an isocyanate functionalized ureidopyrimidinone (UPy‐NCO) as a hydrogen bonding provider, and methylene diphenyl diisocyanate (MDI) as chain extender. Fourier‐transform infrared spectroscopy (FT‐IR) confirmed that by incorporating the UPy‐NCO dimer in the polyurethane (PU) structure, strong hydrogen bonding appears, which can provide the healing function of the polymer. In addition, differential scanning calorimetry (DSC) showed that by increasing the UPy‐NCO amount, the overall Tg decreased and the material becomes more flexible. A rheometric investigation revealed that a sample containing 45% of UPy‐NCO as total diisocyanate shows good shape recovery and an healing efficiency of macroscale cracks of around 94.2%, which is much higher than the corresponding sample without UPy‐NCO (50.4%). Even better performances were obtained with microcracks, where tested samples were significantly healed at around 80°C in 10 min. Furthermore, the introduction of polyethylene glycol 400 (PEG400) into the polymer's backbone led to a reduced Tg and thus higher flexibility at room temperature. The combination of the observed properties makes these materials promising for application as durable and flexible polyurethane coatings. [ABSTRACT FROM AUTHOR]

The purpose of this study is to address the problem of reconstructing damaged styrene–butadiene–styrene (SBS) molecular structures in order to facilitate the effective recycling of aged SBS-modified asphalt (SBSMA). Traditional experimental methods face challenges when attempting to investigate the reconstruction process and reaction mechanism of aged SBS molecules. To explore the reaction mechanism of aged SBSMA with active rejuvenators and to promote the recycling of aged SBSMA, this study employs molecular dynamics and quantum chemistry to investigate the reconstruction process of the damaged SBS molecular structure using two reactive compounds, namely, methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI), from a molecular perspective. The results showed that the carbon–carbon double bonds in the SBS molecules are susceptible to oxidation, leading to the formation of hydroxyl and carboxyl groups. The reaction between the hydroxyl groups in aged SBS and TDI can spontaneously proceed, while the reaction between the carboxyl groups and MDI can also spontaneously proceed. When the proportion of hydroxyl groups in aged SBS molecules is higher, TDI can be the preferred choice for reconstructing aged SBS molecules. Conversely, when the aged SBS molecules contain more carboxyl groups, MDI can be selected as the better reactive compound. By reconnecting the aged SBS molecules, the need for new SBSMA can be reduced, leading to lower demand for original resources, extended material service life, reduced waste generation, and effective resource recycling. This study provides a new method to explore the problem of SBS molecular structure damage reconstruction and offers a possible mechanism explanation of reaction between aged SBS molecules and reactive compounds. These findings are expected to promote the sustainable development and environmental applications of SBSMA. [ABSTRACT FROM AUTHOR]

In the context of growing interest in phosphonic acid proton exchange membranes (PEMs) for fuel cell applications, we report on new PEMs containing low‐cost polyethylene oxide (PEO) covalently linked by siloxane bonds, SiOSi, to phosphonic acid (PA). Key chemistry in the formation of these membranes involves hydrolysis and condensation reactions of triethoxysilyl propyl capped PEO and pre‐hydrolyzed dimethyl phosphonatoethyltrimethoxysilane (DMPTMS) giving PEO‐Si2O3‐PA and cross‐linked chain PEO‐Si2O3‐PEO organosilsesquioxane components. The Si2O3 can enhance membrane thermal and mechanical properties. The membrane formulations were varied by (a) reagent ratios (b) PEO molecular weights or using polypropylene oxide (PPO) (c) incorporating chain extending groups methylene diphenyl diisocyanate (MDI) or hexamethylene diisocyanate (HDI). These variations provided five membrane families, one of which afforded a complete group of robust membranes with weight% x of PA, PAx in range PA0–PA33. These were studied using ATR‐FTIR, dry membrane water uptake capacity, ion exchange capacity (IEC), and conductivity from room temperature to 120°C at 100% relative humidity. Conductivity increased with PAx reaching 15 mS cm−1 at 120°C, activation energy 0.1 eV, for membrane PA33 for which thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and energy dispersive X‐ray analysis (EDAX) are reported. A comparative performance of the five membrane families is presented. [ABSTRACT FROM AUTHOR]

Recycling polyethylene terephthalate (PET) bottles post‐consumption is highly desirable but remains challenging because of their poor properties after recycling. Using a chain extender to rejoin the cleaved polymer chains is considered a reasonable solution to this issue. However, the functionality of the chain extenders affects the cross‐linking and properties of the resulting products. Therefore, this study focuses on the effects of functional groups and number of chain extenders on the properties of recycled polyethylene terephthalate (rPET). Three commercial chain extenders—methylene diphenyl diisocyanate (MDI), triphenyl phosphite (TPP), and Joncryl (JC), represented as di‐, tri‐, and multi‐functional chain extenders, respectively—are introduced into rPET by reactive blending. The intrinsic viscosity, rheological properties, thermal properties, and mechanical properties of the chain‐extended rPET are investigated. The results indicate that all the chain extenders increase the molecular weight of rPET. Di‐ and multi‐functional chain extenders (MDI and JC) induce branching and cross‐linking owing to the highly reactive functional groups, whereas a tri‐functional chain extender (TPP) showed the lowest improvement in mechanical properties, owing to chain scission from by‐products occurring during chain extension. Furthermore, increasing the content of all chain extenders significantly increased their intrinsic viscosity, cross‐linking, and mechanical properties. [ABSTRACT FROM AUTHOR]

A hybrid adhesive system composed of phenol-formaldehyde (PF) resin and polymeric methylene diphenyl diisocyanate (pMDI), modified with two types of alkaline catalysts, namely NaOH and CaCO3 at 20% (w/v), was used for manufacturing the oriented strand board (OSB) from sengon (Paraserianthes falcataria L. Nielsen) wood. The catalyst was added at a concentration of 1% of the solids content of PF adhesive, and pMDI was added at 2.5% and 5.0% of the PF adhesive solids content. Adding catalysts and cross-linking agents increased the solids content and viscosity of the adhesive and accelerated the gelation time. The water absorption of OSB increased with the addition of catalysts and crosslinking agents compared to the control PF. Still, the CaCO3 catalyst worked optimally in reducing the thickness swelling of OSB. The mechanical properties of the laboratory-fabricated OSB panels increased with the addition of catalyst and cross-linker, except for the modulus of elasticity parallel to the grain. The optimal performance of OSB was obtained by adding 1% CaCO3 and 2.5% pMDI based on the PF's solids content. [ABSTRACT FROM AUTHOR]

Polyurethane coatings were synthesized through polyaddition polymerization using various polyols. These polyols included polypropylene glycol with different molecular weights, such as PPG-2000, and PPG-1200, as well as 1,4-butanediol. Additionally different contents of bisphenol F; namely 4.5, 11.5, and 24.2%, as well as methylene diphenyl diisocyanate at an NCO/OH ratio of 2.0. The prepolymer polyurethane films were analyzed to study their characteristics using techniques such as Fourier transform infrared spectroscopy, viscosity measurements, thixotropic index analysis, and mechanical property evaluations. The pot life and dry times of polyurethane coating containing 11.5% bisphenol F were 90 minutes and 10 hours (time to touch), respectively, with full hardening achieved at 28 hours. Furthermore, the coating exhibited excellent mechanical properties: tensile strength of 80 N/m², elongation of 260%, adhesion strength of 10 MPa (crosshatch), hardness of 95, and a contact angle of 118°. These properties, coupled with its strong adhesion (10 MPa) to metal surfaces, contributed to its outstanding chemical and corrosion resistance. The coatings obtained from the prepolymer polyurethane based on 11.5% bisphenol F exhibited the highest mechanical properties and water, chemical, and corrosion resistance followed by 4.5%, and 24.2%, respectively. [ABSTRACT FROM AUTHOR]

Medicinal food raw materials refer to those raw materials with food and possess medicinal value. They were particularly suitable for developing novel functional food. In this study, a novel functional food based on ultrafine grinding treatment of Ganoderma, yam, wolfberry, Rhizoma polygonati, raspberry, and euryale ferox (GYWRRE) with a specifically designed formula was developed and characterized. The results were shown that the ultrafine GYWRRE powder presented a relatively regular structure and smooth surface. It had notable decreases in fluidity and oil‐holding capacity but increases in characteristic nutrient content and antioxidant capacity. The ultrafine GYWRRE powder also could prevent oxidative stress in C2C12 cells by reducing the contents of reactive oxygen species and methylene diphenyl diisocyanate, inhibiting cell apoptosis, and increasing expressions of heme oxygenase‐1 and NQO1. The results of this study were demonstrated that medicinal food raw materials and ultrafine grinding had great applications potentials in developing functional food. Practical applications: Medicinal food refers to those natural ingredients that serve both as food and possess medicinal value. Ultrafine grinding technology is a meticulously engineered method capable of grinding raw materials to the micron level, thereby increasing their surface area, improving their bioavailability, and potentially enhancing their medicinal properties and bioavailability. This study developed an ultrafine grinding treatment of Ganoderma, yam, wolfberry, Rhizoma polygonati, raspberry and euryale ferox (GYWRRE) with a specifically designed formula. The characteristics of the ultrafine GYWRRE powder contained particle size, morphology, colorimetry, liquidity, hydration, adsorption, and characteristic nutrients were characterized. The antioxidant capacity in vitro and in cells as well as the possible mechanism were also explored. The results of this study will be helpful for development of novel functional foods. [ABSTRACT FROM AUTHOR]

An alicyclic acid anhydride containing four stereoisomers, racemic (1S,2R,3R,4R,5R)‐bicyclo[2.2.2]octane‐2,3,5‐tricarboxylic acid‐2,3‐anhydride (7a+7a′) and racemic (1S,2S,3S,4R,5R)‐bicyclo[2.2.2]octane‐2,3,5‐tricarboxylic acid‐2,3‐anhydride (7b+7b′) (BOTA), is synthesized using phthalic anhydride as the starting material. The chemical structures of the products in each step are fully characterized by nuclear magnetic resonance (NMR) spectroscopy, gas chromatography–mass spectrometry (GC–MS), elemental analysis, and single‐crystal X‐ray diffraction. The polycondensation process involving BOTA and several diisocyanates is applied to prepare polyamideimides (PAIs). Furthermore, PAI‐Xs are prepared using methylene diphenyl diisocyanate (MDI) and various mole ratios of BOTA and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA). PAI‐Xs exhibit good solubility in organic solvents such as dimethyl sulfoxide (DMSO), N‐methyl‐2‐pyrrolidone (NMP), N,N‐dimethylacetamide (DMAc), γ‐butyrolactone (GBL), N,N‐dimethylformamide (DMF), and m‐cresol at room temperature. They can form flexible films with low coefficients of thermal expansion (CTE) (51–70 ppm °C−1) and high glass transition temperatures (Tg) (222–272 °C). They also demonstrate high transparency with transmittance at 500 nm (T500 nm) ranging from 77.2% to 82.5%. BOTA can be a significant building block in PAI synthesis, offering an alternative to 1,2,4‐trimellitic anhydride (TMA). [ABSTRACT FROM AUTHOR]

As people became more conscious of the risks associated with pollution in the early 21st century, eco‐friendly adhesives made from plant oil began to be used. Bio‐based adhesives are widely used due to their low price, easy accessibility, and high biodegradability; however, their low adhesive strength is an issue. This work incorporates three natural crosslinkers: tannic acid (TA), sorbitol (SR), and cellulose (CL) to address the drawbacks of bio‐based adhesives, such as low adhesive strength, inferior output in humidity and longer curing time that result from excess water. Methylene diphenyl diisocyanate (MDI) was used to react with soybean oil‐based polyol (SOP) plus the crosslinkers to make bio‐based polyurethane adhesives. The maximum bonding strength of the soybean‐based adhesive containing 10 wt.% of SR (SR‐10%) was measured at 6.19 MPa which is about 44% higher than the sample without SR. The higher strength is due to the crosslinking ability of SR. The effect of crosslinking is also observed in the study of polar protic and polar aprotic solvents used to dissolve the adhesive. As compared with the polar aprotic solvent tetrahydrofuran, TA‐containing adhesive samples showed a maximum tensile strength of 3.69 MPa in methanol; a polar protic solvent that can participate in further hydrogen bonding to form a higher crosslinked complex. The glass transition temperature (Tg) increases with the increase in crosslinker amount. The observed increase in Tg may be attributable to an increase in crosslinking density, which reduces polymer chain flexibility and causes a stronger material. Highlights: Bio‐adhesives based on soybean oil and diisocyanate were synthesized.Natural crosslinking agents such as tannic acid, sorbitol, and cellulose were used.The effect of crosslinking using polar protic and aprotic solvents was studied.The glass transition temperature increases with the increase in crosslinker amount. [ABSTRACT FROM AUTHOR]

Methylene diphenyl diisocyanate (MDI) serves as a primary component of polyurethane in various applications, including household appliances, architectural structures, automobiles, and adhesives. A recent MDI plant explosion in China highlighted the importance of studying MDI's thermal stability and parameters to prevent accidental thermal decomposition. In this study, an extensive array of analytical techniques, including differential scanning calorimetry, thermogravimetric analysis, and adiabatic accelerating calorimeter, was employed to determine the thermokinetic constants of MDI, providing a solid foundation for further in-depth investigations. The findings revealed that MDI containing water reacts at substantially lower temperatures, while pure MDI can release heat and gases in an adiabatic environment, posing a considerable explosion risk. The kinetic constant of MDI was calculated using the Flynn–Wall–Ozawa method, yielding apparent activation energy values ranging from 51.78 to 96.70 kJ mol−1 across a conversion degree range of 0.05–0.70. The Coats–Redfern model pinpointed the kinetic reaction mechanism as a two-stage chemical process based on the apparent activation energy. Molecular optimization, following the energy minimisation principle, was conducted using Gaussian 09 software, which led to the identification of the optimal pathway for generating carbodiimide and carbon dioxide. This investigation offers valuable insights for the effective management of MDI during production, transportation, and storage, contributing to improve loss prevention practices in the industry. [ABSTRACT FROM AUTHOR]

The fouling of a commercial stainless steel (AISI 316L) during the manufacture of polymeric methylene diphenyl diisocyanate (pMDI) has been studied using laboratory‐based fouling apparatus that simulates commercial production conditions. The goal of the work is to understand the mechanisms behind the corrosion and fouling during isocyanate production with a view to improving process efficiency, not only in this process, but also others using similar plant and processes. Steel coupons were exposed to a solution of pMDI and solid amine hydrochloride, with hydrogen chloride gas being bubbled through the reaction cell. A number of different conditions were investigated, the variables being pMDI concentration, HCl gas flow duration, immersion time and temperature. Following the fouling experiments the coupons were removed from the fouling rig, photographed, and examined by XPS and ToF‐SIMS; principal component analysis was used to extend the ToF‐SIMS analysis to identify organic fouling products. The extent of fouling is shown to be relatively insensitive to pMDI concentration, but significantly influenced by continual HCl flow and increased temperature, features which increase the extent of substrate corrosion thought to be a precursor to the fouling process itself. Both XPS and ToF‐SIMS confirm the formation of various nickel chlorides in the corrosion process. Urea and metal corrosion products are found to co‐exist on certain (random) areas of the coupon surface. [ABSTRACT FROM AUTHOR]

Ammonium dinitramide (ADN) has appeared as a promising oxidizer for green propellants and thereby a potential substitute for ammonium perchlorate, largely in use in composite propellants for tactical and strategic long‐range missiles. The novelty lies in replacing ammonium perchlorate with a chlorine‐free oxidizer less harmful to the health and environment. However, ADN is hygroscopic and can potentially react with other chemical components, which could be overcome by microencapsulating the particles. The simple coacervation method was tested herein to microencapsulate ADN with a membrane made of hydroxyl‐terminated polybutadiene as pre‐polymer and methylene diphenyl diisocyanate as the curing agent. The effect of polyamine bonding agents on the capsule formation was tested by adding 0.5 or 2 % of Tepan or Tepanol, whose efficacy to bond to ADN was confirmed by detecting ammonia release through infrared spectroscopy. The capsule membrane was examined by optical and scanning electron microscopy. The dissolution time and rate were the parameters adopted to quantify permeability in a straight dissolution test in water, which demonstrated that 0.5 % Tepanol can provide the most effective protection. The infrared spectroscopy indicated that 60 °C temperature for prolonged periods, normally experienced by propellants, does not chemically affect the capsules' membrane but can turn it lumpy. In conclusion, these polyamine bonding agents can assist the capsule formation over ADN particles using the simple coacervation method, however, their functionality on mechanical properties of propellants needs to be substantiated in forthcoming works as well as the effect of the concentration of bonding agents on propellant formulations. [ABSTRACT FROM AUTHOR]

This study was based on preparation of a new category of polyurethanes with improved glass transition temperature. Firstly, diphenylsilanediol was reacted with methylene diphenyl diisocyanate and also toluene diisocyanate in 2:1 stoichiometric ratio to prepare two different urethane diols. Then, polycondensation reactions of the obtained diols with 4,4′-dichlorodiphenyl sulfone resulted in preparation of novel poly(silyl ether-sulfone-urethane)s. Spectroscopic techniques and elemental analysis were used to wholly characterize the chemical structure of the monomers and the resulting polymers. Viscosity, solubility, thermal behavior and stability, and crystallinity of the polymers were studied and through that, structure-property relationship of the two polymers was investigated. The prepared poly(silyl ether-sulfone-urethane)s had improved glass transition temperature in comparison to conventional polyurethanes with Tg of 143–165°C. The resulted polymer from methylene diphenyl diisocyanate showed higher glass transition temperature but lower solubility (average solubility in polar solvents was 3.7 vs. 4.0 g/dL) than polymer derived from toluene diisocyanate. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) shows no charring ability in burning due to the lack of hydroxyl functional groups; thus, the flame retardant system needs an additional amount of carbonizing agent. An ammonium polyphosphate (APP)-based all-in-one intumescent flame-retardant system was prepared by the in situ polymerization of polymeric methylene diphenyl diisocyanate (pMDI) with a glycerol-based and a glycerol–sorbitol-based polyol of high OH value. The microencapsulated APP with a polyurethane shell (MCAPP) of different polyols was characterized. The MCAPP with speculated improved flame retardant performance was selected for further evaluation in the PP matrix at different loadings by means of standard flammability tests. [ABSTRACT FROM AUTHOR]

This paper investigated the upcycling process of thermoplastic waste polystyrene (WPS) into thermosetting particleboard adhesive using two cross-linkers, namely methylene diphenyl diisocyanate (MDI) and maleic anhydride (MA). The WPS was dissolved in an organic co-solvent. The weight ratio of WPS/co-solvent was 1:9, and 10% of cross-linkers based on the WPS solids content were added subsequently at 60 °C under continuous stirring for 30 min. The adhesive properties, cohesion strength, and thermo-mechanical properties of WPS-based adhesives were examined to investigate the change of thermoplastic WPS to thermosetting adhesives. The bonding strength of WPS-based adhesives was evaluated in particleboard made of sengon (Falcataria moluccana (Miq.) Barneby & J.W. Grimes) wood and rice straw particles at different weight ratios according to the Japanese Industrial Standard (JIS) A 5908:2003. Rheology and Dynamic Mechanical Analysis revealed that modification with MDI and MA resulted in thermosetting properties in WPS-based adhesives by increasing the viscosity at a temperature above 72.7 °C and reaching the maximum storage modulus above 90.8 °C. WPS modified with MDI had a lower activation energy (Ea) value (83.4 kJ/mole) compared to the WPS modified with MA (150.8 kJ/mole), indicating the cross-linking with MDI was much faster compared with MA. Particleboard fabricated from 100% sengon wood particles bonded with WPS modified with MDI fulfilled the minimum requirement of JIS A 5908:2003 for interior applications. [ABSTRACT FROM AUTHOR]

The encapsulation of active components is currently used as common methodology for the insertion of additional functions like self-healing properties on a polymeric matrix. Among the different approaches, polyurea microcapsules are used in different applications. The design of polyurea microcapsules (MCs) containing active diisocyanate compounds, namely isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HDI), is explored in the present work. The polyurea shell of MCs is formed through the interfacial polymerization of oil-in-water emulsions between the highly active methylene diphenyl diisocyanate (MDI) and diethylenetriamine (DETA), while the cores of MCs contain, apart from IPDI or HDI, a liquid Novolac resin. The hydroxyl functionalities of the resin were either unprotected (Novolac resin), partially protected (Benzyl Novolac resin) or fully protected (Acetyl Novolac resin). It has been found that the formation of MCs is controlled by the MDI/DETA ratio, while the shape and size of MCs depends on the homogenization rate applied for emulsification. The encapsulated active compound, as determined through the titration of isocyanate (NCO) groups, was found to decrease with the hydroxyl functionality content of the Novolac resin used, indicating a reaction between NCO and the hydroxyl groups. Through the thorough investigation of the organic phase, the rapid reaction (within a few minutes) of MDI with the unprotected Novolac resin was revealed, while a gradual decrease in the NCO groups (within two months) has been observed through the evolution of the Attenuated Total Reflectance—Fourier-Transform Infrared (ATR-FTIR) spectroscopy and titration, due to the reaction of these groups with the hydroxyl functionalities of unprotected and partially protected Novolac resin. Over longer times (above two months), the reaction of the remaining NCO groups with humidity was evidenced, especially when the fully protected Acetyl Novolac resin was used. HDI was found to be more susceptible to reactions, as compared with IPDI. [ABSTRACT FROM AUTHOR]

The goal of this study is to synthesize, characterize, and analyse a number of chelating polymer resins containing Schiff base ligands that can be utilized to remediate harmful metal-laden industrial wastewater. We create multiple polymer resins to find the ideal conditions for eliminating numerous metal ions. To avoid water pollution, industrial effluent must be cleaned before disposal because it includes high levels of hazardous metals. Several studies on various physical methods for separating, removing, and managing metal toxicants have been conducted. The condensation of 2-hydroxybenzaldehyde L1 and 1,3- benzodioxole-5-carboxaldehyde L2 resulted in the production of isoniazid Schiff base derivatives, specifically isonicotinic acid hydrazide. The azo-methane ligands were detected through the application of spectroscopic techniques, including infrared spectroscopy, mass spectrometry, and 1H-NMR spectroscopy. Two different ways were used to make polymer resins: formaldehyde was used for L1 and methylene diphenyl diisocyanate (MDI) was used for L2. Thermal analysis was used to test the thermal stability of polymers. The cyclic voltammetry method was also used to investigate the electrochemical properties of the Schiff base ligands. Using time and pH, the chelating efficiency and loading capacity of generated ligands toward various metal ions were examined. [ABSTRACT FROM AUTHOR]

Wound plaster polyurethane can make using glycerol from waste cooking oil (WCO). Wound plasters should contain antibacterial ingredients in addition to covering the sore. Traditionally various plants have been used to treat sore and contain sundry antibacterial chemical compounds amid Moringa oleifera Lam. Therefore, it is very potential to make polyurethane wound plasters from glycerol produced from WCO combined with Moringa leaf extract obtained from wound plasters from natural ingredients. Maceration with 96 % ethanol yielded moringa leaf extract. Then, a transesterification reaction carries out by using KOH-methanol at 60 °C to get glycerol and tested by FTIR spectrophotometry. Polyurethane wound plasters were made with a mixture of methylene 4,4 diphenyl diisocyanate, polyethylene glycol (PEG) and various formulas with variations of glycerol 0, 3, 6, 9, 12, 15 and 18 drops. A characteristic test enforced with swelling test to find the best formula and functional group analysis using FTIR spectrophotometry. Into the best wound plaster, improved Moringa leaf ethanol extract at an intensity of 1 - 5 %. An antibacterial activity test carries out on the Moringa leaf ethanol extract and plasters obtained by the agar diffusion method. The FTIR spectrophotometer test showed the formation of glycerol from WCO. The results of the characteristics test for polyurethane wound plaster preparations obtained the best formula using 3 drops of glycerol. The antibacterial activity test results at a concentration of 500 mg/mL Moringa leaf extract produced a muscular inhibition zone of 19.2 mm against Staphylococcus aureus and Antiseptic solution of 17.3 mm; Pseudomonas aeruginosa of 14.3 mm and Antiseptic solvent of 16.2 mm. Antibacterial activity of polyurethane wound plaster against Staphylococcus aureus contains 5 % ethanol extract of 10.3 mm, Plaster Merck X of 11.2 mm, Pseudomonas aeruginosa, only gave resistance at 5 % concentration of 8.3 mm and Plaster Merck X of 9.2 mm. [ABSTRACT FROM AUTHOR]

This study investigated Australian hemp hurd (Cannabis sativa L., "Frog One") as a lignocellulosic raw material for ultra‐low‐density hemp particleboard (ULHPB) with densities ranging from 213 to 309 kg/m3. The hurd was first milled and fractionated into three particle size categories, that is, fine (F), medium (M), and coarse (C). Twelve unique ULHPB variants were then fabricated comprising varying particle loadings from four particle size mixes, that is, 100% C, 100% M, 50%/50% CM, 25%/50%/25% CMF, and adhesive contents of bio‐epoxy (EPX), phenol resorcinol formaldehyde (PRF), and emulsifiable methylene diphenyl diisocyanate (MDI), respectively. The panel assessments, conducted in accordance with the Australian reconstituted wood‐based panels standard AS/NZS 1859.1 (2017), revealed a significant effect of particle dimension on most physico‐mechanical properties. Furthermore, the resination method and pressing temperature controlled post‐cure panel expansion and additional panel characteristics. Notably, MDI‐ULHPB exhibited drastically different behavior and properties compared to EPX and PRF equivalents, demonstrating greater bending strength, stiffness, screw withdrawal strength, and dimensional stability. Importantly, all MDI variants conformed to the 15% thickness swelling limit for moisture resistant particleboard. Surface lamination of MDI‐bonded ULHPB with sheets of aluminum, Masonite, and Kraft liner significantly improved the inherently low flexural properties, suggesting the potential suitability of ULHPB as a core layer in lightweight sandwich composite panels. The integration of agricultural by‐products, such as hemp hurd, into engineered building materials presents a promising opportunity to mitigate the depletion of finite timber resources and aligns well with circular economy principles. Highlights: Utilizing agricultural residue as sustainable raw material in building products.Hemp hurd enables ultra‐low‐density particleboard with thermosetting resins.Coarse particle size mix enhances mechanical performance in panels.Panel characteristics controlled by resination method and pressing temperature.Lamination enhances functionality of lightweight hemp hurd sandwich panel. [ABSTRACT FROM AUTHOR]

Acute intoxication rarely produces conditions that require urgent surgical care. A 45-year-old man presented to the emergency department with severe abdominal pain after the deliberate ingestion of 200 cm3 of polyurethane mixed with methylene diphenyl diisocyanate and urethane primers. On an initial laparoscopic examination, foreign material was observed in the peritoneal space with haemoperitoneum. Emergency exploration was then undertaken for suspected gastric perforation. Full-thickness damage was identified on the stomach wall during the operation. The material in the gastrointestinal tract and peritoneal space was gently removed. Moulded casts of the entire stomach and distal oesophagus were extracted successfully. The patient was discharged 14 days after surgery. Computed tomography revealed foreign material occupying the entire gastric chamber, as well as diffuse gastric perforation. Life-threatening gastric perforation can occur after polyurethane foam ingestion. Clinical/medical toxicologists and emergency physicians need to be aware of the highly expandable nature of this agent. [ABSTRACT FROM AUTHOR]

This paper provides an overview of airborne methylene diphenyl diisocyanate (MDI) concentrations in workplaces across North America and Europe. A total of 7649 samples were collected between 1998 and 2020 by producers of MDI during product stewardship activities at customer sites, primarily using validated OSHA or ISO sampling and analysis techniques. As would be expected from the low vapor pressure of MDI, 80% of the concentrations were less than 0.01 mg/m3 (1 ppb) and 93% were less than 0.05 mg/m3 (5 ppb). Respiratory protection is an integral part of Industrial Hygiene practices; therefore, its use was studied and summarized. While covering a variety of MDI applications, a large number of samples was obtained from composite wood manufacturing facilities, offering specific insight into potential exposures associated with different process sections and job types in this industry sector. Given the potential presence in industrial processes of MDI-containing dust or aerosols, future work should place increased emphasis on also investigating dermal exposure. The data reported in this paper provide valuable information for product stewardship and industrial hygiene purposes throughout the MDI-processing industry. [ABSTRACT FROM AUTHOR]

The study involved producing green thermoplastic polyurethanes (TPUs) that were either partially or fully bio‐based. This was achieved through a one‐shot polymerization process using a combination of sebacic acid‐polyester polyol, 1,4 butanediol derived from renewable sources, and diisocyanate. The diisocyanate used included bio‐aliphatic pentamethylene diisocyanate (PDI), petro‐aromatic methylene diphenyl diisocyanate (MDI), and a combination of PDI and MDI. Various methods were employed to characterize the newly synthesized TPUs, which had a weight average molecular weight exceeding 120,000 g/mol. Increasing the content of PDI improves the bio‐based carbon content up to about 97% and increases the pyrolysis onset temperature. An increase in MDI content results in a rise in the complex viscosity, tensile strength, and strain. However, a PDI‐based TPU (P/M_100/0) achieved an excellent phase separation with a tensile strength of 20.7 MPa and elongation of 587.2%, comparable to an MDI‐based TPU (P/M_0/100). Overall, this research demonstrates the feasibility of utilizing partially or fully bio‐based TPUs as a substitute for conventional MDI, with potential industrial applications. [ABSTRACT FROM AUTHOR]

A new method for the preparation of coatings based on renewable biomaterials such as castor oil and birch flour is suggested in this study. The introduction of birch flour in a polyurethane matrix synthesized from castor oil and oligomeric methylene diphenyl diisocyanate (MDI) leads to a more than doubled value of tensile strength and almost doubled strength of adhesion to steel at 20 wt.% loading. The composite with such level loading has tensile strength equal to 7.1 MPa at an elongation at break of 31%, with an adhesion to steel of 3.71 MPa. Hence, the use of such level loading allows for an increase in tensile strength of 887.5% in comparison with that of polyurethane based on neat (as received) castor oil, leading to a decrease in the value of elongation at break. The adhesion to steel of these composites increases by 185.5% in comparison with starting polyurethane. FTIR and SEM studies identified the mechanism of the reinforcement effect of birch fibers. This reinforcement is based on the good wetting of birch fibers by polyurethane with the formation of chemical bonds between them, and the cellulose and lignin components of wood fillers. As a result, we obtained cheap bio-based coatings with acceptable mechanical and adhesion properties. [ABSTRACT FROM AUTHOR]

Polyurethanes (PUR) are a group of polymers synthesized from different diisocyanate and polyol monomers resulting in a countless number of possible structures. However, the large market demand, and the variety of application fields justify the inclusion of PUR in microplastic (MP) investigation. This study aimed at providing comprehensive information on PUR within MP analysis by pyrolysis–gas chromatography-mass spectrometry to clarify whether (i) it is possible to make a reliable statement on the PUR content of environmental samples based on a few pyrolysis products and (ii) which restrictions are required in this context. PUR were managed as subclasses defined by the diisocyanates employed for polymer synthesis. Methylene diphenyl diisocyanate (MDI)- and toluene diisocyanate (TDI)-based PUR were selected as subclasses of greatest relevance. Different PUR were pyrolyzed directly and under thermochemolytic conditions with tetramethylammonium hydroxide (TMAH). Distinct pyrolytic indicators were identified. The study supported that the use of TMAH greatly reduced the interactions of pyrolytic MP analytes with the remaining organic matrix of environmental samples and the associated negative effects on analytical results. Improvements of chromatographic behavior of PUR was evidenced. Regressions (1–20 µg) showed good correlations and parallelism tests underlined that quantitation behavior of different MDI-PUR could be represented by the calibration of just one representative with sufficient accuracy, entailing a good estimation of the entire subclass if thermochemolysis were used. The method was exemplary applied to road dusts and spider webs sampled around a plastic processing plant to evaluate the environmental spread of PUR in an urban context. The environmental occurrence of MDI-PUR as MP was highly influenced by the proximity to a potential source, while TDI markers were not observed. [ABSTRACT FROM AUTHOR]

The synthesis of a new biobased aromatic diisocyanate derived from lignocellulosic raw material, namely guaiacol and vanillyl alcohol, through phosgene-free route offers the prospect of greener approaches for isocyanate production and the polyurethane industry. Indeed, bisguaiacol F diisocyanate (BGI) was obtained via a three-step process from readily available bisguaiacol F (BGF), involving conversion of aromatic amine into aromatic isocyanate. The unusual transition-metal-free conversion of BGF to bisguaiacol F diamine (BGA) was performed by a two-step approach: (a) the Williamson-type alkylation of BGF and then (b) the base-promoted Smiles rearrangement of bis O-alkylated BGF. In order to improve the sustainability of this process, the first step was realized under solvent-free mechanochemical conditions, and the second step was performed using two different activating methods: thermal and microwave. The thermal process provided an isolated BGA yield of ca. 70%. Microwave activation proved to be an interesting alternative, although a lower yield (32%) of the desired BGA was achieved. Finally, the diisocyanate synthesis was performed via a phosgene-free/room temperature protocol using di-tert-butyl dicarbonate in the presence of a catalytic amount of 4-dimethylaminopyridine (DMAP). Two polyurethane thermosets were designed and synthesized using the aromatic diisocyanates, biobased BGI and petrochemical-based methylene diphenyl diisocyanate (MDI), by a solvent-free two-step polymerization. Their thermo-chemical properties as well as their reactivities for polymer synthesis were evaluated. These preliminary results suggest that BGI could be potentially used as a nearly fully biobased surrogate for MDI. [ABSTRACT FROM AUTHOR]

Performing risk assessments (RA) on household use of flexible polyurethane (PU) foams requires access to reliable data about emission and migration of potential diamine impurities. A toluene diisocyanate (TDI) and a methylene diphenyl diisocyanate (MDI) based foam were thermally treated to enable measurements on samples with defined concentrations of the corresponding diamines, toluene diamine (TDA), and methylene dianiline (MDA). The thermally treated foams used for emission testing contained up to 15 mg.kg−1 of TDA and 27 mg.kg−1 of MDA. Those used for migration testing contained 5.1 mg.kg−1 of TDA and 14.1 mg.kg−1 of MDA. Stability of the thermally generated diamines was sufficient for testing over a 37-day period. Analytical techniques that did not decompose the polymer matrix were applied. Emission rates for TDA and MDA isomers were less than the limit of quantitation (LOQ) of 0.008–0.07 μg.m−2.h−1. Migration was studied using samples of the same thermally treated foams over a 35-day period. Quantifiable migration of MDA from the MDI-based foam was only observed on Days 1 and 2. From Day 3 onward, migration rates were less than the LOQ. Quantifiable migration of TDA from the TDI-based foam rapidly decreased with time and was only observed on Days 1 thru 3. From Day 4 onward, migration rates were less than the LOQ. Theoretically, the migration rate should be inversely proportional to the square root of time (t) as t−0.5. This relationship was confirmed by the experimental data and enables extrapolating migration values to more extended time periods to conduct RAs. [ABSTRACT FROM AUTHOR]

A sampling chamber was developed for emission testing of diisocyanates, methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), and corresponding diamines, methylene diphenyl diamine (MDA), and toluene diamine (TDA) from polyurethane (PU) product surfaces. In addition, a methodology for validation of the sampling chamber was presented, based on the introduction of generated standard atmospheres of the different diisocyanates and diamines to the sampling chamber system. Sampling of diisocyanates and diamines was performed on a circular glass fiber filter (150 mm diameter) impregnated with dihexyl amine (DHA) and acetic acid (AA) positioned inside a cylindrical stainless steel sampling chamber. The diisocyanates were immediately derivatized to DHA derivatives, and the amines were derivatized in a subsequent work-up procedure with ethyl chloroformate (ECF). The design of the sampling chamber and the presented methodology allowed for simultaneous sampling and analysis of diisocyanates and diamines of emission from a large surface area with minimal interior wall interaction in the sampling chamber. Performance characteristics of the sampling chamber for different sampling times and air humidity were obtained by determining collected amounts of the diisocyanates and diamines in the different parts of the sampling chamber. The repeatability of the collected amount on the impregnated filters in the sampling chamber was 15% with an overall recovery for 8 h of sampling in the range of 61% to 96%. The performance of the sampling chamber was not affected by air humidity (5%–75% RH), and no breakthrough during sampling was observed. LC-MS/MS determinations allowed for emission testing of diisocyanates and diamines on product surfaces as low as 10–30 ng m−2 h−1. [ABSTRACT FROM AUTHOR]

4,4′‐Methylene diphenyl diisocyanate (MDI) is an industrially crucial compound, being one of the most utilized linkers in the polyurethane industry. However, its long‐term stability is limited due to dimerization to form insoluble uretdione. Herein we demonstrate an organometallic "catch‐store‐release" concept aiming at improving the long‐term chemical stability of MDI. Treatment of MDI with two equivalents of selected N‐heterocyclic carbenes (NHC) forms stable MDI−NHC adducts. Treatment of the adducts with CuCl forms metastable di‐CuI complexes that undergo decomposition to re‐form MDI (up to 85 %), along with Cu−NHC complexes. The yield of re‐formed MDI can be improved (up to 95 %) by the release of the NHC ligands in the form of thiourea; this prevents subsequent MDI dimerization/polymerization by the carbenes. Furthermore, the need to separate MDI from the reaction mixture can be eliminated by the direct reaction of MDI−NHC complexes with alcohols (as models for diols), that form dicarbamate (as a model for polyurethane) quantitatively. [ABSTRACT FROM AUTHOR]

A series of isosorbide-based thermoplastic polyurethanes (ISB-TPUs) with different soft/hard ratios have been successfully step polymerized using individual two types of polycaprolactone diol (PCL) or poly (tetramethylene glycol) (PTMG) for soft segment and bio-based isosorbide (ISB) or methylene diphenyl diisocyanate (MDI) for hard segment, based on the similar molecular weight. The effect of the molecular structure on the mechanical and thermal properties has been evaluated in terms of the types of soft/hard and polyol, ranging from 6/4 to 9/1 ratio values. With the increasing of PCL content, the thermal properties of the ISB-TPU have enhanced gradually. When the range from PCL was 6/4, the tensile strength has achieved the maximum value in comparison with that of the PTMG block. Elongation at break has increased with the increase of hard segment concentration, due to the superior interaction between ester groups and urethane groups. The obtained ISB-TPUs can be a promising resin for soft, flexible, and biocompatible application fields. [ABSTRACT FROM AUTHOR]

Fiberboards from scrap denim were fabricated using two different resins, melamine urea formaldehyde (MUF) and polymeric methylene diphenyl diisocyanate (pMDI). Resin content and MUF-pMDI weight ratio were studied. Physical and mechanical tests determined the modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB), thickness swell (TS), and water absorption (WA). The resin content had significant impact on all properties. The MOE and IB were affected by the MUF-pMDI ratio. With 17 wt% more pMDI resin portion in the core layer of the denim boards, the IB for the denim fiberboard with a resin content of 15% was enhanced by 306%, while by 205% for the resin content of 25%. The increase in pMDI portion in the core layer of the boards improved both TS and WA of the scrap denim fiberboard. Effective bulk modulus elastography (EBME) was used to measure the acoustic reflection for the estimation of the strength properties of the denim fiberboard. The modulus results from EBME were correlated to the MOR, MOE, and IB of the denim fiberboard. A high correlation was found between the modulus from EBME and IB (R2 > 0.98). EBME can be a great technique to evaluate the bulk modulus distribution of the composites. [ABSTRACT FROM AUTHOR]

In this study, polyurethane (PU)-based xerogels were synthesized by using the biobased polyol derived from chaulmoogra seed oil. These polyol was used for the preparation of PU xerogels using methylene diphenyl diisocyanate hard segment and polyethylene glycol (PEG6000) as soft segment with 1,4-diazabicyclo[2, 2, 2]octane as catalyst. Tetrahydrofuran, acetonitrile and dimethyl sulfoxide were used as the solvents. Nanocellulose (5 wt %) prepared from bagasse were added as filler, and the obtained composite xerogels were evaluated for chemical stability. The prepared samples were also characterized by using SEM and FTIR. Waste sugarcane bagasse nanocellulose proved as a cheap reinforcer in the xerogel synthesis and for the adsorption of Rhodamine-B dye from the aqueous solution. The factors that affect the adsorption process have been studied including the quantity of the adsorbent (0.02–0.06 g), pH (6–12), temperature (30–50) and time (30–90). Central composite design for four variables and three levels with response surface methodology has been used to get second-order polynomial equation for the percentage dye removal. RSM was confirmed by the measurement of analysis of variance. Increase in the pH and quantity of the adsorbent was found to increase the sorption capacities of the xerogel (NC-PUXe) towards rhodamine B, maximum adsorption. [ABSTRACT FROM AUTHOR]

The compatibility between isocyanate and polyol plays an important role in determining a polyurethane product's performance. This study aims to evaluate the effect of varying the ratios between polymeric methylene diphenyl diisocyanate (pMDI) and Acacia mangium liquefied wood polyol on the polyurethane film properties. A. mangium wood sawdust was liquefied in polyethylene glycol/glycerol co-solvent with H2SO4 as a catalyst at 150 °C for 150 min. The A. mangium liquefied wood was mixed with pMDI with difference NCO/OH ratios to produce film through the casting method. The effects of the NCO/OH ratios on the molecular structure of the PU film were examined. The formation of urethane, which was located at 1730 cm−1, was confirmed via FTIR spectroscopy. The TGA and DMA results indicated that high NCO/OH ratios increased the degradation temperature and glass transition from 275 °C to 286 °C and 50 °C to 84 °C, respectively. The prolonged heat appeared to boost the crosslinking density of the A. mangium polyurethane films, which finally resulted in a low sol fraction. From the 2D-COS analysis, the hydrogen-bonded carbonyl (1710 cm−1) had the most significant intensity changes with the increasing NCO/OH ratios. The occurrence of the peak after 1730 cm−1 revealed that there was substantial formation of urethane hydrogen bonding between the hard (PMDI) and soft (polyol) segments as the NCO/OH ratios increased, which gave higher rigidity to the film. [ABSTRACT FROM AUTHOR]

Electronics in furniture and construction materials, in particular technologies which allow for a flexible and cable-free connection of electronics in such materials, are gaining broader interest. This study shows a further development of a concept to obtain highly conductive medium-density fibreboard panels (MDF) for furniture application. MDF were produced using two mixing processes (wet and dry) for wood and carbon fibres to investigate the effects of resin type (urea formaldehyde (UF) and polymeric methylene diphenyl diisocyanate (pMDI)) and carbon fibre content on their mechanical, physical, and electrical properties. Overall, wet mixed fibres showed better electrical but reduced mechanical properties. Modulus of elasticity (MOE) and bending strength (MOR) values of 3500 MPa and 35 MPa, respectively, and internal bond (IB) values of 0.45 to 0.65 MPa with electrical conductivities of up to 230 S/m were achieved. The technology has been successfully implemented in a demonstration object showing the application in a small piece of furniture. [ABSTRACT FROM AUTHOR]

Particleboard (PB) is mainly produced using urea–formaldehyde (UF) adhesive. However, the low hydrolytic stability of UF leads to poor water resistance by the PB. This research aimed to analyze the effect of hot-pressing temperatures and the addition of methylene diphenyl diisocyanate (MDI) in UF adhesive on the physical and mechanical properties of PB. The first experiment focused on pressing temperature treatments including 130, 140, 150, and 160 °C. The particles were bonded using a combination of UF and MDI resin at a ratio of 70/30 (%w/w). Furthermore, the second experiment focused on UF/MDI ratio treatment, including 100/0, 85/15, 70/30, and 55/45 (%w/w), and the particles were pressed at 140°C. All of the single-layer particleboard in this research were produced in 250 × 250 mm, with a target thickness and density of 10 mm and 750 kg/m3, respectively. This research used 12% resin content based on oven-dry weight wood shaving. The pressing time and pressing pressure were determined to be 10 min and 2.5 N/mm2, respectively. Before the tests, the board was conditioned for 7 days. When studying the effect of treatment temperature, good physical properties (thickness swelling and water absorption) and mechanical properties (MOR and MOE) were obtained at 140 °C. However, no significant difference was observed in the UF/MDI ratio between 85/15 and 55/45 using the same temperature. The increase in the MDI adhesive ratio improves the MOE and MOR values. However, the internal bond was the contrary. This study suggests that a combination of UF/MDI at a ratio of 85/15 and hot-pressing temperature at 140 °C could produce a PB panel that meets a type 8 particleboard according to the JIS A5908-2003 standard and type P2 according to the EN 312-2010 standard. [ABSTRACT FROM AUTHOR]

As the interest in self-healing and scratch-resistant coatings has increased, studies on incorporating dynamic covalent bonds in protective elastomeric coating materials have increased. The incorporation of reversible disulfide bonds into polyurethane (PU) elastomers imparts self-healing property and recyclability, which not only reduce maintenance costs but also extend the service lives of the coated products. In this study, we developed two-component self-healing PU spray paint materials with superior healing properties and thermal stability. This achievement involved the synthesis of oligomeric precursor diols of PU incorporating disulfides of different molecular weights and controlling the hardener ratio in the final spray-coating material. Variations in the scratch-healing ability and stability of the coating films were investigated based on the type of the disulfide employed in the aromatic and aliphatic moieties and the combination of diisocyanates. Among the tested specimens, a coating film fabricated from a precursor denoted as H13 (molar feed ratio of isophorone diisocyanate:bis(4-hydroxyphenyl)disulfide:carbonate-type soft diol = 10:5:8) cured with a hardener (molar ratio of methylene diphenyl diisocyanate:isophorone diisocyanate = 1:1) showed excellent healing performance, showing >95 % scratch recovery within 2 h at 30 °C. It also exhibited transparency, solvent resistance, and thermal stability. [Display omitted] • A novel self-healing polyurethane (PU) spray paint coating is developed, utilizing reversible disulfides for recyclability. • Optimal formulation with aromatic disulfide-containing carbonate diol achieves >95 % scratch recovery within 2 h at 30 °C. • Optimized coating shows transparency, solvent resistance, and thermal stability, adding practical benefits for applications. • This PU coating makes it an attractive option for industries requiring both self-healing and durable protective coatings. [ABSTRACT FROM AUTHOR]

Biodegradable plastics in single-use products have increased in popularity as a way to reduce the negative environmental impact of conventional plastics and meet the tightening law regulations. However, their recyclability needs to be assessed, as the environmental behavior of single-use plastics, even if compostable, is not negligible. Polylactide (PLA) is susceptible to thermal, oxidative, hydrolytic, and mechanical degradation during reprocessing, so the conditions of such cycles must be accurately controlled. The necessity of using additives to reduce such degradations during rotational molding, a process with long cycle times and oxidizing atmosphere, has been demonstrated. Chain extenders based on a carbodiimide (Bioadimide® 100 - KI), a methylene diphenyl diisocyanate (MDI), and a polystyrene-acrylic copolymer (Joncryl® ADR-4368c - J) have been added to post-consumer PLA wastes. It has been demonstrated that these three chain extenders enabled obtaining a higher molecular weight of the reprocessed polymer, compared to the ∼50% reduction for the neat PLA. The use of carbodiimide yielded the most similar performance to that of unprocessed raw material. All samples provided adequate thermal stability and processing parameters for the rotational molding. Carbodiimide is considered the most efficient additive, as it increases the molecular mass of the polymer as it remains unchanged after processing. Similarly, KI-modified PLA rheological behavior remains unchanged after processing, which means this compound can reduce thermooxidative and hydrolytic degradation reactions. Thus contributing to the achievement of improved processability and better performance; in particular, impact strength increased from 1.06 ± 0.56 for PLA to 8.12 ± 2.28 kJ/m2 for KI-modified PLA, and toughness of 5.36 ± 1.61 to 61.49 ± 8.01 J/mm3, respectively, leading to rotomolded items without structural defects. On the opposite, the use of Joncryl® and MDI led to structural defects in the rotomolded parts despite a higher molecular weight of the polymer, which resulted in poor mechanical properties, although better than PLA without any additive. All three chain extenders resulted in an amorphous PLA structure with increased glass transition temperature and improved thermal stability, which correlated with the reduced emissions of volatile compounds compared to neat recycled PLA. The presented findings significantly contribute to a better understanding of PLA and its modifications at a molecular scale required for its efficient and possibly environmentally burden-free reprocessing. Gathered knowledge will be crucial for optimizing its environmental performance and widening its applications, particularly in a process with long cycle times and oxidative character, such as rotational molding. [ABSTRACT FROM AUTHOR]

A series of biobased alkyd resins having hydroxyl functionalities was synthesized using Madhuca indica (mahua) seed oil as a renewable source on reaction with various diacids and anhydrides. Functional group transformation and alkyd formation were confirmed by ATR-FT-IR and proton NMR spectroscopies as well as by end group analysis. Polyols containing hydroxyl functionalities were utilized in combination with polymeric methylene diphenyl diisocyanate (PMDI) to produce polyurethane (PU) in the form of coatings, which were examined for their gloss, impact, flexibility, cross-cut adhesion, etc. Anticorrosion property of coatings was investigated by immersion method and by electrochemical method in an aqueous salt solution. Additionally, coatings were subjected to their thermal behavior study using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). While crystalline and amorphous behaviors of PUs were studied by X-ray diffraction (XRD). The mahua oil-based PUs revealed excellent coating properties, thermal stability, and anticorrosion performance. Thus, untapped mahua oil can act as a good source of replacement for petroleum in the preparation PU coatings. [Display omitted] • Mahua oil from barren land is utilized to synthesize alkyd polyols. • Alkyd polyols were used to develop renewable source based of PU coatings. • MO alkyd based PU coatings are with good coating properties. • PU coatings showed better anticorrosion performance as tested by immersion and electrochemical methods than uncoated panel. [ABSTRACT FROM AUTHOR]

Based on the difference in the reaction rate of different groups of urea‐formaldehyde resins and isocyanate resins, this study designed two different urea‐formaldehyde resins: a normal urea‐formaldehyde resin (UF) and one with high mono‐hydroxymethylurea content (UF*) to react with polymeric methylene diphenyl diisocyanate (pMDI) resin. The difference in mono‐ and di‐hydroxymethyl urea content between UF and UF* resins was analyzed by nuclear magnetic resonance (NMR) spectroscopy, and results showed that the mono‐hydroxymethyl urea content of the UF* resin was much higher than that of the conventional UF resin. The fourier transform infrared spectrometer (FTIR) analysis of differences between UF* and UF resin showed that the UF* process did not change the main structure of the conventional urea formaldehyde resin. Differential scanning calorimeter (DSC) analysis showed that the curing temperature of the hybrid UF*‐pMDI resin was reduced 27.3°C compared to that of the UF‐pMDI resin. When these hybrid resins were used to bond plywood respectively, test results showed that the UF*‐pMDI resin improved the dry and wet bonding strength by 2.6% and 3.9%, respectively, compared with the UF‐pMDI resin under the condition of hot pressing time (3 min) and temperature (140°C), meeting the requirement of Chinese standard of GB/T 9846–2015 for Class III board. This study provides a new path for further improving the performance and design of hybrid resins based on isocyanate and urea‐formaldehyde resin. [ABSTRACT FROM AUTHOR]

Bio-based polyureas (PUs) with main-chain furan rings were synthesized by the polyaddition of 2,5-bis(aminomethyl)furan with various diisocyanates, such as methylene diphenyl diisocyanate. Several PU's were soluble in polar organic solvents, and were cast to form thermomechanically stable films with softening temperatures of over 100 °C. The furan rings of the PU main chains underwent a dynamic Diels-Alder (DA) reaction with bismaleimide (BMI) cross-linkers. While the mixed solution of PU and BMI did not show any apparent signs of reaction at room temperature, the DA reaction proceeded to form gels upon heating to 60 °C, which became a solution again by further heating to 80 °C (retro-DA reaction). The solution phase was maintained by rapid quenching from 80 °C to room temperature, while the gel was reformed upon slow cooling. The recovered gels exhibited self-healing properties. A scratch made by a hot knife at temperatures above 80 °C disappeared spontaneously. When two different gels were cut using a knife at room temperature, placed in contact with each other, and heated to 60 °C, they fused. The ability to control the DA/retro-DA reaction allowed gels of varying composition to heal. [ABSTRACT FROM AUTHOR]

For glulam bonding performance assessment, the traditional method of manually measuring the wood failure percentage (WFP) is insufficient. In this paper, we developed a rapid assessment approach to predicate the WFP based on deep-learning (DL) techniques. bamboo/Larch laminated wood composites bonded with either phenolic resin (PF) or methylene diphenyl diisocyanate (MDI) were used for this sample analysis. Scanning of bamboo/larch laminated wood composites that have completed shear failure tests using an electronic scanner allows a digital image of the failure surface to be obtained, and this image is used in the training process of a deep convolutional neural networks (DCNNs).The result shows that the DL technique can predict the accurately localized failures of wood composites. The findings further indicate that the UNet model has the highest values of MIou, Accuracy, and F1 with 98.87%, 97.13%, and 94.88, respectively, compared to the values predicted by the PSPNet and DeepLab_v3+ models for wood composite failure predication. In addition, the test conditions of the materials, adhesives, and loadings affect the predication accuracy, and the optimal conditions were identified. The predicted value from training images assessed by DL techniques with the optimal conditions is 4.3%, which is the same as the experimental value measured through the traditional manual method. Overall, this advanced DL method could significantly facilitate the quality identification process of the wood composites, particularly in terms of measurement accuracy, speed, and stability, through the UNet model. [ABSTRACT FROM AUTHOR]

Palm oil-based polyol from polyethylene glycol-9,10-dihydroxy monostearate has been synthesized to prepare polylactic acid/polyurethane block copolymer via a two-step reaction. Step one is the esterification of oleic acid and polyethylene glycol 400 to produce polyethylene glycol monooleate. The second step is the epoxidation and hydroxylation of polyethylene glycol monooleate to produce polyethylene glycol-9,10-dihydroxy monostearate. Furthermore, the synthesized was used as the raw material for the synthesis of polyurethane prepolymer by reacting with methylene diphenyl diisocyanate in the presence of dibutyltin dilaurate as the catalyst. The prepolymer obtained then reacted with polylactic acid to produce block copolymer.The characterizations of block copolymer were conducted by Fourier transforms infrared and nuclear magnetic resonance (NMR) spectroscopy, thermogravimetry analysis. The isocyanate conversion of block copolymer was 89.3%. This indicated that prepolymer has reacted with polylactic acid to produce block copolymer. [ABSTRACT FROM AUTHOR]

Background: Isocyanates are well‐known occupational allergens, but can also be present in medical devices. Objectives: To highlight that contact sensitization to isocyanates might contribute to allergic contact dermatitis (ACD) from polyurethane (PU)‐containing diabetes devices and wound dressings. Patients and Methods: Nineteen patients with suspected ACD from diabetes devices and/or wound dressings were patch tested to an isocyanate series. Four wound dressings, six diabetes devices and four monomeric isocyanate patch test preparations were analysed with gas chromatography – mass spectrometry. Results: Eight patients reacted to isocyanates and corresponding amines: 3 to isophorone diisocyanate (IPDI), 4 to 4,4′‐diaminodiphenylmethane (MDA), 4 to 2,4‐toluene diisocyanate (TDI) and 1 to polymeric methylene diphenyl diisocyanate (PMDI). Three of four wound dressings contained isocyanates (methylene diphenyl diisocyanate [MDI], TDI and/or IPDI), whereas five of six diabetes devices contained 4,4′‐MDI, and one of them also IPDI. None of the medical devices contained 1,6‐hexamethylene diisocyanate. Contrary to IPDI, and especially MDI, only the concentration of the TDI patch test preparation corresponded approximately (80%) to its label. Conclusion: Patch tests with isocyanates may be worth‐while in patients with suspected ACD from PU‐containing medical devices. Besides MDA, and PMDI, also TDI might potentially be a marker for MDI‐sensitization. [ABSTRACT FROM AUTHOR]

Oil palm (Elaeis guineensis Jacq.) plantations in Indonesia are increasing over the past few years. After economic productivity, however, the unproductive oil palm trunks are felled and mostly go to waste, especially the inner part of the oil palm trunk (IOPT). There are several modification methods to utilize IOPT, such as impregnation and densification. Methylene diphenyl diisocyanate (MDI) is a common resin used for impregnation in composite industries because it is non-toxic and has excellent physical and mechanical properties but it has never been applied for the impregnation of IOPT. This study aimed to analyze the effect of densification on the physical and mechanical properties of the inner part of oil palm trunk (IOPT) impregnated using methylene diphenyl diisocyanate (MDI) resin to obtain valuable information regarding the efficient utilization of unproductive oil palm trunks. IOPT was densified and compregnated with compression ratios (CRs) of 20% and 30%. The physical properties (density, moisture content (MC), and water absorption (WA)) and mechanical properties (modulus of elasticity (MOE), modulus of rupture (MOR), and hardness) of the compregnated samples were better than those of the densified samples. The density and mechanical properties at CR 30% were higher than those at CR 20%. The improvements in density, MC, and WA of the compregnated IOPT with CR 30% were 127%, 54%, and 70%, respectively, compared to that in untreated IOPT. Furthermore, improvements in the MOE, MOR, and hardness of the compregnated IOPT with CR 30% were 489%, 379%, and 393%, respectively. The mechanical properties of the compregnated IOPT at CR 20% and 30% increased two- to three-fold from strength class V in control IOPT to strength class III in compregnated IOPT with CR 20% and to strength class II in compregnated IOPT with CR 30%, respectively. [ABSTRACT FROM AUTHOR]

Aliphatic diol HO― (CH2)6― S― S― (CH2)6― OH containing disulfide bond (DSU) was synthesized by the nucleophilic substitution reaction of halohydrocarbon, which was introduced into polyurethane molecules in the form of hard segment. A series of polyurethane composites modified by disulfide bond were prepared by using methylene diphenyl diisocyanate (MDI), dopamine modified castor oil and DSU as raw materials, and their structures and properties were optimized. The chemical structure of DSU was characterized by 1H-NMR, and the influence of DSU amount on polyurethane was investigated, including the compressive mechanical properties, water contact angle, microstructure and bone bonding strength. The main conclusions include that the compressive properties and hydrophobicity of polyurethane composites increased with the increase of DSU dosage, and the bone adhesion strength increased first and then decreased. As m (DSU)∶ m (DACO)=10%, the composites presented the best comprehensive properties with the bone adhesion strength of 0.97 MPa in the buffer solution and 0.49 MPa in rabbit blood, compression strength of 7.0 MPa, compression modulus of 41.3 MPa and average bubble size of 150 μm. In vitro culture experiments of rat bone marrow mesenchymal stem cells showed that the polyurethane composites had excellent cytocompatibility. The cell staining results by Calcein-AM showed that the porous structure of the material was conducive to cell proliferation and adhesion, which was in favour of fracture healing and reconstruction. This new material prepared in this work is expected to be used in the field of medical bone adhesives. [ABSTRACT FROM AUTHOR]

The sensitization potencies of twenty custom-designed monomer-depleted polymeric polyisocyanate prepolymer substances and their associated toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI) monomer precursors were investigated by means of the mouse Local Lymph Node Assay (LLNA). These polymeric prepolymers were designed to represent the structural features and physical-chemical properties exhibited by a broad range of commercial polymeric polyisocyanate prepolymers that are produced from the reaction of aromatic and aliphatic diisocyanate monomers with aliphatic polyether and polyester polyols. The normalization of LLNA responses to the applied (15-45-135 mM) concentrations showed that the skin sensitization potency of polymeric polyisocyanate prepolymers is at least 300 times less than that of the diisocyanate monomers from which they are derived. The sensitization potency of the prepolymers was shown to be mainly governed by their hydrophobicity (as expressed by the calculated octanol-water partition coefficient, log Kow) and surfactant properties. Neither hydrophilic (log Kow <0) nor very hydrophobic (log Kow >25) prepolymers stimulated lymphocyte proliferation beyond that of the dosing vehicle control. The findings of this investigation challenge the generally held assumption that all isocyanate (-N=C=O) bearing substances are potential skin (and respiratory) sensitizers. Further, these findings can guide the future development of isocyanate chemistries and associated polyurethane applications toward reduced exposure and health hazard potentials. [ABSTRACT FROM AUTHOR]