Diphenylmethane Diisocyanate Research Articles

New Method to Biomonitor Workers Exposed to 1,6-Hexamethylene Diisocyanate.

Isocyanates such as 1,6-hexamethylene diisocyanate (HDI), 4,4'-methylenediphenyl diisocyanate, and toluene diisocyanate are highly reactive compounds that have a variety of commercial applications, including manufacturing polyurethane foam, elastomers, paints, adhesives, coatings, insecticides, and many other products. Their primary route of occupational exposure is through inhalation. Due to their high chemical reactivity, they are toxic and have adverse effects at the cellular and subcellular levels, leading to irritative and immunological reactions associated with lung disease. High concentrations of isocyanates are strong respiratory irritants. Bronchial sensitization and asthma are among the major adverse clinical reactions associated with low-level chronic exposure to isocyanates. Albumin adducts have been linked to the mechanism of occupational asthma caused by isocyanates. Isocyanates react in vivo with albumin, which is recognized by the immune system. Albumin adducts of isocyanates trigger immune responses and are probably the antigenic basis for isocyanate asthma. Sensitization to isocyanates is the main pathway for adverse health effects. Therefore, markers for the biologically effective dose such as albumin adducts of HDI are needed. A new isocyanate adduct of HDI with lysine─Nε-[(6-amino-hexyl-amino)carbonyl]-lysine (HDI-Lys)─was synthesized and characterized by 1H-NMR, 13C-NMR, and mass spectrometry (MS). Appropriate internal standards─HDI-Lys-4,4'-5,5'-d4 (HDI-d4-Lys) and Nε-[(7-amino-heptyl-amino)carbonyl]-lysine (Hep-Lys)─were synthesized to establish a LC-MS/MS method for the analysis of HDI adducts in in vitro modified albumin and in workers. The presence of HDI-Lys was found after pronase digestion of albumin and confirmed by two independent chromatographic approaches: with a C8 reversed-phase column and with a hydrophilic interaction liquid chromatography column. Quantification was performed with positive electrospray ionization (ESI)-MS. The adduct peak found in vivo was confirmed with the less sensitive negative ESI-MS. In summary, these are new compounds and methods to determine isocyanate-specific adducts with albumin in workers exposed to HDI.

Effects of Particle Dimension and Constituent Proportions on Internal Bond Strength of Ultra-Low-Density Hemp Hurd Particleboard

The recent legalisation of hemp seeds for human consumption has revitalised the cultivation of hemp in Australia. This provides opportunities for the valorisation of the stem’s residual xylemic core (hemp hurd). This study investigated the effect of particle dimension and constituent proportions on the internal bond strength (IB) of single-layer, ultra-low-density hemp hurd particleboard (ULHPB) with densities between 219 to 304 kg/m3. Particle size distributions (PSD) and granulometry assessments were conducted on three particle size classes (fine (F), medium (M), coarse (C)) based on digital image analysis using ImageJ. Subsequently, four particle size mixes (100% C, 100% M, 50/50% CM, 25/50/25% CMF) were considered for the ULHPB manufacture with bio-epoxy (EPX), phenol resorcinol formaldehyde (PRF) and emulsifiable methylene diphenyl diisocyanate (MDI) adhesives, respectively. The effect of particle loading and adhesive content varied significantly per adhesive type. Internal bond (IB) performance increased in most ULHPB comprising coarse particles and declined with the addition of smaller particle sizes. The granulometry assessment showed the smallest mean elongation amongst particles in the coarse PSD. The IB results confirmed a strong interdependence of particle size and constituent proportions and indicated that various MDI-ULHPB variants can surpass the minimum IB strength requirement of 0.30 MPa stipulated for standard particleboard (>12–22 mm) in AS/NZS 1859.1. Utilising residual hemp biomass as an alternative, renewable lignocellulosic feedstock in the manufacture of engineered lightweight panel products is a key principle of circular economy and an environmentally friendly strategy to address the increasing resource scarcity in the wood-based panel industry.

Study of hybrid isocyanate and high‐mono‐hydroxymethyl urea content urea‐formaldehyde resins

AbstractBased 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.

Controlled release fertilizer with temperature-responsive behavior coated using polyether polyol (PPG) / polycaprolactone (PCL) blend-based polyurethane performs smart nutrient release

The development of the temperature-responsive controlled release fertilizers (CRFs) can tune the nutrient release matching plant demands even when temperature fluctuates. Herein, polycaprolactone (PCL) with different molecular weights (PCL500, PCL1000, PCL2000 and PCL3000) were used as raw materials and six types of PU films as coating materials for CRFs were synthesized by reacting the polyether polyol (PPG)/PCL blends and methylene diphenyl diisocyanate (MDI). Furthermore, the CRFs coated using PU films (PUCFs) were prepared in a fluidized bed device by in-situ reaction method, and the nitrogen (N) release rate of PUCFs was measured by water immersion experiment. The temperature sensitivity and compositions of PU films were evaluated with differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Results showed that PUCFs based on PCL500 satisfied the CRF ISO standard, but the corresponding PU film had no temperature-responsive property. However, PUCFs based on PCL2000 and the corresponding PU film showed the opposite results. FTIR and XRD results showed that the PPG/PCL2000 blends could copolymerize with MDI to format the block copolymer with the two-phase structure of crystalline phase/amorphous phase. The block copolymer comprising of PPG and PCL2000 at a molar ratio of 8 to 2 was indicated to have shape memory characteristics and the CRFs coated by this copolymer had excellent N release characteristics with a controlled release period of more than 30 days. Moreover, these CRFs showed significant temperature-switch at 33 °C. In conclusion, the production of temperature-responsive PUCF which is suitable for the application into agriculture will improve nutrient availability, indicating that the stimuli-responsive system has potential application in sustainable and green development of agriculture.

Literature review and evaluation of biomarkers, matrices and analytical methods for chemicals selected in the research program Human Biomonitoring for the European Union (HBM4EU).

Humans are potentially exposed to a large amount of chemicals present in the environment and in the workplace. In the European Human Biomonitoring initiative (Human Biomonitoring for the European Union = HBM4EU), acrylamide, mycotoxins (aflatoxin B1, deoxynivalenol, fumonisin B1), diisocyanates (4,4'-methylenediphenyl diisocyanate, 2,4- and 2,6-toluene diisocyanate), and pyrethroids were included among the prioritized chemicals of concern for human health. For the present literature review, the analytical methods used in worldwide biomonitoring studies for these compounds were collected and presented in comprehensive tables, including the following parameter: determined biomarker, matrix, sample amount, work-up procedure, available laboratory quality assurance and quality assessment information, analytical techniques, and limit of detection. Based on the data presented in these tables, the most suitable methods were recommended. According to the paradigm of biomonitoring, the information about two different biomarkers of exposure was evaluated: a) internal dose = parent compounds and metabolites in urine and blood; and b) the biologically effective = dose measured as blood protein adducts. Urine was the preferred matrix used for deoxynivalenol, fumonisin B1, and pyrethroids (biomarkers of internal dose). Markers of the biological effective dose were determined as hemoglobin adducts for diisocyanates and acrylamide, and as serum-albumin-adducts of aflatoxin B1 and diisocyanates. The analyses and quantitation of the protein adducts in blood or the metabolites in urine were mostly performed with LC-MS/MS or GC-MS in the presence of isotope-labeled internal standards. This review also addresses the critical aspects of the application, use and selection of biomarkers. For future biomonitoring studies, a more comprehensive approach is discussed to broaden the selection of compounds.

Preparation of microcapsules with IPDI monomer and isocyanate prepolymer as self-healing agent and their application in self-healing materials

Microcapsules were synthesized with the hybrid of Isophorone diisocyanate (IPDI) and terminal isocyanate prepolymer (CPU) as active healing agent, then the microcapsules were mixed with epoxy resin in order to form a metal anti-corrosion coating with excellent self-healing properties. Through process optimization and molecular design, the core material which was isocyanate hybrid (CPU-IPDI) with 17% Isocyanate group (-NCO) was synthesized by the reaction of IPDI and castor oil, and then the CPU-IPDI was encapsulated in the microcapsule with Diphenylmethane diisocyanate (MDI) as the shell by interface polymerization. Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric spectroscopy (TGA) confirmed the successful encapsulation of CPU-IPDI. The effect of the content of sodium lignosulfonate (NaLS) on the size and morphology of microcapsules were investigated. Optical microscopy (OM) and laser particle size analyzer show that the size of microcapsules decreases with the increase of the content of stabilizing agent. The microcapsules were prepared with 1% NaLS with a core content of 51.3%, an average particle size of 26.3 μm and a shell thickness of 1.44 ± 0.9 μm. In addition, the microcapsules loaded with CPU-IPDI were added to the epoxy coating, and the healing process of blank coating and self-healing coating was detected by SEM. The results show that the coating wound of containing 10% microcapsules has obvious healing. With saline infiltration and electrochemical impedance spectroscopy (EIS) test coating corrosion process, the results prove that after soaking in 3.5% NaCl solution for 7 days, the |Z| f = 0.01Hz value of the coating with 10 wt % microcapsules is about 1.9 × 106 Ω cm2, nearly three order higher than that of pure epoxy coating (3.1 × 103 Ω cm2), demonstrating the enhancement of protection ability.

On the Development of Nanocomposite Covalent Associative Networks Based on Polycaprolactone and Reduced Graphite Oxide.

In this work, the development of nanocomposite systems based on reduced graphite oxide (rGO) was combined with the development of crosslinked materials characterized by dynamic covalent bonds, i.e., a covalent associative network, starting from ad-hoc synthesized hydroxyl terminated polycaprolactone (PCL-OH). The crosslinking reaction was carried out using methylenediphenyl diisocyanate (MDI) to create systems capable of bond exchanges via transesterification and transcarbamoylation reactions, in the presence of stannous octoate as a catalyst. The above materials were prepared at two different temperatures (120 and 200 °C) and two PCL-OH:MDI ratios. FT-IR measurements proved the formation of urethane bonds in all the prepared samples. Crosslinking was demonstrated by contacting the samples with a solvent capable of dissolving the star-shaped PCL. These tests showed a significant increase in the crosslinked fraction with increasing the temperature and the PCL-OH:MDI ratio. In order to evidence the effect of crosslinking on rGO dispersion and the final properties of the material, a nanocomposite sample was also prepared using a linear commercial PCL, with the nanofiller mixed under the same conditions used to develop the crosslinked systems. The dispersion of rGO, which was investigated using FE-SEM measurements, was similar in the different systems prepared, indicating that the crosslinking process had a minor effect on the dispersibility of the nanofiller. As far as the thermal properties are concerned, the DSC measurements of the prepared samples showed that the crosslinking leads to a decrease in the crystallinity of the polymer, a phenomenon which was particularly evident in the sample prepared at 200 °C with a PCL-OH: MDI ratio of 1:1.33 and was related to the decrease in the polymer chain mobility. Moreover, rGO was found to act as a nucleating agent and increase the crystallization temperature of the nanocomposite sample based on linear commercial PCL, while the contribution of rGO in the crosslinked nanocomposite samples was minor. Rheological measurements confirmed the crosslinking of the PCL-OH system which generates a solid-like behavior depending on the PCL-OH:MDI ratio used. The presence of rGO during crosslinking generated a further huge increase in the viscosity of the melt with a remarkable solid-like behavior, confirming a strong interaction between rGO and crosslinked PCL. Finally, the prepared nanocomposites exhibited self-healing and recyclability properties, thus meeting the requirements for sustainable materials.

Development of a Method for Preservation, Extraction, and Quantitation of 4,4’-Methylenedianiline in Soils of Varied Texture and Organic Matter Content

ABSTRACT Despite the reactivity and degradability of 4,4’-methylenedianiline (4,4’-MDA) with organic matter in soils, the improvement of Brunet et al. method makes it possible to monitor the substance in the environment. In fact, 4,4’-MDA can be found in soils, used for agriculture for example, if 4,4’-methylene diphenyl diisocyanate (4,4’-MDI) based fertilizers and pesticides are used. The possible degradation of 4,4’-MDI-based polyurethane could result in formation of 4,4’-MDA. To have a soil where 4,4’-MDA could be uniformly distributed, an impregnation method was developed. The method was validated using 1 g of the impregnated soil ranging 2,4% to 10% of organic matter, and the addition of both internal and surrogate standard to correct any losses of the substance over the different steps of the method. The limit of detection (LOD) and limit of quantification (LOQ) for the determination of 4,4’-MDA in soil are 0.107 and 0.358 μg/kg (dry weight), respectively, with a dynamic range between 5 and 250 μg/kg. For the intra-day precision, the result was 4,28% and for the inter-day, it was 9,32%. The accuracy was 96,4% and the total recovery obtained was 82.02%. Moreover, the stability of 4,4’-MDA was demonstrated in dry soil samples or in samples completely immersed in methanol over a 14-day period.

Bio-Inspired Pangolin Design for Self-Healable Flexible Perovskite Light-Emitting Diodes.

Despite tremendous developments in the luminescene performance of perovskite light-emitting diodes (PeLEDs), the brittle nature of perovskite crystals and their poor crystallinity on flexible substrates inevitably lead to inferior performance. Inspired by pangolins' combination of rigid scales and soft flesh, we propose a bionic structure design for self-healing flexible PeLEDs by employing a polymer-assisted crystal regulation method with a soft elastomer of diphenylmethane diisocyanate polyurethane (MDI-PU). The crystallinity and flexural strain resistance of such perovskite films on plastics with silver-nanowire-based flexible transparent electrodes are highly enhanced. The detrimental cracks induced during repeated deformation can be effectively self-healed under heat treatment via intramolecular/intermolecular hydrogen bonds with MDI-PU. Upon collective optimization of the perovskite films and device architecture, the blue-emitting flexible PeLEDs can achieve a record external quantum efficiency of 13.5% and high resistance to flexural strain, which retain 87.8 and 80.7% of their initial efficiency after repeated bending and twisting operations of 2000 cycles, respectively.

Supramolecular hierarchical polyurethane elastomers for thermal and mechanical property optimization

Supramolecular chemical designs that integrate complementary hydrogen bond donor and acceptor complexes in hierarchical polyurethane elastomers are reported. N2,N6-bis(2-hydroxyethyl)pyridine-2,6-dicarboxamide (PDA) and 5,5-bis(3-hydroxypropyl)barbituric acid (BBA) react with 4,4′-methylenediphenyl diisocyanate (MDI) to produce hard segments capable of multiple intermolecular hydrogen bonds in MDI-PDA/BBA-poly(tetramethylene oxide) (PTMO) polyurethanes. The addition of PDA facilitates the formation of a supramolecular complex, and BBA affords greater intersegmental mixing. As a result, these polyurethanes exhibit higher glass transition temperatures (Tg) and greater strain hardening/strengthening under tensile deformation than a microphase-separated MDI-butanediol (BDO)-PTMO analog. Additionally, increased PDA and BBA contents results in up to a 60 °C increase of Tg determined at 1 Hz via DMA relative to those determined by calorimetric measurements via DSC, which is considerably higher than the 15 °C Tg increase observed in the MDI-BDO-PTMO analog. These results highlight a significant interplay between intersegmental mixing and supramolecular hydrogen bond interactions for the design of robust hierarchical elastomers.

Constitutive Law Identification and Fatigue Characterization of Rigid PUR Elastomers 80 ShA and 90 ShA.

This paper presents the results of a study of polyurethane rigid (PUR) elastomers in terms of the constitutive law identification, and analyses the effect of polyurethane elastomers’ hardness on fatigue properties. The research objects were PUR materials based on 4,4′-diphenylmethane diisocyanate (MDI) with the hardness of 80 ShA and 90 ShA, typically used in various industrial applications. Based on the performed experimental campaign under static and cyclic loading, the constitutive model proposed by Ogden is most appropriate. In addition, a hybrid numerical–experimental analysis (using FEM-DIC) of diabolo specimens’ behaviour is carried out in fatigue tests. Based on the performed fatigue test, it is worth noting that the energy approach describes the fatigue process synonymously compared to the displacement or strain approach. Finally, simple fatigue characteristics were analyzed and statistically validated for both PUR material configurations.

Vitrimeric Polylactide by Two-step Alcoholysis and Transesterification during Reactive Processing for Enhanced Melt Strength.

Because of its rather low melt strength, polylactide (PLA) has yet to fulfill its promise as advanced biobased and biodegradable foams to replace fossil-based polymer foams. In this work, PLA vitrimers were prepared by two-step reactive processing from commercial PLA thermoplastics, glycerol, and diphenylmethane diisocyanate (MDI) using Zn(II)-catalyzed addition and transesterification chemistry. The transesterification reaction of PLA and glycerol occurs with zinc acetate as the catalyst, and chain scission will take place due to the alcoholysis of the PLA chains by the free hydroxyl groups from the glycerol. Long-chain PLA with hydroxyl groups can be obtained and then cross-linked with MDI. Rheological analysis shows that the formed cross-linked network can significantly improve melt strength and promote strain hardening under extensional flow. PLA vitrimers still maintain the ability of thermoplastic processing via extrusion and compression. The enhanced melt strength and the rearrangement of network topology facilitate the foaming processing. An expansion ratio as large as 49.2-fold and microcellular foam with a uniform cell morphology can be obtained for PLA vitrimers with a gel fraction of 51.8% through a supercritical carbon dioxide foaming technique. This work provides a new way with the scale-up possibility to enhance the melt strength of PLA, and the broadened range of PLA applicability brought by PLA vitrimers is truly valuable in terms of the realization of a sustainable society.

Novolac-based microcapsules containing isocyanate reagents for self-healing applications

Microcapsules (MCs) containing isocyanate compounds for use as self-healing materials in waterborne polyurethane coatings have been synthesized, in the presence of modified Novolac resins. With modification of Novolac resin, it is succeeded partial or total protection (Benzylation and Acetylation) of its hydroxyl groups. The idea here is to use a protected Novolac resin as the organic substrate for the encapsulation of the less reactive Isophorone isocyanate (IPDI) while the more reactive one, Methylene diphenyl diisocyanate (MDI), is used for the shell formation. Based on that strategy microcapsules of different morphologies and sizes were obtained, depending on the agitation conditions, as revealed using SEM and optical microscopy. Selective extraction was performed to determine the amount of the less reactive isocyanate (IPDI) stored inside the capsules through FTIR-ATR spectroscopy and isocyanate titration as well as the stability of IPDI inside the capsules over time. As determined, microcapsules based on Acetyl-modified Novolac resin encapsulated 96 wt% of IPDI monomer; this amount is about five and ten times higher than that encapsulated in MCs based on by Benzyl-modified Novolac resin or unprotected Novolac resin, respectively. At the same time, MCs based on Acetyl-modified Novolac resin were stable, maintaining approximately 80 % of the initial isocyanate content after two months of storage under inert conditions. Finally, the self-healing ability of the microcapsules was tested by adding selected IPDI-loaded microcapsules in waterborne polyurethane dispersions. It was proven that the Acetyl-modified Novolac-based MCs showed efficient healing behavior, in the absence of any catalyst, on the polyurethanes’ surfaces when scratched artificially.

Thermal storage properties of polyurethane solid-solid phase-change material with low phase-change temperature and its effects on performance of asphalt binders

Preparing phase change materials (PCMs) with appropriate phase-change temperatures is of great significance in preventing the low-temperature disease in pavements. In this study, several polyurethane solid-solid PCM (PUPCM) samples were prepared via a two-step condensation reaction of polyethylene glycol, polytetramethylene ether glycol, 4,4′-diphenyl methane diisocyanate, and 4,4′-methylenebis-(2-chloroaniline). Considering the phase-change temperature and thermal stability, a PUPCM sample with a suitable molar ratio was used for the asphalt modification. The prepared materials were characterised by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, three indices of asphalt and viscosity tests, rotational viscometer tests, and other techniques. PUPCM samples with different soft and hard segment ratios exhibit different phase-change temperatures and enthalpies, and their physical, chemical, and phase-change properties are stable. When the ratio of soft and hard segments is 8:2 (PU-14), the freezing and melting temperatures were −2.7 °C and 12.9 °C, and the enthalpy was 46.8 J/g. The PUPCM modification of asphalt only involves physical miscibility. Adding PUPCM negligibly affects the high- and low-temperature performances of the modified asphalt binder. The viscosity of the PUPCM-modified asphalt binder is slightly higher than that of the original asphalt binder, and the storage stability of the modified asphalt binder is satisfactory. The addition of PUPCM improves the anti-ageing performance of asphalt, and the improvement becomes significant with increasing PUPCM content. Moreover, the phase-change energy storage properties of PUPCM in asphalt were found to be satisfactory. Hence, PUPCMs can potentially be used for asphalt modification to further improve the low-temperature performance of pavements.

Development of a New Crosslinked Highly Conductive Hybrid Electrolyte based on Polyetherdiamine, Diphenylmethane Diisocyanate and Organosilanes for Efficient Lithium‐Metal Battery

AbstractIn this study, a new crosslinked organic‐inorganic hybrid polymer electrolyte membrane is developed by first reacting polyetherdiamine with diphenylmethane diisocyanate, followed by addition of organosilane precursors 3‐(glycidyloxypropyl) trimethoxysilane and 2‐[methoxy(polyethyleneoxy) propyl] trimethoxysilane and LiClO4 salt. Various characterization methods are employed to probe the crystallinity behavior, morphology, ionic interactions, thermal stability, architectural durability and dynamic performance of the hybrid solid polymer electrolyte (HSPE) membranes. Among the electrolytes, the HSPE membrane with [EO]/[Li] ratio of 32 delivers the excellent ionic conductivity value of 1.2×10−4 S cm−1 at 30 °C. When the hybrid membrane without salt is plasticized with various electrolyte solvents, the ionic conductivity enhances significantly to values in the range of 1.2 to 1.8×10−3 S cm−1 at 30 °C. The lithium metal battery (LMB) assembled with the gel polymer electrolyte (GPE), lithium anode and LiFePO4 cathode provides excellent rate and cycle performances. The LMB delivers very stable discharge capacity of 121.1 mAh g−1 after 150 cycles at the rate of 0.1 C with 97.6 % capacity holding compared to first cycle and exhibits above 99 % Coulombic efficiency values. The present crosslinked hybrid polymer electrolytes are potentially promising for the future development of high performance lithium‐metal batteries.

Effect of densification on the physical and mechanical properties of the inner part of oil palm trunk impregnated with methylene diphenyl diisocyanate

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.

High clarity polyurethane laminating adhesives based on poly (propylene glycol). Effect of hard segment on microphase morphology, haze and adhesion

Within this publication, the performance of high clarity polyurethane adhesives based on a poly(propylene glycol) soft-phase within a polycarbonate or ethanolamine surface-treated polycarbonate laminate, is described. A series of polyurethanes were prepared, with poly(propylene glycol) used as soft-phase due to the high clarity of this polyol and absence of carbonyl functionality, which allows for hard-phase architecture to be resolved with greater resolution. In total, eight adhesives were synthesised, each contained a different chain-extender formulation to gauge what influence hard-phase architecture had on laminate haze and peel strength. This was investigated using either 4,4-methylene diphenyl diisocyanate or isophorone diisocyanate as hard-phase with trimethylolpropane as the only chain-extender or by including one of the following sterically hindered diols: 2,2-diethyl-1,3-propane diol, 1,3-butane diol or 1,2-proane diol. DSC analysis showed that microphase morphology was strongly influenced by the diisocyanate present, as shown by the degree of phase mixing being greater in methylene diphenyl diisocyanate based formulations when compared with isophorone diisocyanate based. ATR complements this observed difference in microphase morphology, with isophorone diisocyanate based formulations having a greater composition of hydrogen-bonded urethane and urea functionality present within the hard-phase which displays a more phase separated composition. Interestingly, differences in microphase mixing did not have a consistent influence on the peel strength obtained, with only 31% of laminate combinations tested recording a peel strength of <3 N mm −1 after 18 months. Diol chain-extended formulations based on methylene diphenyl diisocyanate accounted for 25% of these lower values and was a consequence of their poorer process-ability during lamination. This resulted in higher haze values being encountered for both polycarbonate and ethanolamine surface-treated polycarbonate laminates which contained methylene diphenyl diisocyanate based formulations when compared to isophorone diisocyanate based formulations, where all values were <1.5%.

Synthesis and characterization of biopolyurethane crosslinked with castor oil-based hyperbranched polyols as polymeric solid–solid phase change materials

Novel crosslinking bio polyurethane based polymeric solid–solid phase change materials (SSPCM) were synthesized using castor oil (CO) based hyperbranched polyols as crosslinkers. CO-based hyperbranched polyols were synthesized by grafting 1-mercaptoethanol or α–thioglycerol via a thiol-ene click reaction method (coded as COM and COT, respectively). Subsequently, the three SSPCMs were synthesized by a two-step prepolymer method. Polyethylene glycol was used as the phase change material in the SSPCMs, while the CO-based hyperbranched polyols and two types of diisocyanate (hexamethylene diisocyanate (HDI) and 4,4'-diphenylmethane diisocyanate) served as the molecular frameworks. Fourier transform infrared spectroscopy indicated the successful synthesis of the SSPCMs. The solid–solid transition of the prepared SSPCMs was confirmed by X-ray diffraction analysis and polarized optical microscopy. The thermal transition properties of the SSPCMs were analyzed by differential scanning microscopy. The isocyanate and crosslinker types had a significant influence on the phase transition properties. The SSPCM samples prepared using HDI and COT exhibited the highest phase transition enthalpy of 126.5 J/g. The thermal cycling test and thermogravimetric analysis revealed that SSPCMs exhibit outstanding thermal durability. Thus, the novel SSPCMs based on hyperbranched polyols have great potential for application as thermal energy storage materials.

Hard block length distribution of thermoplastic polyurethane determined by polymerization-induced phase separation

Three thermoplastic polyurethanes (TPUs) based on the same monomers and composition were produced in bulk by hand and machine casting methods. The soft segment was PTHF® 1000 and the hard segment was made of 1,4-butanediol and 4,4′-methylene diphenyl diisocyanate (MDI). The hard segment content amounted to 30%. The hand cast TPUs were prepared at 80 and 125 °C. The temperature conditions for the machine prepared sample were comparable to that of the hand casting process at 125 °C. The samples prepared at high temperature were transparent, whereas the sample produced at low temperature was translucent. The latter showed some crystallinity and in crystallization studies it crystallized more readily than the transparent samples. The distinctions in transparency and crystallization behavior were ascribed to differences in the hard block length distribution. Using thermal fractionation – a series of successive self-nucleation and annealing steps – the minor differences in hard block length distribution could be shown and quantified. The TPU synthesized at low temperatures possessed the longer hard blocks. These facilitated crystallization by enhancing nucleation and crystal growth. Superstructures, induced by the longer hard blocks, scattered visible light and reduced the transparency.

Environmental assessment of different strategies to produce rigid polyurethane foams using unrefined crude glycerol

Rigid polyurethane foams (PUFs) traditionally rely on crude oil (fossil feedstock). Yet, the increasing concerns over environmental issues have been promoting the use of renewable/recycled feedstocks, such as crude glycerol (CG) derived from bio-based feedstocks, like soybean, rapeseed, palm and waste cooking oil (WCO). In turn, from the perspective of a circular economy, recycling PUF waste to recover its polyol or CG content and use it as a partial substituent of virgin polyol or CG in the production of new rigid PUFs (close-loop recovery), rather than disposing it in landfill, is generally seen as a suitable option. To evaluate that perception, this study compares the environmental impacts of rigid PUF produced using polyol derived from crude oil and unrefined CG derived from bio-based feedstocks, based on life cycle assessment following a cradle-to-grave approach. Three optimised formulations of PUF derived from polyol/CG were considered. Furthermore, recycling of rigid PUF wastes, to recover its polyol/CG, was compared with its disposal in landfill. The results obtained revealed that the different formulations used in this study had distinct impacts depending on the scenarios considered. Moreover, these results have also clearly demonstrated that, overall, the environmental superiority of bio-based feedstocks compared to their fossil feedstock counterpart to produce rigid PUFs cannot always be claimed. Regardless of the scenario considered, the methylene diphenyldiisocyanate (MDI) is the main hotspot for all impact categories other than marine eutrophication (ME), ranging from 50 to 98% of the total impacts. As regards the scenarios involving polyol/CG recovery, the environmental impacts from the polyol/CG recovery process exceeded the environmental benefits from the PUF waste recycling and the inherent partial replacement of virgin polyol/CG. Indeed, the polyol/CG recovery resulted in a slight increase of the total impacts compared to those without polyol/CG recovery. These results highlight the need to carry out further studies to improve the environmental performance related with polyol/CG recovery considering different chemical processes.