Dicyclohexylmethane Diisocyanate Research Articles

Structure, morphology, and properties of aliphatic polyurethane elastomers from bio‐based 1,3‐propanediol

AbstractThe utilization of biomass resources in the production of bio‐based or bio‐recycled polyurethanes (PUs) enhances the sustainable development and eco‐friendliness of PU. Herein, a series of new bio‐based aliphatic poly(propylene dicarboxylate) diols were synthesized using bio‐based 1,3‐propanediol (bio‐PDO) and aliphatic dicarboxylic acids with different chain lengths. These bio‐based polyester diols and 1,4‐butanediol (BDO) reacted with 4,4′‐dicyclohexylmethane diisocyanate to produce aliphatic PU elastomers (PUEs). The study aimed to evaluate the impact of the structure of poly(propylene dicarboxylate) diols on the architecture, morphology, mechanical properties, and degradation of PUEs, thereby expanding the application of bio‐PDO. The results indicate a strong correlation between the degree of microphase separation, tensile properties, and degradation behavior of the synthesized PUEs and the number of methylene groups in the repeating unit of the poly(propylene dicarboxylate) diols. Notably, the PUE derived from poly(propylene pimelate) diol demonstrates the highest level of microphase separation and superior elasticity properties because of the high flexibility of the polyester. On the other hand, PUE prepared from poly(propylene succinate) diol exhibits the fastest degradation performance due to its high density of ester groups. Bio‐PDO based polyester diols show significant potential as raw materials for PUEs with biodegradable and adjustable mechanical properties.Highlights Poly(propylene dicarboxylate) diols were prepared from bio‐based 1,3‐propanediol. The poly(propylene dicarboxylate) diols based polyurethane elastomers (PUEs) have high tensile strength (>22 MPa) and elongation at break (>920%). The morphology, mechanical properties and degradation of PUEs are highly related to the structure of the poly(propylene dicarboxylate) diols. The increasing repeating unit length of the poly(propylene dicarboxylate) diols increases elastic recovery of PUEs.

Investigating the structure and properties of polyurethane hydrogels with varying soft and hard segments

AbstractIn this study, polyurethane (PU) hydrogels were synthesized via mercapto curing reaction to elucidate the effect of molecular interactions between isocyanate and soft segments on the properties of hydrogels. Further, the mesh size, mechanical properties, hydrophilicity, and biological properties of the PU hydrogels were determined. In the isocyanate series, the structural regularity and rigidity of 4,4′‐dicyclohexylmethane diisocyanate (HMDI) favored the formation of hydrogel materials with small mesh size, high modulus, and low water absorption. In contrast, l‐lysine diisocyanate (LDI) favored the materials with large mesh size, low modulus, and good hydrophilicity. In the soft‐segment series, the strong hydrogen bonds of polycarbonate diol (PCDL) favored the formation of materials with small mesh size, dense cross‐link points, and high modulus, whereas weak hydrogen bonds of polytetrahydrofuran ether glycol (PTMG) favored the hydrogel materials with small mesh size, few crosslink points, and low modulus. PU hydrogels exhibit excellent cytocompatibility, anti‐cell adhesion, and anti‐inflammatory properties. Therefore, this study offers valuable insights into understanding the chain structure and macroscopic properties, thus contributing to preparing PU hydrogels with varying performances, as desired.

Imidazolium‐based ionic thermoplastic polyurethane with low surface energy and antibacterial activities

AbstractA series of novel thermoplastic polyurethane elastomers with both low surface energy and antibacterial activity were synthesized in this paper. Firstly, four imidazole salt diols with different alkyl chain lengths at the N‐position of imidazolium cation ([CnIm+][Cl−]) were prepared. Then, imidazolium‐based ionic thermoplastic polyurethane elastomers (Si‐ITPUs) were formulated by incorporating polydimethylsiloxane and polytetramethylene glycol as a mixed soft segment, 1,4‐butanediol and [CnIm+][Cl−] as a chain extender, and 4,4′‐dicyclohexylmethane diisocyanate. The structure, thermal stability, mechanical properties, physical crosslinking density, and the anti‐graffiti properties of Si‐ITPUs were evaluated. The surface energy and water absorption were evaluated through static contact angle and water resistance tests, respectively. Furthermore, the antibacterial activities against both Staphylococcus.aureus and Escherichia coli were characterized by the plate colony counting method. The results demonstrated that Si‐ITPUs possessed surface energy of approximately 23 mN/m, which conferred excellent anti‐graffiti and self‐cleaning performance. Furthermore, the increase of the alkyl chain length of substitutions resulted in a decrease in the tensile strength but an increase in the elongation at break. Si‐ITPU‐C4 exhibited optimized antibacterial activities with an antibacterial rate of more than 99.9% against both S. aureus and E. coli. This novel polyurethane is anticipated to find applications in the medical device industry and food processing sector.

Stimuli-Responsive Self-Healing Luminescent Materials Based on Lanthanide Ions and Bipyridine Moieties

Contemporary, luminescent materials possessing rapid stimulus-responsive characteristics demonstrate considerable potential in anti-counterfeiting applications. However, if anti-counterfeiting materials become damaged during use, the integrity of the information will be compromised. Consequently, endowing materials with self-healing ability can ensure the accuracy and integrity of anti-counterfeiting data. In this study, a luminescent metallo-supramolecular polymer is synthesized through the coordination of lanthanide ions (Ln3+) and bipyridine ligands within polyurethane (PU) chains. The PU elastomers created using 4,4′-dicyclohexylmethane diisocyanate display remarkable transmittance and hydrophobic properties following coordination with Ln3+. The dynamic Ln–N coordination imparts self-healing behavior and robust mechanical performance to the PU elastomers. The “antenna effect” imbues the resulting materials with exemplary luminescent properties, and the emission color can be conveniently modulated by adjusting the Eu3+/Tb3+ ratio. Importantly, all luminescent materials exhibit a rapid stimulus-response to acid-base fluctuations through the disruption or restoration of the “antenna effect” between Ln3+ and bipyridine, a critical aspect for the advancement of materials in the anti-counterfeiting and information encryption domains.

Polysiloxane-Based Polyurethanes with High Strength and Recyclability.

Polysiloxanes have attracted considerable attention in biomedical engineering, owing to their inherent properties, including good flexibility and biocompatibility. However, their low mechanical strength limits their application scope. In this study, we synthesized a polysiloxane-based polyurethane by chemical copolymerization. A series of thermoplastic polysiloxane-polyurethanes (Si-TPUs) was synthesized using hydroxyl-terminated polydimethylsiloxane containing two carbamate groups at the tail of the polymer chains 4,4′-dicyclohexylmethane diisocyanate (HMDI) and 1,4-butanediol as raw materials. The effects of the hard-segment content and soft-segment number average molecular weight on the properties of the resulting TPUs were investigated. The prepared HMDI-based Si-TPUs exhibited good microphase separation, excellent mechanical properties, and acceptable repeatable processability. The tensile strength of SiTPU-2K-39 reached 21.5 MPa, which is significantly higher than that of other flexible polysiloxane materials. Moreover, the tensile strength and breaking elongation of SiTPU-2K-39 were maintained at 80.9% and 94.6%, respectively, after three cycles of regeneration. The Si-TPUs prepared in this work may potentially be used in gas separation, medical materials, antifouling coatings, and other applications.

Reprocessable and degradable bio-based polyurethane by molecular design engineering with extraordinary mechanical properties for recycling carbon fiber

In recent years, bio-based covalent adaptable networks (CANs) and vitrimers have developed rapidly in order to meet the renewable and sustainable requirements. It should be emphasized that the performance of the network need be upgraded and optimized to substitute petroleum-based polymers. Herein, a series of high-performance bio-based polyurethane were synthesized containing castor oil, isosorbide, vanillin derivative and 4,4′-Dicyclohexylmethane diisocyanate. By fine-tuning the bio-based diols, the hydrogen bond distribution and the crosslink density of the network were adjustable. The thermal mechanical properties and stress relaxation properties of the bio-based polyurethane were optimized. The bio-based polyurethane CANs shows tensile strength of 38.1 MPa, elongation at break of 243% and toughness of 55.7 MJ m −3 , which is outstanding among most reported bio-based CANs. In addition, the polymer has excellent water resistance, shape memory and re-deformability. Due to the dissociation of imine bonds under mild acid conditions, the carbon fiber composite can readily degrade in mixed solvent for 3 h at 60 °C and the properties of recycled carbon fibers are highly preserved. Fabrication of extraordinary mechanical properties, reprocessably, and degradable polyurethanes through network structure design. • Nonplanar rigid ring of isosorbide brings extraordinary mechanical properties to bio-based polyurethane CANs. • Adjusting the ratio of diols can tune the degree of cross-linking and distribution of hydrogen bonds in the networks. • Isosorbide can also improve fluidity of the network and lower activation energy. • CF composites can be chemically degraded under mild conditions for non-destructive recycling of CF.

Synthesis and fabrication of biobased thermoplastic polyurethane filament for FDM 3D printing

AbstractThis study describes a soft‐actuator grade thermoplastic polyurethane (TPU) with 73 ~ 86 shore A, the method of its fabrication and selected properties. The TPU was produced using bio‐based synthesized TPU (HP 2.5, HP 3.0, HB 2.5, and HB 3.0) pellets with bio‐based polyether‐biol (PO3G‐1000), and dicyclohexylmethane diisocyanate (H12MDI) and bio‐based 1,3 propanediol (PDO) and 1,4 butanediol (BDO) as a chain extender. The TPU was formed into a filament for fused deposition modeling (FDM) 3D printers during a melt‐extrusion process at 180 ~ 220°C. The manufactured TPU filaments were characterized by rheological, chemical, thermal, and mechanical analyses. The equivalence ratio 3.0 with a relatively large amount of HS with BDO as a chain extender, more hydrogen‐bonding peaks occurred. The transition temperature and mechanical properties increased depending on the [NCO]:[OH] ratio, and for BDO as the chain extender. However, it was found that when PDO derived from natural material was used, the thermal stability was better. From these results, samples of auxetic re‐entrant TPU were printed with the filaments with reference to the melt flow index. The results showed that the bio‐synthesized HP 3.0 with a hardness of (82 ± 1) shore A was most suitable for FDM 3D printing.

Effects of polyolefin polyol contents on the properties of waterborne olefin polyurethane adhesives for thermoplastic polyolefins

In this study, water-based polyurethane adhesives (WOPU) with excellent adhesion to thermoplastic polyolefines (TPOs) were synthesized. Polyester polyol and polyolefin polyol, 4,4'-dicyclohexylmethane diisocyanate, and isophorone diamine were used. The properties of the PU dispersion were evaluated by Fourier transfer infrared spectroscopy, differential scanning calorimetry, thermogravimetry and a universal testing machine. The effects of polyolefin polyol on the properties of the PU dispersion adhesives were systematically investigated. The PU dispersion showed highest tensile strength of 278 kgf/cm2 when the ratio of polyester polyols to polyolefin polyols was 9:1. The adhesion strength and water resistance showed the same trend.

PH-Responsive and degradable polyurethane film with good tensile properties for drug delivery in vitro

In this paper, we synthesized a new type of pH-responsive block polyurethane (PMCU) through the condensation polymerization of N-methyldiethanolamine (MDEA), poly(ε-caprolactone) and 4,4′-dicyclohexylmethane diisocyanate. The chemical structure of the PMCU were characterized, and the influence of MDEA content on the physicochemical properties of the casted PMCU films were studied detailly. The tensile test demonstrated the good tensile properties of the PMCU films with the breaking strain of 983–425% and the ultimate strength of 11.7–31.2 MPa. The tertiary amine groups and polyester segments endowed the material with pH sensitivity and hydrolytic degradability, respectively. The pH responsiveness of the films was confirmed from the enhanced equilibrium swelling ratio (ESR) with decreasing pH value of the medium, and the ESR in acidic condition (pH 1.5) was much higher than that in neutral (pH 7.0) and basic (pH 12.0) conditions. The studies of drug sustained-release in vitro at different pH indicated a pH-dependent release efficiency, which was closely related with the ESR and almost unaffected by the slow hydrolytic degradation. In addition, the cytotoxicity assay showed that the PMCU had good cytocompatibility to L929 cells. This study showed that pH-responsive promising platform for targeted drug delivery in the biomedical areas.

Bio-based vitrimer-like polyurethane based on dynamic imine bond with high-strength, reprocessability, rapid-degradability and antibacterial ability

Synthesis of vitrimer with dynamic covalent bond is a surprising solution to overcome the inherent limitations of traditional thermosets. A bio-based vitrimer-like polyurethane formed by castor oil, vanillin, m-xylylenediamine and 4,4′-dicyclohexylmethane diisocyanate in the preparation has superior mechanical properties, good solvent resistance, good thermal stability. Furthermore, the existence of dynamic imine bond in the vitrimer-like polyurethane is prone for polyurethane to rapid stress relaxation behavior, remoldability, weldability, antibacterial ability. With the hydrolysis of the imine bond, the material can be rapidly degraded at 60 °C for 1 h. In addition, it's commendable that the material exhibits excellent reprocessability that can be maintained at 86% even after 3 consecutive smash/mold pressing cycles. This work provides a promising method to manufacture bio-based polyurethane thermosets with excellent reprocessability, rapidly-degradable and antibacterial property, which has also promoted the high-value utilization of biomass materials.

Role of Diisocyanate Structure on Self‐Healing and Anticorrosion Properties of Waterborne Polyurethane Coatings

AbstractOrganic coatings are extensively investigated as possible solution to prevent or at least retard the occurring of corrosion processes on metal surfaces. Their actual breakthrough is still hampered by the risk of barrier properties loss because of local failure of the coating integrity. To address this issue, self‐healing coatings, which are intrinsically able to recover from damages upon exposure to external stimuli, are currently gaining increasing attention. Herein, waterborne polyurethanes (PU) are synthesized, and a Diels–Alder adduct is added into the polymeric backbone to endow the material with self‐healing functionality. The effect of different diisocyanate in PU synthesis is explored, namely isophorone diisocyanate, 4,4′‐dicyclohexylmethane diisocyanate (HMDI), and hexamethylene diisocyanate. The obtained results highlight the key role of the interactions among soft and hard segments in ultimately defining the coating performances. Actually, the combination of Fourier transform infrared spectroscopy, atomic force microscopy and X‐ray diffration analysis reveals that the HMDI‐based PU have showed the best balance in terms of H‐bonding strength among hard segments and crystallinity degree in the soft ones. This allows to reach a good compromise in terms of mechanical resistance, anticorrosion properties, and self‐healing ability.

Synthesis and molecular interaction of tung oil‐based anionic waterborne polyurethane dispersion

AbstractIn the present work, four types of anionic waterborne polyurethane dispersions (APUD) based on polytetramethylene ether glycol (PTMG) and two aliphatic diisocyanates, dicyclohexylmethane diisocyanate (HMDI) or isophorone diisocyanate (IPDI), were prepared by polymerization methods which for the first time controlled the location (soft or hard segment) of hydroxylated tung oil (HTO) incorporation into the final APUD. The resulting HTO‐containing APUD polymers (HTO‐APUDs) with postpolymerization crosslinking capability were characterized using FTIR, DMA, AFM and water imbibition methods, and compared to model compounds synthesized to have the same parts of chemical structural linkages for band assignment. A common PUD sample, as well as polypropylene oxide (PPG) with molecular weight similar to HTO (Mn = 400), was used to replace it for preparing control samples to highlight the role of long branched chains and conjugated double bonds in HTO. Based on the analysis of multiple H‐bond interactions, the relationship of HTO location in the APUD polymer structure to the soft/hard segment compatibility and the diisocyanate structure was further studied. This work is expected to provide basic data for properties regulation in practical applications by adjusting the chain and phase structure, as well as the intermolecular interactions, in these APUDs.

Preparation and properties study of waterborne polyurethane synthesized by mixing polyester diols and isocyanates

AbstractIn view of environmental protection requirements, it is an inevitable trend for waterborne coatings to replace traditional coatings. Waterborne polyurethane (WPU), a kind of typical resin used in coatings, has become a research hot topic of waterborne coatings because of its advantages, such as non‐polluting, safe and reliable, excellent properties, good compatibility, and easy modification. In this article, solvent‐free WPU is prepared by mixing 4,4′‐dicyclohexylmethane diisocyanate/ isophorone diisocyanate (HMDI/IPDI) and polycarbonate diol/ Polycaprolactone diol (PCDL/PCL). Through the comparison of the properties of the polymer, the best amount of raw materials was determined. Specifically, R = 1.35 (R is NCO/OH ratio), the content of dimethylolpropionic acid (DMPA) is 5.5%, the content of trimethylol propane (TMP) is 2.5%, the mole ratio of HMDI/IPDI is 2:1, the mole ratio of PCDL/PCL is 2:1, and the preeminent WPU shows the excellent thermal stability, the contact angle of 118.04°, the hardness is H. The chemical structures and rough surface morphologies of the WPU films were characterized by FT‐IR, TG, AFM, and SEM, respectively. Therefore, considering the film properties, and the low cost, simple, and green process, this research will offer the possibility of application of this free‐solvent WPU in industrial production and large‐scale application.

Polyether-polyester and HMDI Based Polyurethanes: Effect of PLLA Content on Structure and Property

Thermoplastic poly(ether-ester-urethane)s were synthesized from poly(L-lactide) diols (PLLA diols), polytetrahydrofuran diol (PTMG diols), 4,4′-dicyclohexylmethane diisocyanate (HMDI), and 1,4-butanediol (BDO) by a two-step reaction, and the morphology and property of the resultant TPU could be adjusted by varying the PLLA contents. The soft segment was composed of PLLA and PTMG diols. By controlling the percentage of PLLA in the soft segment, the glass transition temperature and mechanical properties of the polyurethanes could be regulated. Based on the FTIR spectrum, we found that two kinds of hydrogen bonding existed individually in soft matrix and hard domain. The hydrogen bonding in soft matrix was unstable, which could be destroyed during elongation. With in situ stretching WAXS and SAXS experiments, we found that the PLLA crystal was destroyed and the PLLA domain oriented along the stretch direction. Finally, we proposed a schematic model to illustrate the microstructures of these elastomers before and after stretch.

The influence of furanyl monomer on the self‐healing polyurethanes by reverse Diels‐Alder cross‐link

In this work, several furanyl diols with amide, imide, or amine groups were synthesized, each diol was subsequently polymerized with 4,4′‐dicyclohexylmethane diisocyanate and polytetramethylenene ether glycol to prepare polyurethanes. Bis(4‐maleimidophenyl) methane was then added as a cross‐linker to give self‐healing polyurethanes. DSC and DMA analysis were used to measure the DA/rDA temperature of these polyurethanes with different chemical structures. It was demonstrated that the polyurethane prepared from amide furanyl diol had the highest DA/rDA temperature, followed with the order of amide > imide > amine. This expands the versatility of monomers that have different self‐healing activity, which is expected to have the application for preparing various polyurethane coatings.

Synthesis and structure/properties characterizations of four polyurethane model hard segments.

Four model polyurethane (PU) hard segments were synthesized by reaction of butanol with four typical diisocyanates. The four diisocyanates were aromatic 4,4′-diphenylmethane diisocyanate (4,4′-MDI) and MDI-50 (50% mixture of 2,4′-MDI and 4,4′-MDI), cycloaliphatic 4,4′-dicyclohexylmethane diisocyanate (HMDI) and linear aliphatic 1,6-hexamethylene diisocyanate (HDI). FTIR, 1H NMR, 13C NMR, MS, X-ray and DSC methods were employed to determine their structures and to analyse their crystallization behaviours and hydrogen bonding interactions. Each of the four PU compounds prepared in the present work displays unique spectral characteristics. The FTIR bands and NMR resonance peaks assigned in the four samples thus provide a reliable database and starting point for investigating the relationship between hard segment structure and the crystallization and hydrogen bonding behaviour in more complex-segmented PU compositions.

Preliminary studies of polyurethane adhesive for thermoplastic polyolefins(TPOs) using polyolefin polyol

ABSTRACTTo develop a halogen-free polyurethane adhesive for thermoplastic nonpolar polyolefins, polyurethanes were synthesized by using polyester polyol, polyolefin polyol, 4,4′-dicyclohexylmethane diisocyanate, and isophorone diamine, The properties of the resulting polyurethanes were evaluated by Fourier transfer infrared spectroscopy, differential scanning calorimetry, and a universal testing machine. As the polyolefin polyol content increased, the elongation and Tg of the synthesized polyurethane increased, while the tensile strength decreased. However, the highest adhesive strength, 6 times of polyester polyol-based one, was obtained when the ratio of polyester polyol to polyolefin polyol was 8: 2.

Synthesis and thermo-mechanical investigation of macrodiol-based shape memory polyurethane elastomers

Abstract Shape memory polyurethanes have been prepared from polycaprolactone diol, 1,6-hexanediol and 4,4′-dicyclohexylmethane diisocyanate. The structural identification of the final polymer was confirmed by Fourier transform infrared spectroscopy. The thermo-mechanical history was studied using thermo-gravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis and shape memory testing by tensile cyclic loading using a temperature controlled chamber. The absence of any peak corresponding to functional groups of monomers confirmed the completion of reaction. The thermo-grams showed a gradual decrease in the thermal transition with increasing crystallinity, with corresponding increase in the molecular weight of macrodiol used as soft segments. The highest value of shape recovery of the sample (PCL, 4 000 g mol−1) obtained was 96%, and retention up to 85%.

Wlasciwosci tribologiczne biodegradowalnych poliuretanow o roznej budowie i zawartosci segmentow sztywnych

Five polyurethanes (PUR) of different chemical structure and variable content of rigid elements have been synthesized using 4,4'-dicyclohexylmethane diisocyanate (HMDI), polycaprolactone diol (PCL) as well as ethylene glycol (GE) and glycerol (G) as chain extenders. The physicochemical properties of the obtained PUR have been investigated with the aid of infrared spectroscopy, differential scanning calorimetry (DSC) and thermogravimetry (TG). The mechanical properties (Shore hardness and tensile strength) and tribological characteristics (pin-on-disc tribometer) of PUR have been determined. The results of the study confirm the influence of structure and rigid segment content on the properties of PUR macromolecules, particularly their tribological characteristics.

Synthesis of MDI-50 and Tung Oil-Based Non-Ionic Waterborne Polyurethanes

A series of MDI-50 based non-ionic waterborne polyurethane dispersions (MDI-NPUD) were prepared by the mixing of 2,4’-diphenylmethane diisocianate (2,4’-MDI) and 4,4’-MDI (MDI-50) which reacted with hydroxylated tung oil (HTO) and polyethylene glycol-800 (PEG-800), Fourier Transform Infrared Spectroscopy (FTIR) and Proton-Nuclear Magnetic Resonance (1H-NMR) were used to characterize and analyze their molecular structures. The results indicated that MDI-50 and HTO were introduced as hard segment while PEG acted as soft segment. The surface tension, Hydrophile-Lipophile Balance (HLB) and stability were investigated. All MDI-NPUDs had much lower surface tension than the dicyclohexyl methane diisocyanate (HMDI) based NPUD (HMDI-NPUD). By changing the feed ratio of MDI-NPUD, the properties of MDI-NPUD could be controlled