Aliphatic Diisocyanate Research Articles

UV-curable aromatic polyurethanes from different sustainable resources: Protocatechuic and cinnamic acids

An innovative aromatic monomer, 3,4-dihydroxybenzyl cinnamate (CDHB), was synthesized from protocatechuic and cinnamic acids. These latter can be obtained from different sustainable resources, such as plastic waste or biomass, by biotechnology and/or chemistry routes. From CDHB, used as chain extender, and aromatic or aliphatic diisocyanates, various aromatic thermoplastic polyurethanes (TPU) with cinnamic pendant chains were carefully synthesized and characterized. Different techniques such as NMR, FTIR, TGA and DSC have been used. The main results show that the TPUs exhibited good phase segregation and thermal stability, due to the aromaticity of the chain extender. The pendant cinnamic chains acted as internal plasticizer with a reduction of the glass transition temperature (Tg). The cinnamic groups were also able to undergo a [2 + 2] cycloaddition under UV irradiation, leading to the crosslinking of PU with a strong evolution of the properties. This reaction was followed by UV–Vis spectroscopy. 80 % of cycloaddition was reached in 20 h, significantly increasing PU gel fraction, Tg, and thermal stability. This study highlights the potential to create modulable sustainable and aromatic PU macromolecular architectures that can be UV curable and display enhanced properties.

Modulating alginate-polyurethane elastomer properties: Influence of NCO/OH ratio with aliphatic diisocyanate

This research addresses the need for enhanced biomaterials by investigating the influence of the NCO/OH ratio on sodium alginate-based polyurethane elastomers(Al-PUEs), offering novel insights into their structural, thermal, mechanical and swelling behavior. Al-PUEs were prepared by blending the chain extenders with key ingredients in a specific molar ratio using aliphatic HMDI and HTPB monomers. The chemical linkages, crystalline behavior, homogeneity, and surface morphology of PUEs were evaluated by FT-IR, XRD, SEM, and EDX analysis. Thermo-mechanical studies were performed using TGA, DSC and tensile testing. Swelling behavior and absorption analysis were analyzed in DMSO and water. The analysis indicated that the hydrophilicity and swelling behavior of the prepared PUEs were affected by the addition of sodium alginate content. The results exhibit the tailor-made network structure of Al-PUEs, resulting in better thermal stability, elasticity of materials via stress-strain behavior and marvelous characteristic features than traditional high-tech yields. Furthermore, the resulting Al-PUEs are potential candidates for biomedical implants.

High melt viscosity, low yellowing, strengthened and toughened biodegradable polyglycolic acid via chain extension of aliphatic diisocyanate and epoxy oligomer

Poly(glycolic acid) (PGA) is a biodegradable plastic with excellent degradation rate, barrier properties, and heat resistance. However, its low melt viscosity and narrow processing temperature severely limit its application. To overcome these drawbacks, the aromatic diisocyanates TDI and MDI, aliphatic diisocyanate HDI, and multifunctional epoxy oligomer ADR were used as the chain extender to modify PGA. The PGA/HDI shows a faster chain extension reaction rate and significantly less yellowing than PGA/TDI or PGA/MDI. The combined use of HDI and ADR to modify PGA can produce long chain branched/crosslinked structures, resulting in a significant increase in melt viscosity, with complex viscosity two orders of magnitude higher than that of pure PGA and minimal yellowing. The T-5% of PGA/HDI/ADR is 45 °C higher than that of pure PGA, and its crystallization temperature, crystallization rate and melting temperature are significantly decreased, suggesting that it has a wider processing temperature window. Moreover, the tensile and flexural strength of PGA/HDI/ADR are 113.8 MPa and 216.8 MPa, respectively, an increase of 25% and 26% over pure PGA, while the elongation at break and impact strength increase to 9.5% and 11.6 KJ/m2, respectively, 42% and 176% higher than pure PGA.

Polyurethane Microstructures for 2'-Deoxycytidinic Acid Delivery: Preparation and Preliminary Characterization.

Background and Objectives: Nucleotide delivery has emerged as a noteworthy research trend in recent years because of its potential utility in addressing a range of genetic defects resulting in the presence of incorrect nucleotides. The primary goals of this research were to create and to characterize polyurethane microstructures, with the aim of utilizing them for nucleotide transport. Materials and Methods: Two samples were prepared using an aliphatic diisocyanate in reaction with a mixture of polyethylene glycol and polycaprolactone diol, where 2'-deoxycytidinic acid was used as the active agent and glycerol 1,2-diacetate was used as an enhancer of the aqueous solubility. The solubility, pH, size distribution, and surface charge of the samples were measured, and encapsulation efficacy and release, cell proliferation, and irritation tests on mouse skin were conducted. Results: The results showed almost neutral acidic-basic structures with a high heterogeneity, and a medium tendency to form clusters with non-cytotoxic and non-irritative potentials. Conclusions: Future research could explore the efficacy of this carrier in delivering other nucleotides, as well as investigating the long-term effects and safety of these microstructures in vivo.

Renewable and Biodegradable Polyurethane Foams with Aliphatic Diisocyanates

Renewable and Biodegradable Polyurethane Foams with Aliphatic Diisocyanates

Hybrid aliphatic and aromatic diisocyanates forming mixed urea segments for high-performance polyurea

Polyurea is gaining more traction in the realm of protective coatings on metal surfaces from corrosion. The properties of polyurea can be controlled by the judicious selection of its reactants. Herein, a series of polyurea based on hybrid aliphatic/aromatic diisocyanates are synthesized from isophorone diisocyanate (IP) and polycarbodiimide-modified diphenylmethane diisocyanate (ISO). The formulation composed of 37.5:62.5 (IP: ISO) weight ratio yields the highest tensile strength at 47.80 MPa, elongation at 500 %, and hardness of 95 HA. The findings are validated through field emission scanning and atomic force microscopic analysis, which reveals phase mixing surface and ductile fracture containing wide-ranging stretching lines due to enhanced resistance to deformation. Furthermore, synthesized polyureas present a unique stress relaxation pattern with gradual increase in stress under constant deformation, due to hydrogen bond reformation and dislocation creations during chain alignment. IP37.5-ISO62.5 demonstrates outstanding corrosion resistance after a 28-day exposure in salt spray test.

Synthesis and characterization of macrodiols and non-segmented poly(ester-urethanes) (PEUs) derived from α,ω-hydroxy telechelic poly(ε-caprolactone) (HOPCLOH): effect of initiator, degree of polymerization, and diisocyanate.

Nine different macrodiols derived from α,ω-hydroxy telechelic poly(ε-caprolactone) (HOPCLOH) were prepared by ring-opening polymerization of ε-caprolactone (CL) using three linear aliphatic diols (HO-(CH2) n -OH, where n = 4, 8, and 12) as initiators and catalyzed by ammonium decamolybdate (NH4)8[Mo10O34]. The crystallization temperature (T c) and crystallinity (x i) were relatively high for HOPCLOH species with a long aliphatic chain [-(CH2)12-] in the oligoester. Also, HOPCLOH was the precursor of twenty-seven different poly(ester-urethanes) (PEUs) with various degrees of polymerization (DP) of HOPCLOH and three types of diisocyanates such as 1,6-hexamethylene diisocyanate (HDI), methylene diphenyl diisocyanate (MDI), and 4,4'-methylenebis (cyclohexyl isocyanate) (HMDI). HOPCLOH exhibited the melting temperature (T m) and crystallinity (x i) with a proportional dependency to the degree of polymerization (DP). PEUs showed significant thermal and mechanical properties, which had a direct correlation in terms of the type of DP and diisocyanate. PEUs derived from HDI versus MDI or HMDI exhibited an apparent effect where aliphatic diisocyanate (HDI) induced a significant x i with respect to aromatic and cyclic diisocyanate (MDI or HMDI). The profile of PEUs films according to mechanical properties is mainly a plastic behavior. The chemical nature and properties of HOPCLOH and PEUs were characterized by NMR, FT-IR, GPC, MALDI-TOF, DSC, and mechanical properties.

A crosslinked waterborne poly(urethane‐urea) oligomer enables mechanically strong waterborne polyacrylate–poly(urethane‐urea) hybrid films with superior film‐forming ability

AbstractIn this article, a crosslinked waterborne poly(urethane‐urea) (WPUU) is synthesized based on the terminal aromatic amine polyether (DP‐1000) and aliphatic isophorone diisocyanate. Then WPUU is compound with acrylate monomer by emulsion polymerization to produce waterborne polyacrylate–poly(urethane‐urea) (WPUUA) hybrid emulsions. Compared with waterborne polyacrylate (WPA) film, the film‐forming ability of WPUUA film is improved and the surface roughness Ra and Rq of WPUUA film decreases from 47.5 and 36.4 nm to 35.2 and 18.8 nm, respectively. Meanwhile, the mechanical properties of WPUUA films are significantly improved compared to WPA film. In addition, the performances of WPUUA hybrid films can be modified according to requirements by adjusting the molar ratio between DP‐1000 and polyisocyanate. As a result, these WPUUA hybrid emulsions have great application potential in waterborne coatings and other fields.

Variation of Aliphatic Diisocyanates in Bio-Based TPUs

Variation of Aliphatic Diisocyanates in Bio-Based TPUs

Fabrication and In Vitro Biological Assay of Thermo-Mechanically Tuned Chitosan Reinforced Polyurethane Composites.

The progressive trend of utilizing bioactive materials constitutes diverse materials exhibiting biocompatibility. The innovative aspect of this research is the tuning of the thermo-mechanical behavior of polyurethane (PU) composites with improved biocompatibility for vibrant applications. Polycaprolactone (CAPA) Mn = 2000 g-mol-1 was used as a macrodiol, along with toluene diisocyanate (TDI) and hexamethylene diisocyanate (HMDI), to develop prepolymer chains, which were terminated with 1,4 butane diol (BD). The matrix was reinforced with various concentrations of chitosan (1-5 wt %). Two series of PU composites (PUT/PUH) based on aromatic and aliphatic diisocyanate were prepared by varying the hard segment (HS) ratio from 5 to 30 (wt %). The Fourier-transformed infrared (FTIR) spectroscopy showed the absence of an NCO peak at 1730 cm-1 in order to confirm polymer chain termination. Thermal gravimetric analysis (TGA) showed optimum weight loss up to 500 °C. Dynamic mechanical analysis (DMA) showed the complex modulus (E*) ≥ 200 MPa. The scanning electron microscope (SEM) proved the ordered structure and uniform distribution of chain extender in PU. The hemolytic activities were recorded up to 15.8 ± 1.5% for the PUH series. The optimum values for the inhibition of biofilm formation were recorded as 46.3 ± 1.8% against E. coli and S. aureus (%), which was supported by phase contrast microscopy.

The Influence of an Isocyanate Structure on a Polyurethane Delivery System for 2'-Deoxycytidine-5'-monophosphate.

The delivery of nucleosides represents an interesting research trend in recent years due to their application in various viral infections. The main aims of this study were to develop and to characterize polyurethane particles that are intended to be used for the transport of nucleosides. Three samples have been prepared using aliphatic diisocyanates, a mixture of polyethylene glycol, polycaprolactone, and diols, respectively. The samples were characterized through refractivity measurements, drug loading efficacy, release and penetration rate investigations, FTIR and Raman spectroscopy, thermal analyses, Zetasizer, SEM, HDFa cells viability, and irritation tests on mice skin. The results indicate the obtaining of particles with sizes between 132 and 190 nm, positive Zeta potential values (28.3-31.5 mV), and a refractivity index around 1.60. A good thermal stability was found, and SEM images show a medium tendency to agglomerate. The samples' color, pH, and electrical conductivity have changed only to a small extent over time, and the evaluations indicate an almost 70% encapsulation efficacy, a prolonged release, and that around 70% of particles have penetrated an artificial membrane in the first 24 h. The synthesized products should be tested in further clinical trials, and the current tests on cell cultures and mice skin revealed no side effects.

Exploring urea hard segment morphology and phase separation behavior in flexible polyurethane foam formulations: Water, lithium chloride and isocyanate structure effects

Flexible polyurethane foams (FPUFs) are versatile materials used in various applications due to their unique properties. Understanding the phase separation behavior in FPUFs is crucial for tailoring their properties to specific applications. In this study, we investigated FPUFs with varying levels of urea phase connectivity using small-angle X-ray scattering (SAXS), Fourier transform infrared spectroscopy (FTIR), and wide-angle X-ray scattering (WAXS). We explored the effect of water, lithium chloride, and isocyanate structures on the phase separation behavior by employing these methods. An increase in water content in the FPUF formulation resulted in a higher amount of formed urea and larger globular size of urea aggregates. Incorporating LiCl into FPUF formulations demonstrated its ability to prevent hydrogen bond formation, leading to alterations in the urea phase. Moreover, we found that foams prepared with asymmetric diisocyanates showed difficulty in forming the urea phase, while foams prepared with symmetric and aliphatic diisocyanates readily formed the urea phase. Our study sheds light on the morphology of the urea phase, the packaging nature of the hard segment, and the hydrogen bonding behavior of the FPUFs. These findings contribute to a better understanding of phase separation in FPUFs and offer insights into tailoring their properties for specific applications.

Enhancement of physical properties of thermoplastic polyurethanes by blending with cyclic olefin copolymer elastomer

AbstractIn this study, two different thermoplastic polyurethanes (TPUs), a poly(ester)‐based TPU including aromatic diisocyanate units (TPU1) and a poly(ester‐ether)‐based TPU including aliphatic diisocyanate units (TPU2) were blended with a cyclic olefin copolymer (COC) elastomer to prepare TPU‐rich blend films via melt compounding in a twin screw extruder equipped with a slit die and film casting rollers. Morphological features and viscoelastic properties of blend films were characterized with scanning electron microscope analysis, different test protocols in melt rheology measurements, and dynamic mechanical analyzer tests, in detail. Viscoelastic properties of blend films were quantified with various mathematical approaches such as Williamson model, discrete retardation spectrum (DRS), Burger, and Findley equation. It was found that COC phase dispersed more homogenously into TPU1 matrix than TPU2. COC elastomer addition significantly increased the melt viscosity and melt elasticity of TPUs and improved the creep strength.Highlights COC addition enhanced the viscosity and elasticity of TPUs in melt state. The creep strains of TPUs decreased by 65% with addition of 40 wt% of COC.

Aromatic thermoplastic polyurethanes synthesized from different potential sustainable resources

Thermoplastic polyurethanes (TPUs) are known for their versatility due to the wide range of macromolecular architectures available. This study focuses on the synthesis and the architecture-properties relationships of new sustainable aromatic TPUs, derived from different potential sustainable resources, such as biomass and plastic waste. Thus, new sustainable aromatic short diols were synthesized from 4–hydroxybenzoic acid and syringic acid, and named HB.diol and Syr.diol, respectively. Subsequently, TPUs were prepared with these original diols as chain extenders, alongside conventional aromatic and aliphatic sustainable chain extenders, like 1,4–benzenedimethanol (BDM) and 1,4-butanediol. The investigation explored the effect of these chain extender structures on the properties of the resulting TPUs, using both aromatic and aliphatic diisocyanates in the synthesis. The thermal and mechanical characteristics of the TPUs were evaluated to identify key structural parameters that influence the properties of the macromolecular architectures. Notably, the presence of aromatic rings enhanced the incompatibility between soft and hard segments (HS), resulting in greater phase segregation. Ether bonds in HB.diol and symmetric structures in BDM enhanced hydrogen bonding, promoting the development of organized and crystalline HS, enhancing phase segregation, thus improving thermo–mechanical and mechanical properties. On opposite, methoxy groups in Syr.diol and the asymmetry of the aromatic diisocyanate hindered the organization of HS, leading to reduced TPUs structuration and lower mechanical properties. Overall, these findings highlight the potential for creating sustainable TPU macromolecular architectures with desirable properties by selecting appropriate raw materials.

Special structures and thermal stabilities of polyurethanes derived from diol and triol having oxazolidone moieties

AbstractWe synthesized regular polyurethanes from the diol having oxazolidone structure (Diol‐1) and the aliphatic diisocyanate by typical polyaddition. The results of the structural analysis suggested that the polyurethane having a cyclic urethane structure such as oxazolidone formed a rod‐like structure, although the control polyurethane having a chain urethane structure formed a linear structure. The polyaddition of Diol‐1 and aliphatic diisocyanate with triol having oxazolidone structure (Triol‐1) as a crosslinker also proceeded successfully to achieve corresponding polyurethanes. However, the polyurethanes containing a molar ratio of Triol‐1 less than or equal 50% were soluble in high polar organic solvents nevertheless those polyurethanes contained some trifunctional units in the polymer chain. On the other hand, the polyurethanes containing a molar ratio of Triol‐1 more than 50% were insoluble in any organic solvents. We hypothesized that the soluble polyurethanes containing Triol‐1 formed multi‐branched structure and the insoluble polyurethanes formed cross‐linking structure. Such structures of polymer chain affected significantly to the thermal properties of the obtained polyurethanes.

Favorable Heteroaromatic Thiazole-Based Polyurea Derivatives as Interesting Biologically Active Products.

This research sought to synthesize a new set of heteroaromatic thiazole-based polyurea derivatives with sulfur links in the polymers' main chains, which were denoted by the acronyms PU1-5. Using pyridine as a solvent, a diphenylsulfide-based aminothiazole monomer (M2) was polymerized via solution polycondensation with varied aromatic, aliphatic, and cyclic diisocyanates. Typical characterization methods were used to confirm the structures of the premonomer, monomer, and fully generated polymers. The XRD results revealed that aromatic-based polymers had higher crystallinity than aliphatic and cyclic derivatives. SEM was used to visualize the surfaces of PU1, PU4, and PU5, revealing spongy and porous shapes, shapes resembling wooden planks and sticks, and shapes resembling coral reefs with floral shapes at various magnifications. The polymers demonstrated thermal stability. The numerical results for PDTmax are listed in the following order, ranked from lowest to highest: PU1 < PU2 < PU3 < PU5 < PU4. The FDT values for the aliphatic-based derivatives (PU4 and PU5) were lower than those for the aromatic-based ones (616, 655, and 665 °C). PU3 showed the greatest inhibitory impact against the bacteria and fungi under investigation. In addition, PU4 and PU5 demonstrated antifungal activities that, in contrast with the other products, were on the lower end of the spectrum. Furthermore, the intended polymers were also tested for the presence of the proteins 1KNZ, 1JIJ, and 1IYL, which are frequently utilized as model organisms for E. coli (Gram-negative bacteria), S. aureus (Gram-positive bacteria), and C. albicans (fungal pathogens). This study's findings are consistent with the outcomes of the subjective screening.

The kinetics of uncatalyzed and catalyzed urethane forming reactions of aliphatic diisocyanates with butan-1-ol

The kinetics of the urethane forming reactions of hexamethylene diisocyanate (HDI), 4,4′-dicyclohexyl-methane-diisocyanate (HMDI) and isophorone diisocyanate (IPDI) with butan-1-ol were studied by electrospray ionization mass spectrometry (ESI-MS).

Correction: The kinetics of uncatalyzed and catalyzed urethane forming reactions of aliphatic diisocyanates with butan-1-ol

Correction for ‘The kinetics of uncatalyzed and catalyzed urethane forming reactions of aliphatic diisocyanates with butan-1-ol’ by Anett Juhász et al., New J. Chem., 2023, 47, 16096–16107, https://doi.org/10.1039/D3NJ02747C.

Preparation of Polyols and Polyurethane Foams from Olein By-Product of Tanning Industry

Olein produced from the solid residues of the tanning industry is already employed as raw material to obtain greasing oil for leather. However, new applications for this product may be advantageous regarding environmental impact and sustainability of this industry. In this work, flexible polyurethane foams (FPUFs) were prepared from polyols obtained from olein. A polyol from olein was prepared through alkaline glycerolysis. The glycerolysis conditions of temperature, glycerol/olein molar ratio, amount of catalyst and reaction time were optimized using a 24 factorial design, resulting in an olein polyol containing around 75% of monoacylglycerols, hydroxyl value (388.68±0.40 mg KOH.g-1), and hydroxyl functionality of 2.89. FPUFs were prepared at NCO/OH ratios of 1.2:1 and 1.3:1, using an aliphatic hexamethylene diisocyanate trimer and water as foaming agent. The foams were characterized through FTIR, thermogravimetry, morphology, extractable materials, and mechanical properties. Characteristics urethane/urea groups formation were verified by FTIR as well as typical mass loss steps in the thermal decomposition curves. The foams morphology showed a structure composed mainly for polygon-type closed-cells. The obtained FPUFs presented a content of extractable materials lower than 3%. The mechanical properties of the foams were dependent on the NCO/OH ratio, and the foam prepared at the ratio of 1.2:1 stood out as a potential material to be used in the production of mattresses. This study demonstrated the feasibility of transforming olein, a solid residue of the tanning industry, as a precursor to prepare PU foams, which may be a promising material for mattress applications, considering the observed features.

Study on synthesizing new urethane epoxy adhesives and their adhesive properties on different substrates

In this work, we prepared urethane epoxy adhesives from the reaction of glycidol and aliphatic diisocyanate, 4, 4-methylene bis (cyclohexyl isocyanate) (HMDI). We modified diglycidyl ether of bisphenol A (DGEBA) with this urethane epoxy and cured by maleic anhydride. We used Fourier-transform infrared (FTIR) for monitoring the reaction progress and confirming the unique structure. We measured the lap shear strength of joints, bonded with different weight ratios of urethane epoxy and DGEBA, on three different substrates aluminum, stainless steel, and glass fiber reinforced epoxy. The effect of substrates with varied materials was studied by scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX) with comparisons with X-ray photoelectron spectroscopy (XPS) results from other studies. The novel urethane-epoxy adhesive exhibited improvements in mechanical properties such as shear strength and elongation in comparison to common DGEBA-based epoxy adhesives.