Aliphatic Polyisocyanate Research Articles

A Study of Hydroxyl-Terminated Block Copolyether-Based Binder Curing Kinetics.

In order to determine the curing reaction model and corresponding parameters of hydroxyl-terminated block copolyether (HTPE) and provide a theoretical reference for its practical application, the non-isothermal differential scanning calorimetry (DSC) method was used to analyze the curing processes of three curing systems with HTPE and N-100 (an aliphatic polyisocyanate curing agent), isophorone diisocyanate (IPDI), and a mixture of N-100 and IPDI as curing agents. The results show that the curing activation energy of N-100 and HTPE was about 69.37 kJ/mol, slightly lower than the curing activation energy of IPDI and HTPE (75.60 kJ/mol), and the curing activation energy of the mixed curing agent and HTPE was 69.79 kJ/mol. The curing process of HTPE conformed to the autocatalytic reaction model. The non-catalytic reaction order (n) of N-100 and HTPE was about 1.2, and the autocatalytic order (m) was about 0.3, both lower than those of IPDI and HTPE. The reaction kinetics parameters of the N-100 and IPDI mixed curing agent with HTPE were close to those of N-100 and HTPE. The verification results indicate a high degree of overlap between the experimental data and the calculated data.

New insights into tailoring physicochemical properties for optimizing the anti‐icing behavior of polyurethane coatings

AbstractThe most popular topcoat in the coatings industry, polyurethane (PU), still lacks an understanding of ice‐related phenomena and hence achieving an icephobic PU‐based coating has remained an important unresolved issue. This work presents fresh perspectives on how factors including chemical characteristics, cross‐link density, and mechanical characterization impact the anti‐icing capabilities and ice‐adhesion of PU coatings. In this regard, the effects of the of aforementioned coatings having various crosslink densities on wettability, ice formation, and ice adhesion were assessed via multiple approaches. Two acrylic polyols with different hydroxyl content and two commonly used aliphatic polyisocyanates with different %NCOs were utilized to fabricate the PU coatings. In addition, coatings were designed with different stoichiometric ratios providing a route to various crosslink densities and mechanical properties. Wettability characteristics were investigated using water contact angle, contact angle hysteresis, and sliding angle. The roles of urethane linkages and hydrogen‐bond formation between water molecules and urethane composition of PU coatings on ice nucleation and ice adhesion were studied through DSC, push‐off, and centrifugal tests. Mechanical characteristics and surface roughness of the coatings were investigated by tensile test and optical profilometer, respectively.

Extending the pot life of polyurethane coatings using organic diones

PurposeThis study aims to extend the pot life without altering the qualities and performance of the coating, which is important to increase when manufacturing polyurethane coatings.Design/methodology/approachAn acrylic polyol from a mixture of different monomers of hydroxypropyl methacrylate, methacrylic acid, 2-ethylhexyl acrylate, methyl methacrylate and n-butyl methacrylate was prepared with different ratios of 2,4-pentanedione as a pot life extender. The reaction takes place in presence of di-tert-butyl peroxide as initiator with samples (T1–T7). The physical properties of prepared acrylic polyol were characterized. Then, coating polyurethane varnish was prepared from the prepared acrylic polyol with an aliphatic polyisocyanate in a 1:1 equivalent ratio of OH:NCO at room temperature, in presence of paint thinner (diluents/solvent) and dibutyltin dilaurate as a catalyst to give samples (T1C–T7C). This coating was evaluated via Fourier-transform infrared spectroscopy, drying time, hardness and gloss, distinctness of image and reflected image quality.FindingsThe coating has a prolonged pot life while still maintaining the other qualities, thanks to the greater 2,4-pentanedione content.Originality/valueIt is desired to have a paint which has a satisfactory pot life, short curing time and reduces many drawbacks such as inefficient working and deterioration of the paint before application.

Glutathione reactivity with aliphatic polyisocyanates.

Isocyanate chemicals known to cause adverse health effects when inhaled are essential to making important products and are used in multiple industries. Glutathione (GSH), a major antioxidant of the lower airways with a well described role in xenobiotic metabolism, is a primary reaction target for di-isocyantes. However, GSHs reactivity with poly-isocyanates which have largely replaced diisocyanates (particularly aliphatic) in most end-user settings remains uncertain. We hypothesized aliphatic polyisocyanates would readily react with glutathione under physiologic conditions and the products could be identified using liquid chromatography (LC) coupled-mass spectrometry (MS) and tandem MS/MS. The data identified (tris)GSH-isocyanate adducts as the major reaction product of GSH with the most commonly used contemporary polymeric (tri-isocyanate) formulations of hexamethylene diisocyanate (HDI), the isocyanurate and biuret, as [M+H]+ ions of 1426.53 and 1400.55 m/z respectively in reverse phase LC-MS using electrospray in positive ion mode. The uretdione form of HDI, a stabilized dimer, formed two reaction products with GSH, a tris(GSH)-isocyanate reaction product recognized as a 1258.44 m/z [M+H]+ ion, and a bis(GSH)-isocyanate product identified as a 951.36 m/z [M+H]+ ion. Predicted structures for the newly described GSH-polyisocyanate reaction products, modeled based on collision induced dissociation (CID) fragmentation patterns in tandem MS/MS, support S-linkage of the GSH to N = C = O groups. In summary, industrially-used aliphatic polyisocyanates readily react with GSH to form primarily S-linked tris(GSH)-conjugates, a process that may play an important role in response to respiratory tract exposure.

Polyurea Networks from Moisture-Cure, Reaction-Setting, Aliphatic Polyisocyanates with Tunable Mechanical and Thermal Properties

Polyurea Networks from Moisture-Cure, Reaction-Setting, Aliphatic Polyisocyanates with Tunable Mechanical and Thermal Properties

Polyisocyanate-based water-soluble polyurethane/CaCO3 composites for gunpowder storage

The need for improved gunpowder storage to recycle used gunpowder is increasing due to global warming and the economic losses incurred by withdrawing the gunpowder and by its storage. Herein, we fabricated an aliphatic water-soluble polyurethane (WPU) to be used for gunpowder storage, which allows for easy separation of the matrix (WPU) from the gunpowder by solubilizing the WPU with water. We used an aliphatic polyisocyanate as the main hard segment and polyethylene glycol as the soft segment. The usage of an aliphatic polyisocyanate is assumed to enhance the thermal stability and mechanical properties of the composites. We applied the solution polymerization process to fabricate the WPU. CaCO3 was used as a fake gunpowder. The tensile strength of the 40% diisocyanate-treated CaCO3 WPU composites was increased by 3.5 times as compared to the neat WPU and the elongation at break point was also significantly improved. The thermal stability of the composites was greatly improved by the utilization of the treated CaCO3 particles in the WPU matrix. The hydrophilic nature, identified by contact angle measurements, of the composite is interesting, less than 65°, which proves a good hydrophilic composite has been fabricated. The structure of the polymer was confirmed via FTIR analysis and proton NMR investigation.

Gel-polymer electrolytes based on polyurethane ionomers for lithium power sources.

Polyurethanes based on the aminoethers of ortho-phosphoric acid and polyisocyanates of an aliphatic nature were studied as a substrate for the preparation of new polymer electrolyte. The conductivity of polyurethane ionomer samples obtained using the optimal amount of aliphatic polyisocyanates and after keeping them in a 1 M LiBF4 solution in γ-butyrolactone reaches 0.62 mS cm−1. It has been established that the transport of positively charged ions through the polymer matrix is due to the formation of clusters of phosphate ions and their association into the conducting channels. The introduction of carboxylate ions into the conducting channels by modifying the aminoethers of ortho-phosphoric acid with phthalic anhydride leads to an increase in their size and rise in the mobility of cations. As a result, the conductivity of polyurethane gel electrolytes increased to 2.1 mS cm−1.

Organic functionalization of clay aerogel and its composites through in-situ crosslinking

Clay aerogel composites have great potential for a wide range of applications; however, their high moisture absorbance and inferior mechanical properties have to be addressed. This paper presents crosslinking techniques to develop clay/PVA aerogel composites through an environmentally freeze-drying process using water as a solvent. Water soluble isocyanate and organosilane compounds, namely aliphatic polyisocyanate (Wcro1™) and 3-glycidoxypropyltrimethoxysilane (Wcro2™) were employed and their crosslinking mechanisms were studied. The results of the aerogels characterizations showed that the chosen crosslinkers were able to generate substantial crosslinking reactions. The crosslinked clay/PVA aerogel gave rise to significant improvements in their mechanical and physical properties. The moisture absorbance of the composites was reduced by 27%, while retaining dimensional stability. The developed functionalized clay/PVA aerogels also increased the liquid absorption capacity by 3 times, the compressive modulus increased by 6 folds from 0.48 to 3.6 MPa and the thermal conductivity reduced from the 0.043 to 0.039 W/mK.

PHOTO-RESPONSIVE AND COLOR CHANGEABLE EMBEDDED IN ALIPHATIC POLYURETHANE

Nowaday, the trend of smart and functional materials is wildly interested as new solutions for modern urban lifestyle. The material that can reversible change its color after inducing with sun light energy is also interesting topic. The light responsive transparent and high abrasive resistance aliphatic polyurethane was successfully prepared by the appropriate combination of rigid polymer, flexible polymers and aliphatic polyisocyanate. The sensitivity (speed of color changing), fatigue resistance and color strength (maximum absorbance) were monitored as evaluation criteria for light responsive efficiency and usable lifetime. The test specimens were prepared by coating the mixed solution on transparent polycarbonate substrate using spinning coat technique. At appropriate ratio between flexible and rigid polymers (0.1 – 0.3) resulted highly transparency film with can suddenly change its color under UV exposure. The fastest sensitivity is shorter than 5 sec. The color cans reversible immediately (shorter than 6 sec) after cut-off UV light source. The color strength and sensitivity of resulting mixed formulations were enhanced by synergistic combination between two species of photochromic color compounds. The light stabilizer additive specie was added in order to extent the usable life time (fatigue resistance) and weathering resistance property of final formulation. Keywords: Photo-responsive materials, light responsibe materials, color changeable dye, polyurethane

Properties related to linear and branched network structure of hydroxyl terminated polybutadiene

AbstractThe correlation between properties and the network structure of hydroxyl terminated polybutadiene (HTPB) based polyurethanes (PUs) was studied through linear and branched structure polymer matrixes formed by toluene diisocyanate (TDI) and an aliphatic polyisocyanate curing agent (N100). The curing reactions were monitored using differential scanning calorimetry (DSC) and viscosity build-up. The swelling capacity of PUs decreased with the increase of crosslink density with a stable solubility parameter according to the equilibrium swelling test. Tensile properties of PUs cured by TDI and N100 in different stoichiometric ratios of NCO/OH groups were tested. Both breaking elongation and tensile strength were remarkably improved by N100. The thermal decomposition processes of HTPB/TDI and HTPB/N100 indicated that a branched structure has higher depolymerization temperature, and hence, improved thermal stability. In addition, PU with a branched network prevented the migration of the plasticizer during isothermal accelerated aging due to the higher crosslink density.

Preparation and characterization of covalently bonded PVA/Laponite/HAPI nanocomposite multilayer freestanding films by layer‐by‐layer assembly

ABSTRACTThe layer‐by‐layer (LBL) assembly technique is an attractive method to make functional multilayer thin films and has been applied to fabricate a wide range of materials. LBL materials could improve optical transmittance and mechanical properties if the film components were covalently bonded. Covalently bonded nanocomposite multilayer films were prepared by employing hydrophilic aliphatic polyisocyanate (HAPI) as the reactive component, to react with Laponite and polyvinyl alcohol (PVA). FT‐IR spectra suggested that HAPI reacted with Laponite and PVA at ambient temperature rapidly. Ellipsometry measurement showed that the film thickness was in linear growth. The influences of HAPI on the optical, mechanical and thermal properties of the films were investigated by UV‐Vis spectroscopy, tensile stress measurement, DSC and TGA. The obtained results showed that the optical transmittance and mechanical strength were enhanced when the film components were covalently bonded by HAPI. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 545–551

Linking of oligoesters hydrolysis to polyurethane coatings

AbstractThe hydrolytic stability of a series of oligoesters comprised of three and four different monomers was evaluated. The hydroxyl terminal oligoesters were prepared from adipic acid (AA) and isophthalic acid (IPA), with six different diols and one triol, which included: 1,4‐butanediol, 1,5‐pentanediol, 1,6‐hexanediol, neopentyl glycol, 2‐methyl‐1,3‐propanediol, trimethylolpropane, and 2‐butene‐1,4‐diol. The hydroxyl terminated oligoesters were reacted with phenyl isocyanate to form telechelic urethane groups. Hydrolysis rate constants were obtained from plots of acid number vs. time. It was observed that ternary oligoester systems had lower hydrolysis rates than quaternary systems. In addition to investigating the hydrolytic stability of the synthesized oligoesters, polyurethane coatings were produced by reacting the hydroxyl‐terminated oligoesters with an aliphatic polyisocyanate (1,6‐hexanediisocyanate trimer). Model oliogester hydrolysis was then correlated to the weatherability of a crosslinked polyurethane film. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40198.

Spatially Resolved Solid-State 1H NMR for Evaluation of Gradient-Composition Polymeric Libraries

Polyurethane libraries consisting of films with composition gradients of aliphatic polyisocyanate and hydroxy-terminated polyacrylate resin were characterized using methods of (1)H NMR microimaging (i.e., magnetic resonance imaging, (MRI)) and solid-state NMR. Molecular mobilities and underlying structural information were extracted as a function of the relative content of each of the two components. Routine NMR microimaging using the spin-echo sequence only allows investigations of transverse relaxation of magnetization at echo times >2 ms. A single-exponential decay was found, which is likely due to free, noncross-linked polymer chains. The mobility of these chains decreases with increasing content of the aliphatic polyisocyanate. The concept of a 1D NMR profiler is introduced as a novel modality for library screening, which allows the convenient measurement of static solid-state NMR spectra as a function of spatial location along a library sample that is repositioned in the rf coil between experiments. With this setup the complete transverse relaxation function was measured using Bloch decays and spin echoes. For all positions within the gradient-composition film, relaxation data consisted of at least three components that were attributed to a rigid highly cross-linked resin, an intermediate cross-linked but mobile constituent, and the highly mobile free polymer chains (the latter is also detectable by MRI). Analysis of this overall relaxation function measured via Bloch decays and spin echoes revealed only minor changes in the mobilities of the individual fractions. Findings with respect to the most mobile components are consistent with the results obtained by NMR microimaging. The major effect is the significant increase in the rigid-component fraction with the addition of the hydroxy-terminated polyacrylate resin.

Studies on the Adhesion and Corrosion Performance of an Acrylic-Epoxy Hybrid Coating

A hybrid acrylic polyol-epoxy polyol coating cured with aliphatic polyisocyanate has been developed to provide corrosion protection on mild steel panels. Polyisocyanate served as a hardener to initiate crosslinking and as a coupling agent to enhance adhesion of the hybrid polymer resin to the metal surface. The hybrid systems were prepared by blending an acrylic polyol resin (A) with an epoxy polyol resin (E) in various weight ratios and by applying them on pre-treated cold rolled mild steel panels. The dry film thickness was maintained within the range of 40 to 80 μm. The panels were allowed to cure under ambient air condition for 1 week prior to testing. Corrosion resistance and mechanical properties of the coating were studied and characterized. This paper discusses several specific examples on the use of electrochemical impedence spectroscopy (EIS) in the study of coatings in accelerated exposure and the analysis of EIS data from such studies. It is observed that, of the nine coating formulations, one has been found to perform well as an effective and durable hybrid coating.

New Biobased High Functionality Polyols and Their Use in Polyurethane Coatings

High-functionality polyols for application in polyurethanes (PUs) were prepared by epoxide ring-opening reactions from epoxidized sucrose esters of soybean oil-epoxidized sucrose soyates-in which secondary hydroxyl groups were generated from epoxides on fatty acid chains. Ester polyols were prepared by using a base-catalyzed acid-epoxy reaction with carboxylic acids (e.g., acetic acid); ether polyols were prepared by using an acid-catalyzed alcohol-epoxy reaction with monoalcohols (e.g., methanol). The polyols were characterized by using gel permeation chromatography, FTIR spectroscopy, (1)H NMR spectroscopy, differential scanning calorimetry (DSC), and viscosity measurements. PU thermosets were prepared by using aliphatic polyisocyanates based on isophorone diisocyanate and hexamethylene diisocyanate. The properties of the PUs were studied by performing tensile testing, dynamic mechanical analysis, DSC, and thermogravimetric analysis. The properties of PU coatings on steel substrates were evaluated by using ASTM methods to determine coating hardness, adhesion, solvent resistance, and ductility. Compared to a soy triglyceride polyol, sucrose soyate polyols provide greater hardness and range of cross-link density to PU thermosets because of the unique structure of these macromolecules: well-defined compact structures with a rigid sucrose core coupled with high hydroxyl group functionality.

Preparation of Novel Hydrolyzing Urethane Modified Thiol-Ene Networks

Novel tetra-functional hydrolyzing monomers were prepared from the reaction of TEOS and select alkene-containing alcohols, ethylene glycol vinyl ether or 2-allyloxy ethanol, and combined with trimethylolpropane tris(3-mercaptopropionate) (tri-thiol) in a thiol-ene “click” polymerization reaction to produce clear, colorless thiol-ene networks using both radiation and thermal-cure techniques. These networks were characterized for various mechanical characteristics, and found to posses Tg’s (DSC), hardness, tack, and thermal stability (TGA) consistent with their molecular structures. A new ene-modified urethane oligomer was prepared based on the aliphatic polyisocyanate Desmodur® N 3600 and added to the thiol-ene hydrolyzable network series in increasing amounts, creating a phase-segregated material having two Tg’s. An increase in water absorption in the ene-modified urethane formulations leading to a simultaneous increase in the rate of hydrolysis was supported by TGA data, film hardness measurements, and an NMR study of closely related networks. This phenomenon was attributed to the additional hydrogen bonding elements and polar functionality brought to the film with the addition of the urethane segment. SEM was utilized for visual analysis of topographical changes in the film’s surface upon hydrolysis and provides support for surface-driven erosion. Coatings prepared in this study are intended for use as hydrolyzing networks for marine coatings to protect against ship fouling.

Thermal conductive and electrical properties of polyurethane/hyperbranched poly(urea-urethane)-grafted multi-walled carbon nanotube composites

Hyperbranched poly(urea-urethane)-grafted multi-walled carbon nanotubes (HPU-MWCNTs) were incorporated in a polyurethane (PU) matrix based on poly(ethylene oxide-tetrahydrofuran) and aliphatic polyisocyanate resin as curing agent. The 9–12 nm thick HPU shell formed on the MWCNTs improved the dispersion of MWCNTs and enhanced the interfacial adhesion between the PU matrix and MWCNTs, leading to improvements in storage modulus and T g of the composites and enhancement of the thermal stability of PU. Thus, composites with 0.5–1 wt% MWCNTs increased the thermal conductivity by about 60–70% when compared to, and retained the high electrical resistivity of, neat PU.

Novel Polyaspartic Ester Polyureas Based on Flexible Polyaspartic Ester

New polyaspartic ester (PAE) chain extender named PAE-f was prepared via two steps of Michael addition reactions:(1) Michael addition reaction between 4,4’-methylenebis(2-methyl cyclohexyl amine) (Laromin C260) and excessive dialkyl maleates（DEF）; (2) The Michael addition reaction of the residual dialkyl maleates of step (1) with polyester polyamine Jeffamine D230. The two-steps method proposed could reduce the reaction time in comparison with the current one step Michael addition reaction method, thus satisfying the industrialized production. New PAE based polyureas were synthesized by reacting the PAE-f chain extender with aliphatic polyisocyanates 4,4’-diisocyanato dicyclohexylmethane (H12MDI) / polyester polyamine Jeffamine D2000 prepolymer at room temperature. FT-IR and GPC were employed to characterize the new PAE prepared, and the morphology, molecular weight distribution and mechanical properties of the prepared PAE based polyureas were investigated by means of FT-IR and GPC. The FT-IR results indicated that the hydrogen bonding degree of amidogen groups in hard segments of the prepared polyureas were high, the length of hydrogen bonding were 0.305nm～0.306nm. The GPC experimental results show that the weight average molecular weight of the PAE-f based polyureas were 4.95×104～6.05×104,Mw/Mn were 1.65～1.97, the molecular weight distribution were relatively narrow. The mechanical properties demonstrated that the tensile strength were 14.7～22.5MPa, Elongation at break were 306～511%, Yang’s modulus were 67～127MPa, Shore A hardness were 64～83. The mechanical properties confirmed that the polyureas based on PAE-f were kinds of elastomeric materials with satisfied flexibility, strength, module and hardness.

Contact allergy to aliphatic polyisocyanates based on hexamethylene‐1,6‐diisocyanate (HDI)

Aliphatic polyisocyanates based on hexamethylene 1,6-diisocyanate (HDI) are components of lacquers, coatings, and spray paints. They are mainly composed of HDI trimers, but also contain larger oligomers, and minute amounts of HDI monomers (<1%). HDI trimers occur as biuret, isocyanurate and asymmetrical types. We report on 4 patients with allergic contact dermatitis/contact allergy resulting from HDI-based polyisocyanates in polyurethane paints. The patients were examined at the Finnish Institute of Occupational Health in 2000-2009. The first two patients were diagnosed by testing with their own polyurethane hardeners and ingredients of the hardeners. In 2002, HDI isocyanurate (HDI-IC) trimer was added to our isocyanate series, and the last two patients were screened with the series. Patient no. 1 was exposed and sensitized to HDI biuret trimer, patient no. 2 to HDI-IC trimer, and patient no. 4 to HDI asymmetrical trimer. Patient no. 3 was positive with HDI-IC trimer. He had been handling several paint hardeners containing HDI-based polyisocyanates, but the subtypes of the trimers remained unidentified. All 4 patients were negative with HDI monomer. HDI trimers are novel contact allergens in workers who handle polyurethane paints. The allergic reactions cannot be explained by sensitization to HDI monomer.

Preparation and properties of dual-cure polyurethane acrylate

Dual-cure polyurethane acrylates (PUA) with different double bonds content were synthesized by using aliphatic polyisocyanate and 2-hydroxyethyl acrylate (HEA). The molecular structures were identified by Fourier transform infrared (FTIR) spectrum and nuclear magnetic resonance (NMR). Molecular weight ( M w) and glass-transition temperature ( T g) of PUA were measured by gel permeation chromatography and DSC, respectively. The pendulum hardness, pencil hardness, flexibility and abrasion resistance properties of dual-cure system were tested, the results indicated that the pendulum hardness, pencil hardness, and MEK resistance increased, but the flexibility reduced with the double bonds content increased. The mechanical properties of dual-cure system were greatly improved after the heat treatment.