Hexamethylene Diisocyanate Biuret Research Articles

Interfacial Polymerization Kinetics of Polyurea Microcapsules Formed Using Hexamethylene Diisocyanate Biuret Low Viscosity Isocyanate

AbstractFor cosmetic industrial applications, polyurea microcapsules were formed by using hexamethylene diisocyanate biuret low viscosity (HDB‐LV) and three different amines: ethylenediamine (EDA), guanidine (GUA), and hexamethylenediamine (HMDA). Toluene droplets containing dissolved HDB‐LV were formed by an oil‐in‐water emulsion before being poured into a water phase containing the required excess of amine. The pH of the aqueous phase was fitted through time to calculate the kinetic constant k' and the diffusion constant DB through the polyurea shell when possible. At 60 °C, EDA and HMDA follow a pure kinetic regime, whereas GUA follows a combination of kinetic and diffusion regimes. The presented kinetic data shows that HDB‐LV is a promising nontoxic isocyanate for cosmetic encapsulation.

Synthesis and Characterization of Green Polyurethane Coatings Derived from Niger‐Seed‐Oil‐Based Polyesteramide Polyols

AbstractPolymeric researchers are trying to use renewable resources for polymeric resins in the coating industry to reduce fossil or petroleum feedstock reliance significantly. The present research attempts to develop a polyurethane (PU) coating for the first time from Niger seed oil (NSO). The polyesteramide polyols are synthesized by amidation of Niger seed oil with diethanolamine and further esterification with different biobased dicarboxylic acids (phthalic, itaconic, and dimer) to introduce a required functionality of hydroxyl group. Spectroscopic studies of Niger‐seed‐oil‐based fatty diethanolamide and polyesteramide polyols are carried out by Fourier‐transform infrared spectroscopy and proton nuclear magnetic resonance. The polyurethane coatings are prepared from synthesized polyesteramide polyols and hexamethylene diisocyanate biuret (HDI‐B). The cross‐link density of PU coatings demonstrated by gel content method and the corrosion study is carried by salt water immersion technique. The PU coatings are also studied for glass transition temperature (Tg) and thermal stability by differential scanning calorimetry and thermogravimetric analysis.Practical Applications: The long aliphatic chain provides flexibility, whereas the rigid structure of polyols enhances the hardness of PU coating. The phthalic‐based PU metal coatings depict excellent hardness, gloss, hydrophobicity, and chemical resistance compared to itaconic and dimer‐acid‐based PU.

Functional Modification of Borassus flabellifer Sheath Fibres Using Isocyanate

An active hydroxyl content of Borassus flabellifer leaf sheath fibers are measured by the isocyanate back titration method, catalytically reacted with 1, 6 – hexamethylene diisocyanate biuret trimer and 2, 4-toluene diisocyanate-trimethylolpropane adduct, which is being used as cross-linkers in most of the automotive and industrial polyurethane coatings. The functional modifications of the fibers are confirmed by NCO titration method and Fourier-transform Infrared Spectroscopy (FTIR). The resultant biochemical fiber is analyzed for the thermal property, and surface topography measurement is done by Scanning Electron Microscope (SEM) and Thermogravimetric analysis (TGA), respectively. Moreover, 1, 6 – hexamethylene diisocyanate biuret trimer (HDT) treated BFSF having higher thermal stability due to higher urethane to urea content and intermolecular hydrogen bonding.

Functional Modification of Borassus flabellifer Sheath Fibres Using Isocyanate

An active hydroxyl content of Borassus flabellifer leaf sheath fibers are measured by the isocyanate back titration method, catalytically reacted with 1, 6 – hexamethylene diisocyanate biuret trimer and 2, 4-toluene diisocyanate-trimethylolpropane adduct which is being used as cross-linkers in most of the automotive and industrial polyurethane coatings. The functional modifications of the fibers are confirmed by NCO titration method and Fourier-transform Infrared Spectroscopy (FTIR). The resultant biochemical fiber is analyzed for the thermal property, and surface topography measurement is done by Scanning Electron Microscope (SEM) and Thermogravimetric analysis (TGA), respectively. Moreover, 1, 6 – hexamethylene diisocyanate biuret trimer (HDT) treated BFSF having higher thermal stability due to higher urethane to urea content and intermolecular hydrogen bonding.

Enzymatic synthesis of andiroba oil based polyol for the production of flexible polyurethane foams

Andiroba oil is a popular Amazonian product that stands out for its numerous medicinal properties, such as anti-inflammatory, antimicrobial, and repellent action. This work reports the synthesis of andiroba oil polyol (AOP) by enzymatic glycerolysis and its use as raw material for the production of polyurethane foams (PUF). The AOP synthesis was carried out in a tubular fixed bed reactor containing commercial lipase Novozym 435®, using a reaction mixture composed of andiroba oil, glycerol and t-butanol. Three percent solvent contents (50, 100, and 150% volume of solvent per weight of substrate) and temperatures (40, 50, and 60 °C) were evaluated. The AOP synthesized at 50 °C with 150% of solvent showed the highest yield of monoacylglycerol – MAG (66.47 %), being the most suitable for PUF production. PUFs were prepared using AOP or AOP/glycerol blends, hexamethylene diisocyanate biuret, dibutyl-tin dilaurate as catalyst and water as blowing agent. Polyurethane formation was confirmed by FTIR. Due to the low average functionality of AOP (F¯(OH) = 1.23), the production of dimensionally stable foams, was possible only through its combination with glycerol.

Polyurethane-based solid-solid phase change materials with in situ reduced graphene oxide for light-thermal energy conversion and storage

Crosslinking polyurethane-based solid-solid phase change materials with in situ reduced graphene oxide (GO) sheets were fabricated by a facile solvothermal treatment. GO sheets could give their full play to the enhancement of the system, which can endow the system with outstanding form-stability over 100 °C for the synergistic effect with hexamethylene diisocyanate biuret, and remarkable light-thermal conversion efficiency up to 78.7% due to the simultaneous in situ reduction of GO. The phase change enthalpy increases to 127.3 J/g from 86.8 J/g with 3.8 wt% GO for the nucleation and alleviating effects in the system. Meanwhile, the system has improved thermal stability and favorable thermal reproducibility. Therefore, the synthesized materials with comprehensive properties would be perspective to be used in energy storage devices such as solar energy collector system.

Graphene oxide/polyurethane-based solid–solid phase change materials with enhanced mechanical properties

Graphene oxide (GO) crosslinked polyurethane-based solid–solid phase change materials, composed by polyethylene glycol (PEG) and hexamethylene diisocyanate biuret (HDIB), were fabricated in-situ polymerization. GO sheets could support the excellent solid framework at 100°C and prevent the leakage of melt in synergy with HDIB by physical and chemical crosslinking network. Meanwhile, GO sheets act as heterogeneous nucleation agents that make the crystallization temperature of system rise to 34.0°C from 24.8°C with 14.5wt‰ GO. Whereas, GO have little effect on the latent heat, which may be an offset of the nucleation and confinement. Besides, the tensile strength increased to 21. 7 from 10.2MPa with 14.5wt‰ GO and Young’s modulus increased to 471.5 from 180.1MPa for 44.6wt‰ one. Also, the strain at break has a slight promotion within 14.5wt‰ GO. The synthesized system would be potential to be applied in thermal energy storage fields.

Synthesis and properties of crosslinking halloysite nanotubes/polyurethane-based solid-solid phase change materials

Polyurethane-based solid-solid phase change materials were first synthesized using polyethylene glycol (PEG) and hexamethylene diisocyanate biuret (HDIB), and the influence of halloysite nanotubes (HNTs) on this system was investigated. HNTs can not only serve as crosslinking agent in synergy with HDIB, which reinforces the solid-solid phase change properties of the system that has no leakage even at the temperature that 40°C higher above the melting temperature of PEG, but also greatly improve the latent heat of the system from 86.8 to 118.7J/g, as a result of heterogeneous nucleation effect, which can make up partial latent heat loss caused by crosslinking. Also, HNTs endows the system with excellent thermal stability, where the temperature at 5% weight loss is increased by 53°C. The synthesized PCMs have extensive applying prospects in thermal energy storage fields.

Self-Healing Performance of Coatings Containing Synthetic Hexamethylene Diisocyanate Biuret Microcapsules

Hexamethylene diisocyanate (HDI) biuret microcapsules were synthesized by modified in situ polymerization and used as self-healing additives in alkyd varnish coatings (AVCs). The water triggered self-healing ability of AVCs with artificial defects was evaluated through 3D laser microscopy, FT-IR spectroscopy, and electrochemical analyses. The FT-IR spectra confirmed that HDI biuret successfully sealed off the artificial defects. Self-healing was divided based on the electrochemical impedance spectroscopy into four stages: pre-self-healing, accelerated self-healing, self-healing-failure competition, and failure. This work investigated the self-healing activity of AVCs with synthetic HDI biuret microcapsules in protecting steel surfaces.

Curing reaction kinetics of HTPE polymer studied by simultaneous rheometry and FTIR measurements

In order to study the curing reactions of hydroxyl-terminated polyether (HTPE) with a curing agent hexamethylene diisocyanate biuret (HDIB), the rheology and chemical processes of the curing reactions have been studied by simultaneous rheometry and FTIR spectroscopy. It was shown that the gel point was a key parameter in the curing reaction of HTPE with HDIB. The gel point was at the intersection of G′ and G″ curves. The gel point was when gelation occurred. After gelation, the polymer could not flow and the viscosity and real modulus increased rapidly. The curing reaction of the HTPE/HDIB kinetics system, monitored by an FTIR technique, showed a characteristic intensity peak at 2270 cm−1, corresponding to the –N=C=O stretching vibration which decreased as a function of time and the curing reaction of the HTPE/HDIB system and obeyed a three-dimensional (spherical symmetric) diffusion model.

The durability of clear polyurethane coil coatings studied by FTIR peak fitting

A step scan phase modulation photo-acoustic (SS-PM-PA) Fourier transform infrared (FTIR) peak fitting method has been developed and applied to study (i) the degradation of the polyurethane (PU) coatings crosslinked with different isocyanates, (ii) the harshness of the natural exposure sites, and (iii) the correlation between the accelerated and natural exposure sites in terms of the degradation. Methyl ethyl ketoxime (MEKO) blocked hexamethylene diisocyanate biuret (HDI-BI), MEKO blocked hexamethylene diisocyanate cyclic trimer (HDI-CT) and 3,5-dimethyl pyrazole (DMP) blocked isophorone diisocyanate cyclic trimer (IPDI-CT) were used as-received to crosslink a cycloaliphatic saturated polyester resin binder. It was found that HDI-CT crosslinked PU coating is more durable compared to the HDI-BI. IPDI-CT crosslinked PU coating gives higher durability than the HDI-CT and the HDI-BI. The areas of deconvoluted peaks with Centre X (cm−1) = 1573, 1553 and 1535 (amide II, NH–CO) and Centre X (cm−1) = 1832, 1813, 1792 and 1770 (acid, anhydride, peracid) are used for degradation index calculation, due to their consistent decreasing and increasing trends, respectively, along with the degradation. It has been found that the natural weathering site in Kuala Lumpur, Malaysia (KL) is harsher than that at Vereeniging, South Africa (SA). The harshness of one year SA and KL natural weathering is comparable to 300 h–900 h of the QUV A exposure test. FTIR peak fitting method outperformed the integration method by giving a better correlation between the accelerated and natural weathering tests in terms of the degradation.

The influence of structural modification and composition of glycidyl carbamate resins on their viscosity and coating performance

The synthesis, characterization, and coatings performance of a series of glycidyl carbamate (GC) resins synthesized from a hexamethylene diisocyanate biuret resin, glycidol, and alcohols were explored. The partial replacement of glycidol with alcohols was explored as a way to reduce the viscosity of multifunctional GC resins. Six modified GC resins were obtained by replacing one-third of the glycidol with alcohols and ether alcohols. The modified GC resins were characterized using FTIR and 13C NMR. The alcohol-modified GC resins had significantly lower viscosity than that of the control GC resin. The effect of amount of alcohol modifier on resin viscosity was also studied by making a series of resins with different levels of modifier. Both amine-cured and self-crosslinked coatings were prepared from the resins. Coating properties such as hardness, impact strength, methyl ethyl ketone double rubs, flexibility, and adhesion were studied. Differential scanning calorimetry and thermogravimetric analysis were also used to study the thermal properties of the coatings. The resin structures and their coating performance showed an excellent correlation. The coating performance was found to be governed by the type of modifier, structural compositions of the modifier in the resins, type of amine crosslinkers, and techniques of crosslinking used.

Perfume‐containing polyurea microcapsules with undetectable levels of free isocyanates

AbstractCore‐shell polyurea microcapsules with a 40% fragrance load were prepared by interfacial polymerization of guanidine and a technical polyisocyanate prepolymer containing mainly the biuret trimer derived from hexamethylene di‐isocyanate (HDI). Residual free polyisocyanates were still present at a level slightly above 100 mg NCO functional group per kg as determined by liquid chromatography hyphenated with tandem mass spectrometry of HDI and of its biuret trimer. This level was decreased by a factor of about 10 when the polymerization process was allowed to proceed for a longer time and by a factor of about 500 when guanidine or NaOH were added to the microcapsule suspension to act as scavengers. In these cases, polyisocyanate conversion was observed to proceed for about one month when the microcapsules were stored at room temperature before reaching a plateau at a level below 1 mg NCO/kg. Overall, ammonia was the most efficient polyisocyanate scavenger as no residual HDI biuret trimer and only less than 2 μg NCO/kg as HDI were detected at the end of the process, a level which had dropped below the limit of detection of 0.25 μg NCO/kg after about 40 days of aging at room temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Preparation of modified polyesters containing triphosphorous and their applications to PU flame-retardant coatings

Three phosphorous functional groups were introduced in one structural unit of polymer backbone to enhance the flame retardancy of PU coatings. In the first step, we synthesized tetramethylene bis(orthophosphate) (TBOP) that contained two phosphorus functional groups in one structural unit. In the next step, we synthesized modified polyesters (ATBTP-10,-20,-30) that contained triphosphorous groups by condensing polymerization of TBOP, 1,4-butanediol, trimethylolpropane, adipic acid, and phenylphosphonic acid (PPA). The amount of PPA in the ATBTPs was 10, 20, and 30 wt%. Then, flame-retardant PU coatings (AHFC−10,−20,−30) were prepared by curing ATBTPs with hexamethylene diisocyanate-biuret (curing agent) at room temperature. From the TGA analysis of diphosphorus-modified polyester (ATBT) and ATBTPs, the residues of ATBT, ATBTP-10, ATBTP-20, and ATBTP-30 were 24.6, 27.5, 29.2, and 31.9%, respectively. From this result, it was found that the residue increased in relation to the amount of PPA. Physical properties of the films of flame-retardant coatings were deteriorated with the addition of PPA (flame retarding component), however, all the films of flame-retardant coatings, except AHFC-30, met the required physical properties standard for coatings. Char lengths of the AHFCs measured by the 45° Meckel burner method were 2.9∼4.8 cm, and LOI values were 28∼31%, which indicates that the prepared AHFCs showed good flame retardancy.

Gene expression profiling in mouse lung following polymeric hexamethylene diisocyanate exposure

Isocyanates are a common cause of occupational lung disease. Hexamethylene diisocyanate (HDI), a component of polyurethane spray paints, can induce respiratory symptoms, inflammation, lung function impairment, and isocyanate asthma. The predominant form of HDI in polyurethane paints is a nonvolatile polyisocyanate known as HDI biuret trimer (HDI-BT). Exposure of mice to aerosolized HDI-BT results in pathological effects, including pulmonary edema, lung inflammation, cellular proliferation, and fibrotic lesions, which occur with distinct time courses following exposure. To identify genes that mediate lung pathology in the distinct temporal phases after exposure, gene expression profiles in HDI-BT-exposed C57BL/6J mouse lungs were analyzed. RNase protection assay (RPA) of genes involved in apoptosis, cell survival, and inflammation revealed increased expression of IκBα, Fas, Bcl-X L, TNFα, KC, MIP-2, IL-6, and GM-CSF following HDI-BT exposure. Microarray analysis of approximately 10 000 genes was performed on lung RNA collected from mice 6, 18, and 90 h after HDI-BT exposure and from unexposed mice. Classes of genes whose expression was increased 6 h after exposure included those involved in stress responses (particularly oxidative stress and thiol redox balance), growth arrest, apoptosis, signal transduction, and inflammation. Types of genes whose expression was increased at 18 h included proteinases, anti-proteinases, cytoskeletal molecules, and inflammatory mediators. Transcripts increased at 90 h included extracellular matrix components, transcription factors, inflammatory mediators, and cell cycle regulators. This characterization of the gene expression profile in lungs exposed to HDI-BT will provide a basis for investigating injury and repair pathways that are operative during isocyanate-induced lung disease.

Urinary hexane diamine to assess respiratory exposure to hexamethylene diisocyanate aerosol: a human inhalation study.

The use of urinary hexane diamine (HDA) as a biomarker to assess human respiratory exposure to hexamethylene diisocyanate (HDI) aerosol was evaluated. Twenty-three auto body shop workers were exposed to HDI biuret aerosol for two hours using a closed exposure apparatus. HDI exposures were quantified using both a direct-reading instrument and a treated-filter method. Urine samples collected at baseline, immediately post exposure, and every four to five hours for up to 20 hours were analyzed for HDA using gas chromatography and mass spectrometry. Mean urinary HDA (microg/g creatinine) sharply increased from the baseline value of 0.7 to 18.1 immediately post exposure and decreased rapidly to 4.7, 1.9 and 1.1, respectively, at 4, 9, and 18 hours post exposure. Considerable individual variability was found. Urinary HDA can assess acute respiratory exposure to HDI aerosol, but may have limited use as a biomarker of exposure in the workplace.

Pulmonary toxicity of polymeric hexamethylene diisocyanate aerosols in mice

The acute pulmonary response of male C57BL/6 mice exposed to respirable polymeric hexamethylene diisocyanate biuret trimer aerosol (HDI-BT), a component of polyurethane spray paints, was examined. Mice were exposed to concentrations of 1 and 10 mg/m 3 HDI-BT for 5 h and were evaluated 6, 18, 42, 90, 186, and 378 h after the end of exposure. Mice exposed to 1 or 10 mg/m 3 HDI-BT exhibited dose-dependent lung function impairment, edema, neutrophilic inflammation, cellular proliferation, and histologic lesions in terminal bronchioles and alveolar ducts. Impairment of pulmonary function, indicated by decreased frequency and increased enhanced pause (Penh), was maximal immediately after exposure and progressively recovered at later time points. Lung weight and lavage fluid protein content peaked at 6 and 18 h after exposure, respectively. Total cells and macrophages recovered in lavage fluid peaked 90 h after exposure. Neutrophils recovered in lavage fluid peaked between 18 and 42 h after exposure. Proliferative lesions, as identified histologically and by bromodeoxyuridine incorporation, were maximal 90 h after exposure. In contrast, no inflammatory cell influx, protein leakage, or lung pathology were observed in mice exposed to 360 ppb HDI monomer vapor. This model will be useful for investigating molecular mechanisms by which HDI-BT causes lung injury, which is known to occur in humans exposed occupationally to this pulmonary toxicant.

Properties of UV-curable polyurethane acrylates using nonyellowing polyisocyanate for floor coating

UV-curable polyurethane acrylates for poly(vinyl chloride) (PVC) floor coating were prepared using nonyellowing polyisocyanates. The effects of the chemical structure of the polyisocyanates and hydroxyacrylates, and the compositions of the prepolymer/diluent on the properties of the UV-curable polyurethane acrylates were investigated. Several different urethane acrylate prepolymers from four different polyisocyanates, isophorone diisocyanate (IPDI) adduct, hexamethylene diisocyanate (HDI) adduct, HDI biuret, and HDI isocyanurate, and two different hydroxyacrylates, hydroxyapropyl acrylate (HPA), polycaprolactone modified hydroxyethylhexylacrylate (PCMHEA). UV-curable coating materials were formulated from the prepolymers and 1-hydroxycyclohexylphenyl ketone as a photoinitiator with polyethylene glycol diacrylate (PEGDA) as a diluent. The polyurethane acrylates prepared with HDI isocyanurate and the equimolar mixture of HPA and PCMHEA showed balanced coating properties such as tensile properties, hardness, weatherability, and good adhesion. The dynamic mechanical studies showed the properties of those polyurethane acrylates were well correlated with their glass transition temperature behaviors. It was also found that the adhesion was best as a PVC floor coating with the appropriate viscosity (below 150 P at 25°C) when 35% PEGDA as a diluent was used. © 1996 John Wiley & Sons, Inc.

Synthesis and characterisation of crosslinked second order nonlinear optical polymer

The present paper reports the synthesis of glycidyl monoether of 4-[(p-nitrophenyl) azo] phenol (GMNA) and crosslinking reaction of GMNA with hexamethylene diisocyanate biuret (HDIB). The Tg of crosslinked polymer was investigated by DSC. The orientation and stability of the poled and crosslinked polymer film were studied by UV-Vis spectra and Maker fringe method.

Validation of a non‐invasive technique to assess immediate or delayed onset of airway hypersensitivity in guinea‐pigs

Conscious Hartley guinea-pigs were sensitized with trimellitic anhydride (TMA) or trimeric hexamethylene diisocyanate biuret (Des-N) by repeated intradermal injections or by inhalation exposure. Immediate- and delayed-onset pulmonary reactions were recorded during/after challenges with the hapten or protein conjugate of the hapten, respectively. The positive control was sensitized and challenged with ovalbumin (OA) by inhalation. Homocytotropic antibodies of the IgG1 type were determined to correlate antibody titres and pulmonary responses. Immediate-onset pulmonary reactions were apparent in guinea-pigs sensitized by inhalation of TMA and OA. Animals sensitized intradermally with TMA demonstrated more vigorous immediate-onset reactions than animals sensitized by inhalation. The measurement of breathing parameters demonstrated that the ability to detect immediate-onset airway hyperreactivity was best when the breathing rate and tidal and minute volumes were measured. None of the measurements for delayed-onset reactions presented conclusive results, since sensitized as well as naive guinea-pigs demonstrated a delayed increase of breathing frequency. Antigen-specific IgG1 antibodies were several orders of magnitude higher in intradermally sensitized animals compared with animals sensitized by inhalation. Although Des-N-sensitized guinea-pigs experienced high IgG1-antibody titres, no response of pulmonary hypersensitivity could be elicited after hapten or conjugate challenge. In summary, it would appear that pulmonary hypersensitivity depends on factors other than IgG1 antibody titres. For the screening of chemicals, the dermal induction and inhalation challenge protocol was revealed to be more sensitive than the inhalation induction and inhalation challenge protocol.