Diisocyanate Monomer Research Articles

One-Pot Preparation of Monolithic Molecular Separation Membranes with Sub-10 nm Reticulated Pores Using Concentration-Polarization-Induced Gelation of Covalent Network Nanoparticles.

Monolithic molecular separation membranes were prepared by utilizing concentration polarization-induced gelation of a particulate covalent network on a porous support. Polymerization of tetra-amine and di-isocyanate monomers produced a stable dispersion of nanoparticles of urea-bonded networks in organic solvent. As the sols were allowed to pass through the support, the critical gelation point was reached due to concentration polarization via accumulation of relatively larger network particles on the substrate surface, resulting in deposition of a nanoporous gel layer, which, upon drying, turned to a monolithic layer of a covalent network with interconnected pores estimated to be 2-10 nm wide. The resulting membrane filters off solutes larger than 3 nm. Facile control of the structure and thickness of the active layer along with the superior chemical and thermal stability are promising features for solvent-resistant nanofiltration membranes suitable for separation of organic, as well as aqueous, solution mixtures.

Synthesis and Evaluation of Urethane Polymers from PET Waste

This study is engaged in synthesis of novel monomer bis(2-hydroxyethyl) by chemicalrecycling of PET waste using excess of thioglycol in prescience of (0.5%) zinc acetateas catalyst. Best yield of monomer was obtained (40%) when using 1:6 PET tothioglygol molar ratio and 16 hours reaction time. The thiolyzed products were purifiedand characterized by FTIR, 1H NMR and CHNS analysis and these characterizationswere proved that nucleophilic attack to carbonyl groups of PET backbone was achievedby thiol groups instead of hydroxyl groups of thioglycol. Also, urethane polymers wereprepared by reaction of various weight ratios of bis(2-hydroxyethyl) thioterephthalatepoly(ethylene glycol) mixtures with 2,4-toluene diisocyanate monomer. Goodmechanical compression of polyurethane polymers were obtained and evaluated showingtransition properties from rigid to flexible urethane polymers.

The Production of Green Polymer - Hyperbranched Curable Palm Oil Oleic Acid

Palm oil is one of the main raw materials available in the country. Hence, the diversification ofpalm oil derivatives into new products has been given priority. The development of new radiation curable materials for applications in radiation ultraviolet (UV) or electron beam (EB) curing technology is an important research area. The hyperbranched curable polyurethane acrylate (HBPUA) from oleic acid of palm oil has been synthesized through a three-step reaction. Dipentaerythritol was initially reacted with 2, 2-bis (hydroxymethyl) propionic acid in a solution medium aided by p-toluene sulfonic acid as a catalyst to form hyperbranched polyol polyester first generation (HBP-1). HBP-1 then used as the core and reacted with palm oil oleic acid to form the hyperbranched polyol polyester second generation (HBP-2). HBPUA was prepared by reacting HBP-2 resin with diisocyanate and hydroxyl-containing acrylate monomer with the presence of 0.1-2 wt% dibutyltin dilaurate as a catalyst. The reaction was confirmed by several analytical data namely hydroxyl value (OHV), fourier transform infrared (FTIR), gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) analyses. The HBPUA was easily curable when subjected to EB radiation. The thermal decomposition of HBPUA showed good thermal stability up to 450 oC.

Synthesis and characterization of protected oligourethanes as crosslinkers of collagen-based scaffolds.

This paper describes the preparation and characterization of water-soluble urethane oligomers bearing protected isocyanate groups. It also points out its ability to crosslink decellularized pericardium, as a model collagen scaffold, and to adjust their structural characteristics. A library of oligourethanes was synthesized by varying the molecular weight (Mw 400, 600, 1000 or 2000 g mol-1) of the poly(ethylene glycol) and the type of aliphatic diisocyanate (isophorone diisocyanate/IPDI or hexamethylene diisocyanate/HDI). 1H and 13C NMR, FTIR and mass spectrometry demonstrated that the crosslinkers are composed of chains with carbamoylsulfonate end groups that have trimeric and pentameric oligourethanes, and monomeric diisocyanate. The degree of crosslinking and hence the in vitro degradation susceptibility of the decellularized pericardium were inversely related to the Mw of the oligourethanes. The toxicity of the extractable products from oligourethane-collagen materials toward fibroblasts and macrophages was found to be lower for the crosslinker derived from IPDI than for those derived from HDI. On the other hand, the resistance to collagenase or oxidative degradation of the bovine pericardium crosslinked with HDI/oligourethane was higher than the one prepared with IPDI/oligourethane. As the Mw of the oligomers regulates the degree of crosslinking while the chemical composition influences the cytocompatibility and biodegradation of decellularized pericardium, these urethane oligomers can be used as safer crosslinkers for other protein-based biomaterials.

Etched glass bubbles as robust micro-containers for self-healing materials

Etched glass bubbles (GBs) with through-holes at the micron level were fabricated by etching them using dilute hydrofluoric acid (HF) in a specially designed mixer. The semi-segmented mixer under mechanical agitation produces circulation of the GBs in solution, purposely completing the processes of the etching reaction on the GBs, filling the etched GBs with solution, and depositing the well etched GBs in the mixer bottom for collection. Highly reactive primary amine and diisocyanate monomer were separately infiltrated into the etched GBs and formulated as self-healing materials with satisfactory healing performance, indicating the robustness and versatility of the etched GBs.

Organic sol–gel synthesis of microporous molecular networks containing spirobifluorene and tetraphenylmethane nodes

AbstractThe microporous molecular networks based on rigid tetrafunctional units are synthesized via organic sol–gel polymerization of 2,2′,7,7′‐tetraamino‐9,9′‐spirobifluorene (TASBF) and/or tetrakis(4‐aminophenyl)methane (TAPM) with a diisocyanate, hexamethylene diisocyanate (HDI), or p‐phenylene diisocyanate. This study is performed as an extension of our previous report on the first organic sol–gel method, which enabled the synthesis of microporous molecular networks via a two‐stage mechanism involving the formation of colloidal dispersions of the nanoparticulate molecular networks and their subsequent growth to monolithic networks on solvent evaporation. The sol–gel‐synthesized molecular networks obtained by incorporating TASBF as a network former show improved porosity, processability, and thermal stability than the TAPM‐based system. The improved porosity of TASBF‐based networks is attributed to higher rigidity of the spirobifluorene compared with the tetraphenylmethane units. We also demonstrate the synthesis of mixed organic molecular networks by sol–gel copolymerization of the two network formers, TASBF and TAPM, and a diisocyanate monomer. The sol–gel transformation of TASBF/TAPM/HDI occurred at longer reaction times with increasing the amount of TASBF in the TASBF/TAPM/HDI mixture. The results indicate that the organic sol–gel method can be further optimized by adjusting various synthesis parameters to create new functional organic molecular network materials. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Synthesis of EB-curable hyperbranched urethane acrylate from palm oil oleic acid

Hyperbranched urethane acrylate (HBPUA) from oleic acid of palm oil has been synthesised by a three-step reaction. Dipentaerythritol was initially reacted with 2, 2-bis (hydroxymethyl) propionic acid in a solution medium aided by p-toluene sulfonic acid as the catalyst. This mixture was then used as the core (HBP) and reacted with palm oil oleic acid to form the hyperbranched polyol (HBP-1). The hyperbranched polyurethane acrylate (HBPUA) was prepared by reacting HBP-1 resin with diisocyanate and hydroxyl-containing acrylate monomer in the presence of 0.1–2 wt% dibutyltin dilaurate as a catalyst. The reaction was confirmed by several analyses, i.e., determination of hydroxyl value (OHV), Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy analyses. HBPUA was found curable when subjected to electron beam (EB) irradiation. The thermal stability of EB cured films of HBPUAs was determined by thermogravimetric analyser (TGA). The thermal decomposition of HBPUAs showed good thermal stability up to 450°C.

Correlation between the polymerization kinetics and the chemical structure of poly(urethane–urea) nanocapsule membrane obtained by interfacial step polymerization in miniemulsion

Kinetics of the interfacial step polymerization in direct miniemulsion between 1,6-hexanediol and isophorone diisocyanate, at different temperatures and with different organic solvents as dispersed phase was investigated. Despite the complexity of the reaction system due to the specific experimental conditions, the profiles of consumption of the isocyanate groups and diisocyanate monomer, and the chemical structure of the being formed polymer membrane, were concurrently determined by gas chromatography, FTIR spectroscopy, 13C NMR and MALDI-TOF mass spectrometry. The results were connected with the key-steps of the membrane formation by interfacial polymerization, pointing out the prevailing influence of the organic dispersed phase on the hydrophilic monomer diffusion and the swelling rate of the polymeric membrane.

Synthesis and characterization of antibacterial polyurethane coatings from quaternary ammonium salts functionalized soybean oil based polyols

In this study, a simple and versatile synthetic approach was developed to prepare bactericidal polyurethane coatings. For this purpose, introduction of both quaternary ammonium salts (QASs), with well-known antibacterial activity, and reactive hydroxyl groups on to the backbone of soybean oil was considered. Epoxidized soybean oil was reacted with diethylamine and the intermediate tertiary amine containing polyol was reacted with two different alkylating agents, methyl iodide and benzyl chloride, to produce MQAP and BQAP, respectively. These functional polyols were reacted with different diisocyanate monomers to prepare polyurethane coatings. Depending on the structure of monomers used for the preparation of polyurethane coatings, initial modulus, tensile strength and elongation at break of samples were in the ranges of 122–339MPa, 4.6–12.4MPa and 8.4–46%, respectively. Polyurethane coatings based on isophorone diisocyanate showed proper mechanical properties and adhesion strength (0.41MPa) for coating application. Study of fibroblast cells interaction with prepared polyurethanes showed promising cells viability in the range of 78-108%. Meanwhile, MQAP based samples with higher concentration of QASs showed better adhesion strength, surface hydrophilicity and antibacterial activity (about 95% bacterial reduction). Therefore, these materials can find applications as bactericidal coating for biomedical devices and implants.

Risk assessment for consumer exposure to toluene diisocyanate (TDI) derived from polyurethane flexible foam

Polyurethanes (PU) are polymers made from diisocyanates and polyols for a variety of consumer products. It has been suggested that PU foam may contain trace amounts of residual toluene diisocyanate (TDI) monomers and present a health risk. To address this concern, the exposure scenario and health risks posed by sleeping on a PU foam mattress were evaluated. Toxicity benchmarks for key non-cancer endpoints (i.e., irritation, sensitization, respiratory tract effects) were determined by dividing points of departure by uncertainty factors. The cancer benchmark was derived using the USEPA Benchmark Dose Software. Results of previous migration and emission data of TDI from PU foam were combined with conservative exposure factors to calculate upper-bound dermal and inhalation exposures to TDI as well as a lifetime average daily dose to TDI from dermal exposure. For each non-cancer endpoint, the toxicity benchmark was divided by the calculated exposure to determine the margin of safety (MOS), which ranged from 200 (respiratory tract) to 3×106 (irritation). Although available data indicate TDI is not carcinogenic, a theoretical excess cancer risk (1×10−7) was calculated. We conclude from this assessment that sleeping on a PU foam mattress does not pose TDI-related health risks to consumers.

Improved Lignin Polyurethane Properties with Lewis Acid Treatment

Chemical modification strategies to improve the mechanical properties of lignin-based polyurethanes are presented. We hypothesized that treatment of lignin with Lewis acids would increase the concentration of hydroxyl groups available to react with diisocyanate monomers. Under the conditions used, hydrogen bromide-catalyzed modification resulted in a 28% increase in hydroxyl group content. Associated increases in hydrophilicity of solvent-cast thin films were also recorded as evidenced by decreases in water contact angle. Polyurethanes were then prepared by first preparing a prepolymer based on mixtures of toluene-2,4-diisocyanate (TDI) and unmodified or modified lignin, then polymerization was completed through addition of polyethylene glycol (PEG), resulting in mass ratios of TDI:lignin:PEG of 43:17:40 in the compositions investigated here. The mixture of TDI and unmodified lignin resulted in a lignin powder at the bottom of the liquid, suggesting it did not react directly with TDI. However, a homogeneous solution resulted when TDI and the hydrogen bromide-treated lignin were mixed, suggesting demethylation indeed increased reactivity and resulted in better integration of lignin into the urethane network. Significant improvements in mechanical properties of modified lignin polyurethanes were observed, with a 6.5-fold increase in modulus, which were attributed to better integration of the modified lignin into the covalent polymer network due to the higher concentration of hydroxyl groups. This research indicates that chemical modification strategies can lead to significant improvements in the properties of lignin-based polymeric materials using a higher fraction of an inexpensive lignin monomer from renewable resources and a lower fraction an expensive, petroleum-derived isocyanate monomer to achieve the required material properties.

Airborne Isocyanate Exposures in the Collision Repair Industry and a Comparison to Occupational Exposure Limits

Isocyanate exposure was evaluated in 33 spray painters from 25 Washington State autobody shops. Personal breathing zone samples (n = 228) were analyzed for isophorone diisocyanate (IPDI) monomer, 1,6-hexamethylene diisocyanate (HDI) monomer, IPDI polyisocyanate, and three polyisocyanate forms of HDI. The objective was to describe exposures to isocyanates while spray painting, compare them with short-term exposure limits (STELs), and describe the isocyanate composition in the samples. The composition of polyisocyanates (IPDI and HDI) in the samples varied greatly, with maximum amounts ranging from up to 58% for HDI biuret to 96% for HDI isocyanurate. There was a significant inverse relationship between the percentage composition of HDI isocyanurate to IPDI and to HDI uretdione. Two 15-min STELs were compared: (1) Oregon's Occupational Safety and Health Administration (OR-OSHA) STEL of 1000 μg/m3 for HDI polyisocyanate, and (2) the United Kingdom's Health and Safety Executive (UK-HSE) STEL of 70 μg NCO/m3 for all isocyanates. Eighty percent of samples containing HDI polyisocyanate exceeded the OR-OSHA STEL while 98% of samples exceeded the UK-HSE STEL. The majority of painters (67%) wore half-face air-purifying respirators while spray painting. Using the OR-OSHA and the UK-HSE STELs as benchmarks, 21% and 67% of painters, respectively, had at least one exposure that exceeded the respirator's OSHA-assigned protection factor. A critical review of the STELs revealed the following limitations: (1) the OR-OSHA STEL does not include all polyisocyanates, and (2) the UK-HSE STEL is derived from monomeric isocyanates, whereas the species present in typical spray coatings are polyisocyanates. In conclusion, the variable mixtures of isocyanates used by autobody painters suggest that an occupational exposure limit is required that includes all polyisocyanates. Despite the limitations of the STELs, we determined that a respirator with an assigned protection factor of 25 or greater is required to protect against isocyanate exposures during spray painting. Consequently, half-face air-purifying respirators, which are most commonly used and have an assigned protection factor of 10, do not afford adequate respiratory protection.

Penetration patterns of monomeric and polymeric 1,6-hexamethylene diisocyanate monomer in human skin

We investigated penetration patterns of monomeric and polymeric 1,6-hexamethylene diisocyanate (HDI), experimentally and as part of commercial products, in excised full-thickness human skin at 5, 10, 30, or 60 min after exposure. We observed that both monomeric and polymeric HDI were readily absorbed into the skin and that the clearcoat composition affects the penetration rate of the individual isocyanates. The short-term absorption rates for HDI monomer, biuret, and isocyanurate were determined and used to estimate the exposure time required to reach a body burden equal to the American Conference of Governmental Industrial Hygienists (ACGIH) inhalation threshold limit value (TLV) or Oregon State occupational exposure limit (OEL). Oregon is the only government entity in the United States to promulgate a short-term exposure limit (STEL) for HDI-based polyisocyanates biuret and isocyanurate. Based on these absorption rates for a slow-drying clearcoat after 10 min (1.33 μg cm(-2) h(-1)) or 60 min (0.219 μg cm(-2) h(-1)), we calculated that 6.5 and 40 min dermal exposure, respectively, is required to achieve a dose of HDI equivalent to the ACGIH TLV. For biuret, the time to achieve a dose equivalent to the Oregon OEL for slow-drying clearcoat was much shorter (<31 min) than that for fast-drying clearcoat (618 min). Isocyanurate had the shortest skin absorption times regardless of clearcoat formulation (14 s-1.7 min). These results indicate that the dose received through dermal exposure to HDI-containing clearcoats has a significant potential to exceed the dose equivalent to that received through inhalation exposure at established regulatory limits. A critical need exists to monitor dermal exposure quantitatively in exposed workers, to use proper protective equipment to reduce dermal exposure, and to re-evaluate regulatory exposure limits for isocyanates.

N-Heterocyclic carbene-catalysed synthesis of polyurethanes

A free N-heterocyclic carbene has been efficiently used for the organocatalysed step-growth polymerisation between aliphatic diisocyanates and diols. Both the nature of the diisocyanate monomer and the order of addition of reactants are critical parameters for the successful synthesis of soluble linear polyurethanes.

Comparative analysis of aromatic diisocyanate conjugation to human albumin utilizing multiplexed tandem mass spectrometry

Diisocyanates are industrially important chemicals that serve as polymerizing agents in a variety of polyurethane products. In addition to their many industrial uses, diisocyanates have been implicated as causative agents of occupational allergic respiratory disease, although the specific mechanism(s) by which these diseases occur remains unknown. In this study the sites of conjugation of the two most industrially important monomeric diisocyanates, methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI) on human serum albumin are identified utilizing multiplexed tandem mass spectrometry on a quadrupole time-of-flight mass spectrometer. Analysis of human albumin reacted with MDI and TDI over the range of 1:1–40:1 (isocyanate:protein) mol ratio reveals that MDI and TDI react with a maximum of 20 and 37 residues, respectively. Conjugation of diisocyanates to albumin proceeds in a concentration-dependant manner with MDI and TDI reacting at a preferred subset of 5 and 10 residues, respectively, in the limiting case of a 1:1 mol ratio. MDI reacts at fewer residues than does TDI, and is not observed to react with any residues exclusive of TDI. These results cannot be explained on the basis of simple sterics or hydrophobicity, but rather on the basis of increased reactivity of one TDI isocyanate moiety due to electron withdrawing character of the second isocyanate moiety. Furthermore, reaction of diisocyanates with albumin in a phosphate buffered saline (PBS) solution provides three additional reactive sites that are not observed in ammonium bicarbonate buffer. Two lysine residues, Lys 199 and Lys 525, are observed to be reactive to both diisocyanates at all concentrations and in all solvent systems employed in this study. This study presents a comprehensive conjugation map of MDI and TDI on human albumin. The results suggest that several albumin residues are reactive toward both MDI and TDI and may be useful for biomonitoring of diisocyanate exposures.

Water‐Free Synthesis of Polyurethane Foams Using Highly Reactive Diisocyanates Derived from 5‐Hydroxymethylfurfural

This paper reports on the synthesis of a new highly reactive diisocyanate monomer based on hydroxymethylfurfural. It further describes its catalyst-free conversion to linear-chain thermoplastic polyurethanes as well as to cross-linked polyurethane foams. In addition, a novel strategy for the synthesis of polyurethane foams without the necessity of using water is developed. Nitrogen is utilized herein as blowing agent which is formed during Curtius rearrangement of a new furan based carboxylic azide into its corresponding diisocyanate.

Synthesis and Characterization of Novel Polyurethanes Based on N,N'-1,2-Ethanediylbis-(4-Hydroxy-Pentanamide) and 4-Hydroxy-N-(2-Hydroxyethyl)-Pentanamide

As diols, N,N'-1,2-ethanediylbis-(4-hydroxy-pentanamide) (1) and 4-hydroxy-N-(2-hydroxyethyl)-pentanamide (2)) are versatile precursors for the manufacture of bio-polymers. Polymer design, by exploiting the variation in structure of both diol and di-isocyanate monomers, such as backbone structure and presence of functional groups, appears to be a promising biopolymer engineering pathway to synthesize polyurethanes. Both diols (1) and (2) were then polymerized by reaction with aliphatic and aromatic di-isocyanates at 140 °C in (N,N-dimethylacetamide (DMA) solvents using triethylamine (TEA) catalysts, to obtain novel polyurethanes. The products were characterized by FTIR, 1H-NMR, 13C-NMR, and Elemental Analysis. This working has created a new chance to synthesis bio-polyurethanes based on levulinic acid, as one of biomass compounds

Hemoglobin adducts in workers exposed to 1,6-hexamethylene diisocyanate

We investigated the utility of 1,6-hexamethylene diamine (HDA) hemoglobin adducts as biomarkers of exposure to 1,6-hexamethylene diisocyanate (HDI) monomer. Blood samples from 15 spray painters applying HDI-containing paint were analyzed for hemoglobin HDA (HDA-Hb) and N-acetyl-1,6-hexamethylene diamine (monoacetyl-HDA-Hb) by GC-MS. HDA-Hb was detected in the majority of workers (≤1.2–37 ng/g Hb), whereas monoacetyl-HDA-Hb was detected in one worker (0.06 ng/g Hb). The stronger, positive association between HDA-Hb and cumulative HDI exposure (r2 = 0.3, p < 0.06) than same day exposure (p ≥ 0.13) indicates long-term elimination kinetics for HDA-Hb adducts. This association demonstrates the suitability of HDA-Hb adducts for further validation as a biomarker of HDI exposure.

Sequestration of naphthenic acids from aqueous solution using β-cyclodextrin-based polyurethanes

The sorption characteristics of naphthenic acids (NAs) in their anion form with β-cyclodextrin (β-CD) based polyurethanes, as sorbents, from aqueous solutions that simulate the conditions of oil sands process water (OSPW) are presented. The copolymer sorbents were synthesized at various β-CD:diisocyanate monomer mole ratios (e.g., 1:1, 1:2, and 1:3) with diisocyanates of variable molecular size and degree of unsaturation. The equilibrium sorption properties of the copolymer sorbents were characterized using sorption isotherms in aqueous solution at pH 9.00 with electrospray ionization mass spectrometry to monitor the equilibrium unbound fraction of anionic NAs in the aqueous phase. The copolymer sorbents were characterized in the solid state using (13)C CP-MAS NMR spectroscopy, IR spectroscopy and elemental analysis. The sorption results of the copolymer sorbents with anion forms of NAs in solution were compared with a commercially available carbonaceous standard: granular activated carbon (GAC). The monolayer sorption capacities of the sorbents (Q(m)) were obtained from either the Langmuir or the Sips isotherm model used to characterize the sorption characteristics of each copolymer sorbent. The estimated sorption capacity for GAC was 142 mg NAs per g sorbent whereas the polymeric materials ranged from 0-75 mg NAs per g sorbent over the experimental conditions investigated. In general, significant differences in the sorption capacities between GAC and the copolymer sorbents were related to the differences in the accessible surface areas and pore structure characteristics of the sorbents. The Sips parameter (K(eq)) for GAC and the copolymer materials reveal differences in the relative binding affinity of NAs to the sorbent framework in accordance with the synthetic ratios and the value of Q(m). The diisocyanate linker plays a secondary role in the sorption mechanism, whereas the β-CD macrocycle in the copolymer framework is the main sorption site for NAs because of the formation of inclusion complexes with β-CD.

The effect of crosslinker on mechanical and morphological properties of tropical wood material composites

In this study, wood polymer composites (WPCs) based on five kinds of selected tropical wood species, namely Jelutong (Dyera costulata), Terbulan (Endospermum diadenum), Batai (Paraserianthes moluccana), Rubber (Hevea brasiliensis), and Pulai (Alstonia pneumatophora), were impregnated with methyl methacrylate (MMA) and hexamethylene diisocyanate (HMDIC) monomers mixture in the ratio of 1:1 for composite manufacturing. All these tropical wood reacted with hexamethylene diisocyanate and crosslinked with MMA which enhanced the hydrophobic (restrained water) nature of wood. The vacuum-pressure method was used to impregnate the samples with monomer mixture. The monomer mixture loading achievable was found to be dependent on the properties of wood species. Low loading was observed for the high density wood species. Mechanical strength of fabricated wood polymer composites (WPCs) in term of modulus of elasticity (MOE) and modulus of rupture (MOR) were found to be significantly improved. The wood–polymer interaction was confirmed by Fourier transform infrared (FTIR) spectroscopy. Morphological properties of raw wood and WPC samples were evaluated by scanning electron microscopy (SEM) and XRD analysis and an improvement in morphological properties was also observed for WPC.