Isocyanate Component Research Articles

Nanoclay‐Modified Rigid Polyurethane Foam

Montmorillonite‐based organoclay was incorporated into rigid polyurethane foams. Clay was dispersed first in the isocyanate component ultrasonically. The dispersion was investigated using small angle X‐ray scattering and rheology. It was found that using toluene as common solvent enhanced dispersion significantly. The addition of 1 wt% clay resulted in reduced cell size from 0.40 to 0.28 mm and increased cell number density on 300‐index foams. Gas chromatography showed that diffusion of blowing agent out of the closed cells of the foam decreased by more than 82% with clay loading. The reduction in permeability is caused by the combined effect of smaller cell size and dispersed nanoclay acting as diffusion barrier. At 1% clay no mechanical strength improvements were observed. Higher levels of clay loading caused significant viscosity increase and a yield stress that made mixing the reactive components difficult. Dedicated to Professor John L. Stanford on the occasion of his 60th birthday.

Efficacy of polymeric MDI/Polyol mixtures for binding wood boards

Components of polyurethane synthesis are tested for their ability to bind pine wood into boards and are compared to the efficiency of using only the isocyanate component of polyurethane synthesis. A variety of polyols are tested varying equivalent weight, functionality, reactivity as determined by the availability of primary hydroxyl endgroups, and viscosity. The boards are fabricated at a variety of densities and under a variety of conditions. The results show that board properties using only the isocyanate component are always superior to those including a polyol component, but the board properties are not always a simple function of the amount of isocyanate put in the board. Furthermore, it is observed that the lower the room temperature surface tension between the polyol and isocyanate, the better the measured board properties; but, the higher the observed surface tension, the better the board will self-release from the metal caul plates.

Spray-painting and chronic airways obstruction.

The aim was to investigate the respiratory response of HDI-based paint aerosol within the context of the protection afforded by current exposure guidelines. A cross-sectional study of 240 painters spraying polyurethane enamels was undertaken at four aircraft maintenance plants. Questionnaire and spirometric data were related to gravimetric measures of cumulative total and respirable paint aerosol (TPA and RPA) and estimated isocyanate in total and respirable aerosols (TIA and RIA). Average cumulative exposures in mg/m(3)-years +/- SD were 159.0 +/- 115.2 TPA, 19.1 +/- 13.8 RPA, 15.8 +/- 11.5 TIA, and 1.9 +/- 1.4 RIA. After adjusting for smoking and asthma symptoms, higher exposures were associated with statistically significant reduction in expiratory flowrates. Significant smoking-related reductions were also observed, without exposure interactions. These results suggest important respiratory effects from exposures to spray paint aerosols at levels generally in compliance with existing standards for otherwise unregulated particulates and for the isocyanate component of the paint.

Zywice epoksydowe i poliuretany — wzajemne oddzialywanie modyfikujace. Cz. II. Przenikajace sie sieci polimerowe (IPN)

The methods of epoxy resins (EP) and polyurethanes (PUR) mutual modification leading to the formation of interpenetrating polymer networks (IPN) and graft polymer networks (graft-IPN) were presented on the basis of literature data. Main aim of EP modification is its elasticity improving. EP modification with PUR containing functional groups (namely OH, NH 2 , NCO or anhydride groups) or urethane - acrylic systems was discussed. Rigid PUR foams modification with EP was also presented. Additionally EP modification with low molecular weight isocyanates, acting as substitutes of PUR with reactive groups, has been described. The effects of EP:PUR weight ratio, molecular weight of isocyanate component and a degree of grafting between both polymer networks on the morphology and mechanical and thermal properties of the products were characterized. EP and PUR phase separation determining the proper elasticity of the products was also presented.

Kinetic study on the reaction of 2,4‐ and 2,6‐tolylene diisocyanate with 1‐butanol in the presence of styrene, as a model reaction for the process that yields interpenetrating polyurethane–polyester networks

AbstractA classical method was utilized for determination of free isocyanates to study the kinetics of a model reaction of 2,4‐ and 2,6‐tolylene diisocyanate (TDI) with 1‐butanol, which was run in the reaction medium of liquid aliphatic hydrocarbons. Such conditions made it possible to find rate constants and activation energy values for the second‐order reactions under isothermal conditions. Those reactions can be employed to produce isocyanate prepolymers, which make intermediates for downstream polyurethanes. The findings are commented upon against the background of earlier kinetic data that can widely be found in the research reports published. Further, part of our work utilized the findings to provide interpretation of kinetic parameters for analogous reactions, the kinetic data being found in the presence of styrene—the monomer employed when producing polyurethane–polyester interpenetrating polymer network (IPN) systems. The hypothesis was put forward that styrene and isocyanate component(s) could react at the final stages of the process when the system becomes short in the hydroxyl substrate. That hypothesis was based on disturbances observed in the reactivity of NCO groups (in 2,4‐TDI) in the reaction system studied. The rate constants and activation energy values were determined and presented for the urethanization reaction of 1‐butanol. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 327–336, 2003

Study of film properties of some urethane oils

In this study, sunflower oil-based urethane oils were obtained from three kinds of isocyanate components: toluene diisocyanate (TDI), hexamethylene diisocyanate (HMDI) and poly(1,4-butandiol) toluene 2,4-diisocyanate (PBTDI) terminated prepolymer. The polymers were prepared at four different ratios of isocyanate component/oil. Sunflower and linseed oil alkyd resin samples were also prepared as the comparative samples. The results suggest that the viscosity and the film properties of urethane oils depend on the amount and type of isocyanate component.

Dependence of the Structure and Properties of Injection Moulding Polyurethanes on the Nature of the Isocyanate Component

Dependence of the Structure and Properties of Injection Moulding Polyurethanes on the Nature of the Isocyanate Component

Photochemistry and photoinduced chemical crosslinking activity of type I & II co-reactive photoinitiators in acrylated prepolymers

The photoreactivity of Type I and II photointiators, namely, 4-(2-hydroxyethoxy)-phenyl-(2-hydroxy2-methylpropyl) ketone (Irgacure 2959, Ciba-Geigy) and 4-hydroxybenzophenone, respectively, have been examined in the free and bound form in melamine and urethane acrylate prepolymers. Co-reaction in the prepolymers was undertaken by partial replacement of the hydroxyacrylate components with the photoinitiators in the reaction with the isocyanate component. Both the photoinitiators were also converted into their corresponding acrylate derivatives for study. The free, bound and acrylated derivatives were then analysed by various spectroscopic techniques to evaluate the relationship between their photophysical properties and photoinitiation activity for photocrosslinking of commercial acrylated monomers and prepolymers. Photocuring studies using Hg sources (conveyor and RTIR) indicated that whilst binding the Type I photointiator reduced its efficiency in cure, the Type II photoinitiator was enhanced. The presence of an amine co-synergist, however, generally eliminated these differentials. Acrylation of the Irgacure 2959 also reduced photoactivity. Absorption spectroscopy indicated the presence of a strongly absorbing nπ * transition in the far UV region for both chromophore types which undergoes a blue shift on binding to the prepolymer. Phosphorescence spectra, lifetimes and quantum yields also indicate the presence of low lying triplet nπ * states for both types of chromophore. Binding appears to enhance the triplet lifetime and reduce the quantum yield of emission due to increased electron donation into the chromophore by the resin component and may in part account for their lower photoactivity. Microsecond flash photolysis identified the formation of benzoyl radicals in the case of the Type I system with a small enhancement in radical formation on binding. The Type II system gave ketyl radicals formed by hydrogen atom abstraction which were enhanced in the bound resin system. The latter would account for increased photoactivity for the bound Type II system. Nanosecond laser flash photolysis experiments identified the triplet–triplet absorption in the case of the Type II initiator. In the presence of a tertiary amine (triethylamine) the transient absorption and its lifetime were significantly enhanced due to exciplex formation. However, binding the benzophenone initiator to the resin significantly quenched the transient absorption and significantly reduced its lifetime. In the case of the Type I initiator the benzoyl radical was observed directly, confirming the microsecond flash photolysis data. Binding of the initiator to the melamine acrylate resin also reduced benzoyl radical formation and reduced the radical lifetime. This may account for the reduced photoactivity of the Type I bound initiator. Radical formation was also reduced when bound to the urethane acrylate but the lifetime was enhanced. For the initiator bound resin systems the presence of an amine co-synergist enhanced benzoyl radical formation. The implications of initiator co-reactions are discussed in terms of both the photochemical and commercial benefits.

The influence of the ratio of the polyurethane coating components on the quality of finished wood surface

The influence of some factors of the wood-coating system on the quality of finished surfaces was examined. The solid wood of some hardwood species — beech and oak — conditioned to various moisture contents corresponding to the wood moisture in interior use was used. Wood samples were finished with two pack clear polyurethane coating. The influence of the coating on the quality was examined through the different ratios of the polyurethane coating components, i.e. the different content of isocyanate component in the coating. The interaction is monitored by adhesion the determination of adhesion expressed by the pull-off strength of the polyurethane coating.

Condensation reactions of benzils with ureas in ethylene glycol

AbstractReactions of benzils and urea in ethylene glycol at 180° for 1‐2 hours gave 2,4,5‐triaryloxazoles as major products and bicyclic imidazoimidazole‐2,5‐diones as minor products. N‐Methylurea and N‐phenylurea gave the oxazoles under similar conditions. The solvent seemed to assist the formation of oxazole by eliminating the isocyanate components as ethylene glycol biscarbamates.

Influence of the composition of rosin-based rigid polyurethane foams on their thermal stability

A series of rosin-based rigid polyurethane foams of different composition were synthesized directly from chemically modified gum rosin. The effect of the composition of these rosin-based rigid polyurethane foams on their thermal stability and compression strength was measured. It was shown that the onset temperature of weight loss and the dimensional stability at high temperature increased with increase of the molar ratio of NCO/OH. The TGA data further confirmed that the second stage weight loss in the two-stage weight loss process of these polyurethane foams was governed by thermal degradation of the isocyanate component. Although density had no significant influence on the TGA curves of the rosin-based rigid polyurethane foams, it had great influence on the dimensional stability at high temperature and compression strength of the foams. It has been shown that the inclusion of rosin in rigid polyurethane foams increases the strength and thermal stability compared with that of polyether-based ones. © 1996 John Wiley & Sons, Inc.

Influence of the composition of rosin‐based rigid polyurethane foams on their thermal stability

A series of rosin-based rigid polyurethane foams of different composition were synthesized directly from chemically modified gum rosin. The effect of the composition of these rosin-based rigid polyurethane foams on their thermal stability and compression strength was measured. It was shown that the onset temperature of weight loss and the dimensional stability at high temperature increased with increase of the molar ratio of NCO/OH. The TGA data further confirmed that the second stage weight loss in the two-stage weight loss process of these polyurethane foams was governed by thermal degradation of the isocyanate component. Although density had no significant influence on the TGA curves of the rosin-based rigid polyurethane foams, it had great influence on the dimensional stability at high temperature and compression strength of the foams. It has been shown that the inclusion of rosin in rigid polyurethane foams increases the strength and thermal stability compared with that of polyether-based ones. © 1996 John Wiley & Sons, Inc.

Influence of structure of hydroxyl‐terminated maleopimaric acid ester on thermal stability of rigid polyurethane foams

AbstractA series of hydroxyl‐terminated maleopimaric acid esters (HTMAEs) and rigid polyurethane (PU) foams based on these HTMAEs were synthesized using chemically modified natural gum rosin and its derivative maleopimaric acid as raw materials. Thermal stability of these polyols and their corresponding rigid PU foams was studied by a thermogravimetric method and a dimensional stability measurement. It was shown that the thermal stability of the final foams was strongly dependent on the structure of their corresponding polyols. The thermogravimetric analysis curves of these rosin‐based rigid PU foams displayed two distinct regions of weight loss. It has been shown that at the initial stage of weight loss the process was dominated by polyol component degradation; the second stage was governed by isocyanate component degradation. © 1995 John Wiley & Sons, Inc.

An Infrared Spectroscopic Study of Chemically Modified Chemithermomechanical Pulp

Abstract FT-IR spectroscopy was used to characterize chemically modified wood pulp and to judge the efficiency of different pulp modification processes. Treatment of wood pulp with aliphatic anhydrides was shown to be more effective in a polar solvent such as DMF compared to a non-polar one typified by xylene. The esterification of hydroxyl group associated with the cellulosic material was indicated by the characteristic absorption bands of the resulting cellulosic esters; the degree of hydroxyl conversion was determined by the ratio of peak intensity of hydroxyl and carbonyl stretching vibrations. The so-called “Infrared Acetyl Index” was shown to give a linear correlation with the gravimetrically determined anhydride uptake. Isocyanate modification of wood pulp yielded more complex infrared spectra, because of various secondary reactions of the reactive isocyanate component. Various aromatic isocyanates, used for chemical treatment of the wood pulp, led mainly to urethane formation, as evidenced by the ...

Combustion Modified Moulded Polyurethane Flexible Foam for the Furniture Industry

Current trends in legislation are based on a move towards more severe fire testing of flexible foam products used in the construction of domestic and contract furniture and mass transit seating. Large scale ignition tests, such as CaliforniaT.B. 133intheU.SA., BS 5852 crib 5in the UKand the AAstandard in Japan, are becoming the accepted norm around the world. ICI has now developed a combustion modified system capable of meeting even these most stringent fire tests. In addition, the polyol blend used is storage stable against any settling out of the solid fire retardant component. This has been achieved in a CFC free system without compromising the superior processing associated with MDI technology. In fact, it is found that the reproducibility of the fire performance of the resulting foam is enhanced due to superior dispersion of the solid fire retardant. Careful development of both polyol and isocyanate components has minimized the detrimental effects of the fire retardant package on foam physical properties. Significant joint customer development work has led to the definition of a seat design concept incorporating ICI's combustion modified foam which can satisfy California T.B. 133, recognized as one of the world's most severe fire performance tests. Formulation development work has been underpinned by the development of an understanding of the fundamental mechanism at work during combustion of the CMHR foam. This has been achieved by the use of analytical techniques including a study by cone calorimetry.

MDI Based Flexible Foam A Status Report on World Developments

Moulded flexible polyurethane foam using hot-cure moulding technology with TDI as the isocyanate component was developed in the mid 1950's. The authors trace the development in the mid 1960's of HR or cold-cure foams which used TDI/MDI blends and more reactive polyether polyols. The logical next step was the introduction of All-MDI based, cold-cure flexible foams in the late 1970's. Much progress has been made since then, and the changes in processability which have led to better durability and greater comfort in seat cushions – both in the automotive industry and the high quality upholstered-furniture market are reviewed. Comfort properties are defined in terms of persons-sitting experience, and the load-bearing and hardness qualities required are defined to achieve good comfort levels. Environmental considerations are discussed with respect to the lower vapour pressures at normal processing temperatures given by MDI as compared with TDI. The current concern regarding the effect of CFC's on the atmosphere is discussed and ways in which the levels are being reduced in the All-MDI based foam moulding process are indicated. Cushions with dual and multiple hardness and pour-in-place techniques are discussed and the commercial experiences with the total range of All-MDI based foam systems – worldwide – is reviewed.

Theoretical study of influence of structure of carbamates on their thermal stability

Energetic and structural characteristics of carbamates of different structure were calculated by the semiempirical quantum-chemical method MINDO/3 (modified intermediate neglect of differential overlap) with geometry optimization of the compounds. The influence was shown of N- and O-substituents on the strength of the bonds, rupturing in both reversible thermal dissociation of the carbamates into isocyanate and alcohol components, and as a result of irreversible thermal decomposition with liberation of CO/sub 2/, amine and olefin.

Exchange, elimination, and ring opening reactions of 2,3-dihydrobenzimidazo[1,2-d][1,2,4]thiadiazoles and 3H-benzimidazo[2,1-c][1,2,4]dithiazoles

The reactions of benzimidazo[1,2-d][1,2,4]thiadiazol-3(2H)-ones (1) with isocyanates, isothiocyanates, carbon disulphide, aryl cyanates, acetylenedicarboxylates, and enamines, with exchange of the isocyanate component of (1), to give the corresponding condensed benzimidazole derivatives (1)–(6) are described. Under more severe conditions the 1-benzothiazol-2-yl-1,3-dihydrobenzimidazole-2-thiones (7) were obtained from aromatic isothiocyanates. Thermolysis of the thiadiazoles (1) led to the triazine derivative (12) with elimination of isocyanate and sulphur, and in the presence of phenols to the 2-aryloxybenzimidazoles (13). With amines and CH-acidic compounds, the S,N bond in compound (1) was cleaved to give benzimidazol-2-ylsulphenamides (14), and the ω-substituted methylthiobenzimidazoles (17) and (18). With cyanide ion, insertion into the S,N bond of compound (1) to furnish the thiadiazine (22) took place. The dithiazoles (2) were fragmented by amines to give 1,3-dihydrobenzimidazole-2-thione and guanidine with loss of sulphur; reaction with cyanide ion then gave the dibenzimidazothiadiazine (25).

Synthesis and study of the thermo-oxidative degradation of organosilicon urethanes

Organosilicon model urethanes of different structure have been synthesized and their stability to thermo-oxidative degradation studied. The methods of IR spectroscopy and derivatographic analysis are used to make a quantitative evaluation of the influence of various factors (length of the carbo functional chain from the silicon atom to the urethane group and the nature of the isocyanate component) on the resistance of the urethane bond to thermo-oxidative degradation.

The Incorporation of Particulate Silica in a Rigid Polyurethane Foam

A commercially available rigid polyurethane foam formulation was modified by addition of increasing quantities of silica fillers of small particle size. The foam products were tested in compression for density and water absorption measurements and were examined by electron scanning microscopy. The reactivity of the fillers to the isocyanate component was examined quantitatively by an infrared technique. The fillers were found to react with the isocyanate component and to cause a collapse of the foam cell structure.