Rigid Polyurethane Foam Production from Palm Oil-Based Epoxidized Diethanolamides

A new type of rigid polyurethane foam was produced by incorporating oxazolidone heterocyclic rings on to polyurethane backbones. Epoxidized diethanolamides were synthesized by reacting palm oil blends of epoxidized palm olein and refined bleached deodorized palm kernel olein with diethanolamine to produce rigid polyurethane foams. Epoxides, retained in the diethanolamides, reacted with isocyanate during foam production in the presence of AlCl₃–THF complex catalyst to form oxazolidone linkages in the polyurethane network. The carbonyl stretch of oxazolidone was identified at 1,750 cm⁻¹ through Fourier Transform Infra Red analysis. Chemical modifications of the polyurethane network also improved the thermal and mechanical properties of the foams. In addition, isocyanate index 1.4 was determined to be the most suitable in the production of foams from this newly synthesized epoxidized diethanolamides.     

Sorption of water vapour into polyurethane foams

The sorption and desorption of water into polyurethane foams have been studied. A cylindrical sample of the foam was suspended from the beam of a microbalance in a sealed envelope to which water vapour was admitted at the start of the experiment. The sorption and desorption kinetics were obtained from the measured weight changes of the specimen and the experiments were repeated for different foams at a number of conditions of relative saturation.Diffusion coefficients and equilibrium saturations were calculated from the experimental results by comparing analytical expressions for diffusion into cylindrical specimens with the experimental values and choosing the coefficients and saturation values so that the difference between experiment and theory was minimal. Good agreement of the experimental values with theory was found for dense foams, but good agreement was found for the more highly expanded foams only when an associated chemical reaction was taken into account.     

Shrinkage and re‐expansion of extruded starch acetate foams

The effects of concentration of steam, heating time, pretreatment, and cooling conditions on the shrinkage and re‐expansion of extruded starch acetate foam were investigated. The re‐expansion ratio was determined from the degree by which the foam cells were moistened under the condition tested. The higher the concentration of steam used, the faster and greater the foam re‐expanded. Shrinkage was a result of the negative pressure resulting from cooling and condensation of steam or ethanol inside the foam and the unbalanced osmosis of steam transported out of the foam and air transported into the foam and the resistance of foam cell walls. Quenching re‐expanded foams led to significant shrinkage, especially for foams re‐expanded with highly concentrated steam. Shrinkage cannot be avoided even if the foam is kept at the same temperature it was expanded at the nozzle. Gradually reducing the degree of concentration of steam could reduce the shrinking tendency of the re‐expanded foam. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4264–4268, 2006     

Stress relaxation of glass-fiber-reinforced rigid polyurethane foam

Flexural stress relaxations were measured for rigid polyurethane foams (PUF) and glass-fiber-reinforced rigid polyurethane foams (FRU). The results were successfully analyzed in terms of the five element Maxwell model: (1) Samples reinforced with longer fibers exhibit reduced stress relaxation and reduced temperature dependency of stress relaxation; (2) The increased expansion ratio reduces the flexural modulus of both reinforced and non-reinforced materials, but the stress relaxation tends to increase greatly at the higher temperature for PUF, while not so greatly for FRU; (3) The temperature dependency of E₁ decreases as longer fibers are used to reinforce the polyurethane. The dependency is minimal for the polyurethane reinforced with continuous fibers, where the reinforcing effect is maximal; and (4) The activation energy calculated from τ₂ according to the Arrhenius plot is smaller for the longer fiber reinforced polyurethane foams.     

Physical properties of water‐blown rigid polyurethane foams from vegetable oil‐based polyols

Fifty vegetable oil‐based polyols were characterized in terms of their hydroxyl number and their potential of replacing up to 50% of the petroleum‐based polyol in waterborne rigid polyurethane foam applications was evaluated. Polyurethane foams were prepared by reacting isocyanates with polyols containing 50% of vegetable oil‐based polyols and 50% of petroleum‐based polyol and their thermal conductivity, density, and compressive strength were determined. The vegetable oil‐based polyols included epoxidized soybean oil reacted with acetol, commercial soybean oil polyols (soyoils), polyols derived from epoxidized soybean oil and diglycerides, etc. Most of the foams made with polyols containing 50% of vegetable oil‐based polyols were inferior to foams made from 100% petroleum‐based polyol. However, foams made with polyols containing 50% hydroxy soybean oil, epoxidized soybean oil reacted with acetol, and oxidized epoxidized diglyceride of soybean oil not only had superior thermal conductivity, but also better density and compressive strength properties than had foams made from 100% petroleum polyol. Although the epoxidized soybean oil did not have any hydroxyl functional group to react with isocyanate, when used in 50 : 50 blend with the petroleum‐based polyol the resulting polyurethane foams had density versus compressive properties similar to polyurethane foams made from 100% petroleum‐based polyol. The density and compressive strength of foams were affected by the hydroxyl number of polyols, but the thermal conductivity of foams was not. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Monte Carlo simulation of microemulsion polymerization

Monte Carlo simulation of chemically reacting systems based on the master equation was used to describe the stochastic time evolution of the microemulsion polymerization system. A model was developed to demonstrate its applicability for hexyl methacrylate and styrene microemulsion polymerization. The properties of final latex, such as the particle size and molecular weight distributions were obtained simultaneously. The polymerization behavior and properties of final latexes were well reproduced. The model is valuable in confirming or elucidating the various mechanisms in the polymerization. The entry and desorption mechanism was well established to account for the polymerization kinetics. The general polymerization behavior of hydrophobic monomer in microemulsions was properly simulated by the model proposed.     

Reaction products of parabanic acid and alkylene carbonates as components of polyurethane foams

Esteramidoimidotetraols are obtained by reacting 8‐ and 12‐molar excess of ethylene carbonate or propylene carbonate with parabanic acid. The parabanic acid ring undergoes opening, and linear polymeric products are formed. The products can conveniently be used as polyols for polyurethane foams. The results of a study on thermal stability and on compressive strength of foams prepared from these tetraols, measured before and after thermal treatment, are reported. Copyright © 2007 Society of Chemical Industry     

原位生成纳米SiO_2及其作为填料对聚氨酯硬质泡沫塑料性能的影响

通过选择适当的乳化剂和水解温度以及控制水对于乳化剂的摩尔比,采用油包水微乳液法在聚醚多元醇中原位合成了纳米SiO2,然后该聚醚多元醇进一步与TDI反应制备出聚氨酯硬质泡沫塑料。TEM照片显示原位合成的SiO2微粒呈球状且分散,粒径分布在50nm-70nm。该聚氨酯硬质泡沫塑料的吸水率,随着SiO2填加量的增加,先升高随后又降低。因为原位生成纳米SiO2的加入,聚氨酯硬质泡沫塑料的拉伸强度得到显著提高,冲击强度缓慢增大,而对于压缩强度则先轻微降低,一直到SiO2的含量为0.9wt%时才开始急剧增大。     

A comparison between lipase-catalyzed esterification of oleic acid with glycerol in monolayer and microemulsion systems

Lipase-catalyzed synthesis-esterification of oleic acid with glycerol-was carried out in L2 microemulsions and in monolayers. The microemulsions were based on isooctane as a nonpolar component and various water-glycerol mixtures as polar component. The substrate, oleic acid/sodium oleate, constituted the microemulsion surfactant. The lipase resides mainly in the water pools. Monolayers of oleic acid/sodium oleate were formed on subsolutions of glycerol and water, and the enzyme solution was injected under the compressed monolayers. Thus, the arrangement of the reactants at the oil-water interface of the microemulsion can be regarded as analogous to that at the airwater interface of the monolayer. The microemulsion structure was characterized by self-diffusion nuclear magnetic resonance. It was found that the higher the glycerol-to-water ratio, the lower are the water D-values. The reactions in microemulsions generally gave a low degree of oleic acid conversion. The yield increased with increasing glycerolto-water ratio. Monoglycerides were the main product, and no triglyceride could be detected. The monolayer experiments gave a somewhat higher degree of conversion, with tri- and diglycerides being the major reaction products. The reason why triglycerides are formed in monolayer experiments but not in microemulsions is believed to be due to an unfavorable partitioning of the diglyceride in the microemulsion systems. Once formed, the diglyceride will partition into the hydrocarbon domain and become inaccessible for reaction with the enzyme-O-acyl intermediate at the oil-water interface. In addition, the interfaces in the two systems are different. The monolayer interface is static, whereas the microemulsion interface is highly dynamic, and this difference may also influence the product patterns.     

Cleaning properties of single-phase hydrocarbon-based microemulsion systems

Single-phase hydrocarbon-based microemulsions with low volatile organic carbon levels can help deliver solvent-like cleaning properties while allowing formulators to meet regulatory requirements. The rheology and petroleum jelly solubilization properties of model microemulsion systems that contained equal volumes of hydrocarbon solvent and water were evaluated as a function of microemulsion structure and composition. Single-phase microemulsions with low surfactant contents and broad formulation flexibility were obtained through the use of efficient anionic surfactants and low electrolyte levels. The microemulsion structure was advanced from solvent-continuous to water-continuous by varying the solvent alkane carbon number or the electrolyte content, whereas the liquid crystal content was controlled via cosurfactant concentration. Both microemulsion structure and viscosity influenced solubilization rates. Low-viscosity, solvent-continuous microemulsions showed solubilization rates comparable to those found with solvent-based systems, while water-continuous microemulsions showed relatively poor solubilization rates. Microemulsions containing dispersed liquid crystals exhibited high viscosity and low solubilization rates.     

微乳液聚合研究进展

概述了微乳液的性质,并对国内外正相微乳液聚合、反相微乳液聚合、双连续微乳液聚合的研究进行了简要综述。     

Ignition,combustion, toxicity,and fire retardancy of polyurethane foams: A comprehensive review

This review provides insight into the ignition, combustion, smoke, toxicity, and fire‐retardant performance of flexible and rigid polyurethane foams. This review also covers various additive and reactive fire‐retardant approaches adopted to render polyurethane foams fire‐retardant. Literature sources are mostly technical publications, patents, and books published since 1961. It has been found by different workers that polyurethane foams are easily ignitable and highly flammable, support combustion, and burn quite rapidly. They are therefore required to be fire‐retardant for different applications. Polyurethane foams during combustion produce a large quantity of vision‐obscuring smoke. The toxicity of the combustion products is much higher than that of many other manmade polymers because of the high concentrations of hydrogen cyanide and carbon monoxide. Polyurethane foams have been rendered fire‐retardant by the incorporation of phosphorus‐containing compounds, halogen‐containing compounds, nitrogen‐containing additives, silicone‐containing products, and miscellaneous organic and inorganic additives. Some heat‐resistant groups such as carbodiimide‐, isocyanurate‐, and nitrogen‐containing heterocycles formed with polyurethane foams also render urethane foams fire‐retardant. Fire‐retardant additives reduce the flammability, smoke level, and toxicity of polyurethane foams with some degradation in other characteristics. It can be concluded that despite many significant attempts, no commercial solution to the fire retardancy of polyurethane foams without some loss of physical and mechanical properties is available. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modeling of the Dynamics of Water and R-11 blown polyurethane foam formation

Polyurethane foam formation involves both polymerization and expansion processes. The dynamics of the water and R-11 blown foams depend on the rates of chemical and physical blowing processes, along with the rate of viscosity increase of the reacting mixture. Experiments were carried out to study the dynamics of free rising, water and R-11 blown rigid polyurethane foams. The density and temperature change during the foam formation were monitored. A theoretical model was developed to predict the density and temperature variation with time. In the model, the physical blowing agent (R-11) evaporation process is assumed to be heat generation–controlled and the carbon dioxide generation process to be controlled by the rate of the water-isocyanate reaction. The kinetic parameters of the reactions of isocyanate with polyol and water were obtained separately and were asssumed to be independent of each other. The water-isocyanate reaction appears to follow first-order kinetics with respect to concentration of water. The theoretical predictions of the model show good agreement with the experimental data for density variation with time. The model predictions for temperature rise also match experimental data, except at the later stages of foaming when it is found to be slower than the experimental measurements. However, this deviation does not affect the dynamics of density change since it occurs after the completion of the expansion process.     

Nonionic Mixed Surfactant Stabilized Water-in-Oil Microemulsions for Active Ingredient In Vitro Sustained Release

Olive oil is an excellent dispersing medium for water‐in‐oil microemulsions as it helps hydrate the skin and enhances the release of the active ingredients. In this study, mixed surfactants containing Span^® 80 with varied Tween^® series at 1:1 ratio were prepared with olive oil and water to produce water‐in‐oil microemulsions. The microemulsions were used to study the in vitro release of the active ingredients with different water solubilities. A microemulsion olive oil/water/mixed surfactant (56:4:40 by weight) was selected from the constructed phase diagram for further physical characterization. The analysis showed that the microemulsion composed of Span^® 80 and Tween^® 80 (ST80) was the most suitable surfactant combination. Equal amounts of ascorbic acid, caffeine and lidocaine were solubilized in ST80 microemulsions to study their release rate. Physical evaluation of ST80 microemulsions incorporating the active ingredients showed no apparent change compared to the ST80 microemulsion alone. The in vitro release study showed that the rate of active ingredients released from the microemulsion into the receptor chamber depends on their hydrophobicity, whereby lidocaine and caffeine were fivefold and twice as fast, respectively, with respect to ascorbic acid. ST80 microemulsions show constant rate of active ingredient release, demonstrating the sustained release properties of the system.     

Silicon Oxycarbide Ceramic Foams from a Preceramic Polymer

Open-cell ceramic foams were obtained from the pyrolysis, at 1000° to 1200°C under nitrogen, of a preceramic polymer (a silicone resin) and blown polyurethanes. The morphology of the expanded polyurethane was reproduced in the final architecture of the ceramic foam. The foams produced in this way consisted of an amorphous silicon oxycarbide ceramic (SiOC), having a bulk density ranging from 0.1 to 0.4 g/cm³ and variable cell size (300 to 600 µm). Young's modulus ranged from 20 to 170 MPa, and the compression strength from 1 to 5 MPa. The foams displayed excellent dimensional stability up to their pyrolysis temperature.     

Intrinsic flame resistance of polyurethane flexible foams: Unexpectedly low flammability without any flame retardant

Virgin polyurethane flexible foams are widely assumed to be highly flammable materials. The flammability of three model polyurethane flexible foams suggests that this may not be universally true. Two of them show unexpectedly low flammability in the limiting oxygen index test and pass flammability tests such as FMVSS 302 and FAR 25.853. Cone calorimetric measurements at 25 kW/m² and 50 kW/m² furthermore show a high resistance against ignition and demonstrate the self‐extinguishing properties of these two virgin, flame‐retardant‐free, polyurethane flexible foams.     

原位生成纳米SiO2及其作为填料对聚氨酯硬质泡沫塑料性能的影响

通过选择适当的乳化剂和水解温度以及控制水对于乳化剂的摩尔比,采用油包水微乳液法在聚醚多元醇中原位合成了纳米SiO2,该聚醚多元醇进一步与TDI反应制备出聚氨酯硬质泡沫塑料.TEM显示原位合成的SiO2微粒呈球状且分散,粒径为50～70nm.随着SiO2填加量的增加,该聚氨酯硬质泡沫塑料的吸水率先升后降.因为原位生成纳米SiO2的加入,聚氨酯硬质泡沫塑料的拉伸强度得到显著提高,冲击强度缓慢增大,而压缩强度则先轻微降低,一直到SiO2的含量为0.9wt%时才开始急剧增大.     

Microemulsion Liquid Membranes. I. Application to Acetic Acid Removal from Water

Abstract

A separation technique utilizing nonionic microemulsions as emulsion liquid membranes has been successfully applied to the removal of acetic acid from an aqueous feed phase. The surfactant systems were carefully characterized in order to assure that they were truly microemulsions. The effects of mixing intensity, feed concentration, treat ratio, and microemulsion viscosity on the separation kinetics were investigated. The microemulsions did not typically display leakage and had negligible swell over 5-minute duration. The reversible phase behavior of the microemulsion was utilized to demulsify the liquid membrane phase and recover the acetate ion via a temperature change of approximately 40°C. Material balances closed to within 10% and rates of separation were faster than the sampling rates when the microemulsion was fully dispersed in the aqueous feed phase.     

Thermal conductivity and thermal expansion behavior of glass fiber-reinforced rigid polyurethane foam

The thermal conductivities and the thermal expansion curves of glass fiber-reinforced rigid polyurethane foams with various fiber lengths, various fiber volume fractions and various matrix densities were determined experimentally. Additionally the thermal expansion coefficients of these materials at room temperature were examined in terms of the interaction between fiber and matrix. The thermal expansion properties were analyzed successfully with the analogous treatment which is applied to the mechanical tensile behavior.     

微乳液聚合制备有机硅材料

介绍了3种有机硅微乳液：聚二甲基硅氧烷微乳液、乙烯基硅氧烷与其他单体的共聚微乳液,以及氨基改性有机硅微乳液,并介绍了有机硅微乳液的应用,微乳液聚合制备的有机硅材料具有许多优异的性能,如优异的渗透性和稳定性等。