Rectorite/thermoplastic polyurethane nanocomposites. II. Improvement of thermal and oil‐resistant properties

Organ‐rectorite/thermoplastic polyurethane (OREC/TPUR) nanocomposites were synthesized via melt intercalation. The dynamic mechanical properties by dynamic mechanical analysis (DMA), thermal and oil‐resistant properties were investigated. The results show that the storage modulus (E′), loss modulus (E″), and glass‐transition temperature (T_g) of the nanocomposites have an increase to some extent than those of pure TPUR. The thermal stability of nanocomposites was also studied in detail by thermal gravity analysis (TGA), which was higher than that of pristine TPUR matrix when the content of organic REC is at 2 wt %, and the decomposition temperature at 10% weight loss of OREC/TPUR is greatly increased up to 330°C from 315°C. Oil uptake of the composites is also significantly reduced in comparison with TPUR matrix, which is ascribed to the good barrier effect of nanosheets of OREC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1165–1169, 2005     

Rheology in the technology of ceramics and refractories. Part 6. Dilatant systems and factors determining their properties

The effects of various factors, including the characteristics of the solid phase, bulk concentration, stabilization, coagulation, temperature, and vibrations, on the dilatant properties of high-density ceramic binding suspensions are considered. The main factor controlling the dilatancy is the proximity of the actual bulk concentrationC _v to the critical valueC _{v cr}, corresponding to the concentration of shape formation (conversion of the suspension into a solid). Suspensions of quartz glass withC _{v cr}=0.91 possessed a Newtonian character of flow forC _v=0.75−0.78, while suspensions withC _{v cr}=0.70−0.75 exhibited a strong dilatancy even in the range ofC _v=0.60−0.64. The dilatancy of some highly disperse suspensions at much lower values ofC _v is caused by a high value of the effective bulk concentrationC _{v ef}, including a considerable volume of bound liquid. On the basis of results of original studies and generalization of published data, a mechanism is formulated according to which dilatancy is treated as due to the effect of constrained volume in disperse systems. Most suspensions are characterized by a bulk dilatancy according to Reynolds. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 4, pp. 2–14, April, 1997. For the previous articles of this series see Refractories and Industrial Ceremics No. 3 (1994), No. 12 (1995), Nos. 1 and 10 (1996), and No. 2 (1997).     

Extrema of isochoric heat capacity of water and carbon dioxide

The experimental and predicted loci extrema behavior of the isochoric heat capacity C_v was examined for water and carbon dioxide along the subcritical and supercritical isotherms and along the liquid and vapor isochores. The studies were based on a nonanalytical Helmholtz energy-volume-temperature equation (AVT, fundamental equation of state), the IAPWS-95 formulation for water, and scaling-type crossover equations of state (CREOS). The measured isochoric heat capacity data for these fluids near the critical point were analyzed to study the behavior of loci of C_v maxima and to compare these with predictions by the equations of state. A CREOS was applied to study the behavior of the isochoric heat capacity maxima in the immediate vicinity of the critical point. Good agreement with the CREOS prediction and experimental isothermal C_v maxima loci was observed near the critical point. The basic characteristic points on the C_v extrema loci curves in the P-T and 𝜌-T planes were determined on the basis of detailed analysis of the experimental and prediction of C_v extrema loci behavior. Qualitative explanations are given for the nature of isochoric and isothermal C_v maxima-minima curves. The role of C_v extrema loci behavior in developing high-accuracy equations of state in the supercritical region and in the study of supercritical phase-transition phenomena are discussed.     

Role of Different Parameters in the Optimization of Hydrodynamic Cavitation

Low pressure setups (up to 150 psi) for creating hydrodynamic cavitation are investigated in this study. The decomposition of chloroform in water is used as a model reaction. The effects of upstream pressure, fluid velocity, Cavitation number, C_v, and β₀ on the conversion are compared with regard to the effectiveness (conversion per pass) with changing flow conditions and scale‐up terms within three different setups. The values of C_v and β₀ are seen to be significant parameters in optimizing the hydrodynamic cavitation. Moreover, the optimal values of these parameters shift to smaller values with increasing pipe diameter. The influence of a new orifice plate specific parameter, δ, on the collapse conditions, is also described.     

Microgelation of unsaturated polyester resins in the presence of poly(vinyl acetate) by static and dynamic light scattering

The partially cured unsaturated polyester (UPE)/styrene resins with various degrees of conversion lower than gel conversion blended with PVAc and 2‐fluorotoluene solvent were investigated using both static and dynamic light scattering (SLS and DLS). The solvent (i.e., 2‐fluorotoluene) is isorefractive with PVAc; thus, one sees only primary and partially cured UPEs in light‐scattering experiments. DLS was used to follow the variations of primary UPE and UPE microgel particle sizes, and SLS was used to follow the variations of UPE molecular weight, second virial coefficient (A₂), anisosymmetry (ρ_v), and differential index refraction (dn/dC) with degree of UPE conversion and PVAc concentration. The experimental data showed that, at a fixed degree of UPE/styrene conversion, increasing PVAc concentration in the UPE/styrene system caused decreases in dn/dC, A₂, ρ_v, and particle sizes of UPE microgels. These results suggest that mixing PVAc into UPE/styrene resins causes an increase in the compactness of UPE coils and favors intramolecular UPE/styrene cyclization in the early stage of curing. Thus A₂, ρ_v, and particle sizes of microgels decreased with increasing PVAc concentration. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1439–1449, 2001     

Thermophysical properties of laboratory-prepared corn/wheat dried distillers grains and dried distillers solubles dehydrated with superheated steam and hot air

The objective of this study was to dry–wet distillers grains and centrifuged solubles and to examine the effect of two different drying media, superheated steam and hot air, at different drying temperatures (110, 130, and 160°C), moisture contents (5–30% wb), and percentages of solubles’ presence (0 or 100%) on some thermophysical properties of laboratory-prepared corn/wheat dried distillers co-products, including geometric mean diameter (d_g), particle density (ρ_p), bulk density (ρ_b), bulk porosity (?_b), specific heat (C), effective thermal diffusivity (α_eff), and bulk thermal conductivity (λ_b). The values of d_g of corn/wheat dried distillers co-products ranged from 0.358 ± 0.001 to 0.449 ± 0.001 mm. Experimental values of ρ_p, ρ_b, and ?_b varied from 1171 ± 6 to 1269 ± 3 kg m^?3, from 359 ± 7 to 605 ± 5 kg m^?3, and from 0.54 ± 0.01 to 0.71 ± 0.01 kg m^?3, respectively. The values of α_eff were between 0.58 × 10^?7 and 0.93 × 10^?7 m² s^?1. The calculated values of C ranged from 1887 ± 11 to 2599 ± 19 J kg^?1 K^?1, and the values of λ_b of corn/wheat dried distillers co-products ranged from 0.06 ± 0.01 to 0.09 ± 0.01 W m^?1 K^?1. Multiple linear regression prediction models were developed to predict the changes in d_g, ρ_p, ρ_b, ?_b, C, α_eff, and λ_b of laboratory-prepared corn/wheat dried distillers co-products with different operational factors.     

Permanent antistatic polypropylene based on polyethylene wax/polypropylene wax grafting sodium acrylate

Two types of permanent antistatic agents, polyethylene wax grafted with sodium acrylate (PEW‐g‐AAS) and polypropylene (PP) wax grafted with sodium acrylate (PPW‐g‐AAS), were prepared using a solution grafting method and applied to PP for enhancing antistatic properties. The grafting degree was determined using back titration method and structures were confirmed by Fourier transform infrared spectroscopy. The antistatic properties of PEW‐g‐AAS/PP blends and PPW‐g‐AAS/PP blends were characterized by surface resistivities (ρ_s) and volume resistivities (ρ_v), and a combination of contact angle measurements, scanning electron microscope, permittivity, and dielectric loss were used to investigate the surface and inner structures of the blends. Results showed ρ_s and ρ_v of PEW‐g‐AAS/PP blends dropped significantly (4–7 magnitudes) above a critical addition at 10%, where a electrostatic dissipative network formed; PPW‐g‐AAS revealed an inferior antistatic performance than PEW‐g‐AAS due to its better compatibility and smaller dispersed phase in the matrix. Further, the antistatic blends treated in 80°C water, 80°C air, and room temperature were investigated, and the results were interpreted from surface energy. Moreover, the addition of antistatic agent had little impact on tensile strength of the PP matrix. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Separation of the protease enzymes of Bacillus licheniformis from the fermentation medium by crossflow ultrafiltration

The separation from fermentation medium of extracellular serine alkaline protease (SAP) enzyme produced by Bacillus licheniformis was investigated using a crossflow ultrafiltration system. SAP was separated from the high molecular weight neutral protease (NP) and amylase (AMY) enzymes and from the low molecular weight organic acids and amino acids in a crossflow ultrafiltration system with 30 000 Da and 10 000 Da MWCO polysulfone membranes, respectively. The effects of transmembrane pressure (TMP), recirculation velocity (v), and initial enzyme concentration (C_E) on the permeate flux, on the activities of SAP, NP and AMY enzymes, and on the recovery of SAP were investigated. High permeate flux was obtained at high recirculation velocity and TMP, but at low initial enzyme concentration. SAP enzyme recovery and activity measured in the system also showed alterations with hydrodynamic conditions. The best operation conditions for the separation of SAP from NP and AMY were TMP = 20 kPa, v = 0.50 ms⁻¹ and C_E = 0.28 gdm⁻³. The separation of SAP from the organic and amino acids was best performed at TMP = 100 kPa, v = 0.33 ms⁻¹ and C_E = 0.40 gdm⁻³. © 2000 Society of Chemical Industry     

Impact behavior of a short glass fiber reinforced thermoplastic polyurethane

The temperature dependence of critical strain energy release rate (G_c′) and standardized Charpy notched impact strength (CNIS) were measured for a thermoplastic polyurethane (TPUR) reinforced with 30 wt% of short glass fibers (SGF) over a temperature interval ranging from −150°C 23°C (RT) at two strain rates, 70 and 150 s⁻¹, respectively. Fractographic observation of fracture planes was used to qualitatively assess the fracture modes and mechanisms. Adhesion between the reinforcement and the matrix was excellent and the integrity of the fiber‐matrix interfacial contact was relatively insensitive to exposure to hydrolysis during the immersion in boiling water for 100 hours. At temperatures above −30°C, there was a large extent of plastic deformation in the vicinity of crack planes while at temperatures below −50°C, the extent of plastic deformation was substantially reduced. This resulted in a change in the major energy dissipation mechanism and led to a decrease of both CNIS and G_c′ values for SGF/TPUR composites. It was suggested that the plastic deformation of TPUR matrix in the immediate vicinity of glass fibers was the primary source of energy dissipation at temperatures above −30°C, while the friction and fiber pull‐out was the main dissipative process below −50°C. Over the whole temperature interval investigated, greater G_c′ values were obtained at higher strain rate of 150 s⁻¹, without any significant change in the fractographic patterns observed on the fracture planes. The CNIS/G_c′ ratio, used to assess suitability of CNIS for comparison of materials, changed with temperature substantially suggesting that the functional dependences of CNIS and G_c′ on temperature differ substantially. Hence, CNIS data do not provide a reliable base for material selection and for design purposes in this case.     

Characterisation of cellulose treated by the steam explosion method. Part 2: Effect of treatment conditions on changes in morphology,degree of polymerisation,solubility in aqueous sodium hydroxide and supermolecular structure of soft wood pulp during steam explosion

An attempt was made to clarify the effect of steam explosion conditions on the changes in morphology, degree of polymerisation P_v, solubility towards aqueous alkali solution S_a, and supermolecular structure of a soft wood pulp and to elucidate the mechanism by which the steam explosion treatment makes natural cellulose completely soluble in aqueous alkali solution. For this purpose, scanning electron microscopic (SEM) observation and X-ray diffraction, solid-state cross-polarisation/magic-angle sample-spinning (CP/MAS) ¹³C nuclear magnetic resonance (NMR), S_a and P_v measurements were carried out on a series of soft wood pulps treated systematically by the steam explosion method. It was found that (1) the maximum S_a (c. 100%) was obtained when the soft wood pulp was treated under the conditions of steam pressure P = 2.9MPa and treatment time t = 30s, (2) the decrease in P_v of the pulp by the steam explosion resembled conventional acid hydrolysis of cellulose, (3) a higher water content in the sample to be treated gave a lower degree of decrease in P_v, (4) the repeated steam explosion method gave more fibrillated sample with higher S_a than the corresponding batch steam explosion, (5) the amorphous content of the samples as estimated by X-ray analysis decreased by the steam explosion, in spite of an increase in S_a, and (6) the structural parameters expressing the degree of breakdown in the intramolecular hydrogen bonds at the C₃ and C₆ positions, X_am(C₃) and X_am(C₆), of the samples as estimated by CP/MAS ¹³C NMR changed as functions of P and t, being almost parallel to S_a. This suggests that these parameters may be more closely correlated with S_a than with X_am(X) from X-ray analysis.     

Molar volumes of cadmium halides in aqueous dioxane

The apparent molar volume, φ_v, of cadmium chloride, cadmium bromide and cadmium iodide in aqueous dioxane (10%, 20%, 30%) at different temperatures and concentrations are estimated from the densities of the solutions measured by a hydrostatic balance. The φ_v values vary linearly with square root of concentrations. Deviations in the slopes of φ_v versus √C are observed at higher concentrations of the salt and φ_vo, limiting apparent molar volume, have been interpreted in terms of solute-solvent interactions. The φ_vo values varies with temperature and can be represented in the power series of temperature. Structure making/breaking capacity of the electrolyte is inferred from the sign of ?²φ_v/?t² values.     

Effect of interchain interactions on the translocation of polymer chains through small holes

The translocation of polymer chains through a small hole was simulated with the dynamic Monte Carlo method. The dependence of the relaxation time (τ₁) and escaping time (τ₂) on the chain concentration (C) was studied. The interchain interaction played an important role in the translocation process. Different behaviors were discovered at low and high C regions. τ₁ presented a power law behavior with C at low and high C values with exponents of ?1 and ?3, respectively. τ₂ was roughly independent of C at low C values but decreased with power law exponent ?1.3 at high C values. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1200–1205, 2007     

Zum Protonenaustausch im NH3 · HCl-Gasphasen-Komplex

Proton Exchange in the NH₃ · HCl Gas Phase Complex The cyclic proton exchange in NH₃ · HCl is studied by quantum chemical ab initio calculations in order to characterize the chemical flexibility of the NH₃ · HCl gas phase system, and to present a model for studying electrophilic substitution reactions. In contrast to the hydrogen bonded molecular complex, the cyclic structure II (C_2v) is found to be highly ionic. It represents the transition structure of the proton exchange within the isolated complex. The potential barrier (ΔE_pot = E_II – E_I) of the reaction can only sufficiently be described when including correlation energy. The C_3v cage III is also ionic and similar in energy in comparison with the transition structure II .     

A Method for Determining Bulk Density,Material Density,and Porosity of Melter Feed During Nuclear Waste Vitrification

Glassmelting efficiency largely depends on heat transfer to reacting glass batch (melter feed), which in turn is influenced by the bulk density (ρ_b) and porosity (?) of the reacting feed as functions of temperature (T). Neither ρ_b(T) nor ?(T) functions are readily accessible from direct measurements. For the determination of ρ_b, we monitored the profile area of heated feed pellets and calculated the pellet volume using numerical integration. For the determination of ?, we measured the material density of feeds quenched at various stages of conversion via pycnometry and then computed the feed density at heat‐treatment temperature using thermal expansion values of basic feed constituents.     

Modelling the temperature dependence of kinematic viscosity for refined canola oil

Viscosities of refined, bleached, deodorized (RBD) and refined, bleached, winterized (RBW) canola oils were measured at temperatures from 4 to 100°C. The viscosities of these refined canola oils were exponentially related to the oil temperature. Viscosity of the RBW oil was slightly greater than that of the RBD oil when the temperature was below 15°C. Compared to refined soybean oil, the canola oils were substantially more viscous. The viscosity of canola oil was modelled asv = exp(C₀ + C₁T + C₂T²). The maximum predicted error was less than 1.6% over the tested temperature range.     

Parametric studies of carbon dioxide absorption into highly concentrated monoethanolamine solutions

Carbon dioxide (CO₂) absorption into highly concentrated solutions of monoethanolamine (MEA) was studied. The effect of operating parameters on the overall mass transfer coefficient (K_Ga_v) was determined in a pilot‐plant scale absorption unit. The (K_Ga_v) increased at low solution concentrations, decreased at intermediate concentrations, and increased as the concentration became high (54 wt%). The (K_Ga_v) increased with an increasing liquid flow rate, decreased with an increase in either the CO₂ loading or the CO₂ partial pressure, and was not affected by the inert gas flow rate. Finally, structured 4A Gempak packing produced (K_Ga_v) values twice as high as randomly packed IMTP#15 or 16‐mm Pall Ring systems.     

Dispersed phase characteristics in three phase (liquid-liquid-solid) fluidized beds

Two ideal droplet length (l,) distributions have been derived for two different droplet shapes. The dispersed phase holdup (?_d) increases with increasing dispersed phase velocity (U_d), but decreases with increasing continuous phase velocity, (U_c) in three-phase fluidized beds. In the droplet-coalescing flow regime, l_v and the droplet rising velocity (v_d) increase, but the spherical droplet fraction (k) decreases with increasing U_d and u_c. In the droplet-disintegrating flow regime, the effects of u_d and U_c on l_v and k are insignificant, but v_d increases with increasing U_c. Maximum values of l_v, occur in the bed containing 1.7 mm diameter particles and l_v has an uniform length of around 2.0 mm in beds with particle size larger than 3.0 mm.     

Elutriation characteristics of solids from liquid–solid fluidized bed systems Part III: A study of the possible causes of non-linearity in the elutriation of fine particles from fluidized beds

The “critical concentration” of solids, defined by Trawinski as the break-point from linearity in the plot of log (C/C_o) versus θ in any elutriation process, represents the attainment of a sudden increase in bed viscosity which finally leads to a retentive capacity of the bed with respect to the fines, characterized by the “equilibrium bed concentration”, C_E. Experimental data on C_c have been correlated empirically with various system parameters as The ranges of the parameters are 1.1 ≤ G/G_me ≤ 1.4; 1.28 ≤ d₁/d₂ ≤ 2.85; 1.0 ≤ ρ₁/ρ₂ ≤ 2.6; 0.50 ≤ w/W ≤ 0.90; and 2.7 ≤ H_a/H_s ≤ 17.7.     

Elastic constants and thermal expansivity of gel-spun polyethylene fiber and its composites

The five independent stiffness constants, C₁₁, C₃₃, C₄₄, C₆₆, and C₁₃, and the axial and transverse thermal expansivity of unidirectional gel-spun polyethylene fiber reinforced composites have been measured as functions of fiber volume fraction V_f. The axial extensional modulus C₃₃ and axial Poisson's ratio v₁₃ follow the rule of mixtures, while the axial shear modulus C₄₄, transverse shear modulus C₆₆, and transverse plane-strain bulk modulus C_t ( = C₁₁ − C₆₆) obey the Halpin-Tsai equation. Extrapolation to V_f = 1 gives the five stiffness constants of gel-spun polyethylene fiber. The tensile property of the fiber is highly anisotropic, with the axial Young's modulus about 40 times higher than the transverse Young's modulus. In contrast, the axial shear modulus exceeds the transverse shear modulus by only 5%. A similar treatment of the thermal expansivity data in terms of the Schapery equations gives an axial thermal expansivity of −1.25 × 10⁻⁵ K⁻¹ and a transverse thermal expansivity of 11.7 × 10⁻⁵ K⁻¹ for the fiber.     

Influence of Electrostatic Interactions on Complexes with Short O···O Hydrogen Bonds in Basic Salts of Pyridine Betaines and Acid Salts of ω-Phenyloalkanocarboxylic Acids

The isostructural complexes [C₅H₅N⁺(CH₂)_nCOO]₂HX and [C₆H₅(CH₂)_nCOO]₂HK (n = 1–4), which differ in their counterions and charge on the ring, were synthesized, and their powder FT-IR spectra analyzed. All complexes containing a charged pyridine ring are of Hadži type iii, characterized by an intense broad (continuum) absorption below 1600 cm⁻¹ typical of a short-strong hydrogen bond (SSHB) with a delocalized proton and a single vC=O band. The positively charged nitrogen atoms interact electrostatically with the X⁻ ion and, additionally, with one of the oxygen atoms of the carboxylic group, producing a more or less symmetric environment of the H-bonded proton, and stabilizing the SSHB. The broad absorption of [C₆H₅CH₂COO]₂HK is very similar to that of other pyridine complexes. Upon addition of methylene groups the broad absorption moves to higher wavenumbers, the O···O distance is elongated, and the H-bonded proton becomes more localized. In the spectrum of [C₆H₅(CH₂)₄COO]₂HK the vC=O and v_asCOO bands were found at 1704 and 1641 cm⁻¹, respectively, which shows that the H-bonded proton is asymmetrically located. The observed variation of absorption with the number of CH₂ groups reflects changes of contacts between the K⁺ ion and COO⁻ groups.