Simultaneous SAXS/WAXS experiments on shear induced iPP crystallization near nominal melting temperature

Simultaneous small- and wide-angle synchrotron radiation X-ray scattering was performed to monitor the evolution of crystalline structure within the iPP melt during and after applying pulse shear. The iPP melt was subjected to a strong pulse shear of 240 s^?1 for 6 s at temperatures between 150 and 170 °C below and above the nominal melting temperature T_m. It was found that the imposed shear affected the melt only at lowest temperature. Structures generated during flow above 150 °C were too dilute to be detected. To extract the hidden structure, the melt was cooled to crystallization temperature of 150 °C either immediately after shearing or after annealing at shear temperature for up to 30 min. This treatment manifested with an anisotropic structure in a few minutes after quenching, undetectable when both shear and annealing temperatures presented the same value. The data obtained revealed also close correlations between annealing time, shear temperature and incubation time.     

Sonocrystallization of Interesterified Soybean Oil With and Without Agitation

Interesterified soybean oil was crystallized at 29, 34, and 35 °C with and without the use of high‐intensity ultrasound. Samples were crystallized using either (1) continued agitation for the entire crystallization process (CA) or (2) agitation for 10 min (A10) followed by static crystallization. Sonication and agitation decreased the induction period of nucleation at higher temperatures and changed the crystal morphology, crystallization kinetics, and viscoelasticity of the sample. Sonication reduced the crystal sizes and significantly (P <0.05) increased the viscosity (5.2 ± 1.2 to 2369.6 ± 712.1 Pa s) and elastic modulus (83.2 ± 4.1 to 69,236.7 ± 26,765 Pa) of the crystalline networks obtained at 29 °C under A10 condition. An increase in viscosity and elasticity was also observed for sonicated samples crystallized at 34 and 35 °C under A10 and all CA conditions but these differences were not statistically significant (P >0.05). Sonication increased crystallization rates for all conditions tested. Kinetic constants obtained from an Avrami fit increased from1.3 × 10^?5 to 6.8 × 10^?5 min^?n for samples crystallized at 29 °C A10 without and with sonication, respectively, and from 2.6 × 10^?9 to 2.4 × 10^?7 min^?n for samples crystallized at 34 °C A10 without and with sonication, respectively. This increase in the crystallization rate was also observed for samples crystallized under the CA condition at 29 °C.     

Shear yield and crazing stresses in selected glassy polymers

The plane strain shear yield stress and the triaxial crazing stress were determined for several commercial glassy polymers as a function of temperature. The polymers considered were: polycarbonate (Lexan^®), polysulfone (Udel^®), polyetherimide (Ultem^®), polyarylate (Arylon^®), and an amorphous nylon (Zytel^® 330). When normalized to T_g the data for the various polymers were similar but not identical. An exception may be the triaxial crazing strains. In the temperature region between [T–T_g] = ?300° and ?50°C the crazing strains were all small (<1.5%), showed little temperature dependence, and appeared identical within the precision of our measurements. For temperatures below T_g and above any major secondary relaxation, Poisson's ratio was found to be constant for all of the polymers examined, 0.42 (±5%). © 1993 John Wiley & Sons, Inc.     

Parametric analysis of sonication and centrifugation variables for dispersion of single walled carbon nanotubes in aqueous solutions of sodium dodecylbenzene sulfonate

Dispersion of single-walled carbon nanotubes with the aid of surfactants has become a common procedure for generating aqueous solutions containing a high fraction of individualized nanotubes, though methodologies vary greatly among the literature. A parametric study was performed in order to analyse the effect of ultracentrifugation temperature, duration and applied force on dispersions of arc-discharge nanotubes in sodium dodecylbenzene sulfonate. The amount of metallic impurities remaining after varying levels of centrifugation was investigated by electron microscopy and X-ray spectroscopy. The effect of intensity and duration of exposure to ultrasound was also examined. Solutions were characterized with UV–vis–NIR absorbance spectroscopy, Raman spectroscopy and atomic force microscopy in order to find optimal ranges of these parameters for this particular system. In general, optimal conditions were accomplished via tip sonication at a power below 0.6 W mL⁻¹ to deliver around 450 J mL⁻¹ to the solution, followed by centrifugation at ∼120 × 10³g for 1–2 h. The scission of nanotubes was found to follow a power law such that the average length of the ensemble decreased proportional to t^−0.38 under continuous tip sonication, while the relationship between mean nanotube length and the Raman D:G ratio was approximately linear for both 1.58 and 2.33 eV excitation.     

Effect of sonication assisted by titanium dioxide and ferrous ions on polyaromatic hydrocarbons (PAHs) and toxicity removals from a petrochemical industry wastewater in Turkey

BACKGROUND: In Izmir (Turkey) polyaromatic hydracarbon (PAH) removal efficiencies are low in petrochemical industry aerobic biological wastewater treatment plants because bacteria are not able to overcome the inhibition of these toxic and refractory organics. In order to increase PAHs removal, sonication process was chosen among other advanced treatment processes include sonication processes. The effects of ambient conditions, increasing sonication time, sonication temperature, TiO₂ and Fe⁺² concentrations on sonication at a petrochemical industry wastewater treatment plant in Izmir (Turkey) was investigated in a 650 W sonicator, at a frequency of 35 kHz and a 500 mL glass reactor. RESULTS: Increasing the temperature improved PAH removal after 150 min sonication at 30 °C and 60 °C. The maximum total PAH removal efficiencies were the same in a reactor containing 20 mg L^?1 TiO₂ and in a TiO₂‐free reactor at 30 °C and 60 °C after 150 min sonication. Maximum 91% and 97% total PAH removals were obtained in a control reactor and a reactor containing 20 mg L^?1 Fe⁺² at 30 °C and 60 °C, respectively, after 150 min sonication. The PAH concentration was toxic to Daphnia magna, so that the EC₅₀ value decreased significantly from 342.56 ng mL^?1 to EC₅₀ = 9.88 ng mL^?1 and to EC₅₀ = 3.35 ng mL^?1, at the lowest TiO₂ (0.1 mg L^?1) and Fe⁺² (2 mg L^?1) concentrations, respectively, after 150 min sonication at 30 °C. CONCLUSION: PAHs and the acute toxicity in a petrochemical industry wastewater were removed efficiently through sonication. Copyright © 2010 Society of Chemical Industry     

A parametric study of a platinum ruthenium anode in a direct borohydride fuel cell

Data on the performance of a direct borohydride fuel cell (DBFC) equipped with an anion exchange membrane, a Pt–Ru/C anode and a Pt/C cathode are reported. The effect of oxidant (air or oxygen), borohydride and electrolyte concentrations, temperature and anode solution flow rate is described. The DBFC gives power densities of 200 and 145 mW cm⁻² using ambient oxygen and air cathodes respectively at medium temperatures (60 °C). The performance of the DBFC is very good at low temperatures (ca. 30 °C) using modest catalyst loadings of 1 mg cm⁻² for anode and cathode. Preliminary data indicate that the cell will be stable over significant operating times.     

Thermal decomposition and pore structure of pure and doped stannic oxide gel

The surface properties of a stannic oxide gel and its thermal dehydration products obtained both in vacuo and in the presence of air in the temperature range 100–600°C have been examined by N₂ adsorption. Phase and structural changes have been followed by differential thermal analysis and X-ray diffractometry. Complete pore structure analysis showed that samples dehydrated at or below 250°C were microporous. Above 250°C the pores were found to widen with increase of temperature, the widening occurring concurrently with the crystallisation process. Doping with cations of lower valency (Li⁺ and Al³⁺) than the host cation (Sn⁴⁺) had little effect on the pore structure and specific surface area for the low temperature samples (≥250°), whereas at higher temperatures, e.g. 600°C, it increased the specific area remarkably. The dope ions produce oxygen vacancies and hinder or retard sintering in SnO₂.     

THE RELATIVE MAGNITUDE OF RADIATION AND CONVECTION HEATING IN A MUFFLE KILN1

Rates of Heating by Convection and by Radiation in a Muffle Kiln, 38°×18°× 36° high, were each determined for temperatures from 350° to 800°C from measurements with a steady flow water calorimeter whose surface was first gold plated and then covered with a mixture of platinum black and lamp black. Taking the reflecting powers as 91 and 4 per cent, respectively, for the two surfaces, the radiation heating increases approximately according to the Stefan-Boltzmann fourth power law, while the convection heating comes out proportional to the temperature difference between calorimeter and muffle; that is, C=γ(T-t) where γ= 2.34×10⁻⁴ gm. cal./cm.² sec. The ratio of convection to radiation decreases from about .40 at 350° to .10 at 800°C, so that for the higher temperatures the convection heating may be neglected in rough computations of the rate of heating in such a kiln.     

Catalytic dry oxidation of aniline,benzene, and pyridine adsorbed on a CuO doped activated carbon

Adsorption of aniline, benzene and pyridine from water on a copper oxide doped activated carbon (CuO/AC) at 30 °C and oxidation behavior of the adsorbed pollutants over CuO/AC in a temperature range up to 500 °C are investigated in TG and tubular-reactor/MS systems. Results show that the AC has little activity towards oxidation of the pollutants and CuO is the active oxidation site. Oxidation of aniline occurs at 231–349 °C and yields mainly CO₂, H₂O and N₂. Oxidation of pyridine occurs at a narrower temperature range, 255–309 °C, after a significant amount of desorption starting at 150 °C. Benzene desorbs at temperatures as low as 105 °C and shows no sign of oxidation. The result suggests that adsorption-catalytic dry oxidation is suitable only for the strongly adsorbed pollutants. Oxidation temperatures of CuO/AC for organic pollutants are higher than 200 °C and pollutants desorbing easily at temperatures below 200 °C cannot be treated by the method. This work was presented at the 7 ^th China-Korea Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

Studies on moisture sorption in coir fibers (cocos nucifera L)

Moisture desorption characteristics in coir fibers have been studied at several temperatures (53°C, 68°C, 86°C, and 105°C) as a function of time. Moisture absorption at room temperature after heating to 53°C, 68°C, 86°C, and 105°C are also reported. The results indicate that the relation between percentage moisture loss (A) (moisture loss is the ratio of the difference between initial moisture and final moisture to initial moisture) and temperature (T°K) is of the type A = A_oe^?B/T in the range of intervals studied. The constants A_o and B are dependent on time, and they decrease with time. The fraction moisture loss/gain (w) is related to time (t) by the equation w = m/t + b₀ at all temperatures investigated. The constant m decreases with temperature while b₀ increases with temperature. The equilibrium moisture content (the condition reached by the sample when it no longer takes up moisture from or gives up moisture to the surrounding atmosphere) increases with increase in relative pressure and decrease in temperatures. As the moisture content in the fiber increases, the tensile strength (tenacity) decreases and the % elongation increases. The observed results are explained on the basis of structural rearrangement on heating/cooling of lignocellulosic material.     

Postfiring stress‐strain hysteresis of concrete subjected to various heating and cooling regimes

This paper reports an experimental investigation involving 90 siliceous aggregate concrete cores (75 mm dia. 175 mm long), which were subjected to 18 different heating and cooling regimes in the temperature range (217°C–470°C). The cores were heated to the point when the centre of the core reached the same temperature as the outer surface, the point of uniformity. Subsequently, the cores were either taken out of the furnace to cool or soaked at the test temperature for 2 h. Cooling was either by spraying the heated core with water for 5 min or by air‐cooling in a controlled environment of 20°C and 65% RH. The extent of damage and internal fracture were assessed using the stiffness damage test (SDT) and the ultrasonic pulse velocity (UPV) as well as petrography methods. Both prolonged duration of thermal exposure and rapid cooling by water quenching resulted in a further loss of stiffness of fire damaged concrete cores. Extending the duration of thermal exposure by 2 h from the point of uniformity resulted in an approximately 10% further reduction in the residual chord modulus (E_c). However, spraying hot concrete with water after reaching the point of uniformity caused more reduction in stiffness than a 2 h extended duration of thermal exposure to temperatures below 320°C. The damage index (DI), which represents the dissipated strain energy in a hysteresis loop, showed a similar effect. The damage index of cores subjected to water quenching was significantly higher than the damage index of cores soaked at temperatures below 320°C. The residual plastic strain (PS), which is measured at the end of a hysteresis loop, showed very similar variation to that of the damage index. The ultrasonic pulse velocity (UPV) test method confirmed that spraying hot concrete with water from the point of uniformity was more damaging than a 2 h extended duration of thermal exposure to temperatures below 320°C. The extended duration of thermal exposure did not seem to affect the degree of non‐linearity of the stress‐strain response of fire affected concrete while water quenching resulted in a more concave response. The results are explained by identifying the various damage mechanisms associated with the various heating and cooling regimes. Copyright © 2002 John Wiley & Sons, Ltd.     

Production and Characteristics of an Enantioselective Lipase from Burkholderia sp. GXU56

The lipase production of Burkholderia sp. GXU56 was influenced by carbon and nitrogen sources, inorganic salts, initial pH of the medium and cultivation temperature. The maximum lipase production was 580.52 U/mL and reached 5 times the level of the basic medium in the optimum medium at pH 8.0, 32 °C, 200 rpm and 40–48 h. The lipase was purified 53.6 fold to homogeneity and the molecular weight was 35 KDa on SDS‐PAGE. The optimum pH and temperature of the lipase were 8.0 and 40 °C, respectively, and it was stable in the range of pH 7–8.5 and at temperatures below 45 °C. The lipase activity was strongly inhibited by Zn²⁺, Cu²⁺, Co²⁺, Fe²⁺, Fe³⁺ ions and SDS, while it was stimulated by Li⁺ and Ca²⁺ ions and in presence of 0.1 % CTAB, 0.1 % Triton X‐100 and 10 % DMSO. K_m and V_max of the lipase were calculated to be 0.038 mmol/L, and 0.029 mmol/L min^–1, respectively, with PNPB as the substrate. The GXU56 lipase showed enantioselective hydrolysis of (R,S)‐methyl mandelate to (R)‐mandelic acid, which is an important intermediate in the pharmaceutical industry.     

Dynamic mechanical and impact properties of PP/SEBS blend

Studies on impact behaviour of the blend of isotactic polypropylene (PP) with styrene-b-ethylene-co-butylene–b-styrene triblock copolymer (SEBS) in the composition range 0–25 wt % SEBS at three temperatures, viz., ambient, ?30°C, and ?190°C, are presented. Dynamic mechanical properties on a torsion pendulum in the temperature range ?100?100°C are also studied for this blend at various compositions. Scanning electron microscopic studies of the impact-fractured surfaces are presented to illustrate the differences in the mode of fracture at the three temperatures of impact tests. Choice of the three temperatures for impact tests was such that the effect of shear yielding mechanism of toughening of PP at ambient temperature remains suppressed at ?30°C, whereas at the lowest temperature (i.e., ?190°C) the elastomeric role of the inclusion SEBS is suppressed. The observed considerably large difference in impact toughening at ambient temperature and at ?;30°C seems not entirely accountable by the prevalence of shear yielding or crazing mechanisms in the respective temperature regions. A third mechanism, viz., viscoelastic energy dissipation, is invoked to account for the observed large difference of impact toughening at these two upper temperatures. Correlation of peak area of dynamic mechanical loss peaks occurring below the impact test temperature with the impact strength is also shown. This suggests greater significance of viscoelastic energy dissipation mechanism in the toughening of this blend at ambient temperature than at ?30°C.     

Development of the ultrasonic conditions as an advanced technique for extraction of phenolic compounds from Eucalyptus robusta

This study is designed to develop ultrasonic conditions as an advanced technique for optimal recovery of phenolics and antioxidants from Eucalyptus robusta leaf and to evaluate the impact of solvents, temperature, sonication time and power on ultrasound-assisted extraction of these compounds. Temperature has the greatest impact on the total phenolic content (TPC) yield followed by time and power. A yield of 163.68 ± 2.13 mg GAE/g of TPC is observed using 250 W ultrasonic power for 90 min at 60°C with water. This study validates UAE as an efficient, green, and sustainable technique for extracting phenolics from E. robusta.     

The β‐δ‐Phase Transition and Thermal Expansion of Octahydro‐1,3,5,7‐Tetranitro‐1,3,5,7‐Tetrazocine

Phase behavior of octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) is investigated by X‐ray powder diffraction (XRD). The XRD patterns at elevated temperature show that there is a co‐existing temperature range of β‐ and δ‐phase during the phase transition process. Additionally, mechanical forces can catalyze the conversion from δ‐ back to β‐phase. Based on the diffraction patterns of β‐ and δ‐phase at different temperatures, we calculate the coefficients of thermal expansion by Rietveld refinement. For β‐HMX, the linear coefficients of thermal expansion of a‐axis and b‐axis are about 1.37×10⁻⁵ and 1.25×10⁻⁴ °C⁻¹. A slight decrease in c‐axis with temperature is also observed, and the value is about −0.63×10⁻⁵ °C⁻¹. The volume coefficient of thermal expansion is about 1.60×10⁻⁴ °C⁻¹, with a 2.2% change from 30 to 170 °C. For δ‐HMX, the linear coefficients of thermal expansion of a‐axis and c‐axis are found to be 5.39×10⁻⁵ and 2.38×10⁻⁵ °C⁻¹, respectively. The volume coefficient of thermal expansion is about 1.33×10⁻⁴ °C⁻¹, with a 2.6% change from 30 to 230 °C. The results indicate that β‐HMX has a similar volume coefficient of thermal expansion compared with δ‐HMX, and there is about 10.5% expansion from β‐HMX at 30 °C to δ‐HMX at 230 °C, of which about 7% may be attributed to the reconstructive transition.     

Combustion behaviour of bituminous and anthracite coal char between 425 and 900 °C

The combustion behaviour of bituminous and anthracite coal char has been studied for temperatures ranging from 425 to 900 °C. The combustion reaction was carried out in a thermogravimetric analyser at 1 atm. A wide range of oxygen partial pressures, from 5×10^?4 to 10^?1 MPa was used. For bituminous char, below 600 °C the intrinsic reaction order and activation energy are 0.75 and 29.0 kcal gmol^?1, respectively, while above 650 °C, the intrinsic reaction order and activation energy are 0.3 and 45.2 kcal gmol^?1. For anthracite char, below 600 °C the intrinsic reaction order and activation energy are 0.9 and 32.8 kcal gmol^?1, while above 650 °C, the intrinsic reaction order and activation energy are 0.3 and 43.6 kcal gmol^?1. The changes in the reaction order and activation energy in the temperature ranges above and below 600 °C imply that the dominant reaction mechanism is different for these two temperature ranges.     

A study on multiple melting of isotactic polypropylene

Multiple melting characteristics of a highly isotactic polypropylene (iPP) were studied by means of differential scanning calorimetry (DSC). Double melting characteristics were observed on melting iPP crystallized isothermally at temperatures ranging from 110 to 140°C. iPP crystallized below and above 125°C exhibited different double melting characteristics from each other. For iPP crystallized below 125°C, the single melting peak split into two peaks during slow DSC heating scans without changing the total crystallinity in the polymer. On the other hand, the double melting endotherm of iPP crystallized above 125°C seemed to come from two preexisting crystal fractions having different T_m. There existed an optimum annealing temperature range where the five-minute annealing of iPP raised T_m of the polymer significantly. The treatment also increased the crystallinity of iPP crystallized isothermally at 110°C by 12%.     

Preparation of poly(vinyl alcohol)-graft-N-isopropylacrylamide copolymer membranes and permeation of solutes through the membranes

Thermosensitive copolymers were prepared by graft copolymerization of N-isopropylacrylamide onto poly(vinyl alcohol) in dimethyl sulfoxide (DMSO) using potassium peroxodisulfate as an initiator. The phase transition temperature was measured by differential scanning calorimetry. The copolymers exhibited almost the same transition temperature (about 33°C) as that of poly(N-isopropylacrylamide) regardless of the composition of the copolymers. The copolymer membranes were obtained by evaporating solvent from the DMSO solution of the graft copolymers and were insolubilized by annealing the membranes at 120°C for 10 h. Permeation of the lithium ion and Methylene Blue through the membranes was investigated at various temperatures. The permeation of solutes was greatly affected by temperature, i.e., the permeation of the solutes could be controlled at temperatures below and above 33°C. © 1994 John Wiley & Sons, Inc.     

Structures and pyroelectric properties for [111]-oriented Mn-doped rhombohedral 0.36PIN-0.36PMN-0.28PT crystal

The crystal structures, pyroelectric properties, and thermal stability of [111]-oriented 0.5 mol% Mn-doped 0.36Pb(In_1/2Nb_1/2)O₃-0.36Pb(Mg_1/3Nb_2/3)O₃-0.28PbTiO₃ (Mn-0.36PIN-0.36PMN-0.28PT) ternary single crystal were investigated. The temperature dependence of the Raman spectra and dielectric properties revealed that the crystal exhibited a rhombohedral (R) structure at room temperature, and ferroelectric R → tetragonal (T) and ferroelectric T to paraelectric cubic (C) phase transitions at 130 and 175°C respectively. The single crystal had a high remnant polarization of P_r = 38 μC cm^–2 and coercive field of E_C = 12 kV cm^–1 at room temperature and a frequency of f = 100 Hz. The values of P_r and E_C decreased with increasing temperature, exhibiting anomalies near their phase-transition temperatures, which coincided with changes in the Raman spectra and dielectric properties. Furthermore, at 25°C and f = 100 Hz, the single crystal had high pyroelectric coefficients of p = 8.7 × 10⁻⁴ C m⁻² K⁻¹, figures of merit for the current responsivity of F_i = 3.5 × 10⁻¹⁰ m V⁻¹, the voltage responsivity of F_v = 0.08 m² C⁻¹, and the detectivity of F_d = 30.1 × 10⁻⁵ Pa^−1/2. These values were weakly dependent on temperature below 120°C. In addition, the room-temperature pyroelectric coefficients of the ternary single crystal maintain over 83% of the original value at thermal annealing temperatures below 120°C. These outstanding pyroelectric properties, together with high thermal stability, indicate that [111]-oriented rhombohedral Mn-0.36PIN-0.36PMN-0.28PT ternary single crystal is a new potential candidate for infrared detection applications.     

Physical aging in poly(methyl methacrylate)poly(styrene-co-acrylonitrile) blends. Part II: Enthalpy relaxation

An investigation of the effect of physical aging on excess enthalpy of compatible polymer blends was carried out. Poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN) were chosen for this study. Blends of different ratios of PMMA and SAN were physically aged at different times and temperatures below their glass transition (T_g) and then subjected to enthalpy relaxation measurement in a differential scanning calorimeter (DSC). An improved procedure was developed and, employed to analyze the data. The error associated with the calculation of the normalized deviation in enthalpy, known as the “Φ” function, was below 4%. The relaxation was observed to proceed faster at higher aging temperature. It was also found that at higher aging temperatures of T_g – 20 and T_g– 35°C, enthalpy relaxation in SAN-rich blends proceeds faster than in PMMA rich blends, while at the low aging temperature of T_g– 50°C the rate of relaxation becomes independent of the composition.