Determination of wax concentration in sunflower seed oil

Isothermal crystallization of waxes was studied by using an optical setup. The induction time of crystallization was assessed as a function of wax concentration. The relationship was found to be a decreasing exponential curve. The wax content of some of the solutions prepared in the laboratory was determined by calculating the crystallization induction time. The values obtained were compared to those from different methods (cold test, microscopic, and turbidimetric methods). The results obtained with the optical setup method are similar to those obtained with other methods for concentrations greater than 100 ppm. An analysis of variance test was used to verify the authenticity of the values obtained with the optical method. Results showed that the method used to determine wax concentration, the concentration of the sample, and the relationship between both parameters do not affect significantly the values of percentage relative errors (P<0.05) obtained for concentrations greater than 100 ppm. Values obtained for wax content within the range 0–100 ppm could not be compared since the microscopic and turbidimetric methods are not sensitive enough, unlike the optical setup, to detect wax amounts in such low concentration.     

Solubility parameters of polymers from turbidimetric titrations

The solubility parameters of sixteen polymers have been determined by the turbidimetric titration method. The results agree well with the reported values obtained from swelling and viscosity measurements. The method is sensitive to the choice of nonsolvents and to small changes in the copolymer composition.     

Reference materials of defined particle size certified recently by the community bureau of reference of the european economic community

Some results from an international projects, supported by the Community Bureau of Reference of the European Economic Community, on the certification of five reference materials of defined particle size covering the overall range 0.35 – 650 μm are presented and discussed. Four of the reference materials were certified with respect to the mass distributions of the Stokes' diameters measured by an agreed gravitational sedimentation (Andreasen pipette) method. The coarsest of the reference materials was certified with respect to the mass distribution of the volume diameters of the particles using sieves, the ‘cut sizes’ of which were calibrated with respect to their equivalent volume diameters.Data were also obtained using several other methods, including X-ray gravitational sedimentation, sedimentation balance, centrifugal sedimentation, electrical sensing zone and photo-sedimentation methods. These were not used for certification but are presented for comparison purposes and to indicate the usefulness of the certified reference materials for the checking and calibration of many particle sizing techniques.     

Turbidimetric analysis of amine oxides and amine oxide-anionic surfactant mixtures

Automatic turbidimetric analysis has been shown to be a simple and accurate method to determine the actives in anionic surfactants as well as the actives in amine oxides. This technique has been applied to dilute solutions of these surfactants in the μM range. Solutions containing mixtures of anionic surfactants and amine oxides can be positively resolved by turbidimetric titration without interferences. Performing two titrations at different pH values ensures that the amine oxide is completely in its nonionic form or totally protonated and behaving as a cationic surfactant.     

A new turbidimetric approach to measuring polyethylene short chain branching distributions

A new instrument to analyze the short chain branching distribution of polyethylenes has been described. Turbidity analysis of ethylene/α-olefin copolymers by turbidity fractionation analysis can provide short chain branching distribution information that is similar to CRYSTAF and TREF. In these experiments, the turbidity of a polymer solution is monitored while changing its temperature at a controlled rate. The turbidimetric response is to the precipitation or dissolution of the crystallized polymer at a given temperature. With an approach similar to CRYSTAF, the differential of the turbidity profile provides valuable SCBD information for polymers with broad and narrow compositions such as Ziegler-Natta LLDPE and homogeneous polymers catalyzed by single-site catalysts.     

Untersuchungen zur Optimierung der Fällfraktionierung von Polymeren

The possibilities for a systematic selection of the conditions for fractional precipitation in polymer/solvent/nonsolvent-systems based on data of the turbidimetric titrations have been tested experimentally. As criticism for the fractionation efficiency the molecular weight distribution of the fractions (determined by ultra-centrifuge) and the uniformity M?_w/M?_n (calculated therefrom) was taken. The successiv- and subfractionation, the dependence of the initial concentration and particularly the influence of the solvent/nonsolvent-system on the fractionation efficiency were investigated. Therefore a simple new method was developed, which allows to arrange systematically different solvent/nonsolvent-systems with few turbidimetric titrations as to be suitable for fractionation. For three selected solvent/non-solvent-systems the correctness of the selection method could be proved experimentally.     

Concentration profiles in a laboratory flotation machine: development of a simple sampling technique

The method uses a pipette with pilot tube-shaped sampling orifice. Error analysis, statistical methods, and consideration of hydrodynamic factors have led to a simple and accurate sampling technique. The incremental volume RTD method used to verify the pipette method confirms agreement between procedures, but the pipette method provides far more detail with no more effort.The concentration profile of the Denver D1 laboratory flotation machine was studied at different impeller speeds and impeller/stator clearances. Closely sized glass beads were used as tracer. Within its operating speed range, the machine is far from ideally mixed, and the profiles are very irregular near the impeller/stator assembly. The results are discussed and suggestions made for further research.     

Synthesis and thermo-responsive behavior of fluorescent labeled microgel particles based on poly(N-isopropylacrylamide) and its related polymers

Poly(N-isopropylacrylamide) (PNIPAM) microgel particles labeled with 3-(2-propenyl)-9-(4-N,N-dimethylaminophenyl)phenanthrene (VDP) as an intramolecular fluorescent probe were prepared by emulsion polymerization. The thermo-responsive behavior of the VDP-labeled PNIPAM microgel particles dispersed in water was studied by turbidimetric and fluorescence analyses. The transition temperature of the VDP-labeled PNIPAM microgel particles in water determined by turbidimetric analysis was ca. 32.5 °C. The wavelength at the maximum fluorescence intensity of the VDP units linked directly to the microgel particles dramatically blue-shifted around the transition temperature. In addition it gradually blue-shifted even below the transition temperature where there was no change observed in the turbidity. These findings suggest that the gradual shrinking of microgel particles occurs with increasing temperature and the subsequent dramatic shrinking results in the increasing in the turbidity. The transition temperatures of VDP-labeled poly(N-n-propylacrylamide) and poly(N-isopropylmethacrylamide) microgel particles determined by turbidimetric analysis were ca. 23 and ca. 42.5 °C, respectively, and their thermo-responsive behavior was similar to that for the VDP-labeled PNIPAM system. In these three systems the microenvironments around the fluorescent probes above the transition temperatures became more hydrophobic than those below the transition temperature, and the estimated values of microenvionmental polarity around the VDP units on their collapsed states were almost the same.     

Turbidimetric determinations of theta compositions

The turbidimetric titration method of determining theta conditions developed by Elias and modified by Cornet and van Ballegooijen has been extended and generalized for different types of polymer–solvent–nonsolvent systems. The modified procedures for the determination of theta compositions have been verified with the following systems: polystyrene–cyclohexane–n-hexane, polystyrene–cyclohexane–n-butanol, and polystyrene–toluene–nonsolvent.     

Determination of the Nanoparticle Size Distribution in Media by Turbidimetric Measurements

For incorporation of nanoparticles into matrices, it is necessary to control the particle size distribution during processing. In this paper, a turbidimetric method was applied that uses spectroscopic data to determine the nanoparticle size distribution and, consequently, to control the material properties with a non‐contact measurement method. This method is based on the scattering and absorption of light by the particles. Unlike conventional turbidimetric methods, this method uses not only a few wavelengths but a whole spectral range for evaluation. To determine the distribution parameters, a nonlinear numerical least squares fit routine was established. It was validated by comparing data of water‐silica nanosuspensions with the results from the sedimentation method. The results show that this method is an accurate and easy‐to‐use analysis instrument for the characterization of nanosuspensions, emulsions, and aerosols.     

Agglomeration of alumina powders: A turbidimetric study

Turbidimetry has proved to be an efficient method for the quantitative study of powder agglomeration for particle sizes in the region of 1 μm. This work presents a new application of the technique for the agglomeration of α-alumina in water and in n-heptane. The method of determining the kinetic parameters of agglomeration from the initial time-evolution of turbidity is explained. Turbulent flow in the reactor has also been characterised by laser anemometry. From the turbulence intensity, the number of collisions per unit time is calculated and the agglomeration rate can therefore be determined. Good agreement is found between the values obtained respectively from turbidimetric and hydrodynamic measurements. Addition of KOH modifies the zeta potential of alumina in water and influences the agglomeration kinetics. This can also be quantitatively characterised by turbidimetry. The experimental results obtained for alumina particles of diameter 0.3 μm and 1 μm are interpreted according to the DLVO model of interaction between particles.     

Pyrolysis kinetics of forestry residues from the Portuguese Central Inland Region

The pyrolysis behaviour and kinetics of forest shrub wastes (Cytisus multiflorus, Spartium junceum, Acacia dealbata and Pterospartum tridentatum) from the Portuguese Central Inland Region have been studied in a thermobalance, as a previous step for their valorization by pyrolysis in order to obtain fuels and chemicals within the framework of the BioREFINA-Ter project. The kinetic model consists of a multi-component mechanism that describes the volatile formation involving three independent and parallel reaction networks corresponding to the decomposition of the three main biomass pseudo-components: hemicellulose, cellulose and lignin. The thermogravimetric curves and kinetic parameters have been compared with those obtained for other materials, and the chemical features of the biomasses have been determined. Although the samples are highly heterogeneous because of their bark and leaf content, the degradation of these shrubby biomasses is similar to other lignocellulosic materials, evidencing that their valorization by pyrolysis is feasible.     

测定与去除采油废水中聚丙烯酰胺方法的探讨

介绍了黏度法与浊度法测定三次采油污水中聚丙烯酰胺(PAM)的残余浓度和次氯酸盐法及化学凝沉法去除PAM的原理和方法,并对影响因素及技术可行性进行了探讨.结果表明:当测定温度在2～22℃范围内,浊度法受溶液中可溶性盐和有机物以及环境温度的影响比黏度法要小,结果的重现性好,适合于含油污水PAM浓度的检测.化学凝沉法可快速去除三次采油废水中残留的PAM,处理工艺简单,水质可以达到油田回注水或外排水的标准.     

Polymer-Derived SiOC/ZrO2 Ceramic Nanocomposites with Excellent High-Temperature Stability

Polymer-derived SiOC/ZrO₂ ceramic nanocomposites have been prepared using two synthetic approaches. A commercially available polymethylsilsesquioxane (MK Belsil PMS) was filled with nanocrystalline zirconia particles in the first approach. The second method involved the addition of zirconium tetra( n -propoxide), Zr(OⁿPr)₄, as zirconia precursor to polysilsesquioxane. The prepared materials have been subsequently cross-linked and pyrolyzed at 1100°C in argon atmosphere to provide SiOC/ZrO₂ ceramics. The obtained SiOC/ZrO₂ materials were characterized by means of X-ray diffraction, elemental analysis, Raman spectroscopy as well as transmission electron microscopy. Furthermore, annealing experiments at temperatures from 1300° to 1600°C have been performed. The annealing experiments revealed that the incorporation of ZrO₂ into the SiOC matrix remarkably increases the thermal stability of the composites with respect to crystallization and decomposition at temperatures exceeding 1300°C. The results obtained within this study emphasize the enormous potential of polymer-derived SiOC/ZrO₂ composites for high-temperature applications.     

毛细滴管数滴法野外快速测定水中氯离子

以自制的液滴体积为0.01～0.02 mL的聚乙烯毛细滴管对水中氯离子含量进行数滴分析,其主要仪器外形小巧、便于携带,滴定快速、准确,试剂消耗量约为常量法的二十分之一,滴定剂用量约为20～100滴,氯离子含量不确定度Urel(C)为3.03%,与常量法略小,相对标准偏差比常量法的相当。该法克服了常量法中滴定管、移液管、铁架台和蝴蝶夹等仪器携带不方便的不足,适用于水中氯离子含量的室外快速分析。     

Interpolymer complexes of hydroxypropylmethylcellulose with polycarboxylic acids in aqueous solutions

The interactions between hydroxypropylmethylcellulose (HPMC) and poly(acrylic acid) (PAA) as well as poly(methacrylic acid) (PMAA) resulting in formation of hydrophobic interpolymer complexes (IPC) via hydrogen bonding have been studied in aqueous solutions in acidic medium. The formation of IPC of two different compositions (2:1 and 4:1) has been detected for complexes of PAA and HPMC. The critical pH values for complexation of HPMC with PAA and PMAA were determined by the turbidimetric method. It was found that PAA shows the lower complexation ability compared to PMAA due to the more hydrophobic nature of the latter polyacid. The temperature‐induced phase separation in HPMC–PAA solution mixtures depends greatly on the components ratio and PAA molecular weight. The complexation ability of hydroxypropylmethylcellulose with respect to poly(acrylic acid) was found to be similar to the complexation ability of methylcellulose, lower than that of hydroxypropylcellulose and higher than that of hydroxyethylcellulose. Copyright © 2006 Society of Chemical Industry     

Physicochemical basis of the sol-gel process giving selective layers of ultrafiltration ceramic membranes from zirconia hydrosol

Selective layers of ceramic ultrafiltration membranes were prepared by the sol-gel method using zirconia hydrosol as the initial material. On the basis of turbidimetric investigations, a compatibility diagram was constructed in the zirconia (sol) — polymer thickener — water system. The results of x-ray phase analysis and thermogravimetric analysis were used to choose the regime for heat treatment of the sol — polymer thickener compositions in order to prepare selective layers. The characteristics of the pore structure of the selective layers meet the requirements imposed on ultrafiltration membranes.     

Rapid determination of wax in sunflower seed oil

A rapid turbidimetric method for determining wax content in sunflower seed oil is described. Oil is heated to 130 C, filtered, and after cooling, added to an equal volume of acetone. The mixture is then reheated under tap water to dissolve waxes which may have crystallized and is placed in an ice bath for 5 min. Turbidity is then measured and ppm wax is read from a previously prepared calibration curve. The amount of wax as determined by the turbidimetric method is in good agreement with the gas liquid chromatographic values. An erratum to this article is available at .     

Modification of epoxy resins by the addition of PVC plastisols

An epoxy resin based on bisphenol A has been modified by the addition of different amounts of a plastisol, based on poly(vinyl chloride) (PVC) and diethylhexyl phthalate (DOP). The fluid state of those materials makes their blending easier. After a curing process, some different materials, with properties ranging from the rigidity of a thermosetting resin to the flexibility of a plastisol, can be obtained. The variation of different parameters, such as tensile strength, Young's modulus, dielectric constant, and others, with the concentration of plastisol, has been studied. Some materials with properties similar to common thermoplastics (PP, ABS, or SB) can be processed, depending on the epoxy-to-plastisol ratio. The obtained results enable us the use of those materials in prototyping and other industrial processes. The obtained prototypes should have a similar mechanical behavior to thermoplastics. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1769–1777, 1998     

Temperature Drop Turbidimetry as a Means for the Rapid Determination of the Polydispersity of Polymers Part III. Polyethylene

The molecular weight averages of narrow and broad distribution polyethylene have been determined by controlled precipitation from a mixed solvent of xylene/n-hexanol in the temperature range 433 to 33K. Estimates of the distribution (D) which compared unfavourably with and considerably under-estimated those determined by gel permeation chromatography (g.p.c.) were obtained by a calibration procedure between the temperature of initial onset of precipitation and the weight average molecular weight which have been used previously _1,2 to characterise turbidimetric curves. However, the calibration curves gave an accurate estimate of the weight average molecular weight. There was also an accurate correlation between the reciprocal of the breadth of the turbidity-temperature curves as measured by 1/T_max (dτ/dT) ^?1 i.e. (S)^?1, and the logarithm of the g.p.c. dispersity which enabled the breadth of distribution to be determined. With these two correlations molecular weight characteristics could be determined rapidly which compared favourably with g.p.c. data. The method has been applied to fractions obtained for 3 methods of fractionating polyethylene in order to compare their relative efficiencies.