Showing papers on "Distilled water published in 2007"

Water retention and hydraulic conductivity of cross-linked polyacrylamides in sandy soils

Abstract: Mixing superabsorbents, such as cross-linked polyacrylamides (PAM), with sandy soils may decrease water percolation rates and increase water availability to crops. Four polymers were evaluated for their effects on water retention and hydraulic conductivity (HC) in the presence of either tap or distilled water and within sand mixtures. Water retained by the absorbents alone (at low suction) ranged between 200 and 500 kg kg -1 of polymer; water retained by the polymers when mixed with sand ranged between 40 and 140 kg kg -1 . Water retained per kilogram of polymer increased with an increase in polymer concentration in the sand while undergoing desorption, but absorbed water decreased with polymer concentration during sorption, indicating an effect of hysteresis and absorption kinetics in the water absorption process. Applying a hydraulic head of tap water initially caused a decrease in the HC, explained by the decrease in the volume of the soil-absorbents mixtures, followed by a steady increase in HC ascribed to drainage of water from the swollen polymer granules that led to an increase in the size of pores available for water flow. Leaching the soil-absorbent mixtures with distilled water, simulating rainwater, increased the volume of the mixtures (due to polymer swelling) and decreased their HC due to pore blockage by the swollen polymer grains. Better understanding of the interaction among absorbents, soil, and water quality may produce an efficient and economic technology for improving the water management of sandy soils.

Surface characterization of poly(hydroxyethyl methacrylate) and related polymers. I. Contact angle methods in water

Abstract: The characterization of the gel-water interface is considered, particularly with respect to obtaining the interfacial free energy between the gel and water, γ utilizing contact angle data. The question of contact-angle-induced deformation of the three-phase region is examined and visual documentation of such deformation is presented. Air in water and octane in water contact-angle data are used to estimate γdsv γpsv γsv, and γsw for the gel-water interface as a function of bulk water fraction in the gel. It is shown that γ °0 ± 5 erg/cm2 when the bulk water fraction is greater than 0.2. All interfacial parameters determined appear to reach a constant value at a bulk water fraction of about 0.4. These results are for poly(hydroxyethyl methacrylate), poly(methoxyethyl methacrylate), poly(dihydroxypropyl methacrylate), and selected copolymers at 25°C in distilled water.

Determination of dissolved oxygen by the winkler method and the solubility of oxygen in pure water and sea water

Abstract: Values for the solubility of oxygen in water obtained by a modification of the Winkler method are shown to be low because of losses of iodine vapour. Iodine vapour is also lost in two of the standard modifications of the Winkler method in common use, the amount lost depending on the technique of the analyst. The volatilisation of iodine can be avoided by the use of the alkaline iodide reagent of Pomeroy & Kirschman; a procedure employing this reagent is described. Interference by pitrites and ferric iron may be eliminated by sodium azide and phosphoric acid respectively. The accuracy of the Winkler method, modified to prevent the loss of iodine vapour, has been confirmed using gaseous oxygen as a standard. Using the procedure recommended, determinations have been made of the solubility of atmospheric oxygen in distilled water between 0·4° and 37°, and in sea water between 2° and 27°. The results for distilled water are in excellent agreement with those of Klots & Benson between 2° and 27°; the new values for sea water agree fairly well with those of Fox. In measurements of the rate of solution of oxygen, the approach to equilibrium using these values was consistent with the law of Adeney & Becker.

Macromolecular Nanotechnology Study on superabsorbent composite XVI. Synthesis, characterization and swelling behaviors of poly(sodium acrylate)/vermiculite superabsorbent composites

Abstract: A series of superabsorbent composites were synthesized by copolymerization reaction of partially neutralized acrylic acid on unexpanded vermiculite (UVMT) micropowder using N,N 0 -methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator in aqueous solution. And the samples were further characterized by means of fourier-transform spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The effects of vermiculite content on water absorbency were studied. Swelling behaviors of the superabsorbent composites in various cationic salt solutions (NaCl, CaCl2 and FeCl3), anionic salt solutions (NaCl, Na2SO4 and Na3PO4) and pH solutions were also systematically investigated. Results obtained showed that the equilibrium water absorbency increased with increasing UVMT content and the concentration of 20 wt.% clay gave the best absorption (1232 g/g in distilled water and 89 g/g in 0.9 wt.% NaCl). Data achieved also suggested that the water absorbency in various saline solutions decreased with an increase in the ionic strengths of these solutions. And it was found that at a higher ionic strength (>1 · 10 � 3 M), the water absorbency in monovalent cationic solutions was higher than those in multivalent cationic solutions. However, at the same ionic strength (>1 · 10 � 3 M), the effect of three anionic salt solutions on the swelling has the following order: NaCl < Na2SO4

Preparation of superabsorbent slow release nitrogen fertilizer by inverse suspension polymerization

Abstract: A superabsorbent, slow release nitrogen fertilizer (SSRNF) was prepared by inverse suspension polymerization of partially neutralized acrylic acid using N,N′-methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of urea. The polymer was characterized using infrared spectral analysis, and network structural parameters such as molecular weight between crosslinks (Mc) and crosslink density (q) were calculated. The effects of reaction conditions, such as reaction time, reaction temperature, initiator, crosslinker and the degree of neutralization of acrylic acid, on water absorbency were investigated. The nitrogen content of SSRNF synthesized under optimal conditions was 22.7%, and the water absorbencies were about 965 g g−1 in distilled water and 185 g g−1 in tap water. The nitrogen slow release behaviors of the SSRNF in water and water retention capacity of soil with the SSRNF were also investigated. A possible slow release mechanism was proposed and the release rate constant K and the diffusion coefficient D of urea in the hydrogel was calculated. The results showed that the product not only had good slow release properties but also excellent soil moisture preservation capacity, which could effectively improve the utilization of fertilizer and water resources simultaneously. Therefore, the SSRNF is a multifunctional water managing material, which would find application in agriculture and horticulture, especially in drought-prone areas where the availability of water is limited. Copyright © 2006 Society of Chemical Industry

Antioxidants and their migration into food simulants on irradiated LLDPE film

Abstract: Effects of γ-irradiation on residual and migration levels of antioxidants, tris-(2,4-di-tert-butylphenyl) phosphite (Irgafos 168) and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (Irganox 1076), and their radiolysis products were investigated in the linear low density polyethylene (LLDPE) packaging samples treated at doses from 0 to 200 kGy. The content of Irgafos 168 was not detected in 5 kGy treated samples and the content of Irganox 1076 decreased by 34.9% from the initial level in 10 kGy treated samples. The radiolysis products, 2,4-di-tert-butylphenol (2,4-DTBP), 1,3-di-tert-butylbenzene (1,3-DTBB), and toluene were identified and their concentrations gradually increased as the irradiation dose increased. Migration of Irgafos 168 from the LLDPE pouch into food simulants, distilled water, acetic acid (4 ml/100 ml distilled water) or ethanol (20 ml/100 ml distilled water), was not detected at dose levels up to 200 kGy while that of the Irganox 1076 was detected in a decreasing mode with increasing dose.

Zinc-containing phosphate-based glasses for tissue engineering

Abstract: It has been shown that the addition of zinc to hydroxyapatite promotes osteoblast cell adhesion (Ishaug et al 1994 J. Biomed. Mater. Res. A 28 1445–53). Therefore, this study presents a series of phosphate-based glass compositions that contain varying amounts of zinc in order to promote osteoblast cell adhesion. The compositions investigated were P50Ca(40−x)Na10 where x = 0, 1, 2, 3, 4 and 5 mol%. The dissolution rate and effect on pH of glass discs were investigated and ion release from the glass discs was examined in distilled water at 37 °C after 1, 2, 3, 4 and 7 days. The attachment of osteoblast-like cells (HOB) was observed by SEM on the glass discs. A linear decrease in the %mass of the glass discs was observed for all compositions for the duration of the study. The dissolution rates were similar for all the compositions. After 7 days, a mass loss of 3–6% was observed for all the compositions. The pH of distilled water decreased to a range of pH 4.5–5.5 from pH 7 after 1 day, and remained in this range for the duration of the study. The composition containing 0 mol% Zn reduced the pH to a lesser extent than the composition containing the highest amount of Zn. Furthermore, Zn2+ ion release was observed from all the Zn-containing compositions. These glass compositions may therefore be suitable for tissue engineering applications.

Investigation of water absorption in pultruded composites containing fillers and low profile additives

Abstract: This work investigates the humidity absorption process in the polyester/glass fiber composite materials containing fillers and low profile additives. These composite materials were exposed to both distilled and sea water at different temperatures. The moisture diffusivity and the moisture equilibrium reached by these composites were determined using the gravimetric test method and their humidity distribution profile across the thickness direction was characterized using the microtome technique. The obtained results indicate that the distilled water diffuses in all composites much more rapidly than the sea water, particularly at high immersion temperatures. However, the opposite is observed at low immersion temperature (5°C), since at this temperature the distilled water is almost in its icy state. For high immersion temperatures, a mass loss of the aged specimen in the sea water was observed 2 months after the first immersion. Such behavior was not observed during the immersion in the distilled water. Moreover, it is observed that the water absorption is higher in the composite materials containing low profile additives. This behavior is explained in terms of microvoids formation promoted by low profile additives. The microtome technique reveals clearly that the humidity profile across the thickness of the aged specimen follows a parabolic trend with a maximum at the outside surface of that specimen and a minimum at its center. These experimental results were found to confirm the theory. POLYM. COMPOS., 28: 355–364, 2007. © 2007 Society of Plastics Engineers

Mechanical, morphological and thermal properties of rigid polyurethane foam : Effect of the fillers

Abstract: Rigid polyurethane foam (PUF) having different fillers such as precipitated silica (SiO2), precipitated calcium carbonate (CaCO3) and glass powder (GP) were prepared by blowing with distilled water...

Water in oil (w/o) and double (w/o/w) emulsions prepared with spans: microstructure, stability, and rheology

Abstract: The objective was to analyze the microstructure, stability, and rheology of model emulsions prepared with distilled water, refined sunflower oil, and different Spans (20, 40, 60, and 80) as emulsifiers. The effects of the water content and Span 60 concentration were studied. The lowest water contents led to w/o emulsions, whereas higher percentages gave w/o/w emulsions. Microscopy analysis showed that w/o/w emulsions of higher water contents had a lower number of internal water droplets. W/o emulsions were destabilized by coalescence and sedimentation, whereas creaming was observed in unstable w/o/w emulsions. In the last ones, the creaming stability decreased with increasing water content and enhanced with higher Span 60 concentration; the same effect was observed in their viscoelasticity: They were from unstable liquids to stable gels. Solid Spans (40 and 60) produced more consistent w/o/w emulsions at low water contents and more stable systems at high water percentages in comparison with liquid Spans (20 and 80).

Dissolving efficacy of some organic solvents on gutta-percha.

Abstract: The aim of this study was to evaluate the solubility of gutta-percha in four organic solvents used in endodontics. The solubility of gutta-percha (Dentsply) was assessed in xylol, orange oil, eucalyptol, chloroform and distilled water. A hundred and fifty samples of gutta-percha were prepared using a standardized stainless steel mould and divided into five groups for immersion in the different solvents tested and in distilled water (control group) for 2, 5 and 10 minutes. The means of gutta-percha dissolution in the solvents were obtained by the difference between the pre-immersion original weight and the post-immersion weight in a digital analytical scale (Gehaka-AG2000). Data were statistically analyzed by Analysis of Variance (ANOVA) and multiple comparisons with Scheffes test (p<0.05). The best solvency capacity was obtained with xylol. Chloroform, orange oil and eucalyptol presented similar results, and distilled water did not promote alterations in the gutta-percha.

Effect of temperature, plastic type and virginity on the water uptake of sawdust/plastic composites

Abstract: Water absorption of wood plastic composites (WPCs) manufactured from sawdust and virgin and recycled plastics (HDPE and PP) was studied. Wood flour was prepared from sawdust and mixed with different virgin or recycled plastics at 50% by weight fiber loading. The mixed materials were compression molded into panels. Water absorption of manufactured WPCs was determined after 2 and 24 h immersion in distilled water at different temperatures (25, 50 and 70 °C). WPCs containing recycled plastics exhibited higher water absorption especially when the two recycled plastics were mixed together. Immersion temperature had a significant effect on water absorption.

An in vitro study of the pH of three calcium hydroxide dressing materials

Abstract: Calcium hydroxide is widely used as a root canal dressing material because of its favorable alkalinizing effect. It has been suggested that the action comes from diffusion of hydroxyl ions through the apical foramen. The purpose of this in vitro study was to test the pH changes that occurred over a period of 30 days using a mixture of calcium hydroxide and distilled water and two commercial calcium hydroxide products in a simulated periapical environment. The materials were inserted in glass tubes closed at one end, which were placed in individual vials containing distilled water at a pH 7.4. Unfilled glass tubes were used as controls. Alkalinity changes of the medium were measured at 1 and 24 h and 15 and 30 days. The alkalinizing properties of all materials showed a rapid increase at 1 and 24 h followed by a continuous but more gradual increase from 15 to 30 days. The control tubes did not cause a change in pH of the medium, which remained at pH 7.4. At the end of the observation period, the alkalinizing properties of Calasept and Ultracal XS were significantly higher (P < 0.05) than the calcium hydroxide/distilled water paste.

Preparation, characterization and evaluation of coenzyme Q10 binary solid dispersions for enhanced solubility and dissolution.

Abstract: Phase solubility behavior of coenzyme Q10 (CoQ10) at 25 °C in various molar solutions of poloxamer 188 (P188) in water was observed and their binary solid dispersions (BSD) at different weight ratios were prepared by a simple, rapid, cost effective, uncomplicated and potentially scalable low temperature melting method. BSDs were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), and evaluated for improved solubility at 25 °C and 37 °C and in-vitro release of CoQ10 at 37 °C in distilled water. Solubility of CoQ10 increased with increasing concentrations of P188 in water. Gibbs free energy (ΔG°tr) values were all negative indicating the spontaneous nature of CoQ10 solubilization and decreased with increasing concentration of P188 demonstrating that the reaction conditions became more favorable as the concentration of P188 increased. DSC and SEM analysis indicated that the homogeneity of dispersion was not at the molecular level. However, BSDs exhibited a remarkably improved aqueous solubility and dissolution of CoQ10.

Two step sol-gel processing of TEOS based hydrophobic silica aerogels using trimethylethoxysilane as a co-precursor

Abstract: The experimental results on the surface modification of tetraethoxysilane (TEOS) based silica aerogels using trimethylethoxysilane (TMES) as a co-precursor by two step sol-gel process are reported. The molar ratio of MeOH/TEOS was fixed at 17 and TMES/TEOS ratio was varied from 0.38 to 1.14. The concentration and quantity of acidic water (oxalic acid) added in the first step and base water (ammonium hydroxide) in the second step were also varied. The best quality superhydrophobic aerogels could be obtained with only distilled water (without any acid catalyst) in the first stage and the basic water in the second step of the sol-gel process. The molar ratio of TEOS: TMES: MeOH: distilled water: basic water was optimized at 1:0.86:17:4.9:4.9, respectively. The surface modification has been confirmed from the Fourier transform infrared spectroscopy measurements while the hydrophobicity was quantified in terms of the contact angle measurements. The TMES/TEOS based aerogel powder could be used to transport micro-liters of water in the form of water marbles. The aerogels have been characterized by the bulk density, porosity, thermal conductivity, contact angle measurements and the transmission electron microscopy (TEM).