Morphology and properties of nanocomposites formed from ethylene/methacrylic acid copolymers and organoclays

Nanocomposites were prepared by melt mixing ethylene/methacrylic acid copolymers and organoclays, which were compared to equivalent composites prepared from low-density polyethylene (LDPE) and a sodium ionomer of poly(ethylene-co-methacrylic acid). The effects of matrix modification and organoclay structure on the morphology and properties of these nanocomposites were evaluated using stress-strain analysis, wide-angle X-ray scattering (WAXS), and transmission electron microscopy coupled with particle analysis. With all four polymers, the use of a two-tailed organoclay, M₂(HT)₂, led to the formation of more exfoliated nanocomposites than a one-tailed organoclay, M₃(HT)₁. Nanocomposites prepared from ethylene/methacrylic acid copolymers revealed better exfoliation compared to similar composites prepared from LDPE. It seems that the presence of relatively small quantities (1.3-3.1 mol%) of the polar methacrylic acid monomer aids in improving the organoclay exfoliation efficiency of these polymers. Nanocomposites prepared from the sodium ionomer of poly(ethylene-co-methacrylic acid) exhibited the highest levels of organoclay exfoliation compared to all other polymers examined in this study. However, from the observations made in this study, it was not possible to determine conclusively the relative interaction of carboxyl acid groups versus the salt form with the organoclay and, thus, their influence on exfoliation; additional studies will be needed to reach a conclusion on this important point.     

Gas-liquid interface temperature rise in the case of temperature-dependent physical,transport and reaction properties

This paper anlyzes the problem of gas-liquid interface temperature rise for a first order gas-liquid reaction when the diffusion coefficient, solubility and reaction rate coefficient are dependent upon temperature. The analysis indicates that as long as the quantity ?_eff, which is numerically equal to ?_S − (? + ?_R/2 (wherein ?_S, ?_D and ?_R are the dimensionless temperature-solubility, temperature-diffusion coefficient and temperature-reaction rate constant coefficients) is zero, Danckwerts' analysis [1–3] is useful for the calculations of large rise in gas-liquid interface temperature. For ?_eff ≠ 0, the paper presents approximate empirical correlations for calculating gas-liquid interface temperature rise with the knowledge of Danckwerts' analysis and the magnitude of ?_eff.     

Effect of particle dimension on biocompatibility of carbon nanomaterials

With various emerging applications ranging from medicine to materials and electronics, the risk of exposure to nanomaterials is rapidly increasing. Several routes of exposure to nanomaterials exist; the most important being dermal contact and inhalation. In this dermal toxicity study, the cellular effects of carbon-based materials with diameters ranging from micro- to nano-dimension were investigated using mouse keratinocytes (HEL-30). The carbon materials tested included carbon fibers (CF; 10 μm diameter), carbon nanofibers (CNF; 100 nm diameter), multi-walled carbon nanotubes (MWCNT; 10 nm diameter), and single-walled carbon nanotubes (SWCNT; 1 nm diameter). CF and CNF did not significantly affect cell viability; however, MWCNT and SWCNT reduced cell viability in a time-dependent manner up to 48 h, with full recovery of mitochondrial function by the 72 h time point. After a 24 h exposure, cells exposed to MWCNT produced up to 3-fold higher increase in reactive oxygen species than those exposed to SWCNT. The results of this study suggest that high-aspect ratio carbon material toxicity is dependent on dimension and composition.     

Urban water demand,climatic variation,and irrigation-water insecurity: interactive stressors and lessons for water governance from the Angat River basin (Philippines)

Climatic variation and intersectoral water competition increasingly challenge the effective provision of irrigation services. This article explores their combined effects on irrigation allocation from the Angat Reservoir (Philippines), where domestic water use in Metro Manila has overtaken regional irrigation as the dominant right-holder. Rules protecting Metro Manila’s large right to water ‘interact’ with dry spells to affect irrigation security in wet and dry seasons. Historically, irrigators were uncompensated because re-allocation’s cause was contested as (1) an unforeseeable climatic event (releasing domestic utilities of liability), or (2) produced by urban demand (requiring compensation). Trade-off rules must be prepared to navigate combinatory effects.     

Uptake of Pb(II) and Cd(II) by a new phenolformaldehyde polymer resin derived by the insertion of sulfur ligands in the form of xanthate

A new phenolformaldehyde polymer resin containing potential soft‐type donor atoms (sulfur atoms) was synthesized by the reaction of sodium salt of 2,4‐dihydroxyacetophenone formaldehyde resin with carbon disulfide. The resin was characterized by elemental analysis, IR, and ¹H‐NMR spectral studies. Because of its insolubility in aqueous media, the resin was successfully used in the removal of Pb(II) and Cd(II). Parameters such as the effect of pH, the effect of time, competitive studies, the effect of initial metal‐ion concentration, and the recyclability of the polymer resin were studied. The amount of metal removed by the resin was determined with atomic absorption spectrophotometry. The retention properties were strongly dependent on pH. The elution of metal ions was investigated in acid media. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1932–1936, 2004     

Surface tension and contact angle of herbicide solutions affected by surfactants

Contact angle and surface tension were measured for distilled and hard water solutions of adjuvants, Ortho X-77, Span-20, Sterox-NJ. Surfactant-WK, Triton B-1956, Triton X-114, Tween-20, and Sun Oil 11E. The same parameters were measured for suspensions of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and ametryne [2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine] with and without each adjuvant. All adjuvants reduced surface tension and contact angle of distilled water; Surfactant-WK was most effective and Tween-20 was least effective. Increasing concentration of surfactants from 0 to 0.1% (v/v) gave progressive reduction in surface tension and contact angle while higher concentrations, 0.1 to 2.0% (v/v), had no further effect. Surfactant-WK at 0.1% (v/v) in distilled water reduced the surfact tension from 72.8 dynes/cm to 27 dynes/cm and contact angle from 110° to 41°. An additional increase in Surfactant-WK concentration from 0.1% (v/v) to 2% (v/v) did not further reduce surface tension and contact angle. Sun Oil 11E was identical in behavior except that it was less effective than the surfactants. Water hardness up to 1,000 ppm as Ca ions did not affect surface tension and contact angle in surfactant solutions. An aqueous solution of atrazine had a higher surface tension and contact angle than ametryne in the absence of surfactants. However, these differences were not observed when surfactants were added to either herbicide.     

Kinetics of thermal liquefaction of coal

A model is presented for the kinetic study of the thermal liquefaction of Belle Ayr subbituminous and Burning Star bituminous coals with anthracene oil, hydrogenated anthracene oil and hydrogenated phenanthrene. All experiments were performed in a continuous-feed, stirred tank reactor, at a temperature of 450 °C and a space time of approximately 5 to 55 min. A kinetic model which includes a reaction: coal + oil→more reactive coal, correlates the data reasonably well. This reaction explains the net consumption of anthracene oil during the initial stages of liquefaction. Such a reaction may account for a portion of the swelling of coal at low space times and the sizable increase of viscosity of reaction slurry during these initial stages of liquefaction. It is also observed that the yield of oil increases when solvents of increasing hydrogen donor capacity are used.     

Early age microstructure of Portland cement mortar investigated by ultrasonic shear waves and numerical simulation

This paper investigates the ability of a shear wave reflection (WR) method to monitor microstructural changes of Portland cement mortar during hydration. The wave reflection method measures the reflection loss of shear waves at an interface between a steel plate and mortar. Mortars with water/cement ratios of 0.35, 0.5 and 0.6 were tested at isothermal curing conditions of 25 °C. The numerical model HYMOSTRUC3D was used to simulate the evolution of microstructural properties of the cement paste phase of the tested mortars. The parameters obtained from the simulations were the volume fraction of the total and connected solid phase and the specific contact area of the hydrated cement particles. The investigations have shown that the wave reflection measurements are governed primarily by the degree of the inter-particle bonding of the cement particles as calculated from the specific contact area of a simulated microstructure.     

Economical and Efficient Fading Lamps*

Tests have been made with over 300 dyed or pigmented materials exposed to mercury-tungsten or mercury lamps. The colorations were of a wide range of hue and light-fastness properties (1 to 8 and above) and in several depths on different substrates. The mercury-tungsten fluorescent lamp (500 W) gave results identical with those obtained with daylight or xenon arclight for 75% of the very varied selection of 174 patterns examined, and 25 % were within one-half of a grade, except for five which differed by one grade. When the blue standards are faded in this lamp (at 45% r.h.), they have an average interval factor of about 2.1. The required times of exposure are similar to those for the xenon arclight. The equipment required is extremely simple, and its initial and operating costs are considerably lower than those of methods hitherto used for testing in artificial light. The equipment can readily be used on the laboratory bench and is suitable for routine testing of the light fastness of any coloured material. In addition to the control of humidity, temperature control is possible, though this is not usually necessary. The mercury-vapour lamp (400 W) has also been similarly examined, using 138 patterns. It is not recommended for general use but is valuable for routine sorting tests of materials of very high fastness (BS grading above 7). The blue standard patterns fade, under exposure to these lamps, in the same sequence and with similar interval spacings, as in daylight or xenon light.     

Influence of Distributed Particle Size on the Determination of the Parabolic Rate Constant for Oxidation by the Powder Method

The established analysis for the study of oxidation using powder specimens is based on the assumption of monosized particles. The experiments, however, are conducted on powders with a distributed particle size. Here we present a statistical approach for the calculation of the rate constant for oxidation. The results of the analysis are applied to new data on oxidation studies of dense powders of silicon carbonitride amorphous ceramics. The monosized model requires a wide range of values for the rate constant to fit the short term and the long-term data, leading to considerable ambiguity in the estimate of the parabolic rate constant, k _p, for oxidation. In contrast the statistical model fits over the entire range of data, yielding a much more reliable value for k _p. For example, the monosized approach gave a value in the range 19.7 × 10⁻¹⁸ < k _p < 2.7 × 10⁻¹⁸ m²/s. In contrast, the statistical model yields a specific value of 4.5 × 10⁻¹⁸ m²/s.