The Relationship Between the Microhardness and Glass Transition Temperature of Inorganic Glasses Compared with Polymeric Glasses

ABSTRACT

In this article an attempt is undertaken to verify the approach already successfully applied to polymeric glasses for deriving a simple analytic relationship between the glass transition temperature, T_g , and Vickers microhardness, H_v , (for polymers it is H_v  = 1.57 T_g –571, H_v in MPa, T_g in K). On the basis of previously reported data for H_v and T_g of 12 inorganic glasses (lead-silicate-, alkali-silicate-, alumosilacate, and quartz glasses) a linear relationship in the form H_v  = 5.87 T _g + 1740 (H_v in MPa, T_g in K) is derived. In addition, a critical analysis of the published attempt for theoretical deriving of the relationship between H_v and T_g is also offered.     

UNIFORMITY OF CHANGE IN POROUS CATALYST ACTIVITY DURING A MULTI-PULSE TAP EXPERIMENT

Uniformity of change in catalyst activity during a multi-pulse TAP experiment with porous catalyst was theoretically analyzed for a TAP reactor with the ratio of the catalyst bed thickness to the reactor length of 1/30. The analysis was performed by simulation of an irreversible adsorption process. The catalyst change is described by the change in the occupied/unoccupied fractional surface coverages. The intraparticle uniformity is indicated by a small magnitude of Δθ _p,max , the maximum difference between the occupied fractional surface coverages at the outermost and the innermost of the catalyst pellet during the multi-pulse experiment. In the interparticle region, the indicating quantity is Δθ _b,max , the maximum difference between the pellet-outermost fractional surface coverages at the inlet and the outlet of the catalyst bed. It was found that Δθ _p,max generally depends only on the effectiveness factor in the first pulse experiment, η. For η ≥ 0.94, Δθ _p,max  ≤ 0.05. In addition, Δθ _b,max depends only on the gas conversion in the first pulse experiment, X. For X ≤ 0.7, Δθ _b,max  ≤ 0.05.     

Influence of Different Solvents on the Morphology of the Hybrid Layer Using Two-Step Etch-and-Rinse Adhesives

To evaluate if different etch-and-rinse adhesive solvents influenced the hybrid layer's morphology.

Four one-bottle etch-and-rinse adhesive systems containing different solvents—Group A: Scotchbond 1XT?– 3 M ESPE, Group B: XP – Bond? – Dentsply, Group C: Prime&;Bond NT® – Dentply, and Group D: One Coat Bond® - Coltène Whaledent—were applied onto 32 dentin discs which were thermocycled, prepared, and examined using field-emission scanning electron microscopy. Micrographs were scanned and the data were processed using Statistical Package for Social Sciences. The mean value and standard deviation were calculated and the Anova Multivariant Test was used.

The hybrid layer thickness average found was 3.23 µm (±0.53) in Group A, 3.13 µm (±0.73) in Group B, 2.53 µm (±0.50) in Group C, and 1.84 µm (±0.27) in Group D. Prime&;Bond NT® presented a more inconsistent hybrid layer.

The solvent seems to play a significant role in hybrid layer structure and thickness.     

EXPERIMENTAL STUDY OF GRAVITY-DRIVEN FILM FLOW OF NON-NEWTONIAN FLUIDS

In this research the problem of a thin layer of a power law liquid falling down an inclined plate was studied experimentally. Three different carboxymethyl cellulose (CMC) solution concentrations (1.1%, 1.5%, and 2%), which are extensively used in industry, have been selected as the operating fluid, and their rheology, surface tension, and contact angle have been determined. Dynamics of the falling film has been studied by image acquisition techniques, and by using image processing methods the velocity of falling film, film thickness, and the shape of the falling film have been investigated. The inclined plate with different inclination angles φ (0 < φ < π/2), and nonidentical surfaces (ceramic, aluminum, and glass) were used to study the effect of inclination, rheological properties, and contact angle on the vital parameters mentioned earlier. These variables are embedded in dimensionless groups, Weber (We), Reynolds (Re), and Froude (Fr) numbers, and some correlations were devised to relate dimensionless velocity distribution parameters and film thickness to these dimensionless groups.     

Effect of Calcium Salts of Glutaric Acid and Pimelic Acid on the Formation of β Crystalline Form in Isotactic Polypropylene

The effect of calcium glutarate (Cagt) and calcium pimelate (Capt) on the formation of β crystalline form in isotactic polypropylene (iPP) after isothermal crystallization at 130°C for 30 min has been investigated. The maximum K_WAXD and K_DSC values were 31.97% and 38.06%, respectively, for iPP doped with 0.2 wt.% Cagt. The maximum values of K_WAXD and K_DSC were 73.60% and 68.44% for iPP doped with 0.3 wt.% and 0.15 wt.% Capt, respectively. The crystal size of iPP doped with Capt is finer than that of iPP doped with Cagt. It is shown that the β nucleation ability of Capt is superior to that of Cagt. The difference in the β nucleation ability between Cagt and Capt is explained by the structural difference of the nucleators with β-iPP.     

Analysis of Physical and Thermodynamic Properties of Poly(2-Phenyl-1,3-Dioxolane-4-Yl-Methyl-Methacrylate-Co-Styrene) Polymer with Inverse Gas Chromatography

In this study, physical and thermodynamic properties of poly(2-phenyl-1,3-dioxolane-4-yl-methyl-methacrylate-co-styrene) (PDMMA-ST) were investigated by using inverse gas chromatography. Two groups of solvents with different chemical natures and polarities were used to obtain information about PDMMA-ST-solvent interactions: alcohols and alkanes. The specific retention volume (V_g ⁰), the sorption enthalpy (ΔH₁ ^S), sorption free energy (ΔG₁ ^S), sorption entropy (ΔS₁ ^S), the weight fraction activity coefficients of solute probes at infinite dilution (Ω ₁ ^∞), and Flory-Huggins interaction parameters (χ ₁₂ ^∞) between polymer and solvents were determined for the interactions of PDMMA-ST with alcohols and alkanes by inverse gas chromatography in the temperature range of 333–473 K. Also, the solubility parameters of PDMMA-ST at infinite dilution were found by plotting the graph of [(δ ₁ ²/RT) - χ ₁₂ ^∞/V₁] versus solubility parameters, δ ₁, of probes.     

Using a β-Cyclodextrin-functional Fe3O4 as a Reinforcement of PLA: Synthesis,Thermal, and Combustion Properties

In this work, Fe₃O₄ nanoparticles were chemically grafted with β-cyclodextrin (β-CD@Fe₃O₄). Fe₃O₄ nanoparticles were modified using N,N-dimethylformamide as a solvent, β-cyclodextrin as a modifier, and 3-glycidoxypropyltrimethoxysilane as a coupling agent at room temperature. The obtained modified Fe₃O₄ were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis techniques. β-CD@Fe₃O₄ was incorporated into a poly(lactic acid) matrix to prepare new green nanocomposites with modified properties. β-CD@Fe₃O₄ showed good dispersion in the poly(lactic acid) matrix and thermal and combustion properties of the nanocomposites were improved.     

The Effect of Hydrotalcite Content in Microporous Composite Membrane on Gas Permeability and Permselectivity

Microporous silica membrane containing hydrotalcite (HT) was prepared successfully without losing the former’s molecular sieving property. The microporous HT-silica membrane (200 nm in thickness) was formed on the surface of mesoporous γ-alumina layer (9 μm in thickness) and supported by macroporous α-alumina substrate (ca. 2 mm in thickness). The pore size of the microporous HT-silica membrane was 8.5Å, slightly larger than the pristine silica membrane (5Å). The composite membrane was found to enhance the permeability of gases and permselectivity of carbon dioxide from gas mixture comprising methane, hydrogen or nitrogen. Microporous HT-silica membrane with 15 vol.% HT displayed the highest permselectivities in the order of CO₂/CH₄ > CO₂/N₂ > CO₂/H₂ and the permselectivities decreased with increasing HT content.     

PREDICTION OF CO2 FREEZE-OUT CONDITIONS AND CO2 HYDRATE FORMATION CONDITIONS WITH A SINGLE EQUATION OF STATE

A recent study by Eggeman and Chaffin (2005 Eggeman , T. , and Chafin , S. ( 2005 ). Beware of pitfalls of CO₂ freezing predictions , Chem. Eng. Prog. , 101 ( 3 ), 39 – 44 . [Google Scholar]), which showed large discrepancies in CO₂ freeze-out conditions as predicted by several commercial simulators, prompted a reexamination of using the TBS equation of state for phase equilibrium calculations involving solids. Salim and Trebble (1994 Salim , P. , and Trebble , M. A. ( 1994 ). Modelling of solid phases in thermodynamic calculations via translation of a cubic equation of state at the triple point , Fluid Phase Equilib. , 93 , 75 – 99 .[Crossref] , [Google Scholar]) had previously presented a methodology for extending the Trebble-Bishnoi-Salim (TBS) equation of state (Salim, 1990 Salim , P. ( 1990 ). A modified Trebble-Bishnoi equation of state, M.Sc. thesis , University of Calgary . [Google Scholar]) to calculations involving a solid phase. In this study, the CO₂ freeze-out conditions in CO₂/CH₄ and CO₂/C₂H₆ mixtures are calculated from the TBS equation of state, and it is shown that they provide a better data fit than the traditional Poynting correction method. Furthermore, since the use of an equation of state in SLE/SVE calculations does not require the explicit assumption of a pure solid phase, the model was assessed for its ability to correlate CO₂ gas hydrate equilibrium conditions. Gas hydrates were simply treated as an impure solid phase, and it was seen that the predictions of gas hydrate equilibrium were in very good agreement with the experimental data. Computationally, the use of the TBS equation of state has the advantage, over the model of Yokozeki (2005 Yokozeki , A. ( 2005 ). Methane gas hydrates viewed through unified solid-liquid-vapour equation of state , Int. J. Thermophys. , 26 ( 3 ), 743 – 765 . [Google Scholar]), that it does not require a modifying factor (c_b) in the repulsive term to handle the presence of hydrates; they are instead handled using a unique binary interaction parameter for the hydrate phase.     

RELEASE OF β-GALACTOSIDASE FROM INDIGENOUS LACTOBACILLUS ACIDOPHILUS BY ULTRASONICATION: PROCESS OPTIMIZATION

Lactobacillus acidophilus isolated indigenously from Eleusine coracana has been reported by us to be a good producer of β-galactosidase (Akolkar et al., 2005 Akolkar , S. K. , Sajgure , A. , and Lele , S. S. ( 2005 ). Lactase production from Lactobacillus acidophilus , World J. Microbiol. Biotechnol. , 21 , 1119 – 1122 .[Crossref], [Web of Science ®] , [Google Scholar]). Recovery of this intracellular enzyme using ultrasonication was found to be the rate-limiting step for subsequent downstream processing. Among the various chemical and mechanical methods tried, ultrasonication was found to be the most effective. However, prolonged ultrasonication can result in partial to complete degradation of the released enzyme. This article reports the optimization of the ultrasonication process for release of β-galactosidase using response surface methodology (RSM). Factors like cell density, sample volume, and ultrasonication time, which were critical for the release of the enzyme at a constant acoustic power, were considered in the optimization to develop an efficient release process. Increase in the release of β-galactosidase from 320 U/gm DCW to 483 ± 1.9 U/gm DCW was achieved at the optimized ultrasonic process conditions (cell density 2.1% wet weight, suspension volume 11 mL, and ultrasonication time 15 min) at a constant acoustic power of 50 W.     

Studies on the Preparation of Polystyrene Thermal Conductivity Composites

Various thermally conductive fillers including aluminum oxide(Al₂O₃), magnesium oxide(MgO), β-silicon carbide particle(β-SiCp) and β-silicon carbide whisker(β-SiCw) were used to prepare polystyrene thermal conductivity composites. Experimental results showed that, for given filler loading, the thermal conductivity of the composites was higher for PS flake than that of PS particle, and the thermal conductivity was optimal by powder blending method. The SiCw filler was more favorable to improve the thermal conductivity of the composites; a much higher thermal conductivity of 1.18 W/mK could be achieved for the composite with 40 vol% SiCw, about six times higher than that of native polystyrene. The experimental thermal conductivity values were in agreement with those predicted by lower bound of Maxwell-Eueken model. For given SiC loading, the thermal conductivity increased with the increasing shape parameter of n. The SiCw was much easier to form the thermal conductivity chains and network than that of SiCp.     

Extraction and Separation of α-lactalbumin and β-Lactoglobulin from Skim Milk by Microfiltration and Ultrafiltration at High Shear Rates: A Feasibility Study

Abstract

This paper presents a two-stage membrane filtration process for extracting and separating α-Lactalbumin (α-La) and β-Lactoglobulin (β-Lg), from UHT skim milk, using dynamic filtration. The 1st stage separates casein micelles in retentate from whey proteins in the permeate with rotating 0.2 µm pores ceramic membrane disks. Casein micelles rejection was excellent, while α-La and β-Lg transmissions remained between 80 and 90%. The permeate flux at 40°C ranged from 105 to 40 Lh^?1m^?2 at a volume reduction ratio of VRR = 4. The 2nd stage consisted of ultrafiltration of the previous permeate with a metal disk rotating at 2000 rpm near a fixed 50 kDa PES membrane, in order to concentrate β-Lg in retentate, while collecting α-La in the permeate. The flux dropped from 270 Lh^?1m^?2 at VRR = 1, and remained nearly constant at 200 Lh^?1m^?2 until a VRR of 3.3. α-La transmission increased with VRR to reach 23% at VRR = 3.3, while β-Lg transmission decayed at increasing VRR to 3%, to give a maximum selectivity of 8.     

Morphological and Functional Expression of Fibroblast on Poly(lactide-co-glycolide)/β-Tricalcium Phosphate/Nature Bone

The in-vitro biocompatibility of degradable and bioactive composites consisting of poly(lactide-co-glycolide) (PLGA), β-tricalcium phosphate (β-TCP), and nature bone (NB) was investigated by culturing fibroblasts on the PLGA/β-TCP/NB substrates, and the cell morphology, proliferation, alkaline phosphatase (ALP) activity, and von Kossa mineralization were evaluated. The results showed that the incorporation of β-TCP and NB benefited fibroblasts attachment and the fibroblasts cultured on the PLGA/β-TCP/NB composite substrates spread better as compared to those on the pure PLGA after culturing for different times. MTT assay showed that the fibroblasts cultured on the PLGA/β-TCP/NB extraction revealed a higher proliferation rate than those on the pure PLGA extraction. ALP and von Kossa assay indicated that β-TCP and NB could promote biomineralization in vitro. All of the results showed that the addition of β-TCP and NB into PLGA could stimulate fibroblasts to proliferate and differentiate.     

CORROSION INHIBITION OF CARBON STEEL IN ACIDIC MEDIA BY BIFURCARIA BIFURCATA EXTRACT

The effect of extract of brown alga Bifurcaria bifurcata (Bb) on the corrosion of steel in 1 M HCl solution was studied using weight loss, potentiodynamic, and polarization resistance measurements. Experimental data revealed that Bb extract acted as an inhibitor in the acid environment. The extract was a mixed-type inhibitor, predominating as an anodic inhibitor at higher concentration. It was found that the inhibition efficiency increased with an increase in Bb extract concentration. The corrosion inhibition of Bb extract on carbon steel in 1 M HCl solution was also investigated by infrared and UV-visible spectrophotometry to obtain information on bonding mechanism between the metallic surface and the inhibitor. The process of inhibition is attributed to the adsorption of the extract molecules, the precipitation of Fe-chelates, and/or formation of complex at the electrode surface.     

Application and Comparison of High-Speed Countercurrent Chromatography and High Performance Liquid Chromatography in Preparative Enantioseparation of α-Substitution Mandelic Acids

This paper is mainly about extending research on application and comparison of preparative high-speed countercurrent chromatography (HSCCC) and preparative high performance liquid chromatography (HPLC) in chiral separations. Preparative enantioseparations of α-cyclopentylmandelic acid and α-methylmandelic acid by HSCCC and HPLC were compared using hydroxypropy-β-cyclodextrin (HP-β-CD) and sulfobutyl ether-β-cyclodextrin (SBE-β-CD) as the chiral mobile phase additives. In preparative HPLC the enantioseparation was achieved on the ODS C₁₈ reverse phase column with the mobile phase composed of a mixture of acetonitrile and 0.10 mol L^?1 phosphate buffer at pH 2.68 containing 20 mmol L^?1 HP-β-CD for α-cyclopentylmandelic acid and 20 mmol L^?1 SBE-β-CD for α-methylmandelic acid. The maximum sample size for α-cyclopentylmandelic acid and α-methylmandelic acid was only about 10 mg and 5 mg, respectively. In preparative HSCCC the enantioseparations of these two racemates were performed with the two-phase solvent system composed of n-hexane-methyl tert.-butyl ether-0.1 molL^?1 phosphate buffer solution at pH 2.67 containing 0.1 mol L^?1 HP-β-CD for α-cyclopentylmandelic acid (8.5:1.5:10, v/v/v) and 0.1 mol L^?1 SBE-β-CD for α-methylmandelic acid (3:7:10, v/v/v). Under the optimum separation conditions, totally 250 mg of racemic α-cyclopentylmandelic acid could be completely enantioseparated by HSCCC with HP-β-CD as a chiral mobile phase additive in a single run, yielding 114-116 mg of enantiomers with 98-99% purity and 89-92% recovery. But, no complete enantioseparation of α-methylmandelic acid was achieved by preparative HSCCC with either of the chiral selectors due to their limited enantioselectivity. In this paper, preparative enantioseparation by HSCCC and HPLC was compared from various aspects.     

Study on the Preparation and Characterization of Biodegradable Polylactide/SiO2–TiO2 Hybrids

In this study, the silicic acid produced from sodium metasilicate hydrate and titanium tetraisopropylate were chosen as the ceramic precursors for the modification of biodegradable polylactide (PLA) through an in situ sol-gel process and the melt blending method. In addition, acrylic acid grafted polylactide (PLA-g-AA) was studied as an alternative to PLA. Hybrids were characterized by Fourier transform infrared spectroscopy, ²⁹ Kumar , P. ; Badrinarayanan , M.S. ; Sastry , M. Nanocrystalline TiO₂ studied by optical, FTIR and X-ray photoelectron spectroscopy: correlation to presence of surface states . Thin Solid Films 2000 , 358 , 122 – 130 .[Crossref], [Web of Science ®] , [Google Scholar]Si solid-state nuclear magnetic resonance (NMR), thermogravimetry analysis (TGA), scanning electron microscope (SEM), and Instron mechanical tester. The result was that properties of the PLA-g-AA/SiO₂–TiO₂ hybrid were superior to those of the PLA/SiO₂–TiO₂ hybrid. This was because the carboxylic acid groups of acrylic acid acted as coordination sites for the silica-titania phase to allow the formation of stronger chemical bonds. The ²⁹ Kumar , P. ; Badrinarayanan , M.S. ; Sastry , M. Nanocrystalline TiO₂ studied by optical, FTIR and X-ray photoelectron spectroscopy: correlation to presence of surface states . Thin Solid Films 2000 , 358 , 122 – 130 .[Crossref], [Web of Science ®] , [Google Scholar]Si solid-state NMR showed that Si atoms coordinated around SiO₄ units were predominantly Q₃ and Q₄. The 10 wt.% SiO₂–TiO₂ content gave the maximum values of tensile strength and glass transition temperature in PLA/SiO₂–TiO₂ and PLA-g-AA/SiO₂–TiO₂ both because excess SiO₂–TiO₂ particles caused separation between the organic and inorganic phases.