THE PARTICLE SIZE DISTRIBUTION OF TYPICAL FELDSPARS AND FLINTS1

The results of particle size analyses of a number of commercial feldspars and flints by the sedimentation method are reported. A comparison of batch and continuous grinding is given as well as a study of the progress of ball mill grinding.     

POROSITY: V. RECOMMENDED PROCEDURES FOR DETERMINING POROSITY BY METHODS OF ABSORPTION

Detailed Procedure. —For shaped test pieces details of the procedure are given under the headings. “Preparation of Test Piece.”“Determination of Dry Weight,”“The Absorption Apparatus,”“Preparation of Standard Vaseline,”“Saturation Procedure,”“Calculation,” and “True Density.” A Pycnometer Method. —A new and accurate method, which is applicable equally to shaped test pieces or to granular material, is described. Among other advantages it gives the operator control over the max. size opening which he desires to class as part of the pore space. It also can be made to indicate directly the necessary soaking period.     

Linear dynamic mechanical properties of an SBS block copolymer

Dynamic viscosity and elastic modulus for a low molecular weight styrene-butadiene-styrene (SBS) block copolymer ate measured as a function of temperature (80-170°C) and frequency using the eccentric rotating disc geometry. These linear properties are superimposed to yield master curves each of which exhibits two branches below different (critical) reduced frequencies. At lower temperatures, the non-Newtonian behavior characteristic of SBS block copolymers is observed. In contrast, Newtonian response occurs at higher temperatures. As a consequence, plots of the viscoelastic properties vs temperature exhibit discontinuities below the critical frequencies, reflecting a narrow transition at about 142°C. Above this temperature, it is inferred, consistent with the equality of dynamic and steady state viscosities, that the polystyrene (S) blocks, existent in dispersed domains at low temperatures, exceed a critical degree of compatibility with the continuous polybutadiene phase. The activation energies indicate that the S blocks affect the temperature dependence of the dynamic properties in proportion to their presence in an interphase which is assumed to continuously grow in size as temperature is raised to the transition temperature. Below the critical reduced frequencies, it is inferred that S domain disruption may increasingly occur in conjunction with the observed property enhancement due to these domains, relative to the miscible blocks, as reduced frequency is lowered. However, above these frequencies, the presence of frequency-temperature superposition implies that the S domains and the miscible blocks are equivalent in their effects on properties. At still higher reduced frequencies, the domains present at the low temperatures studied are assumed to remain intact, but plateau behavior similar to the response characteristic of homopolymers is observed.     

Effects of hexadecylphosphocholine on protein kinase C and TPA-induced differentiation of HL60 cells

Several structural analogs of alkylphosphocholine (APC) were studied for their effects on protein kinase C (PKC) and 12-O-tetradecanoylphorbol-13-acetate (TPA) elicited biochemical and cellular events in HL60 cells. Hexadecylphosphocholine (He-PC₂), the APC prototype, inhibited PKC competitively with respect to phosphatidylserine and noncompetitively with respect to CaCl₂, both with an apparent K_i of about 15 μM. Inhibition of PKC by He-PC₂ was selective, since cyclic AMP dependent protein kinase and Ca²⁺/calmodulin dependent protein kinase II were relatively unaffected. He-PC₂ inhibited TPA-induced depletion of PKC and TPA-stimulated phosphorylation of cellular proteins in HL60 cells. TPA-induced differentiation of HL60 cells was also inhibited by He-PC₂, and this inhibition was synergistic or additive to the effects of 1-(5-isoquinoline-sulfonyl)-2-methylpiperazine (H-7), a PKC inhibitor. The present findings are consistent with the hypothesis that inhibition of PKC might be related, in part, to the antineoplastic effect of He-PC₂ and ether lipid analogs such as ET-18-OCH₃ (1-octadecyl-2-methyl-glycero-3-phosphocholine).     

Aldol condensation of butanal over alkali metal zeolites

Alkali metal zeolites and metal oxides were used for the aldol condensation of n-butanal to 2-ethyl-2-hexenal. The order of activity at 150 °C and 1 atm. was: CsNaY > NaY > LiNaY > MgO >Al₂O₃. Selectivity to 2-ethyl-2-hexenal was 100% for both pure and mixed isomer feed. Infrared spectroscopic studies showed that stable catalysts were produced by propene pretreatments which blocked Lewis acid sites. Adsorption of ammonia and carbon dioxide on CsNaY during aldol condensation of n-butanal causes a decrease in rate. This result, along with the order of activity, suggests that the presence of both acid and basic sites produce higher activity than strongly basic MgO.Work performed at San Jose State University.     

Microstructure of high modulus solid state extruded polyethylene: 2. X-ray scattering studies of 12, 24 and 36 extrusion draw ratio

The microstructure of a series of solid state extruded polyethylene fibres was examined by wide- and small-angle X-ray scattering. By measuring absolute intensities using a two dimensional position sensitive detector, accurate values of the small-angle invariant for anisotropic samples were obtained. This measurement coupled with wide-angle X-ray scattering and d.s.c. permitted determination of the density of the noncrystalline component. The use of a two phase model for solid state extruded polyethylene is justified if consideration is given to the effective densities of the crystalline and noncrystalline phases, which change with deformation. The effective density of the crystalline phase decreases by 1% (0.999–0.990 g cm^?3) from the unextruded billet compared to a 36 draw ratio extrudate, while the noncrystalline phase density increases by 6% (0.84–0.89 g cm^?3). These changes lead to an overall decrease in the mean squared electron density fluctuation of 63%. The average axial crystallite length measured by wide-angle X-ray scattering increases with extrusion draw ratio while the SAXS long period decreases and weakens considerably. These observations and the electron microscopy results from the previous paper, (Polymer, 1982, 23, 1069), are fully consistent with the key features of the Peterlin model of fibre microstructure.     

Neutron Reflectometry Characterization of Interface Width between Sol-Gel Titanium Dioxide and Silicon Dioxide Thin Films

Neutron reflectometry (NR) was used to directly measure the interface width between a titanium dioxide and a silicon dioxide film deposited by sol-gel processing. In a bilayer heated to 450°C, NR measurements showed that the interface width is 0.8 nm. This width is the same as the roughness of a sol-gel silicon dioxide surface after the same heat treatment, suggesting no interdiffusion or mixing at the bilayer interface.     

Vinyl composites—fiberglass reinforced PVC

Glass fiber reinforced PVC has several distinctive and useful properties. Its tensile strength can be twice that of unreinforced PVC. Excellent coupling of the glass fibers to the PVC matrix is required for good retention of tensile strength when exposed to warm water, Its modulus can be twice that of unreinforced PVC and equal to that of wood. PVC's high load carrying capability is not significantly increased to higher temperatures by adding glass fibers as judged by its 264 psi heat deflection temperature. However, by changing the polymeric matrix, glass reinforced vinyl with an increased HDT of 86°C has been produced for higher use temperature. The coefficient of linear thermal expansion of PVC can be cut in half by the addition of glass fibers and has a coefficient equal to that of aluminum. Glass fiber reinforced PVC has exceptionally good resistance to crack propagation and resists shattering as judged by sawing, punching, stapling, and hammering. When properly formulated for weathering resistance, glass fiber reinforced PVC has good color retention, impact retention, and outstanding dimensional stability. As for all glass fiber reinforced plastics, processing equipment must be built for high abrasion resistance for long economical manufacturing runs.     

Catalytic effect of mineral matter of high ash onakawana lignite on steam gasification

Reactivities of untreated and acid washed Onakawana lignite during steam gasification were compared in a thermo-balance reactor. The acid treatment resulted in removal of Ca, Mg, Ba and Sr from mineral matter. This was accompanied by a marked decrease in the rates of H₂, CO and CO₂ formation. The decrease of gasification rate was attributed to the decrease in concentration of gasification sites during the acid treatment.     

Cyclic fatty acid monomer: Isolation and purification with solid phase extraction

The application of a combined solid phase extraction (SPE)/clean-up procedure to the isolation of a purified fraction containing all the monomeric cyclic fatty acid methyl esters is described. Extraction of the nonpolar lipid components from nonurea-adducting (NUA) filtrates is performed on a reverse phase octadecyl bonded silica minicolumn. Stepwise elution of the SPE-retained materials through silica gel using several solvents allowed the separation of a pure fraction containing the cyclic monomers that can be used for a more reliable quantitative estimation of these compounds in edible fats and oils.