Softening phenomenon by remilling of styrene–butadiene copolymer rubber–general-purpose polystyrene resin blend

The softening phenomenon by remilling of uncured blends of various commercia styrene—butadiene copolymer rubber (styrene content, 23.5 to 48 wt-%, styrene block 0 to 18 wt-%) with general-purpose polystyrene resin was mainly studied by examining the blend ratio dependence of hardness and compression modulus (in logarithmic form), with special attention to the state of dispersion of the polymers. It was found that the blend of styrene—butadiene copolymer rubber with general-purpose polystyrene resin forms a microheterogeneous polymer blend system and that the hardness and the compression modulus change in S-shaped curves versus blend ratio. However, the degree of softening phenomenon by remilling (roll surface temperature, 70°–90°C) was found to be different for the two blend systems, i.e., random styrene—butadiene copolymer rubber and block styrene—butadiene copolymer rubber. The softening phenomenon is more pronounced in random-type rubbers; and in some block-type rubbers, no softening phenomenon was observed. The influence of the styrene content of the polymer is small. Further discussions have shown us that the strong interaction between the polystyrene block of the copolymer and the styrene homopolymer of the general-purpose polystyrene resin controls the state of dispersion of polymers thereby causing this difference in the softening phenomena among the different kinds of styrene—butadiene copolymer rubbers.     

Origin of Grain-Boundary Diffusion in MgO

Preferential diffusion of Ni²⁺ and Co²⁺ along grain boundaries was observed in certain bicrystals of MgO. This enhancement is attributed to impurity segregation at the boundary. The identified impurities responsible for the effect are the principal impurities in the single-crystal MgO: Ca, Si, and Fe. No enhancement was observed in any bicrystal prepared above 1300°C, a temperature similar to that at which studies of the mechanical properties of MgO have implied a reabsorption of impurity precipitates into solid solution. It is concluded that enhanced grain-boundary diffusion of cations in MgO is an extrinsic, rather than an intrinsic, property of the boundary.     

Refractories with a Boron nitride base

Conclusions A technique for the reaction sintering of a new refractory made of 82–83% boron nitride and 17–18% graphite has been developed.The refractory possesses high specific resistance up to 1500–1800°, a low coefficient of thermal expansion, a moderative evaporation rate in a vacuum, satisfactory strength and machinability, as well as high resistance to cryolite-aluminum melts, borate, chloride and also silicide and boron-silicon alloy melts (at between 900 and 2000°).     

Control of neutral delay linear systems using feedback with dynamic structure

To solve the problem of modal controllability of linear autonomous systems of neutral type, a new class of linear difference-differential controllers with feedback of dynamic structure is proposed. The construction principle of these controllers is based on the use of aftereffect in the control action. The domain of application of such controllers includes systems that do not possess the modal controllability property in the class of conventional classes of feedback controllers of constant structure.     

Preparation of 6FDA-based polyimide composite membrane by CVDP process

Preparation of polyimide composite membranes by a chemical vapor deposition and polymerization process (CVDP) was studied for the development of pervaporation or gas separation membranes. Hexafluoroisopropylidene-2,2-bis [phethalic acid anhydride] (6F-dianhydride) (6FDA) and 4,4′-diaminodiphenyl ether (ODA) were used as monomers and were simultaneously deposited on an asymmetric polyimide membrane in vacuum of 10⁻⁶ Torr. The deposited layer of the monomers was converted to polyimide by heating at 250°C at 3 h in an ordinary vacuum oven, and its separation performance for water-ethanol and CO₂−N₂ systems was characterized.     

Heat transfer to laminar flow with temperature — dependent heat generation

Two problems were solved theoretically on the heat transfer to circular tube flow with internal heat source. The one problem is to maintain the mixed-mean temperature of fluid at the inlet temperature. The other is a conjugated problem with a uniformly specified temperature at the outside surface of the wall, accounting for the wall conduction. From the numerical example for the former, it is shown that the mixed-mean temperature can be controlled within 15% error under the estimated condition. From the numerical results for the latter, it is concluded that the influence of wall conduction is more serious than the case without heat generation.     

Influence of genetics,environment and admixtures on low erucic acid rapeseed in Canada

Single plant isolates in theBrassica napus andBrassica campestris species of rapeseed yielded glyceride oil containing small amounts of erucic acid. Agronomically suitable varieties were grown commercially in 1971 as the first phase in a changeover of Canadian rapeseed production from varieties with erucic contents of 20–45% to low erucic acid varieties. A program to monitor the erucic content by gas chromatographic analysis in the stages of production, handling and transportation from seed to export shipment was undertaken to evaluate the effects of genetics, environment and admixture. The individual increase in erucic content ranged from 0.5 to 1.0, resulting in total increases of 1–2%. NRCC No. 13471. One of six papers presented in the symposium “Rapeseed Marketing and Breeding,” AOCS Meeting, Ottawa, September 1972.     

Grafting onto polyester fibers. III. Electrokinetic properties of acrylic acid and acrylonitrile-grafted polyester fibers in the presence of cationic dyes

The electrokinetic properties such as zeta potential, surface charge density, and surface conductivity of polyester fibers grafted with acrylic acid and acrylonitrile were measured when cationic dye solutions were streamed through. The presence of the cationic dyes on the surface of the fibers and their specific adsorption at the carboxylic groups in the acrylic acid graft copolymer produce lowering of zeta potential. The decrease in surface charge density as the percent graft increases is due to the decrease in surface area of the fibers due to the adsorption of the cationic dyes. The same trend is observed with acrylonitrile-grafted fibers. The surface conductivity of the acrylonitrile-grafted polyester fibers increases with increase in dye concentration of the streaming solution. The results for the 27.4% grafted sample differed from those of the 7.32% and 12.1% grafts, which is indicative of the formation of a three-dimensional network causing change in both the physical structure as well as the chemical nature of the surface of the substrate.     

Studies of structure and cycleability of LiMn2O4 and LiNd0.01Mn1.99O4 as cathode for Li-ion batteries

Lithium manganese oxides LiMn₂O₄ and rare earth elements doped LiNd_0.01Mn_1.99O₄ were synthesized by microwave method. The structure and the electrochemical performances of the samples were characterized. XRD data shows both samples exhibit the same pure spinel phase. But due to the introduction of Nd³⁺ ion into the unit cell, the lattice parameter of the Nd-doped spinel was larger than that of the undoped one. The two samples had a similar morphology including small particle size and homogeneous particle distribution as tested by SEM. The cyclic voltammmetry and constant-current charge-discharge tested that Nd-doped spinel displayed a better reversibility and cycleability.     

Effect of different acids with Δ9,12-dienoic structures on Δ9 desaturation activity in rat liver microsomes

The effect of oral administration, for 24 or 48 hr, of different octadeca fatty acids containing a 9,12-dienoic structure on the fatty acid composition and Δ9 desaturation activity of liver microsomes of rat fed a fat-free diet was studied. The ethyl esters of linoelaidic and γ-linolenic acids, the methyl ester of linoleic acid and free columbinic acid were administered to rats maintained on a fat-free diet. The supplementation of the fat-free diet with linoelaidate produced no relevant changes in the fatty acid composition pattern of liver microsomes and did not modify the percentage of conversion of palmitic to palmitoleic acid. The addition of linoleate or γ-linolenate to the fat-free diet returned liver microsome Δ9 desaturation activity toward the control and partially restored the liver microsome fatty acid spectrum found in the fat-free diet. Columbinic acid (5-trans-9-cis,12-cis-18∶3), which cannot be transformed into arachidonic acid, also decreased the Δ9 desaturation activity enhanced by the fat-free diet and evoked changes in the microsomal fatty acid composition similar to those produced by the ω6 fatty acids. These results suggest that the modulation of Δ9 desaturase activity evoked by dietary administration of unsaturated acids of ω6 series would depend on thecis double bond configuration of these acids.