Keeping properties of edible oils—Part I. The use of accelerated tests for assessment of the keeping properties of oils and the value of antioxidants

Assessment of oil quality by two accelerated oxidation tests gave little or no correlation with organoleptic asessment during storage. Improvements in quality of oils refined in the factory, to which antioxidants had been added, are indicated by the accelerated tests but are not reproduced in normal storage. Howver a treatment of the oils with alumina, as a part of the refining process replacing earth bleaching, appears to remove antagonistic factors, and under these circumstances the addition of antioxidant has a pronounced effect.     

A circuit design for a motor-speed controller of high precision

A design for a motor-speed controller of low cost and high precision, is presented. It makes possible the regulation of the rotation speed of a series-wound electric motor to an accuracy of ± 1.5 rpm over the range 15 to 5000 rpm. The design incorporates a digital display of the rotation speed, and provides for the programming of the speed by an external voltage source.     

Substrate-mediated interactions and intermolecular forces between molecules adsorbed on surfaces

Adsorbate interactions and reactions on metal surfaces have been investigated using scanning tunneling microscopy. The manners in which adsorbates perturb the surface electronic structure in their vicinity are discussed. The effects these perturbations have on other molecules are shown to be important in overlayer growth. Interactions of molecules with surface steps are addressed, and each molecule's electron affinity is shown to dictate its adsorption sites at step edges. Standing waves emanating from steps are demonstrated to effect transient molecular adsorption up to 40 A away from the step edge. Halobenzene derivatives are used to demonstrate how the surface is important in aligning reactive intermediates.     

Redox Reactions of Thallium Clusters in Aqueous Solution

The redox chemistry of thallium clusters in aqueous solution has been investigated by pulse radiolysis and γ-radiolysis. Using Ru(bpy)₃²⁺ as a redox indicator, it is shown that the redox potential of the Tl₄^2+/+ couple is more positive than −1.27 V NHE, and that the Tl⁺/Tl₂⁺ couple's redox potential is more negative than −1.27 V NHE. Ru(bpy)₃⁺ reduces Tl₄²⁺ with a second-order rate constant of 6±2 × 10⁸ M⁻¹s⁻¹. Metallic particles of thallium are predicted to have a surface plasmon absorption band at 205 nm in water. The reduced Tl content in a sol can be measured by air-free titration with CCl₄ or methylviologen.     

Phase behavior of blends of aliphatic polyesters with a vinylidene chloride/vinyl chloride copolymer

A series of aliphatic polyesters having CH₂/COO ratios from 2 to 14 in their repeat units were blended with a copolymer of vinylidene chloride containing 13.5% by weight of vinyl chloride. Blends of polyesters having CH₂/COO < 4 did not form completely miscible amorphous phases, whereas polyesters having CH₂/COO ≥ 4 did form completely homogeneous amorphous phases for all temperatures below the decomposition point except for the polyester with CH₂/COO = 14 which showed reversible phase separation on heating, i.e., lower critical solution temperature behavior. Interaction parameters were estimated by melting point depression and by analog calorimetry. The behavior reported here is qualitatively similar to that reported earlier for blends of aliphatic polyesters with poly(vinyl chloride), polyepichlorohydrin, polycarbonate, styrene–allyl alcohol copolymers, and the hydroxy ether of bisphenol A.     

Flow regime, hydrodynamics, floc size distribution and sludge properties in activated sludge bubble column, air-lift and aerated stirred reactors

This paper presents a comparative study how reactor configuration, sludge loading and air flowrate affect flow regimes, hydrodynamics, floc size distribution and sludge solids-liquid separation properties. Three reactor configurations were studied in bench scale activated sludge bubble column reactor (BCR), air-lift reactor (ALR) and aerated stirred reactor (ASR). The ASR demonstrated the highest capacity of gas holdup and resistance, and homogeneity in flow regimes and shearing forces, resulting in producing large numbers of small and compact flocs. The fluid dynamics in the ALR created regularly directed recirculation forces to enhance the gas holdup and sludge flocculation. The BCR distributed a high turbulent flow regime and non-homogeneity in gas holdup and mixing, and generated large numbers of larger and looser flocs. The sludge size distributions, compressibility and settleability were significantly influenced by the reactor configurations associated with the flow regimes and hydrodynamics.     

Chlorinated polyethylene modification of blends derived from waste plastics Part I: Mechanical behavior

Recycling of waste plastics as a blend of generic types is attractive since a difficult separations problem is avoided. However, blends of incompatible polymers are frequently very brittle and cannot be considered for many applications. Additives which modify the blend to give it ductility may provide a solution to this problem. Chlorinated polyethylene (CPE) made by a slurry process has been suggested for this application by Schramm and Blanchard. Further documentation of the effectiveness of this approach is given here. Addition of CPE to such a blend generally increases the elongation at break and the energy to break very dramatically with ordinarily some loss in strength and modulus. This approach works most effectively in blends of high polyethylene and poly(vinyl chloride) content. Three grades of CPE were studied here which revealed that the specific structure of the CPE molecule is a factor. The effectiveness of CPE for blend modification is believed to derive from the graded molecular structure acquired during chlorination.     

Polyester–polycarbonate blends. V. Linear aliphatic polyesters

Polycarbonate blends with the linear aliphatic polyesters poly(ethylene succinate) (PES), poly(ethylene adipate) (PEA), poly(1,4-butylene adipate) (PBA), and poly(hexamethylene sebacate) (PHS) were prepared by solution casting. Blends containing PES, PEA, and PBA exhibited a single T_g by DSC and thus form a single, miscible amorphous phase with polycarbonate. However, blends containing PHS exhibited only partial miscibility. Crystallinity of the polyesters was reduced by mixing with polycarbonate; however, plasticization by the polyesters induced crystallization of the polycarbonate. Miscibility in these systems is the result of an exothermic heat of mixing stemming from an interaction of the carbonyl dipole of the ester group with the aromatic carbonate. The effect of polyester structure on miscibility with polycarbonate is interpreted by and correlated with heats of mixing obtained by direct calorimetry of low molecular weight liquid analogs of the polymers.     

Aryl phosphate ester fire‐retardant additive for low‐smoke vinyl applications

Additives that act as flame retardants can contribute significantly to smoke generation because they decrease the efficiency of the fuel source and, as a result, create a sooty combustion. Work on a new phosphate ester material has shown interesting results and synergies that complement both flame retardancy and low smoke generation in flexible vinyl compositions. This new proprietary aryl phosphate was examined in both neat and blended systems and compared to other typical phosphate ester fire‐retardant (FR) compounds for vinyl. Additionally, the flammability and smoke effects were measured with and without other common vinyl FR additives (zinc borate and ammonium octamolybdate). J. Vinyl Addit. Technol. 10:187–192, 2004. © 2004 Society of Plastics Engineers.     

Phase behavior for blends of styrene containing triblock copolymers with poly(2,6-dimethyl-1,4-phenylene oxide)

The extent to which the styrene end-blocks of three commercially available triblock copolymers can mix with a particular poly(2,6-dimethyl-1,4-phenylene oxide) (M_n = 22,600 and M_w = 34,000) or PPO has been examined by investigation of the glass transition behavior of the PPO and polystyrene (PS) portions of the blends using differential scanning calorimetry. Each block copolymer has a butadiene-based mid-block which was hydrogenated for two of these materials, but not the third. The three copolymers differ substantially in overall molecular weight and in molecula weight of the blocks. However, in analogy with the literature on blends of homopolymer polystyrene with styrene-based block copolymers, the molecular weight of the PS block should be the principal factor affecting the phase behavior in the present blends. Mixtures of the PPO with the block copolymers having PS blocks with M = 14,500 (nonhydrogenated midblock) and with M = 29,000 (hydrogenated mid-block) exhibited single composition-dependent T_gs for the hard phase, indicating complete mixing of PS segments with the PPO, for all proportions. On the other hand, the block copolymer having a PS block with M = 7,500 and a hydrogenated mid-block exhibited two separate hard phase T_gs corresponding to an essentially pure PPO phase and a PS-rich phase. For blends of homopolymer PS with styrene-based block copolymers, the similar two-phase behavior of the glassy portion can be readily explained by entropic considerations. For the present case, the favorable enthalpic contribution for mixing PPO and PS is an additional factor which seems to influence the restrictions on molecular weight for complete mixing; however, additional work is needed to develop a more quantitative assessment of this new issue.