Polyacrylic acid macromolecule—complexed zinc phosphate crystal conversion coatings

When water-soluble polyacrylic acid (PAA) macromolecules are introduced into zinc phosphating liquids, significant improvements in the yield of conventional zinc phosphate conversion films deposited on carbon steel surfaces are obtained. The improvements include controllability of crystal dimensions, degree of crystallinity, and coating weight. The conversion layer formed is a composite microstructure consisting of a bulk PAA polymer and complexed PAA continuously overlaying a uniform array of fine dense zinc phosphate crystals. Interfacial studies of the composite layer using infrared spectroscopy, energy-dispersive X-ray spectrometry associated with scanning electron microscopy, and X-ray photoelectron spectroscopy indicated that the functional carboxylic acid groups in the PAA molecules were strongly chemisorbed by the Zn atoms at the outermost surface sites of the crystal layers. The intermolecular bridging action of the surface Zn atoms which connect the PAA and the zinc phosphate crystal layers results in good adhesion at the PAA–crystal interfaces. In addition, the plasticized complex formation plays an essential role in increasing the stiffness and the ductility of the normally conventional crystal films. The flexibility of the complex coating surface and the thickness and surface roughness of the thin PAA overlayer all affect the adhesive force at the interface between the organic polymer topcoat and the complexed coating.     

Antiplasticization. III. Characteristics and properties of antiplasticizable polymers

Antiplasticization is applicable to polymers which contain rigid, polar groups and stiff chains, such as many bisphenol polycarbonates and polyesters, 2,2,4,4-tetramethyl-1,3-cyclobutanediol polycarbonates and polyesters, cellulose triacetate, and a commercial poly(sulfone ether). The stiffness, hardness, and tensile strength of these polymers are increased by antiplasticizers, and the elongation, impact strength, and heat-distortion temperature are decreased. The stiffness of antiplasticized polymers can be further increased by crystallization. A clear, hard, stiff, tough, self-extinguishing molding plastic with good electrical properties and improved resistance to stress cracking is obtained by antiplasticizing bisphenol A polycarbonate with 20% Aroclor 5460.     

Short-term prediction of traffic flow using a binary neural network

This paper introduces a binary neural network-based prediction algorithm incorporating both spatial and temporal characteristics into the prediction process. The algorithm is used to predict short-term traffic flow by combining information from multiple traffic sensors (spatial lag) and time series prediction (temporal lag). It extends previously developed Advanced Uncertain Reasoning Architecture (AURA) k-nearest neighbour (k-NN) techniques. Our task was to produce a fast and accurate traffic flow predictor. The AURA k-NN predictor is comparable to other machine learning techniques with respect to recall accuracy but is able to train and predict rapidly. We incorporated consistency evaluations to determine whether the AURA k-NN has an ideal algorithmic configuration or an ideal data configuration or whether the settings needed to be varied for each data set. The results agree with previous research in that settings must be bespoke for each data set. This configuration process requires rapid and scalable learning to allow the predictor to be set-up for new data. The fast processing abilities of the AURA k-NN ensure this combinatorial optimisation will be computationally feasible for real-world applications. We intend to use the predictor to proactively manage traffic by predicting traffic volumes to anticipate traffic network problems.     

High-Thermal-Conductivity Aluminum Nitride Ceramics: The Effect of Thermodynamic, Kinetic, and Microstructural Factors

Improvement in the thermal conductivity of aluminum nitride (AlN) can be realized by additives that have a high thermodynamic affinity toward alumina (Al₂O₃), as is clearly demonstrated in the aluminum nitride-yttria (AlN-Y₂O₃) system. A wide variety of lanthanide dopants are compared at equimolar lanthanide oxide:alumina (Ln₂O₃: Al₂O₃, where Ln is a lanthanide element) ratios, with samaria (Sm₂O₃) and lutetia (Lu₂O₃) being the dopants that give the highest- and lowest-thermal-conductivity AlN composites, respectively. The choice of the sintering aid and the dopant level is much more important than the microstructure that evolves during sintering. A contiguous AlN phase provides rapid heat conduction paths, even at short sintering times. AlN contiguity decreases slightly as the annealing times increase in the range of 1–1000 min at 1850°C. However, a substantial increase in thermal conductivity results, because of purification of AlN grains by dissolution-reprecipitation and bulk diffusion. Removal of grain-boundary phases, with a concurrent increase in AlN contiguity, occurs at high annealing temperatures or at long times and is a natural consequence of high dihedral angles (poor wetting) in liquidphase-sintered AlN ceramics.     

Adhesion aspects of levulinic-acid-modified furan polymers to crystalline zinc phosphate metal surfaces

The nature of the interfacial interactions between functional levulinic-acid-modified furan resin coatings and crystalline zinc phosphate hydrate films deposited on carbon steel surfaces has been systematically investigated. The typical surface topography of the highly crystallized zinc phosphate films was found to be characterized by the presence of a dendritic microstructure array of interlocking triclinic crystals. This structure acts significantly to develop mechanical interlocking bonds with the functional blend polymer which penetrates into the open surface structure of the films. Both the thickness of deposition film and the polar H₂O molecules of hydrate at the outermost film surface sites play essential roles in wetting by the functional liquid resin. When the polarized furan polymers spread on the oxide film surfaces, the carboxylate groups derived from the levulinic ester and acid molecules react to form strong hydrogen bonds with the crystallized H₂O molecules on the hopeite film. This formation of hydrogen bonding was shown to be a major factor affecting the chemical intermolecular attractions. A formulation consisting of 95 parts furan to 5 parts levulinic acid was found to yield the optimum protective coating. More than 5 parts levulinic acid resulted in the transformation of the characteristics of the polymer film from hydrophobic to hydrophilic.     

Dicyandiamide precipitation in epoxy solutions and latex dispersions: threshold concentration analysis using a two-stage drying model

We examined drying in solventborne and waterborne latex impregnating resins using gravimetric methods, focusing on the precipitation of dicyandiamide (DICY) curing agent during coalescence, in neat resin films and glass-reinforced composites. A two-stage drying model was applied to the drying data yielding a threshold concentration for DICY surface segregation in latex epoxy to be between 3 and 4.5 wt%. Faster drying kinetics correlated with reduced surface DICY segregation. Drying model results show the rapid coalescence of both a ‘skin’ layer in the drying latex and trapped DICY within the lattice before its conveyance to the surface by percolating water. The presence of dispersed obstructions led to deviations from the latex drying model, particularly at higher DICY concentrations as more DICY crystallized.     

An ion-exchange process with thermal regeneration XVI oxygen-resistant polyamine resins

The rate of oxidation (by dissolved oxygen) of a number of weakly basic ion-exchange resins has been determined at 80°C. Polystyrene-based systems with only tertiary or only secondary amino groups are the most resistant to oxidation. The presence of a mixture of primary, secondary and tertiary amino groups or of hydroxyalkylamino groups increases the rates of oxidation by about a factor of five. The more basic high capacity allylamine-type resins oxidize even faster and, within this series, the higher the basicity the greater the rate of oxidation. Also within this series, the greater the amount of residual unsaturation — from the presence of pendant allyl groups — the greater the rate of oxidation. The oxidation occurs by a free radical chain process but the chains are very short and therefore the oxidation cannot be significantly inhibited by antioxidants. Certain polymeric backbone structures favour resins which are more resistant to oxidation than allylamine systems. Of the former, only those with polyether backbones are suitable for thermally regenerable ion-exchange systems. Resins with a polyether backbone were prepared by crosslinking polyepichlorohydrin and aminating with secondary amines. The predicted capacities for thermally regenerable systems made by combining these oxygen-resistant resins with polyacrylic acid are comparable with those for the polyallylamine resin systems.     

Mobil Zeolite Catalysts for Monomers

It has been about 20 years since Plank, Rosinski, and Hawthorne reported their spectacular results with metal-modified zeolite cracking catalysts for more efficient production of gasoline [1]. This discovery has saved an estimated 200 million barrels of crude oil each year in the United States alone [2]. In 1972, a patent by Argauer and Landolt described the preparation of a member of a generation of new synthetic zeolites, called ZSM- 5. It was unique because of its high silica/alumina ratio and greatly reduced coking rates for reactions with hydrocarbons by comparison with known low silica zeolites [3]. This material was an early member of a series of over 50 synthetic zeolitic substances prepared in Mobil laboratories.     

Use of15N for fertilizer N recovery and N mineralization studies in semi-arid Kenya

Maize and beans were grown on a ferralsol at Kiboko, Kenya, with up to 120 kg N ha^–1. Within the 10 kg N ha^–1 plots,¹⁵N labelled fertilizer was applied in microplots. There was no significant response in yield to fertilizer N and labelled N recovery was low, being 7.5% or less in one season and 17.7% or less in the second season. Samples of Kiboko soil at four different water contents were incubated and the rate of gross N mineralization over 7 days was calculated, utilizing¹⁵N labelling of the mineral N. Gross N mineralization increased greatly with soil moisture and a fitted relationship between gross N mineralization rate and soil water content was obtained. Using measurements of soil water content at the field site, daily values of the soil N supply by gross mineralization were calculated. On average, modelled gross soil N mineralized could supply much (> 69%) of the N removed from the plots. It is suggested that the lack of response to fertilizer N may be explained by the coincidence of a high rate of N mineralization, and increased crop demand, caused by the onset of rain.     

A review of the unique features of HDL apoproteins

The human plasma high density lipoproteins (HDL) are a heterogeneous ensemble of five proteins associated with both neutral and polar lipids. The sequences of all five proteins are known. ApoA-I and apoA-II are the major protein components; apoC-I, apoC-II and apoC-III are the minor protein components. All these apoproteins spontaneously recombine with phospholipids to give stable lipid-protein complexes and freely exchange between the two major HDL subclasses, HDL₂ and HDL₃. In addition, ApoC-I, apoC-II, and apoC-III exchange between HDL and very low density lipoproteins. Furthermore, certain HDL apoproteins are activators for plasma enzymes that are important in lipid metabolism. ApoA-I and apoC-I activate lecithin/cholesterol acyltransferase; apoC-II is an activator of lipoprotein lipase. The regions of apoC-I and apoC-II that are involved in the activation of these enzymes have been localized with synthetic peptides. Studies of synthetic and native fragments of apoA-II, apoC-I, apoC-II, and apoC-III as well as model lipid-binding peptides have identified specific regions with structural features common to lipid-binding proteins. These special properties, which include helical potential, sequences with a critical amphipathic length, and high hydrophobicity of the nonpolar side of the amphipathic helix, are the determinants of HDL structure and metabolism.