The effect of a magnetic tape coating process on the structure and properties of a semi-crystalline polymer

A combination of structure identifying and bulk property experiments were combined with a two-phase analytical methodology to elucidate the influence of a magnetic tape coating process on the substrate polymer film. Employing a typical tape manufacturing process that utilizes coating, drying, and calendering stages, polyethylenete-rephthalate polymer film samples with and without the magnetic coating were prepared.Experiments and modeling studies performed on these samples demonstrate that the drying and calendering processes may increase the crystallinity and noncrystalline orientation of the substrate film. In addition, dynamic mechanical experiments identified a viscoelastic transition at 50 °C for the PET substrate film sample which is near the glass transition of the magnetic coating utilized. Overall, the results of this investigation provide a basis for evaluating structure property interrelations of polymer-based magnetic tapes.     

Interfacial structure and properties of polyurethane/poly(methylacrylate-co-styrene) coating to regenerated cellulose film

A semiinterpenetrating polymer network (IPN) containing 72 wt % polyurethane (PU) and 6 wt % poly(methylacrylate-co-styrene) [P(MA-St)] was coated onto surfaces of regenerated cellulose (RC) film, which was prepared by coagulating a cellulose cuoxam from bagasse pulp. The interfacial structures, bonding manner, and the strength of the coated film were studied by infrared (IR),¹³C nuclear magnetic resonance (NMR), differential thermal analysis (DTA), transmission electron microscopy (TEM), and electron probe microscopy analysis (EPMA). It was shown that the RC film coated with PU/P(MA-St) has strong interfacial interactions, where covalent and hydrogen bonds are formed across the interface between cellulose and the PU/P(MA-St) coating. The interfacial structure of the coated film is regarded as a shared PU network crosslinked simultaneously with P(MA-St) and cellulose film. The tensile strength, water resistivity, and optical transmission of the coated films were considerably higher than that of the uncoated films. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2495–2501, 1997     

Preparation and properties of sol-gel coating films

The present state of our knowledge on sol-gel coating films has been reviewed. A qualitative discussion is made on the limit of the film thickness which can be achieved in the sol-gel method and the factors affecting the film thickness. Considering that properties of the film are intimately related to the microstructure, types of microstructures accomplished by the sol-gel coating are introduced with examples.     

The influence of substrate charge and molecular structure on interphase transfer in cloud point extraction systems

The specificity of interphase transfer of organic reagents of different types between water and the nonionic-surfactant-rich phases at the cloud point temperature was investigated. In contrast to organic solvents, the ability of the micellar phases to extract highly charged ions of organic reagents was shown. Further evidence of the specificity of interphase transfer in micellar-extraction systems is independent and cooperative influence of substrate molecular structure and hydrophobicity on their distribution. The appearance of host-guest phenomenon in cloud point extraction systems that is inherent in organized systems with molecules of the receptors was established. The possibility of describing reagent distribution using regressions that consider substrate hydrophobicity and molecular structure in the cloud point extraction systems was shown.     

The structure and properties of carbonyl compounds

The (planar) minimum energy configurations of cis and trans glyoxal, and of parabenzoquinone, have been determined using the MINDO/2 method. Good agreement with the experimental structures is obtained. Other molecular properties for these systems are reported.     

Molecular models for the structure of solvent in an interphase

In view of the difficulties encountered in the discussion of interfacial solvent structure in terms of simple dipolar molecules in a small number of orientations, an attempt is made here to investigate more realistic models for this region. A new technique of searching for minimum energy configurations is developed. The results confirm that even with a more realistic point charge model of the water molecule the dipole tends to be oriented in the plane of a two-dimensional array.     

Thermal properties and volume fraction of the boundary interphase in metal-filled epoxies

Summary A previous study (1) on the thermomechanical behaviour of metal-filled Epoxies led us to conclude that the concept of the boundary interphase is a very useful tool for describing quantitatively the quality of adhesion between the matrix and the filler particles. It was shown that this interphase exists in reality and is an area between filler and matrix, which contains both areas of adsorption interaction in polymer surface layers into filler particles, as well as an area of mechanical imperfections.In the present paper, under the assumption that the interphase is homogeneous and isotropic, exhibiting perfect adhesion with both main phases, a theory was developed to describe the thermomechanical behaviour of this interphase.Thermal expansion coefficients and volume fraction of the interphase of a large number of composites were determined and the effect of various parameters, such as temperature, volume fraction of filler and particle size, were examined for specimens exhibiting imperfect as well as perfect adhesion between matrix and filler.With 12 figures and 1 table     

Estimation of interphase thickness and properties in PP/layered silicate nanocomposites

Nanocomposites were prepared from sodium montmorillonite (NaMMT) and organoclays (OMMT) with different particle sizes as a function of silicate content. Composite structure was characterized by various methods including X-ray diffraction (XRD), scanning electron microscopy (SEM) and rheology. Model calculations were carried out to estimate the thickness and yield stress of the interphase forming in the composites. The results proved the formation of an interphase, but the determination of interphase properties was hampered by several factors. First of all, the particle size of the filler changed quite considerably in PP/OMMT composites in spite of earlier observations and expectations. Particle characteristics changed even further when a relatively small amount (5 vol.%) of functionalized polymer (MAPP) was added to the composite. As a consequence, the estimation of the contact surface between the silicate and the polymer became extremely difficult. In spite of the uncertainties overall values of interphase properties were obtained using the results of all composites prepared. The prediction for the average thickness of the interphase is 0.23 μm and we obtained 51.2 MPa for interphase yield stress, but this estimate neglects the different interactions developing in composites containing the uncoated and the modified silicate, respectively.     

Synthesis,acid-base properties,and interphase distribution of new aminoalkylphosphates and -phosphonates

Using the Todd-Atherton reaction, we synthesized new ω-aminoalkylphosphates differing by location of phosphate amino group in the molecule. For these compounds and for α-, β-, and γ-amino-phosphonates of similar structure ionization constants of phosphate and phosphonate groups were determined which turned out to be similar. In all the cases the increase in basicity of amine centers was shown with the growing distance between them and the phosphorus-containing substituent. By the method of two-phase potentiometric titration the constants of partition between water and a series of organic solvents were measured. The data obtained are interpreted in the framework of additive Leo-Hansch model that allows estimation of the increments of phosphate and amidophosphate groups. These data can be applied to the study of biological activity and extraction properties of the compound of such class.     

The properties and structure of N-chloro-N-methoxy-4-nitrobenzamide

The XRD study of N-chloro-N-methoxy-4-nitrobenzamide revealed the high pyramidality degree of its amide nitrogen atom in O–N–Cl moiety. N-Chloro-N-methoxy-4-nitrobenzamide reacts with AcONa in MeCN selectively forming N-acetoxy-N-methoxy-4-nitrobenzamide, whereas its methanolysis in the presence of AcONa yields N,N’-bis(4-nitrobenzoyl)-N,N’-dimethoxyhydrazine.     

The fine structure and properties of fibrous alumina

Summary The structure and composition of Wislicenus' fibrous alumina was studied by solubility in acids, birefringence, water content, aging in water, x-ray and electron diffraction and by electron microscopy. It was found that fibrous alumina is constituted mainly of amorphous aluminum hydroxide and contains some adsorbed water and some aluminum oxide. The birefringence of the fibers was due to the existence of non-crystalline fibrils of various length and about 70–80 A. U. diameter, which were more-or-less well oriented parallel to the length of the fiber. Amorphous particles, arranged linearly, <50 A. U. in diameter were found to be the ultimate building blocks of these fibrils. These fibrils were often observed to lie together in bundles or fibers about 200–300 A. U. across. Sometimes such groupings of the fibrils did not exist but the whole macroscopic fiber seemed to be composed of an oriented bundle of fine fibrils. The binding between particulates in a fibril and between fibrils was very weak. This fact may account for the low density of the material. It has been shown that the formation of fibrous alumina is dependent on the existence of a small amount of water and a small amalgamation on distinct spots on the aluminum surface. The mechanism of the formation of fibrous alumina is suggested as similar to that of anodic films on aluminum. It was observed that strongly amalgamated aluminum or aluminum amalgam itself did not produce fibrous alumina even in air, but formed a grey powder of which the main component was mercuric oxide and aluminum.

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Zusammenfassung Die Struktur und Zusammensetzung fasriger Tonerde nach Wislicenus wurde aus L?slichkeit in S?uren, Doppelbrechung, Wassergehalt, Alterung in Wasser mit R?ntgen- und Elektronenbeugung und im Elektronenmikroskop untersucht. Es wurde festgestellt, da? Fasertonerde haupts?chlich aus amorphem Aluminium-hydroxyd besteht und etwas absorbiertes Wasser sowie etwas Aluminiumoxyd enth?lt. Die Doppelbrechung der Fasern ist dem Bestehen von nichtkristallinen Fibrillen variierender L?nge und von ungef?hr 70–80 ? Durchmesser zuzuschreiben, die mehr oder weniger gut parallel zur L?ngsrichtung der Fasern orientiert sind. Amorphe Teile linear angeordnet kleiner als 50 ? im Durchmesser bilden die letzten Bausteine dieser Fibrillen. Diese Fibrillen liegen oft zusammen in Bündeln mit 200–300 ? Querschnitt. Zuweilen bestehen solche Gruppierungen nicht, doch scheint die ganze makroskopische Faser zusammengesetzt aus einem orientierten Bündel feiner Fibrillen. Die Bindung zwischen den Teilchen in einer Fibrille und zwischen den Fibrillen ist sehr schwach. Diese Tatsache mag für die geringe Dichte des Materials verantwortlich sein. Es wurde weiter gezeigt, da? die Bildung fasriger Tonerde von der Existenz geringerer Wassermengen abh?ngt und von einer geringen Amalgamierung an ausgezeichneten Punkten der Aluminiumoberfl?che. Der Mechanismus der Bildung ist vermutlich ?hnlich der eines anodischen Films auf Aluminium. Es wurde beobachtet, da? stark amalgamiertes Aluminium oder Aluminiumamalgam selbst keine faserige Tonerde erzeugt, auch nicht in Luft, sondern da? ein graues Pulver entsteht, in dem die haupts?chlichen Komponenten Quecksilberoxyd und Aluminium sind.

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This work has been aided in part by grants from the Conselho Nacional de Pesquisas do Instituto Butantan. It was presented in part before the fourth International Congress of Crystallography in Montreal, July 1957.     

Effect of interphase interaction within zinc-filled composite coating on the potential of the cathodic protection of steel

The potential of cathodic protection of steel with composite coatings based on polystyrene (PS) filled by highly dispersed powders of zinc (Zn) of different forms and dispersivities is investigated. The potential for all PS/Zn systems with a low content of filler is shown to be less than for pure metal; as some critical value (the percolation threshold) is reached, the negative values of potential increase abruptly and become higher in absolute value than the potential of pure metal. The threshold zinc contents are found to depend on the particle shape and rise from 9 to 30 vol% upon transitioning from spear-shaped to spherical particles. The electrochemical protection properties of a composite coating are correlate with the enthalpy of mixing of filled composites. The enthalpy of mixing in regions of low filling is shown to be negative, indicating strong interphase interaction; that in regions of high filling is positive. The positive enthalpy of mixing corresponds to compositions that generate the potential of cathodic protection. It is found that an increase in the concentration range of positive values of a composition’s enthalpy of mixing occurs symbatically with a decrease in the threshold concentration of metallic zinc within the composition. We conclude that cathodic protection by zinc-filled polymeric composites is due to weak interphase interaction that results in the aggregation of particles of metallic zinc within a polymeric matrix and the appearance of an infinite cluster. In the case of PS/Zn compositions, it is shown that the infinite cluster appears at enthalpies of mixing greater than 0.6 J/g of the composition.     

Effects of solid polymer electrolyte coating on the composition and morphology of the solid electrolyte interphase on Sn anodes

In order to discuss the effect of polymer coating layer on the Sn anode, the composition and morphology of the solid electrolyte interphase (SEI) film on the surface of Sn and Sn@PEO anode materials have been investigated. Compared with the bare cycled Sn electrode, the SEI on the surface of cycled Sn@PEO electrode is thinner, smoother, and more stable. Therefore, the Sn@PEO nanoparticles can basically keep the original appearance during cycling. Based on the results obtained from X-ray photoelectron spectroscopy (XPS), the SEI formed on the Sn@PEO electrode is characterized by inorganic components (Li₂CO₃)-rich outer layer and organic components-rich inner which could make the SEI more stable and inhibit the electrolyte immerging into the active materials. In particular, the elastic ion-conductive polyethylene oxide (PEO) coating could increase the toughness of SEI and allow the SEI to endure the stress variation in repetitive lithium insertion and extraction process. As a result, the Sn@PEO electrodes show significantly better capacity retention than bare Sn electrodes. The findings can serve as the theoretical foundation for the design of lithium-ion battery electrode with high energy density and long cycle life.     

The effect of fiber coating on the tensile properties of ionomer-based composites

Asbestos fibers, of the chrysotile variety, were coated with a thin polyamide film by an in situ polycondensation technique. Ionomer-based composites were prepared containing the so-modified asbestos fibers in a random in-plane orientation; results of testing the tensile properties of these asbestos/polyamide/ionomer composites are presented. Parameters investigated comprise the asbestos content in the composite and the polyamide content deposited on asbestos. A significant improvement in the tensile performance was established, especially at the intermediate polyamide content of 3.4 phr. The behavior is discussed in terms of possible interactions between the phases present in the composite material.     

Electrolyte and interphase engineering through solvation structure regulation for stable lithium metal batteries

Lithium metal batteries (LMBs) are considered to be one of the most promising high-energy-density battery systems. However, their practical application in carbonate electrolytes is hampered by lithium dendrite growth, resulting in short cycle life. Herein, an electrolyte regulation strategy is developed to improve the cyclability of LMBs in carbonate electrolytes by introducing LiNO₃ using trimethyl phosphate with a slightly higher donor number compared to NO₃⁻ as a solubilizer. This not only allows the formaion of Li⁺-coordinated NO₃⁻ but also achieves the regulation of electrolyte solvation structures, leading to the formation of robust and ion-conductive solid-electrolyte interphase films with inorganic-rich inner and organic-rich outer layers on the Li metal anodes. As a result, high Coulombic efficiency of 99.1% and stable plating/stripping cycling of Li metal anode in Li||Cu cells were realized. Furthermore, excellent performance was also demonstrated in Li||LiNi_0.83Co_0.11Mn_0.06O₂ (NCM83) full cells and Cu||NCM83 anode-free cells using high mass-loading cathodes. This work provides a simple interphase engineering strategy through regulating the electrolyte solvation structures for high-energy-density LMBs.