Esters of hydroxystearic acids as primary low-temperature plasticizers for a vinyl chloride—Vinyl acetate copolymer

Summary Thirty-one acyloxy or aryloxy esters prepared from hydroxystearic acids have been evaluated as plasticizers for a vinyl chloride-vinyl acetate copolymer (95∶5). Many of them were found to be primary plasticizers, having outstanding low-temperature performance when employed at the 35% level. Formulations with these compounds compared quite favorably in tensile properties with those containing the di-2-ethylhexyl esters of phthalic, sebacic, azelaic, and adipic acids. Volatility losses were similar to those of the four di-2-ethylhexyl esters. The loss of plasticizer through migration was equal to or less than that from compositions containing the esters of sebacic, azelaic, and adipic acids but was greater than that of the phthalate ester. A mechanistic scheme of plasticizer-polymer interaction has been presented, proposing that the rate of diffusion of plasticizer through the polymer mass is a controlling factor in both good low-temperature performance and the resulting high migration losses. Methyl esters, some aromatic esters, and esters containing three or more polar centers have improved permanence but show a more rapid change in torsional modulus as the temperature is lowered during the determination of the Clash-Berg stiffening temperature. Eastern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Possible use of methylbenzenes as electrolyte additives for improving the overcharge tolerances of Li-ion batteries

Based on the voltammetric behaviour of a series of methyl-substituted benzenes in 1M LiPF₆/EC-DMC electrolyte, xylene was selected and tested as an electrolyte additive for overcharge protection of Li-ion batteries. From the overcharge curves, CV behaviour and SEM observations of the cells in the presence of xylene, it was found that the additive can polymerize at the overcharged voltage to form a dense layer of isolating polymer film at the cathode surface, which blocks off further oxidation of the electroactive material and electrolyte and, therefore, improves the overcharge tolerance of the Li-ion battery. In addition, the xylene additive has shown only a slight influence on the cycling behaviour.     

Thermal properties of poly(tetramethyl-p-silphenylene siloxane) and (tetramethyl-p-silphenylene siloxane-dimethyl siloxane) copolymers

Some physical properties of poly(tetramethyl-p-silphenylene siloxane) homopolymer and random block copolymers of tetramethyl-p-silphenylene siloxane-dimethyl siloxane have been determined and correlated with polymer structure. Differential scanning calorimetry (d.s.c.), differential thermal analysis (d.t.a.), density gradient column measurements and optical hot stage melting point determination and diluent techniques were used. The thermodynamic melting temperature of the homopolymer was estimated to be 160°C and its heat of fusion, ΔH_u, found to be 54.4 J/g (13 cal/g or 2710 cal/mol of monomer repeat units). Its limiting glass transition temperature, T_g, was ?20°C. T_g of the copolymer was found to vary almost monotonically with increasing dimethyl siloxane (DMS) content ranging from ?20° (0% DMS) to just above ?123°C, for pure DMS polymer. The copolymer melting temperature was found to increase as the fraction of the crystalline (hard) TMPS constituent was increased. Based upon copolymer theory and extrapolated melting point data, it was estimated that the block size of soft DMS component in the copolymer most probably consists of twelve monomer units distributed amongst TMPS sequences of varying length.     

The Role of Cations in Some Inorganic Hydrolysis Reactions

Cations which shift certain equilibria from left to right by forming a compound with one of the reaction products were investigated with respect to their kinetic role in the process. Silver ions have no influence on the rate of the hydrolysis of cyanogen iodide. Similarly, cations which form sparingly soluble carbonates do not influence the rate of hydration of carbon dioxide. On the other hand, the hydrolysis of chlorine is accelerated by Ag⁺ and, to a lesser extent, by Cd²⁺ and Fe(III). It is shown that the effect is not due simply to a bimolecular reaction between chlorine and the cation. In the case of Ag⁺, heterogeneous catalysis may play some role, in analogy with the solvolysis of organic halides. In the case of Cd²⁺, there is spectrophotometric evidence for compounds between Cl₂ and HOCl on the one hand, and the cation on the other. It is suggested that these compounds interconvert more rapidly than do the parent substances. A similar mechanism may be operative in the case of Fe(III), and, possibly, also in the case of Ag⁺.     

Composition of mixed octadecadienoates via ozonolysis,chromatography and computer solution of linear equations

An approach to the analysis of 55 possible nonconjugated positional isomers of octadecadienoic acid is described and tested with mixtures of individual synthetic methyl esters. In the first example, by ozonolysis a sevencomponent mixture consisting ofcis,cis 5,12-, 6,10-, 6,11-, 6,12-, 7,12-, 8,12-, and 9,12-octadecadienoates was converted to aldehydes, aldehyde-esters and dialdehydes. These fragments were separated on a 50 m×0.2 mm free fatty acid phase (FFAP) vitreous silica capillary column. Equations for an arbitrarily restricted 12×15 matrix of linear simultaneous equations and a computer solution of the matrix provided the composition of the initial methyl octadecadienoate mixture. The power and significance of this method became apparent with the observation that only two of the seven isomers in the known mixture were resolved as single peaks by state-of-the-art capillary gas chromatography, but all seven were identified and estimated with acceptable error by the ozonolysis-capillary gas chromatography-computer procedure. In a generalized approach to the analysis of the 55 possible nonconjugated isomers, a computer program selects the appropriate matrix of linear simultaneous equations based on the aldehyde data supplied by the analyst. Twenty of 21 combinations of seven isomeric esters taken five at a time have been analyzed to assess the efficiency of the method. To illustrate applicability at this stage of development, the method has been used to analyze the diene products of the hydrazine reduction of γ-linolenic acid and the diene products from the biological desaturation of isomeric monoenes. The possibility of distinguishing geometric and positional isomers of 18∶2 has been opened by the observed separation ofcis-andtrans-unsaturated aldehydes and aldehyde-esters. Presented in part at the 16th World Congress of the International Society for Fat Research, October 4–7, 1983, in Budapest, Hungary, and at the American Oil Chemists' Society Meeting, May 15, 1986, in Honolulu, Hawaii.     

On-line process control of a fluidized bed reactor with non-catalytic gas/solid reaction

In a bench-scale, stainless steel reactor, experiments were carried out to investigate fluidized bed behavior by means of on-line process control. The non-catalytic thermal decomposition of sodium hydrogen carbonate to sodium carbonate, carbon dioxide and water was used a model reaction. The experimental equipment was provided with control systems and reulating units which were connected to a PDP 11/40 computer by means of suitable analogue and digital input/output interfaces. The operating conditions are highly influenced by the chemical reaction as well as by the fluid-dynamical behavior of the reactor. Several experiments were carried out to evaluate the kinetics of the model reaction. The fluid-dynamics was investigated by means of on-line experiments with and without chemical reaction. Based on the experimental results, a model was developed to describe the whole process so that model simulations should yield information on the process itself. With this model, strategies are tested before they are applied to the process computer for on-line process control.     

Modification of leather properties by grafting. I. Effect of monomer chain on the physico‐mechanical properties of grafted leather

Although leather has a number of desirable properties such as thermal stability and fire retardancey, in addition to high toughness, it has a few drawbacks such as weight, high water absorption, poor soil and rot resistance, and nonuniformity. If these defects are overcome, leather's usefulness would be further enhanced and its competitive position with respect to synthetics would increase. This study reports the physical and mechanical properties of buffalo leather after chemical graft copolymerization with ethyl acrylate, butyl acrylate, and 2‐ethyl hexyl acrylate using benzoyl peroxide as an initiator. The optimum conditions for grafting (e.g., monomer and initiator concentrations, temperature and time of grafting, and solvent leather ratio) were extensively investigated. The study achieved outstanding properties for buffalo leather in reduction of water uptake after grafting, especially on using 2‐ethyl hexyl acrylate and butyl acrylate monomers. FT‐IR and solid ¹³C‐NMR for leather before and after grafting confirmed the grafting process.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1478–1483, 2003     

Permittivite complexe de solutions electrolytiques non aqueuses

The complex permittivity * = ′ — j″ of ethanolic solutions of electrolytes has been measured between wavelengths 90 and 3·2 cm, at 25°C. Methods of measurement are briefly described. The results are interpreted by separating the conductivity and the dielectric losses. For solutions of LiClO₄, Mg(ClO₄) ₂, LiCl and LiI, a dielectric relaxation analogous to that of the solvent is observed, ie the dielectric loss factor passes through a maximum at a wavelength of about 30 cm. The ‘static’ permittivity, defined in terms of the relaxation spectrum, undergoes an important fall with increase of concentration. Solutions of (n-Bu)₄NI give more complicated behaviour, characterized by the probable existence of a new relaxation domain at longer wavelengths. The results are discussed in relation to data in the literature on the intermolecular structure of alcohols and the dielectric properties of electrolyte solutions in other types of solvent.

Zusammenfassung

Man ermittelte bei 25°C die komplexe Permittivität * = ′ — j″ verschiedener Elektrolytlösungen in Äthanol bei Wellenlängen zwischen 3,2 und 90 cm. Die Messmethoden werden kurz beschrieben. Die Ergebnisse werden interpretiert, indem die Leitfähigkeitsverluste von den dielektrischen Verlusten getrennt werden. Bei en Lösungen LiClO₄, Mg(ClO₄)₂, LiCl und LiI stellt man eine dem Lösungsmittel analoge dielektrische Relaxation fest, m.a.W.: der dilektrische Verlustfaktor geht bei Wellenlängen in der Nähe von 30 cm durch ein Maximum. Die “statische Permittivität”, welche aud dem Relaxationsspektrum definiert werden kann, nimmt mit zunehmender Konzentration stark ab. Lösungen von (n-Bu)₄NI zeigen ein komplizierteres Verhalten, welches möglicherweise durch das Auftreten eines neuen Relaxationsgebietes bei längeren Wellenlängen gekennzeichnet ist. Man diskutiert die Ergebnisse mit Bezug auf die Literaturdaten der intermolekularen Struktur von Alkoholen, und das dielektrische Verhalten von Elektrolylösungen in anderen Lösungsmitteln.     

Alkaline fuel cells: contemporary advancement and limitations

ZeTek Power recently introduced mass manufacturable and cost effective alkaline fuel cells on the market. Today's research is focused on further improvement both in terms of performance increase and cost reduction. This research is classically performed using small (4 cm²) experimental electrodes in the half-cell configuration. This allows the primary electrochemical losses in an anode or cathode to be determined independently. Additional performance losses occur when one integrates large electrodes into a module of 24 cells and in a stack comprised of many modules. By comparing the performance of half-cell experiments to that of modules, these losses can be distinguished and addressed. The information thus obtained, both for the small electrodes and in up-scaling is vital if one is to identify the key areas in which improvement is possible and where to focus future research. Furthermore, the identification of the losses in a module and system allows us to predict the final performance from half-cell measurements of a new laboratory scale experimental electrode.