Diffusion of large molecules in polymers: a measuring technique based on microdensitometry in the infra-red

A technique based on infra-red microdensitometry has been developed for studying the centre-of-mass translational diffusion of large additive molecules in polymeric matrices. In this technique the diffusion broadening with time of a known initial concentration profile of the additive within the bulk polymer is monitored. The shape of the concentration profile after diffusion broadening readily yields D, the diffusion constant; it may also yield the concentration dependence of D where this is significant. The technique is found to be reasonably flexible, and applicable to a number of polymer—additive combinations. Values of D in the range 10^?5 to 10^?10 cm²/sec and initial additive concentrations of down to 0.3% may be studied. The technique is viable over a wide range of temperatures and pressures. Some results obtained by this technique are presented, for the case of various linear long-chain amides diffusing in low density polyethylene.     

Electrochemical and spectroscopic characterization of lithium titanate spinel Li4Ti5O12

Herein we describe electrochemical and spectroscopic properties of lithium titanate spinel as well as an easy method based on colorimetry to determine the lithium content of electrodes containing lithium titanate spinel as active material. Raman microspectrometry measurements have been performed to follow lithium insertion into and extraction from the active material, respectively. The Raman signals display a pronounced fading of intensity already at low levels of lithium intercalation and disappear at a SOC higher than ∼10%. However, the colorimetric method can be used up to a SOC of 50%.     

Two-component aqueous epoxy binders free of volatile organic content (VOC)

Water-borne two-pack coatings based on a novel epoxy resin emulsion, cross-linked with three different amine group containing curing agents, are discussed. The aqueous binders developed at the Research Laboratory at Dow Deutschland Inc. are free of volatile organic content. The epoxy resin emulsion has a low MFFT (minimum film formation temperature) and is hence capable of forming a continuous film at low temperatures and good emulsifying properties. The interaction is discussed between the epoxy emulsion, pigments and hardeners which are in aqueous solution, emulsion or hydrophobic (non-aqueous) form. Some of the described systems will gain interest in a wide range of applications because of their excellent properties, including adhesion to various substrates, resistance to chemicals, solvents and water, hardness and toughness. The predicted major applications for such systems include concrete, plastic and wood coatings, and anti-corrosive systems for steel and other metals.     

The generalized Lévêque equation and its practical use for the prediction of heat and mass transfer rates from pressure drop

Based on the generalized Lévêque equation (GLE) a new type of analogy between pressure drop and heat transfer has been discovered, that may be used in the cross corrugated channels of chevron type plate heat exchangers, in packed beds, in tube bundles, in crossed rod matrices or in many other spacewise periodic arrangements.Experimental data on heat transfer in tube bundles in crossflow, both inline, and staggered arrangements, had been recently tested in greater detail. Using an empirical correlation for pressure drop in these arrangements from the literature that has been successfully tested against a large number of experimental pressure drop data, heat transfer data collected earlier could be very well represented from the pressure drop correlation and the GLE. The data for staggered bundles have been shown to be in better agreement with this new method, than with the existing empirical heat and mass transfer correlations. Somewhat larger deviations for inline tube bundles had been found at lower Reynolds numbers. Here a simple and physically reasonable correction function of Re is presented, which leads to a better agreement for the inline bundles, too.Additionally, it can be shown for a number of literature data on tube bundles and on crossed rod matrices that the agreement with the GLE prediction is even better if original pressure drop data from the same sources are available in place of a pressure drop correlation.The method results in reasonable heat or mass transfer predictions from frictional pressure drop, which may be widely used in chemical engineering applications.     

Simulation and analysis of industrial crystallization processes through multidimensional population balance equations. Part 2: a study of semi-batch crystallization

A bi-dimensional population balance model was presented in the previous part of this series of papers to simulate the time variations of two characteristic sizes of hydroquinone particles during crystallization. The multidimensional population balance equations combined with kinetic models and mass balance equations were shown to allow the simulation of the solution crystallization of hydroquinone characterized by a rod-like habit. Semi-continuous isothermal operations were performed at the lab-scale in the presence of various additive concentrations. Both the experimental solute concentration trajectory and the final bi-dimensional crystals size distribution were correctly predicted by the model. The simulated elongation shape factor characterizing the crystal shape was therefore in agreement with the experimental one. Due to the use of tailor-made additive, inhibition effects were observed to affect both primary nucleation and growth kinetics in the length direction. For secondary nucleation, indirect effects were assumed to occur which allowed satisfactory predictions of the final number of fine particles. The representation of the kinetics involved required the evaluation of a set of nine parameters. As a result it was observed that the elongation ratio characterizing the shape of the rod-like particles increases with the length in a nonlinear way. A major interest of the two-dimensional model lies in its ability to relate the time variations of the crystal habit: the particles lengthen in the first moments of their growth and then progressively get thicker until the end of the process.     

Simulation and analysis of industrial crystallization processes through multidimensional population balance equations. Part 1: a resolution algorithm based on the method of classes

In order to obtain constant solid properties with particles exhibiting a low order of symmetry, it is necessary to monitor and to control several distributed parameters characterising the crystal shape and size. A bi-dimensional population balance model was developed to simulate the time variations of two characteristic sizes of crystals. The nonlinear population balance equations were solved numerically over the bi-dimensional size domain using the so-called method of classes. An effort was made to improve usual simulation studies through the introduction of physical knowledge in the kinetic laws involved during nucleation and growth phenomena of complex organic products. The performances of the simulation algorithm were successfully assessed through the reproduction of two well-known theoretical and experimental features of ideal continuous crystallization processes: the computation of size-independent growth rates from the plot of the steady-state crystal size distribution and the possibility for MSMPR crystallizers to exhibit low-frequency oscillatory behaviours in the case of insufficient secondary nucleation.     

Hydrophobic polymers for liquid cleaning formulations

A patented method to provide acrylic acid:styrene (AA:Sty) copolymers with a variety of AA:Sty mole ratios is described. This method allows the polymer to be provided as a solution in water with up to 50 mol% styrene. The addition of significant amounts of styrene provides increased polymer solubility in liquid laundry detergents without sacrificing the traditional benefits of typical polycarboxylates. Studies were run in a Tergotometer and full-scale U.S. washing machine, showing particulate soil antiredeposition performance equivalent to poly(acrylic acid) with a molecular weight of 4500 and improved oily soil antiredeposition. The dry polymer is soluble in several glycols, a behavior not typically seen with polycarboxylates.     

Elastomeric films from structured latexes

A model structured latex that is capable of forming a self-curable elastomeric film under mild temperature conditions was developed. In this model latex system, a small amount of dimethyl meta-isopropenyl benzyl isocyanate (TMI®) was copolymerized with n-butyl acrylate (BA) onto poly(butadiene-co-styrene) [(P(Bd-S)] seed latex particles. In the final stage of the film formation process, the latex particles coalesce with each other, and interdiffusion of PBA-based polymer chains in the shell layers of adjacent structured particles occurs. At this stage, the isocyanate groups in the P(BA-TMI) shell layer would begin to crosslink by either a moisture-cure reaction via trace amounts of water remaining in the latex film or by a post-added crosslinker that contains amine groups. Improved elastomeric properties of the latex film are expected from this kind of “interphase” crosslinking structure. However, latex films prepared from the model P(Bd-S)/P(BA-TMI) core/shell latexes were cracked and brittle, which was explained by the formation of a highly crosslinked/grafted core/shell interphase zone. Saturation of the residual double bonds in the P(Bd-S) seed latex particles by hydrogenation was found to be an effective way to reduce the development of the interphase zone and the degree of crosslinking during the second-stage polymerization. An elastomeric film with good mechanical and anti-aging properties was formed from this hydrogenated-P(Bd-S)/P(BA-TMI) structured latex. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1143–1152, 1997     

Coal flotation by ozonized spent motor oil

The influence of ozonization on the composition and flotation properties of spent motor oil is investigated. Preliminary ozonization increases the proportion of low-boiling components in the spent oil, reduces its viscosity, and improves its flotation properties in the enrichment of coking coal.