Polyurethane solution behavior

Interfacial behavior of different silicones was extensively studied, as indicated in Section 3.12.4.6. To add a few more examples, solution behavior of water-soluble polysiloxanes carrying different pendant hydrophilic groups, thus differing in hydrophobicity, was reported.584 A study of the aggregation phenomena of POSS in the presence of amphiphilic PDMS at the air/water interface was conducted in an attempt to elucidate nanofiller-aggregation mechanisms.585 An interesting phenomenon of the spontaneous formation of stable microtopographical surface domains, composed primarily of PDMS surrounded by polyurethane matrix, was observed in the synthesis of a cross-linked PDMS-polyurethane films.586... 

Melting and Solution Behavior of Polyurethanes Polymer and Treatment... 

Liquid Sorption. Liquid sorption measurements were performed gravlraetrlcally on polymer A In methanol-water and methanol-Isooctane solutions. The results are plotted In Figs. 11 and 12. In Fig. 11, a linear tle-llne was drawn through the solvent uptake data points for the pure liquids. It appears that the amount of methanol (or water) absorbed by the polymer Is linearly proportional to the mole fraction of methanol In the solution. However, proof of this assertion requires the Independent measurement of the species dissolved In the polymer. In other words, the partitioning of the solvents within the polyurethane Is not known. In contrast to the aforementioned behavior, positive deviations were observed from the linear tle-llne In Isooctane-methanol solutions. This Indicates that an excess of one liquid, and of possibly both, was sorbed by the polymer (Fig. 12). These results also demonstrate that methanol Is much more compatible with the polyurethanes than water (I.e., methanol Is absorbed to a much greater degree In the polymer than water). 

These results confirm the observation that polyelectrolyte aqueous solutions show two separate decay modes in the autocorrelation function and support our contention that ionic polymer systems generally behave similarly in polar solvents [23], To support this, it may be added that similar dynamic scattering behavior was recently reported for another type of ionomer, polyurethane ionomer, dissolved in a polar solvent, dimethylacetamide (e = 38) [92], Finally, it should be stressed that the explanation given above for light scattering (both static and dynamic) behavior of salt-free polyelectrolytes is based on the major role of intermolecular electrostatic interactions in causing characteristic behavior. No intramolecular interactions are explicitly included to explain the behavior. This is in accord with our contention that much of the polyelectrolyte behavior, especially structure-related aspects, is determined by intermolecular interactions [23]. 

Sophiea et al. published the first classical composition-temperature phase diagram, working with the semi-IPN net-polyurethane-mter-poly(vinyl chloride) [Sophiea et al., 1994b]. They found a lower critical solution temperature, LCST = 120°C below this temperature the system was one-phased, and above, two-phased. Such behavior is now known to be characteristic of most polymer blends (see Chapter 2). 

Sudha et al. (2008) and Dinesh Karthik et al. (2009) reported on the removal of heavy metal cadmium and chrominm from industrial wastewater using chitosan-coated coconut charcoal and chitosan impregnated polyurethane foam, respectively. Adsorption and determination of metal ions such as zinc (11) and vanadium (II) onto chitosan from seawater have been studied (Muzzarelli et al. 1970, Muzzarelli and Sipos 1971, Muzzarelli and Rocchetti 1974). Adsorption of strontium (II), cobalt (11), zinc (11), and iron (III) on chitosan from sodium chloride solution have been reported (Nishimura et al. 1995). Adsorption behavior of Cu (II) (Minamisawa et al. 1996, Wu et al. 2000) and cobalt (11) (Minamisawa et al. 1999) were investigated. The amount of cadmium removed by chitin increases with increase of these parameters at a specific time. The application to experimental results of the Langmuir and Freundlich models shows that the Langmuir model gives a better correlation coefficient. 

Electrospinning behavior of elastomeric polyurethane urea copolymer in solution studied. The effects of electrical field, temperature, conductivity, and viscosity of the solution evaluated. 

Kounaves and coworkers [70] have studied the Ag AgCl systems covered by membrane made of Nafion or polyurethane. These polymers were used to protect the studied solution from a NaCl leakage from the electrode solution. The studies on the stability of potentials of such electrodes have shown that the potentials of the electrodes protected by Nafion were significantly less stable than those covered by the polyurethane membrane. The drift of the potential, in the initial stage, could result from a slow equilibration between the Ag AgCl phase and KCl immobilized in the internal membrane. Further drift could be a consequence of the hydration of the external Nafion membrane. In the case of chloride solutions electrodes of both types exhibited decrease of the potential (about —41 ( 1) mV dec ) with the increase of chloride ions concentrations (from 10 mol dm to 1 mol dm ), showing a behavior similar to that of an indicator electrode. This change could result from the diffusion of more concentrated solution of chloride ions to the electrolyte immobilized in the poly(vinyl chloride) membrane situated under the external protective layer made of Nafion or polyurethane. 

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