Polystyrene dissolution mechanism

To perform simulations with the model, the system methyl ethyl ketone (MEK)/polystyrene was used as a model system. The effect of the polymer molecular weight on the dissolution mechanism vm investigated. Figure 5 shows the solvent concentration profile in the polymer (Mn = 52,000) as a function of normalized position based on the undeformed coordinate system. The center of the slab is at =... 

These dyes have affinity for one or, usually, more types of hydrophobic fibre and they are normally applied by exhaustion from fine aqueous dispersion. Although pure disperse dyes have extremely low solubility in cold water, such dyes nevertheless do dissolve to a limited extent in aqueous surfactant solutions at typical dyeing temperatures. The fibre is believed to sorb dye from this dilute aqueous solution phase, which is continuously replenished by rapid dissolution of particles from suspension. Alternatively, hydrophobic fibres can absorb disperse dyes from the vapour phase. This mechanism is the basis of many continuous dyeing and printing methods of application of these dyes. The requirements and limitations of disperse dyes on cellulose acetate, triacetate, polyester, nylon and other synthetic fibres will be discussed more fully in Chapter 3. Similar products have been employed in the surface coloration of certain thermoplastics, including cellulose acetate, poly(methyl methacrylate) and polystyrene. 

The kinetics of the reaction of solid sodium iodide with 1-bromooctane were studied with a 95 % RS graft of polyethylene oxide) 6-mer methyl ether on 3 % CL polystyrene as catalyst (51)176). The rates were approximately first order in 1-bromooctane and independent of the amount of excess sodium iodide. The rates varied with the amount of the solid catalyst used, but there was not enough data to establish the exact functional dependence. All experiments employed powdered sodium iodide, magnetic stirring, and 75-150 pm catalyst beads. Thus the variables stirring speed and particle size, which normally are affected by mass transfer and intraparticle diffusion, were not studied. Yanagida 177) favors a mechanism of transfer of the sodium iodide by dissolution in the solvent (benzene) and diffusion to the catalyst particle... 

The first commercial microfibers were obtained by way of co-extmsion of polyesters or polyamides with another polymer, mostly polystyrene. Due to the lack of compatibility, the sections of different components usually separate during neck drawing or during the finishing process with the aid of mechanical force or some chemical agents. The need of dissolution makes such processes exceptionally cumbersome and expensive, and right now, some water-soluble polymers are used [45]. The Japanese first introduced microfibers in an attempt to reproduce silk-like properties with the... 

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