Polystyrene tension

Plot the scaling behavior for the surface tension of polystyrene solutions using Eq. III-64, for N = 1,000 and T from zero to Tc- Now plot the behavior for T = 0.87 for N = 100-1000. Comment on the influence of polymers on surface tension. 

Addition of poly(styrene-block-butadiene) block copolymer to the polystyrene-polybutadiene-styrene ternary system first showed a characteristic decrease in interfacial tension followed by a leveling off. The leveling off is indicative of saturation of the interface by the solubilizing agent. 

The classic studies of Saunders( 17) demonstrated that in the presence of excess surfactant methyl cellulose (MC) would desorb from monodispersed polystyrene latices. MC is one of the most surface active water-soluble polymers (W-SPs) and it will readily dominate the surface pressure 7T (7T = cre - cr t where cr is the surface tension of water and is the surface tension of the aqueous polymer solution) of the aqueous solution. For example, hydroxyethyl cellulose (HEC) lowers the surface tension of water much less than MC or HPMC, and when the combination of HEC and MC or HPMC in water is studied, there is no notable influence of HEC on the surface pressure (Figure 2). 

Structural parameters of crosslinked polystyrene determined from tension-deformation dependence and swelling in solvents of different activity. Collection Czech. Chem. Commun. 32, 1554 (1967). 

Koberstein and coworkers121 have examined the effects of a polydimethylsiloxane-polystyrene (PDMS-PS) block copolymer on the interfacial tensions of blends of PDMS and polystyrene. As little as 0.002 wt% of the copolymer, added to the siloxane phase, was sufficient to lower the interfacial tension by 82% in the case of a blend of polystyrene (Afn = 4,000) and PDMS (Mn = 4,500). No further reduction in interfacial tension was observed at higher copolymer levels due to micelle formation. Riess122 has polymerized styrene in the presence of a silicon oil and a polydimethylsiloxane-polystyrene block copolymer to obtain a polystyrene in which 0.1-1 pm droplets of silicone oil are dispersed. This material displayed a lowered coefficient of kinetic friction on steel compared to pure polystyrene. 

Some plastic materials have different tensile and compressive characteristics. For example, polystyrene is tough under compressive load but very brittle in tension. However, for most elastoplastic materials, the stress-strain curves in compression are the same as in tension. Hence, the deformation properties of these materials in tension may also be applied to those in compression, which is of great interest to gas-solid flows. 

Figures 7.18(b) and 7.18(c) show the breakup into droplets of an extended filament of high density polyethylene in a polystyrene matrix. In Fig. 7.18(b) the distance between the extruder die and the quenching bath is short and the fiber freezes before breaking up, whereas in Fig. 7.18(c) the distance was increased, giving the filaments sufficient time for breakup. As the filament extends, its diameter is reduced until shear forces no longer dominate the surface tension cohesive forces and the filaments breaks into droplets, just like a stream of water from a faucet breaks up into droplets.

W. Hu, J. T. Koberstein, J. P. Lingelser, and Y. Gallot, Interfacial Tension Reduction in Polystyrene/Poly(dimethylsiloxane) Blends by the Addition of Poly(styrene-b-dimethylsilox-ane), Macromolecules, 28, 5209-5214 (1995). 

HuW et al. (1995) Interfacial tension reduction in polystyrene/poly(dimethyl-siloxane) blends by the addition of poly(styrene-b-dimethylsiloxane). Macromolecules 28(15) 5209—5214... 

It is a matter of course that the different surfactant coverages are also reflected in the corresponding surface tensions y of the latexes (see Fig. 4b). An increase of the surface tension with increasing diameter is observed. The miniemulsions based on polystyrene particles exceeding 100 nm have a surface tension of close to the one of pure water (72 mN nr1)- This is due to the fact that the bare particle surface is so large that adsorption equilibrium ensures a very low surfactant solution concentration. Smaller particles with their higher sur-... 

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