Polystyrene surface 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. 

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). 

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.

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-... 

Fig. 4. a Polystyrene particle size vs amount of SDS (KPS as initiator) b Surface tension of the latexes and coverage of the particles in dependence of particle size... 

TABLE 8.4 Molecular weight dependence of the surface tension of polystyrene... 

Figure 6. Critical surface tension for wetting (yc) of polystyrene as a function of irradiation time...

Compatibility of polymers implies a semi-quantitative measure can be used to predict whether two or more polymers are compatible. The use of one of the semi-quantitative approaches, solubility parameter, was demonstrated by Hughes and Britt (22). It was concluded (8) that one parameter was insufficient to predict the compatibility. In this paper, we now introduce critical surface tension which is determined from the surface properties of a polymer. Though both of these parameters have been related by Gardon (15), we are inclined to use the latter because we can further describe the wettability between two polymers. For instance, by the use of yc, we can predict equally well that compatibility between polystyrene and polybutadiene can be improved if butadiene is... 

Where < , the interaction parameter, is assumed to be unity. If we neglect the presence of the monomer in both phases, we can use the following critical surface tension values to estimate 712 71 (polystyrene), 36 y2 (ungrafted polybutadiene), 31 and 72 (grafted polybutadiene), 34, dyne/cm. The estimated yi2 s are 0.2 dyne/cm. for the ungrafted polybutadiene interface and —0.2 dyne/cm. for the grafted polybutadiene interface. 

---