Polystyrene interfacial 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. 

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. 

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... 

Ellingson PC, Strand DA, Cohen A, Sammler RL and Carriere C (1994) Molecular weight dependence of polystyrene/poly(methyl methacrylate) interfacial tension probed by imbedded-fiber retraction. Macromolecules 27 1643-7. 

In the case of mass ABS, the variety of rubber particle morphology is less diverse. Typical examples of morphology are shown in Figure 14.6. If polybutadiene rubber is used (linear or star), cellular particles are obtained with SAN occlusions. In the case of styrene-butadiene block rubber (typically 30% styrene) also cellular particles are obtained but besides the SAN occlusions, polystyrene domains are clearly visible in the particles. To be able to make the other morphologies that are possible in HIPS, the interfacial tension has to be manipulated. Controlling the grafting reaction is a way to achieve this but the possibilities are limited with the tools (mainly initiator) that are currently available. 

Figure 9.12 Droplet radius versus wt% dispersed polystyrene (PS) in a blend with polypropylene (PP) at an average shear rate of 10 sec in a single twin screw extruder at T = 200°C. The viscosities of pure PS and PP at these conditions are about 5 x 10 and 2 X 10 Pa-s, respectively both melts are modestly shear thinning (power-law slopes —1/3). The interfacial tension T was measured to be 4.9 dyn/cm. The predicted Taylor limit, a = 0.5 T/rfsy, is shown. (From Elmendorp and van der Vegt 1986, reprinted with permission from the Society of Plastics Engineers.)...

Figure 9.13 Number averaged diameter of droplets d of polypropylene (M = 60,000) in polystyrene (M = 200,000) as a function of wt% polypropylene mixed in three different mixers at a nominal shear rate of around 65 sec and T — 200°C. The viscosities of the the PP and PS under these conditions are 840 and 950 Pa-s, respectively. The interfacial tension F is 5.0 dyn/cm. The error bars represent the distribution of droplet sizes, and they encompass one standard deviation in each direction from the mean. The deviation from the Taylor limit at low concentrations is attributed to non-Newtonian effects, while the increase in droplet size at higher concentrations is attributed to droplet coalescence. Note that similar droplet sizes are obtained in all three different mixers. (Reprinted with permission from Sundararaj and Macosko, Macromolecules 28 2647. Copyright 1995, American Chemical Society.)...

This paper compares the swelling of monodisperse polystyrene and polymethyl methacrylate latexes with their monomers and the estimated particle-water interfacial tensions with the theoretical curves from Morton s equation. A new model which takes into account the effect of water dissolved in the swollen particles and in the monomer phase on the swelling of relatively hydrophilic systems is presented. 

Swelling of polystyrene latex particles with styrene. The swelling ratios and the corresponding interfacial tensions for the different-size latexes with added anionic surfactants Aerosol MA and sodium dodecyl sulfate are listed in Table II. Those values obtained with added nonionic surfactant Triton X-100 and polymeric surfactant polyvinyl pyrrolidone are listed in Table III. Figure 1 compares theoretical curves from Model I with all of the experimental data. It is found that a curve corresponding to Xmp = 0.35 fits the data best. Therefore, a semi-empirical... 

In summary, the thermodynamic Model I based on Morton s theory has been used to successfully fit experimental data and obtain semi-empirical equations for the swelling of polystyrene and polymethyl methacrylate latexes. The semi-empirical equations offer a quick method for estimating swelling ratio from particle size and interfacial tension. The generalized form of Model II might prove to be more suitable for describing the swelling phenomena of relatively hydrophilic systems. ... 

Figure 7.5. Interfacial tension coefficient vs. concentration of compatibilizer for polystyrene blends with polybutadiene, compatibilized with styrene-butadiene block copolymer. Data points [Anastasiadis and Koberstein, 1988], fine computed from Eq 7.15.

Polyolefin-polyamide melt blends are striking in not only the lack of miscibility, but also the large interfacial tensions between the two melt phases. Investigations of these phenomena in our laboratories (118,124-126) have made numerous studies of these polymer blend systems and found that their phase morphology are quite unstable and trend to coalesce especially under quiescent or low deformation rate conditions. Similar to polyolefin-polystyrene blends, they also show weak interfacial adhesion (118,124,127) (as shown in Fig. 2.9). The mechanical properties of the... 

It has been mentioned above that foams can unfavourably affect the refining processes. Formation processes of non-aqueous foams are not well enough studied. In a vast review [264], comparison between aqueous and non-aqueous foams has been made. The stabilisation of non-aqueous foams (e.g. on a hydrocarbon basis) seems to be impossible with usual hydrocarbon surfactants because of the weak liquid-gas interfacial tension lowering gradients. Fluorinated or silicone-type surfactants can be used as eventually better stabilisers. These recommendations are, in our opinion, only applicable to the production of the so-called hardening foams (polystyrene foams, polyurethane foams etc.). 

Modifications to the MKA equation have been proposed to take into account the swelling pressure and the dependence of the interfacial tension (y) and the Flory-Huggins interaction parameter (/) on particle size [62, 63] as well as the presence of adsorbed surfactant on particle swelling [64, 65], These modifications have allowed to obtain better agreement between theory and experimental data for the swelling of polystyrene particles using reasonable parameter values. 

Wu, S., Surface and interfacial tensions of polymer melts 2. Poly(methyl methacrylate), poly(normal-butyl methacrylate), and polystyrene, J. Phys. Chem., 74, 632 (1970). 

The formation of the fibril is a eonsequence of dispersed phase deformation and orientation correlating with the viscous force and interfacial tension between the dispersed phase and the matrix [236,237]. For good fibrillation to be achieved, the viscosity of dispersed phase should be lower than that of the matrix (i.e., / = rjd/ mtemperature dependence of p of PS to PP is shown in Figure 3.68. Experimental results showed that p is less than 1 above 210°C and reduces to about 0.5. This indicates that polystyrene is able to form the fibrils in polypropylene matrix when the processing temperature is over 210°C, but finds it difficult below 210°C [239]. 

Before leaving the subject of interfacial behavior in polymers, it is instructive to consider the interfacial tension, and resulting interfacial density profiles. Making effective use of the Flory interaction parameter x, Helfand and Tagami (1972), Gaines (1972), Wu (1974), and others estimated the interfacial surface tension between incompatible polymer pairs (see Table 13.1). Also shown in Table 13.1 are theoretically estimated values of x-(See Section 4.7 and especially Sections 4.7.3 and 9.6 for related discussion.) Helfand and Tagami found that the characteristic thickness of the interface is proportional to x — y for small /. For a polystyrene/poly(methyl methacrylate) system, the value of / leads to an estimated interfacial thickness of 50 A. This value is much less than that estimated by Voyutskii and Vakula... 

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