Polystyrene pressure, effect

SCH Schultze, J.D., Zhou, Z., and Springer, J., Gas sorption in poly(butylene terephthalate). A critical test of the influence of gas Asta,Angew. Makromol. Chem., 185-186, 265, 1991. 1991SZY Szydlowski, J. and van Hook, W.A., Isotope and pressure effects on hquid-liquid equilibria in polymer solutions. H/D solvent isotope effects in acetone-polystyrene solutions. Macromolecules, 24, 4883, 1991. 

IMR Imre, A. and van Hook, W.A., Polymer-solvent demixing tmder terrsioa Isotope and pressure effects on liquid-liquid transitions. VII. Propionitrile-polystyrene solutions at negative pressure, J. Polym. Sci. PartB Polym. Phys., 32, 2283, 1994. 

JI1 Jiang, S., An, L., Jiang, B., and Wolf, B. A., Pressure effects on the thermodynamics of fra 5-decahydronaphthalene/polystyrene polymer solutions apphcation of the Sanchez-Lacombe lattice fluid theory (experimeirtal data by S. Jiang), Macromol. Chem. Phys., 204, 692, 2003. 

Except for supercritical extraction conditions, hydrostatic pressure effects are typically of negligible importance for simple solvent vapors diffusing in polymers, since the saturation vapor pressure is low, <101.3 kPa (1 atm), in most applications. The predictive power of the approach is indicated by the results for the mutual diffusion coefficient of toluene in a toluene-polystyrene system (Fig. 14) (35). 

In practice the clamping pressure will also depend on the geometry of the cavity. In particular the flow ratio (flow length/channel lateral dimension) is important. Fig. 4.42 illustrates typical variations in the Mean Effective Pressure in the cavity for different thicknesses and flow ratios. The data used here is typical for easy flow materials such as polyethylene, polypropylene and polystyrene. To calculate the clamp force, simply multiply the appropriate Mean Effective Pressure by the projected area of the moulding. In practice it is... 

Boric acid esters provide for thermal stabilization of low-pressure polyethylene to a variable degree (Table 7). The difference in efficiency derives from the nature of polyester. Boric acid esters of aliphatic diols and triols are less efficient than the aromatic ones. Among polyesters of aromatic diols and triols, polyesters of boric acid and pyrocatechol exhibit the highest efficiency. Boric acid polyesters provide inhibition of polyethylene thermal destruction following the radical-chain mechanism, are unsuitable for inhibition of polystyrene depolymerization following the molecular pattern and have little effect as inhibitors of polypropylene thermal destruction following the hydrogen-transfer mechanism. 

The trapping efficiency of polymeric, microporous adsorbents [e.g., polystyrene, polyurethane foam (PUF), Tenax] for compound vapors will be affected by compound vapor density (i. e., equilibrium vapor pressure). The free energy change required in the transition from the vapor state to the condensed state (e.g., on an adsorbent) is known as the adsorption potential (calories per mole), and this potential is proportional to the ratio of saturation to equilibrium vapor pressure. This means that changes in vapor density (equilibrium vapor pressure) for very volatile compounds, or for compounds that are gases under ambient conditions, can have a dramatic effect on the trapping efficiency for polymeric microporous adsorbents. 

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