Polystyrene flow rate effect

The use of stabilisers (antioxidants) may, however, have adverse effects in that they inhibit cross-linking of the rubber. The influence of phenolic antioxidants on polystyrene-SBR alloys blended in an internal mixer at 180°C has been studied. It was found that alloys containing 1% of certain phenolic antioxidants were gel-deficient in the rubber phase.The gel-deficient blends were blotchy in appearance, and had lower flow rates compared with the normal materials, and mouldings were somewhat brittle. Substantial improvements in the impact properties were achieved when the antioxidant was added later in the mixing cycle after the rubber had reached a moderate degree of cross-linking. 

Fig. 14 a, b. Effect of gradient steepness on the very fast separation of polystyrene standards in a molded monolithic poly(styrene-co-divinylbenzene) column (Reprinted with permission from [121]. Copyright 1996 Elsevier). Conditions column, 50 mm x8 mm i.d., mobile phase, linear gradient from 100% methanol to 100% tetrahydrofuran within a 1 min b 12 s, flow rate, 20 ml/min, peaks represent polystyrene standards with molecular weights of 9200,34,000 and 980,000 (order of elution), 3 mg/ml of each standard in tetrahydrofuran, injection volume 20 pi, UV detection, 254 nm... 

FIGURE 9.1 Chromatograms showing the effect of temperature on the separation of aUcylphenones. Experimental conditions mobile phase A, 30% ACN (v/v) and flow rate is 4mL/min at 25°C mobile phase B, 25% ACN (v/v) and flow rate is 15mL/min at 150°C. Peaks 1, acetophenone 2, octanophenone 3, decanophenone 4, dodecanophenone 5, tetradecanophenone. Column 50x4.6 mm packed with 2.5 pm polystyrene coated zirconia. (Reprinted from Yan, B. et al.. Anal. Chem., 72, 1253, 2000. Copyright 2000, American Chemical Society. With permission.)... 

The Vel data as a function of flow rate, Q, are shown for a 10 g/mol molecular weight polystyrene in Figure A. Both the Ubbelohde viscometric data and the membrane viscometer data are platted on the same graph for a 0.6 urn pore membrane at a low concentration of 100 ppm. The flow is Newtonian. The actual agreement of the capillary and membrane viscosities at low flow rates is always excellent when << Dj., and the concentration is extremely low. At small pore size, high concentrations, and high shear rates the flow can become non-Newtonian. The latter effects are only briefly discussed in this paper, but it is this effect that offers an oportunity to characterize the shape rather than the overall size. Even for a relatively large pore (0.6, Hi , membrane the shear rates vary from 100 s at E mi/Hr to 10 s at 200... 

First, the sample was examined by GPC, for which four columns of styragel of 106,10s, 104 and 103 A nominal pore size were used. The total number of theoretical plates as determined by acetone at a flow rate of 1 ml/min was ca. 26,000. The eluent was tetrahydrofuran. The chromatogram is shown in Figure 9, which indicates two peaks at ca. 21 and 24 counts. The former may be assigned to the tetra-chain, star-draped component, and the latter to the precursor. However, no complete separation of the two peaks was observed. For another comparison, velocity ultra-centrifugation was performed for the sample at 59,780 rpm using a 6-solvent for polystyrene, cyclohexane. The operation temperature was established at 35 °C, the 6-temperature, to minimize the concentration dependence of sedimentation velocity and other effects. A sedimentation pattern taken by UV-absorption is shown in Figure 10. It is seen that the separation of S-A sample into the two components was quite difficult even at a very low polymer concentration, 0.077 g/dl. 

A solution in THF of a set of polystyrene standards of known molecular mass was injected onto a column whose stationary phase is effective for the range 400-3000 daltons. The flow rate of the mobile phase (THF) is 1 ml/min. The chromatogram below was obtained. 

Accordingly, die swell increases with increasing flow rate and decreases with increasing length of the capillary. Both effects are depicted in Fig. 15.33 for high-density polyethylene (Han et al., 1970). This is also in agreement with Fig. 15.34, where die swell and viscosity of polystyrene are plotted vs. shear rate (Greassley et al., 1970). Die swell decreases with... 

As model samples for the verification of the conventional SdFFF as a concentration methodology monodisperse polystyrene latex beads (Dow Chemical Co.) with nominal diameters of 0.357 fum (PSl) and 0.481 /Ltm (PS2) were used. They were either used as dispersions containing 10% solids or diluted with the carrier solution (triple-distilled water -r 0.1% (v/v) detergent FL-70 from Fisher Scientific Co. -l- 0.02% (w/w) NaNj) to study sample dilution effects. Diluted samples in which the amount of the polystyrene was held constant (1 /u-L of the 10% solids) while the volume in which it was contained was varied over a 50,000-fold range (from 1 to 50 mL of carrier solution) were introduced into the SdFFF column. During the feeding step, the flow rate was 5.8 mL/h for the PSl polystyrene, and 7.6 mL/h for the polystyrene PS2, and the channel was rotated at 1800 rpm for the PSl sample and at 1400 rpm for the PS2 sample. In the sep-I aration (elution) step, the experimental conditions for the two samples were as follows ... 

In the first experimental work on FIA-FIFF [1], the system efficiency was studied by examining the effect of the ratio of injection flow rate to frit flow rate on hydro-dynamic relaxation the initial tests showed a possibility of using hydrodynamic relaxation in asymmetrical flow FFF with a number of polystyrene latex standards, in both normal and steric/hyperlayer modes of FFF Normally, relaxational band broadening under hydrodynamic relaxation arises from a broadened starting band. The length of an initial sample band during hydrodynamic relaxation is dependent on flow rates as... 

Figure 4.1 Instrumental broadening of the chromatograms polystyrene standard reference materials. (A) Effect of solution concentration on observed chromatogram Mp = 1.43 x 10. Concentrations (a) 0.50 (b) 0.20 (c) 0.05 (d) 0.02 wt vol" %. 10 fim particles mixed gel (PS/DVB) column, 60 cm long (Polymer Lab. Ltd.) flow rate 1 cm min" 140°C ODCB mobile phase RI detector. (B) Separation of the individual oligomers by degree of polymerization, from 3 to 9. Mp = 580. Concentration 0.2 wt vol" %, flow rate 1 cm min" 140°C ODCB mobile phase RI detector. 2 x 10 /zm columns (PS/DVB gel) 50 and lOOA. (C) Polystyrene molecular weight/elution volume calibration curve. Experimental conditions as in (A).

Figure 10.7 Effect of flow rate on specific resolution for bimodal mixtures of polystyrene standards (in nm) as noted. From Silebi and Viola [23].

Fig 5.18. — The effect of carrier gas flow rate on retention diagrams of n-hexadecane on polystyrene (a) calculated (b) experimental [209]. 

The effect of the stationary phase percentage on the retention diagram of n-tetradecane on polystyrene after extrapolation to infinite dilution and for zero flow rate is shoAvn in Figure 5.25 [220]. As in Figure 5.15,... 

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