Staging ratio

A series of latex samples with varying stage ratios (LS-1 to LS-4) was prepared at 90°C by emulsion polymerizing styrene and butadiene monomer mixes (S/B/AA/CHBr3 59/40/1/0.5) in the pre-... 

Two latex samples (LS-5 and LS-6) were prepared in the same manner as described above except that 5 parts of carbon tetrachloride were added in both the first and second stage monomer mixes, based on 100 parts monomer mix. The stage ratios were 50/50 and 20/80, respectively. 

A series of latex samples with varying S/B ratios in the second stage (LS-7, LS-8 and LS-9) was prepared at 90°C, using an externally prepared polystyrene latex of 1350 A. The second-stage S/B ratios were 70/30, 90/10, and 95/5, respectively. The stage ratio was 20/80. Neither vinyl acid nor chain transfer agent was used. 

Two latex samples (LS-10 and LS-11) were prepared by switching the order of monomer addition between a styrene mix (S/AA 98/2) and a high butadiene mix (S/B/AA 28/70/2) at the stage ratio of 50/50. The polymerization temperature was 80°C during the continuous addition of monomer mixes and then raised to 100°C for one-hour cook-down. 

Figures 3A, 3B, and 3C show the ultra-thin cross-sections of OsOi+-stained two-stage (styrene//styrene-butadiene) latex particles at the stage ratio of 20/80, whose S/B ratios in the second stage are 70/30 (LS-7), 90/10 (LS-8), and 95/5 (LS-9), respectively. It can be seen from the micrographs that the size of polystyrene phase domains decreases with decreasing butadiene level in the second-stage S-B copolymers and becomes so small at the S/B ratio...

Figure 2. Ultrathin cross sections of OsO,-stained two-stage (S//S-B) latex particles at the stage ratios of 50/50 and 20/80, respectively, showing the effect of molecular weight ((A) LS-5, (B) LS-6)...

The ratio (Seff/Sb.dck) is known as the staging ratio or gradation. 

The staging ratio can then be obtained from Sb.dck values and k0 from the manufacturer s data. 

Roots efficiencies of about 70% or more can be achieved if k0 > 20 and Sth/Sback < io. Although such values for the staging ratio are satisfactory in the medium vacuum range, lower values are desirable if there are large variations in operating pressures or if the Roots pump is working where k0 is small. 

Stage Ratio Recovery (%) Impurity (%) Impurity (%) Rejection (%) (L/m h)... 

Staging ratio (vacuum technology) The ratio of the pumping speed of one pump (or stage) to the next pump (or stage) in a multistage pump or train of pumps. 

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