Viscosity injection time

Following Poiseuille s law, the amount of sample loaded will increase with an increase in pressure the sample concentration and the injection time and will decrease with increases in solution viscosity and the length of the capillary. 

Due to the low filling times and high melt viscosities, injection pressures are quite high, as mentioned previously. Generation of this pressure would not be possible without a check valve located at the tip of the screw, as illustrated in Figure 14-44. This... 

Because of the low melt viscosity of LCPs, thin sections can he molded with highly filled (70%) LCPs. The addition of hulk lubricants reduces the melt viscosity. Injection molded parts are produced with a minimum of molded-in stress, little or no flash, and high dimensional stability. Fast cycle times, reduced mold wear, elimination of secondary operations, and other processing and performance gains of LCPs often lead to lower overall finished part costs even below those of less-expensive resins. 

Plastic temperature, °C Plastic viscosity, Pa s Injection pressure, bar Injection time, s Mold cavity pressure, bar Gates... 

It should be stressed once again, thongh, that the filling balance for this monld will be dependent on use of the same plastic and the given injection time and processing temperature. A change in these parameters will cause a change in the melt viscosity and different pressure drops in the flows to cavities A-D. 

The right side of Fig. 20.15 gives a proof of this thesis. Three different raw data sets of the viscosity versus time are given, but in two cases the solution was pretreated. If the reactive solution is injected in the rheometer without any pretreatment, a typical measurement with an induction period of about 32 s is determined. But if the solution is purged with a high gas flow of nitrogen for 10 s before the injection into the rheometer, the induction time is decreased drastically. The same result is observed, if a distilled acrylic acid is used instead, because... 

It is well-established that both polyacrylamides and biopolymers are susceptible to oxidative attack by dissolved oxygen in the injected water. Degradation is detected by the loss of solution viscosity with time. At low temperatures, the reaction rate is slow and can go undetected in short tests. The degradation rate increases as temperature increases, which is consistent with chemical reaction kinetics. The oxidative degradation reaction is catalyzed by dissolved metal ions, such as Fe+ + +. i Degradation by oxidative attack can be prevented or minimized by reducing the oxygen content of the water or brine to less than a few parts per billion. 

For a long time the official specifications for diesel fuel set only a mciximum viscosity of 9.5 mm /s at 20°C. Henceforth, a range of 2.5 mm /s minimum to 4.5 mm /s maximum has been set no longer for 20°C but at 40°C which seems to be more representative of injection pump operation. Except for special cases such as very low temperature very fluid diesel fuel and very heavy products, meeting the viscosity standards is not a major problem in refining. 

Steam is injected into a reservoir to reduce oil viscosity and make it flow more easily. This technique is used in reservoirs containing high viscosity crudes where conventional methods only yield very low recoveries. Steam can be injected in a cyclic process in which the same well is used for injection and production, and the steam is allowed to soak prior to back production (sometimes known as Huff and Puff). Alternatively steam is injected to create a steam flood, sweeping oil from injectors to producers much as in a conventional waterflood. In such cases it is still found beneficial to increase the residence (or relaxation) time of the steam to heat treat a greater volume of reservoir. 

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