Injection pressure release

When calcium carbonate goes into solution, it releases basic carbonate ions (COf ), which react with hydrogen ions to form carbon dioxide (which will normally remain in solution at deep-well-injection pressures) and water. Removal of hydrogen ions raises the pH of the solution. However, aqueous carbon dioxide serves to buffer the solution (i.e., re-forms carbonic acid in reaction with water to add H+ ions to solution). Consequently, the buffering capacity of the solution must be exceeded before complete neutralization will take place. Nitric acid can react with certain alcohols and ketones under increased pressure to increase the pH of the solution, and this reaction was proposed by Goolsby41 to explain the lower-than-expected level of calcium ions in backflowed waste at the Monsanto waste injection facility in Florida. 

The flask in its wire basket is placed in a water bath at 50 °C. After 5 h the polymerization has finished and the color of the solution is then yellow. After cooling to room temperature, 1 ml of 2-propanol is injected and the excess pressure released by insertion of an injection needle.The flask is opened, 0.5 g of 2,6-di-ferf-butyl-4-methylphenol added as stabilizer, and the polymer precipitated in a three-fold volume of methanol.The viscous product is dried in vacuum at 50 °C.The yield is quantitative.The limiting viscosity number is determined in toluene at 25 C. 

Close the outlet port before the injection pressure is released and try to build up a high cure pressure. 

Another proposed process employed injection molding in which starch and limited amounts of plasticizing water are heated under pressure to temperatures above the Tg and Tm to transform the native starch into a homogenous, destructured, thermoplastic melt. The process melt is then cooled to below the Tg of the system before pressure release to maintain the moisture content. Additives include natural and synthetic polymers, plasticizers and lubricants.136-139 159 160 The technology has been used to prepare pharmaceutical capsules and shaped objects, such as disposable cutlery, straws and pens. 

It is quite usual to find a high internal pressure maintained in autoclaves at the end of their sterilization phases until some cooling has taken place. This is typical for fluid load cycles, which may be held under air pressure until the signals from all of the sensors indicate that the temperature is lower than 80°C. In these cases the signal is to close the air injection valve and open a pressure release valve at the appropriate temperature. Cooling may be subject to a phase time excess. 

During injection well pressure releasing, the open flow discharge must be controlled under the value in order to prevent casing damage. 

Forming an optimal molding may require the addition of an external or internal lubricant to the formulation. Lubricants arc added in only small amounts, up to 1 wt %. External lubricants are insoluble in the phenohe matrix resin and are often non- polar materials such as parafiins and waxes. External lubricants act as mold release agents. In contrast, internal lubricants improve melt homogeneity, lower viscosity, and lower injection pressure. Therefore, internal lubricants such as fatty alcohols, fatty acid salts, acid esters, and acid amides must be fully soluble in the phenohe prepolymer [1]. 

An ammonium carbonate leaching pilot plant has been described which consists of five towers, each 10 ft high by 4 in. internal diameter, connected in series. The slurry of acid and ore is pumped in a co-current manner from the bottom to the top of each tower and then allowed to pass via 0-5 in. piping from the top of one tower to the base of the next. Air is injected at the base and mid-point of each tower. Typical pressures in the first and last towers are 130 psi and 90 psi. The system is fed from an agitated mixing tank, via a positive displacement piston pump located at the base of the first tower. After leaching, the gases are separated off by means of a pressure release valve and the leach liquor then removed from the spent ore in a hydrocyclone. 

The PET melt, either coming from virgin PET or from PET flakes, is accumulated in the head-space of the barrel head and released into the hot runner (melt-channel system) under high injection pressure and at a certain melt-stream velocity. The melt is kept in a molten stage, inside the hot runner system because of the electric heating systems. The two melt-streams (virgin and reground PET) are kept, up to the injection nozzle, in separate hot runner channels. 

One of the most surprising ways to affect the dimensions of an injection-molded part is to vary the injection pressure hold time. Generally, the injection pressure is applied and then released after a specified time to allow the injector to recharge for the next shot. Releasing the injection pressure early versus late can have a profound effect on the dimensions of the finished part. This has been observed many times but has not yet been thoroughly studied or quantified. However, on large diameter parts such as O-Rings, this can be the difference between dimension-ally compliant and dimensionally rejected parts. In the initial setup of the injection process, injection pressure hold time should be a variable studied for its effects on the finished parts. If the relationship of injection hold time is established in the initial production approval process, it is more likely to be monitored and controlled in routine production. 

Liquid-Injection Molding. In Hquid-injection mol ding (LIM), monomers and oligomers are injected into a mold cavity where a rapid polymerization takes place to produce a thermoset article. Advantages of these processes are low cost, low pressure requirement, and flexibiHty in mold configuration. Conventional systems, such as isocyanate with polyol, release Htfle or no volatiles. The generation of substantial volatiles in the mold is obviously undesirable and has represented a significant obstacle to the development of a phenoHc-based LIM system. A phenoHc LIM system based on an... 

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