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Temperature-pressure-time processing cycle

The process by which a thermoplastic matrix composite consolidates to form a laminated structure has been attributed to autohesive bond formation at the ply interfaces. Autohesive bond formation is controlled by two mechanisms (1) intimate contact at the ply interfaces, and (2) diffusion of the polymer chains across the interface (healing). The rate of autohesive bond formation and hence the speed of the composite consolidation process is directly related to the temperature-pressure-time processing cycle. [Pg.236]

Level of cleanliness required Type and amount of organic contaminant Type, size, composition and amount of particulate contaminant Co-solvent requirements Type of parts to be cleaned (e.g., size, complexity, porosity, loading density, pressure sensitivity) Production capacity Breadth of application Temperature, pressure, separator efficiency, cycle time Temperature, pressure, co-solvents Flow rate, agitation, filtration Type, quantity, emission control and recycle considerations Dimensions, fixturing and flow pattern within cleaning vessel process control strategy Parts per cycle and cycles per work period Number of different processes that must be performed by the system... [Pg.247]

The basic fusible-core technique, a take-off of cored metal casting, makes it possible to produce simple to very complex hollow structural products. It involves using a fusible core inside the plastic part or structure. This core permits forming the desired plastic shape. The core material is a type that will not collapse or change shape during a pressure-temperature-time processing cycle. Shape is not usually the problem, since the core material is restricted. [Pg.693]

Figure 10-12. An example of developing a wire-frame system to depict the image in the mold cavity. It is generated by CAD/CAM using data on the dimensions of a bottle and includes other information stored in the data bank (or incorporated at the time the image is displayed) the shrinkage characteristics of the plastic based on how it is affected by the blow-molding process, the temperature/pressure/time cycle of the melt, the die or mold materials of construction, and so on. Figure 10-12. An example of developing a wire-frame system to depict the image in the mold cavity. It is generated by CAD/CAM using data on the dimensions of a bottle and includes other information stored in the data bank (or incorporated at the time the image is displayed) the shrinkage characteristics of the plastic based on how it is affected by the blow-molding process, the temperature/pressure/time cycle of the melt, the die or mold materials of construction, and so on.
In the major catalytic processes of the petroleum and chemical industries, continuous and steady state conditions are the rule where the temperature, pressure, composition, and flow rate of the feed streams do not vary significantly. Transient operations occur during the start-up of a unit, usually occupying a small fraction of the time of a cycle from start-up to shut-down for maintenance or catalyst regeneration. [Pg.63]

The interply bond strength for thermoplastic matrix composites has been shown to be dependent upon the processing parameters, pressure, temperature, and contact time. If the temperature distribution in the composite is nonuniform during processing, the ply interfaces will bond (or heal) at different rates. Thus, for a specified processing cycle, it is important to know precisely the temperature and degree of autohesive bonding at every point in the composite laminate in order to estimate the required process time. [Pg.234]

This section describes some of the tools available for intelligent development of process cycles, such as the time-temperature cycles used in curing composites. Current industrial practice is typically limited to the use of cure cycles. The cycles are based on a series of autoclave temperature and pressure states so that traditional linear, regulatory process control methods can be used. These recipes may not be the ideal method for process control of batch processes because they do not ... [Pg.445]

Ludwig investigated carefully the behaviour of spores under different conditions of HPT [19, 20] and introduced the cycle-type treatment that proved to be more efficient than the double level treatment [21-23], Particularly studied was how the treatment time and pressure influenced the cycle processes. Furthermore, it was noted that the temperature, pressure, contact time under pressure, and average time of treatment were fundamental parameters in the optimization of germination. [Pg.627]

N diffuses into the structural pores of clinoptilolite 10 to 10 times faster than does CH4. Thus internal surfaces are kinetically selective for adsorption. Some clino samples are more effective at N2/CH4 separation than others and this property was correlated with the zeolite surface cation population. An incompletely exchanged clino containing doubly charged cations appears to be the most selective for N2. Using a computer-controlled pressure swing adsorption apparatus, several process variables were studied in multiple cycle experiments. These included feed composition and rates, and adsorber temperature, pressure and regeneration conditions. N2 diffusive flux reverses after about 60 seconds, but CH4 adsorption continues. This causes a decay in the observed N2/CH4 separation. Therefore, optimum process conditions include rapid adsorber pressurization and short adsorption/desorp-tion/regeneration cycles. [Pg.215]

Duration of a cycle of HHP operation is defined as time required for reaction hydrogenation/dehydrogenation in pair hydride system. This time determines heat capacity of HHP. Duration of a cycle depends on kinetics of hydrogenation reactions, a heat transfer between the heated up and cooling environment, heat conductivities of hydride beds. Rates of reactions are proportional to a difference of dynamic pressure of hydrogen in sorbers of HHP and to constants of chemical reaction of hydrogenation. The relation of dynamic pressure is adjusted by characteristics of a heat emission in beds of metal hydride particles (the heat emission of a hydride bed depends on its effective specific heat conductivity) and connected to total factor of a heat transfer of system a sorber-heat exchanger. The modified constant of speed, as function of temperature in isobaric process [1], can characterize kinetics of sorption reactions. In HHP it is not sense to use hydrides with a low kinetics of reactions. The basic condition of an acceptability of hydride for HHP is a condition of forward rate of chemical reactions in relation to rate of a heat transmission. [Pg.386]

The developed mathematical model has been applied for calculation of processes in MHHP intended for vehicle air conditioning [4, 7]. Study of influence of the basic heat pump parameters (pressure of hydrogen charging, temperatures and coolant consumption, cycle time) on its power characteristics has been carried out. It was shown that the estimated data well agreed with experimental results. It was found that the developed model could be used for qualitative investigation of various parameters influence and approximate quantitative assessments. [Pg.847]

The goal was to determine vapor pressures of tars cycle-by-cycle, where between each cycle, certain amounts of higher volatility species were evaporated. As the effusion technique built in this laboratory was best suited for measuring vapor pressures from lO" to 10 torr, the temperature had to be continuously increased as more and more volatile species were lost in the process. The process is further complicated by the fact that pyrolysis tars generally have a tendency to age wifli time, especially, at higher temperatures. It is known that condensation/polymerization type reactions become considerably facile at temperatures above 100 °C. [Pg.1231]

Extensive measurements of the kinetics to determine rate constants for the nanocrystal transition have been made only on the CdSe system (Chen et al. 1997, Jacobs et al. 2001). Both the forward and reverse transition directions have been studied in spherically shaped crystallites as a function of pressure and temperature. The time-dependence of the transition yields simple transition kinetics that is well described with simple exponential decays (see Fig. 5). This simple rate law describes the transformation process in the nanocrystals even after multiple transformation cycles, and is evidence of the single-domain behavior of the nanocrystal transition. Rate constants for the nanocrystal transition are obtained from the slope of the exponential fits. This is in contrast to the kinetics in the extended solid, which even in the first transformation exhibits complicated time-dependent decays that are usually fit to rate laws such as the Avrami equation. [Pg.65]


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Cycle time

Cycling temperatures

Pressure cycle

Pressure process

Pressures processing

Process cycle times

Process temperatures

Process time

Processes cycles

Processing temperatures

Processing time

Time Pressure

Time-temperature

Time-temperature cycles

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