Heat-setting stages

Unless all physical anisotropy can be removed from the noncrystalline fraction of biaxial PET film, the product will undergo residual shrinkage at elevated temperature. By managing both the film temperatnre and a relaxation of strain, achieved by a small convergence of the stenter rails (known as toe-in) during the heat set stage, it is possible to achieve considerable control of this film property (9). 

Heat-setting incorporates conduction heat via the blow moulds to increase the crystallinity values within the sidewall of a PET container. Therefore, improvements to the dimensional stabihty of a PET container at elevated temperatures are observed. The heat-set stage involves... 

Heat-setting can be carried out after scouring if it is suspected that the goods will shrink or for the cloth in which stretch or other properties are developed during a carefully controlled scouring process. However, this stage requires drying the cloth twice. 

Mount the electrotaxis chamber on a heated microscope stage set at 37°C. 

The flask is then inverted and the wax removed by melting in steam or in air in a furnace (the burnout oven). The investment mold is then carefully heated in the burnout oven in set stages to the maximum burnout temperature of 750°C for several hours and then cooled down to the temperature required for casting (typically in the range 450-650°C). 

Partially vaporized feed reverses these effects. For a given separation, the feed conditions can be optimized. No attempt should be made to do this at this stage in the design, since heat integration is likely to change the optimal setting later in the design. It is usually adequate to set the feed to saturated liquid conditions. This tends to equalize the vapor rate below and above the feed. 

Place 80 g, of hydroxylamine sulphate (or 68-5 g. of the hydrochloride), 25 g. of hydrated sodium acetate, and 100 ml. of water in a 500 ml. flask fitted with a stirrer and a reflux water-condenser, and heat the stirred solution to 55-60°. Run in 35 g (42 nil,) of -hexyl methyl ketone, and continue the heating and vigorous stirring for ij hours. (The mixture can conveniently be set aside overnight after this stage.) Extract the oily oxime from the cold mixture twice with ether. Wash the united ethereal extract once with a small quantity of water, and dry it with sodium sulphate. Then distil off the ether from the filtered extract, preferably using a distillation flask of type shown in Fig. 41 (p. 65) and of ca, 50 ml, capacity, the extract being run in as fast as the ether distils, and then fractionally distil the oxime at water-pump pressure. Collect the liquid ketoxime, b.p. 110-111713 mm. Yield, 30-32 g. 

Pressures can be specified at any level below the safe working pressure of the column. The condenser pressure will be set at 275.8 kPa (40 psia), and all pressure drops within the column will be neglected. The eqnihbrinm curve in Fig. 13-35 represents data at that pressure. AU heat leaks will be assumed to be zero. The feed composition is 40 mole percent of the more volatile component 1, and the feed rate is 0.126 (kg-mol)/s [1000 (lb-mol)/h] of saturated liquid (q = 1). The feed-stage location is fixed at stage 4 and the total number of stages at eight. 

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