Cooling squeeze flow

Athletic trainers use instant ice packs that can be cooled quickly on demand. Squeezing the pack breaks an inner container, allowing two components to mix and react. This reaction makes the pack become cold. Describe the heat flow for this spontaneous process. 

The material softens under heat and pressure, flowing to fill the mold. Excess material is squeezed from the mold. If it is a thermoset plastic, cross-linking occurs in the mold. In thermoplastic molding, the part is hardened under pressure by cooling the mold. 

Figure 9.39 Trace of normal stress for a compression-molded 73/27 HBA/HNA copolyester specimen (a) during sample loading at 320 °C, (b) during squeezing and cooling to 290 °C, (c) during temperature equilibration at 290 °C for 4 h, (d) transient and steady-state shear flows at y = 0.5 for 200 s, and (e) during relaxation after cessation of shear flow. An unrelaxed normal stress of 195 Pa was present in the specimen before being subjected to shear flow. (Reprinted from Han et al., Molecular Crystals and Liquid Crystals 254 335. Copyright 1994, with permission from Taylor Francis Group.)...

One section of the pinch-off r on is the flash pockrt. Varying the depth of this area ean affect the strength of the weld line. This r on of the pineh-off has the greatest contribution to the sfrength of the weld line [4]. The purpose of the flash pockrt is to squeeze the parison as the mold closes which causes the plastie to flow upwards to the weld line and out of the mold. It also transfers heat from the material to the cooling chaimels. 

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