Tubular film blowing operation

Figure 11.6 illustrates the general configuration of a film blowing operation. Molten polymer from the extruder is pumped into an annular die, where it is distributed around a tubular melt channel before emerging vertically as a relatively thick-walled molten tube. The top of... 

Tubular linear low-density polyethylene (LLDPE) film of thickness equal to 34.1 qm is produced (Kanai and White, 1984) by a blown film operation with draw ratio equal to 4. The annular die has an inner diameter 1.387 cm and outer diameter 1.496 cm. Calculate the pressure of the air to blow a bubble (i.e., the internal overpressure) of the given specifications and the axial tension to draw such a bubble. Consider that LLDPE is Newtonian with viscosity 720 Pa s, the process is isothermal at 180 °C, and LLDPE freezes at an axial distance of 15 cm. The mass fiow rate of the polymer is 0.21 g/s, and its density is 0.919 g/cm-. 

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