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exam 2 problems jfs

exam 2 problems jfs - Material Properties(LDPE T m =125°C...

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25. You are extruding LLDPE through a 100 mm diameter annular die at a screw speed of 60rpm. Machine calibration data indicates this screw speed results in a shear rate ( γ ) of 0.1 sec -1 on the polymer melt. Calculate the pressure output (Q p ) of the EXTRUDER for the given screw dimensions. Make assumptions about the rheology of the polymer melt pool and use the appropriate model for pressure output. Use the information and charts given below to solve the problem. Processing Conditions: T barrel =170°C N=60rpm ΔP/L=20MPa mass throughput=70kg/hr

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Unformatted text preview: Material Properties (LDPE): T m =125°C ρ=915 kg/m 3 s=2.5 (viscosity power law index) 26. A PE film is blown to a thickness of 100 µm from a 40 mm diameter annular die with a 1 mm thick slit. Calculate the required take-up speed (v f ) for an extruder mass throughput of 100 kg/hr and draw ratio, DR, of 5. The freezing point is 200 mm above the die exit; the polymer is assumed to be Newtonian with a viscosity of 1000 Pa-s; and the density is 920 kg/m 3 . The die swell ratio is approximately 2....
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