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Unformatted text preview: Film Blowing Analysis (Dimensionless) (Dimensionless) Nip rolls Guide rolls BR = DR = Rf R0 vf v0 Blowup ratio Draw ratio hf vf Δp Rf Freezeline Z h0 h0 = BR DR Thickness hf
Molten polymer Molten from extruder from R0 v0 Die Air supply Film Blowing Analysis (Dimensionless) (Dimensionless) Nip rolls Guide rolls πR0 3 ∆p P= Pressure µQ
R0 f z Takeup force F= µQ Z X= Freezeoff point R0 hf vf Δp Rf Freezeline Z h0 R0 v0 Molten polymer Molten from extruder from Die Air supply Film Blowing Analysis (Dimensionless) (Dimensionless) πR0 3 ∆p P= Pressure µQ
R0 f z Takeup force F= µQ Z X= Freezeoff point R0 Example Problem Example
A PE film is blown to a thickness of 50 µm PE from a 40 mm diameter annular die with a 1 mm thick slit. Determine the required bubble pressure and takeup force for an extruder mass throughput of 100 kg/hr and draw ratio, DR, of 4. The freezing and of point is 200 mm about the die exit; the polymer is assumed to be Newtonian with a viscosity of 1000 Pas; and the density is 920 kg/m3. The die swell ratio density The is approximately 2. What is the required bubble pressure for this process? bubble A PP film is blown to a thickness of 50 µm from a 40 mm diameter annular die with a 1 mm thick slit. Determine the required bubble pressure and takeup force for an extruder mass throughput of 100 kg/hr and draw ratio, DR, of 4. The and of freezing point is 200 mm about the die exit; the polymer is assumed to be Newtonian with a viscosity of 1000 Pas; and the density is 920 kg/m3. The the The die swell ratio is approximately 2. What is the required bubble pressure for this process? this hf vf Δp Rf R0 v0 Molten polymer Molten from extruder from Z h0 Die Air supply BR = DR = Rf R0 vf v0 πR0 3 ∆p P= µQ
F= R0 f z µQ Z X= R0 h0 = BR DR hf 100 µm vf Δp 200 X= = 10 20 h0 0.002 = = 20 −6 h f 100 *10 h0 BR = hf 20 = =4 5
Molten polymer Molten from extruder from Rf 200 mm
20 mm v0 2 mm DR Die Air supply P ≅ 0.12 µQP ∆p = 3 πR0 m Q = = vA ρ (1000)(100 / 920)(1 / 3600)(0.12) ∆p = = 144 Pa 3 π (0.020) HW: Calculate the takeup speed (vf) ...
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 Spring '08
 Brennan

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