May 2018 (section B) Q3(a) 6.15 x 10-6 m/s; (b) 2.24 mm, (d) 18.36 mm, 1.87 mm Q3. a) A single screw extruder has a sc

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May 2018 Section B Q3 A 6 15 X 10 6 M S B 2 24 Mm D 18 36 Mm 1 87 Mm Q3 A A Single Screw Extruder Has A Sc 1 (8.09 KiB) Viewed 39 times

May 2018 Section B Q3 A 6 15 X 10 6 M S B 2 24 Mm D 18 36 Mm 1 87 Mm Q3 A A Single Screw Extruder Has A Sc 2 (53.83 KiB) Viewed 39 times

May 2018 Section B Q3 A 6 15 X 10 6 M S B 2 24 Mm D 18 36 Mm 1 87 Mm Q3 A A Single Screw Extruder Has A Sc 3 (53.84 KiB) Viewed 39 times

May 2018 Section B Q3 A 6 15 X 10 6 M S B 2 24 Mm D 18 36 Mm 1 87 Mm Q3 A A Single Screw Extruder Has A Sc 4 (47.46 KiB) Viewed 39 times

May 2018 (section B) Q3(a) 6.15 x 10-6 m/s; (b) 2.24 mm, (d) 18.36 mm, 1.87 mm
Q3. a) A single screw extruder has a screw with a diameter of 48 mm and the screw angle is 17.7º. The screw length is 0.8 m and the flight depth is 3 mm. If the screw speed is 50 rpm and the viscosity of the plastic is 250 Ns/m?, calculate the output when the extruder is producing a medical tube through a die with an outside diameter of 12 mm, an inside diameter of 10.4 mm and a length of 13 mm. You may assume that leakage losses from the extruder are negligible. [9 marks) b) If the details given in a) describe the geometry of the second metering zone of a vented extruder, calculate the flight depth in the first metering zone if it has a length of 1.2 m. You may assume that all other screw dimensions and processing conditions are the same as in a). [6 marks] c) What types of polymers are processed in a vented extruder? [2 marks] d) ) If the extruder is producing tube as described in a), what is its diameter and wall thickness immediately after it emerges from the die? The polymer is polyethylene and its extrusion temperature is 170°C. You should use the data provided in Figs. 23.1 and Q3.2. (8 marks)
1E+006 Tensile modulus 100000 Tensile viscosity Shear modulus Figure Q3.1. Flow Curves for Polyethylene at 170°C (Ns/m2 or N/m2) 10000 1000 Shear viscosity Onset of non-laminar flow in unstreamlined dies 100 0.1 1000 10000 10 100 Strain rate (s)
2.6 2.4 BSH 2.2 2 B SR Figure 23.2. Shear Swelling Ratios Swelling Ratio 1.8 1.6 1.4 B ST 1.2 1 0 7 8 CO 2 3 4 5 6 Recoverable Shear Strain