GATE XE 2021 Paper 1 — page 42

Questions 124–126 of 175. Imported answers require review unless explicitly marked reviewed.

A single screw extruder is operating at a rotational speed of 2 revolutions per second for the extrusion of a Newtonian polymer under open-discharge conditions (in absence of a die, the pressure drop,

= 0). The extruder has a screw diameter,

= 5 cm, a channel depth,

= 0.4 cm, distance between flights,

= 1 cm, and a helix angle,

= 20°. Assume the value of

= 3.14. The volumetric flow rate (rounded off to 2 decimal places) is ______ cm³/s.

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At 215 °C, the viscosity of a polystyrene of molecular weight 250 × 10³ g/mol is 8.0 × 10³ Pa s. The critical molecular weight of polystyrene,

= 35 × 10³ g/mol. For a similar polystyrene of molecular weight 500 × 10³ g/mol, the viscosity (rounded off to nearest integer) will be ______ × 10³ Pa s.

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There are two different PTFE polymer specimens of the following density (

) and % crystallinity. For PTFE- specimen-1,

is 2.144 g/cm³ and % crystallinity is 50. For PTFE- specimen-2,

is 2.215 g/cm³ and % crystallinity is 75. Assuming the polymer is pure and defect free, the density (rounded off to 3 decimal places) of 100% amorphous PTFE specimen will be ______ g/cm³.

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2021 · Paper 1

Question 15

Question 16

Question 17