ENGM 445 FINAL EXAM REVIEW
QUESTIONS AND ANSWERS GRADED A+
2025/2026
A polymer melt exhibits what four properties and characteristics? - ANS 1 - Becomes less
resistant to flow as temperature increases
2 - Becomes less resistant to flow at high shear rates
3 - Low viscosity
4 - Viscoelasticity
The coefficient of shear viscosity is defined as: - ANS Shear stress divided by shear rate
The die swell ratio for a polymer melt has a value that is never less than one. - ANS True
Extrusion is a compression process in which material is forced to flow through a die orifice to
provide long continuous product whose cross-sectional shape is determined by the shape of the
orifice. - ANS True
Extrusion is used for thermoplastics and elastomers but rarely for thermosets. - ANS True
1 @COPYRIGHT 2026 ALLRIGHTS RESERVED.
, The forward movement of polymer melt in an extruder barrel is resisted by drag flow, which is
caused by the resistance to flow through the die orifice. - ANS False, drag flow is the forward
motion of the melt caused by the Archimedian screw principle in the barrel. The resistance to
forward flow is called back pressure flow
The extruder characteristic indicates that flow rate in the extruder barrel increases as head
pressure decreases. - ANS True
To compensate for die swell, the extrudate is often stretched to offset expansion from die swell.
- ANS True, to control the diameter increase of the extrudate, two measures are taken:
passing through a calibrating die (sizing plate) while cooling with air/water and develop tension
by twin belts
Bambooing is a severe case of which defect in plastic extrusion. - ANS Sharkskin
Which three of processes are used to produce plastic sheet and film? - ANS 1 - blown-film
extrusion process
2 - calendering
3 - chill-roll extrusion
As the term is used in the production of synthetic fibers and filaments, spinning involves the
extrusion of a polymer melt through which one of the following. - ANS spinneret
Turbulent flow of polymer melt through the die orifice is likely to cause which one of the
following defects in plastic extrusion. - ANS melt fracture
In a reciprocating-screw injection molding machine, the injection of polymer melt into the mold
cavity is accomplished by the rotation of the screw in the barrel. - ANS False, injection of
2 @COPYRIGHT 2026 ALLRIGHTS RESERVED.
QUESTIONS AND ANSWERS GRADED A+
2025/2026
A polymer melt exhibits what four properties and characteristics? - ANS 1 - Becomes less
resistant to flow as temperature increases
2 - Becomes less resistant to flow at high shear rates
3 - Low viscosity
4 - Viscoelasticity
The coefficient of shear viscosity is defined as: - ANS Shear stress divided by shear rate
The die swell ratio for a polymer melt has a value that is never less than one. - ANS True
Extrusion is a compression process in which material is forced to flow through a die orifice to
provide long continuous product whose cross-sectional shape is determined by the shape of the
orifice. - ANS True
Extrusion is used for thermoplastics and elastomers but rarely for thermosets. - ANS True
1 @COPYRIGHT 2026 ALLRIGHTS RESERVED.
, The forward movement of polymer melt in an extruder barrel is resisted by drag flow, which is
caused by the resistance to flow through the die orifice. - ANS False, drag flow is the forward
motion of the melt caused by the Archimedian screw principle in the barrel. The resistance to
forward flow is called back pressure flow
The extruder characteristic indicates that flow rate in the extruder barrel increases as head
pressure decreases. - ANS True
To compensate for die swell, the extrudate is often stretched to offset expansion from die swell.
- ANS True, to control the diameter increase of the extrudate, two measures are taken:
passing through a calibrating die (sizing plate) while cooling with air/water and develop tension
by twin belts
Bambooing is a severe case of which defect in plastic extrusion. - ANS Sharkskin
Which three of processes are used to produce plastic sheet and film? - ANS 1 - blown-film
extrusion process
2 - calendering
3 - chill-roll extrusion
As the term is used in the production of synthetic fibers and filaments, spinning involves the
extrusion of a polymer melt through which one of the following. - ANS spinneret
Turbulent flow of polymer melt through the die orifice is likely to cause which one of the
following defects in plastic extrusion. - ANS melt fracture
In a reciprocating-screw injection molding machine, the injection of polymer melt into the mold
cavity is accomplished by the rotation of the screw in the barrel. - ANS False, injection of
2 @COPYRIGHT 2026 ALLRIGHTS RESERVED.
