Plastic Processing Flashcards
The forward movement of polymer melt in an extruder barrel is resisted by drag flow, which is caused by resistance to the die orifice: true or false?
False
Which of the following are sections of a conventional extruder barrel for thermoplastics
a) Compression section
b) Die section
c) Feed section
d) Heating section
e) Metering section
f) Shaping section
a, c, e
Which of the following processes are associated with the production of plastic sheet and film?
a) Blown film extrusion process
b) Calendaring
c) Chill-roll extrusion
d) Doctor blade method
e) Spinning
f) Thermoforming
g) Transfer molding
a, b, c
The principal components of an injection molding machine are which two of the following:
a) Clamping unit
b) Hopper
c) Injection Unit
d) Mold
e) Part ejection unit
a, c
The parting line in injection molding is which one of the following:
a) the lines formed where polymer melt meets after flowing around a core in the mold
b) the narrow gate sections where the parts are separated from the runner
c) where the clamping unit is joined to the injection unit in the molding machine
d) where the two mold halves come together
d
The function of the ejection system is which one of the following:
a) move polymer melt into the mold cavity
b) open the mold halves after the cavity is filled
c) remove the molded parts from the runner system after molding
d) separate the part from the cavity after molding
d
A three-plate mold offers which of the following advantages when compared to a two-plate mold:
a) Automatic separation of parts from runners
b) gating is usually at the base of the part to reduce weld lines
c) sprue does not solidify
d) stronger molded parts
a, b
Which of the following defects or problems is associated with injection molding?
a) bambooing
b) die swell
c) drag flow
d) flash
e) melt fracture
f) short shots
g) sink marks
d, f, g
In rotational molding, centrifugal force is used to force the polymer melt against the surfaces of the mold cavity where solidification occurs:
a) true
b) false
false
Use of a parison is associated with which one of the following plastic shaping processes:
a) Bi-injection molding
b) Blow molding
c) Compression molding
d) Pressure thermoforming
e) Sandwich molding
b
A thermoforming mold with a convex form is called which one of the following?
a) a die
b) a negative mold
c) a positive mold
d) a three plate mold
c
The term encapsulation refers to which one of the following plastics shaping processes:
a) Casting
b) Compression molding
c) Extrusion of the hollow forms
d) Injection molding in which a metal insert is encased in the molded part
e) Vacuum thermoforming using a positive mold
c
The two most common polymer forms are which of the following:
a) polyacetal
b) polyethylene
c) polystyrene
d) polyurethane
e) PVC
c, d
In which of the following do plastic parts often compare favourably with metals:
a) Impact resistance
b) Resistance to UV radiation
c) Stiffness
d) Strength
e) Strength-to-weight ratio
f) Temperature resistance
a, e
Which of the following processes are generally limited to thermoplastic polymers?
a) Blow molding
b) Compression molding
c) Reaction injection molding
d) Thermoforming
e) Transfer molding
f) Wire coating
a, d
