Chapter 13 Multiple Choice
Which of the following processes are associated with the production of plastic sheet and film (three correct answers):
(a) blown-film extrusion process (b) calendering (c) chill-roll extrusion
Use of a parison is associated with which one of the following plastic shaping processes:
(b) blow molding
A thermoforming mold with a convex form is called which one of the following:
(c) a positive mold
The two most common polymer foams are which of the following:
(c) polystyrene (d) polyurethane
Which of the following are sections of a conventional extruder barrel for thermoplastics (three best answers):
(a) compression section (c) feed section (e) metering section
In which of the following properties do plastic parts often compare favorably with metals (two best answers):
(a) impact resistance (e) strength-to-weight ratio
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
(b) false
The principal components on an injection molding machine are which two of the following:
(a) clamping unit (c) injection unit
The function of the ejection system is which one of the following:
(d) separate the part from the cavity after molding
The parting line in injection molding is which one of the following:
(d) where the two mold halves come together
The term encapsulation refers to which one of the following plastics shaping processes:
(a) casting
Which of the following processes are generally limited to thermoplastic polymers (two best answers):
(a) blow molding (d) thermoforming
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: (a) true (b) false
(b) false
Which of the following defects or problems is associated with injection molding (three correct answers):
(d) flash (f) short shots (g) sink marks
The three-plate mold offers which of the following advantages when compared to a two-plate mold (two best answers):
(a) automatic separation of parts from runners (b) gating is usually at the base of the part to reduce weld lines
Which of the following processes would be applicable to produce hulls for small boats (three best answers):
(a) blow molding (d) rotational molding (e) vacuum thermoforming