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