General Industry Exam 1 Chapter 13,

13.4 Which of the following are sections of a conventional extruder barrel for thermoplastics (three correct answers): (a) compression section, (b) die section, (c) feed section, (d) heating section, (e) metering section, and (f) shaping section?

a, c, e

13.15 Reaction injection molding is used for which one of the following plastic types: (a) thermoplastics or (b) thermosets?

b

13.18 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, or (e) sandwich molding?

b

13.19 Stretch blow molding is a variation of which one of the following: (a) extrusion blow molding, (b) injection blow molding, or (c) rotational blow molding?

b

13.21 Thermoforming is limited to which one of the following plastic types: (a) elastomers, (b) thermoplastics, or (c) thermosets?

b

13.6 Bambooing is a more severe case of which one of the following defects in plastic extrusion: (a) melt fracture, (b) sharkskin, or (c) viscoelasticity?

b

13.16 Compression molding differs from injection molding in which of the following respects (two correct answers): (a) faster production rates, (b) molds are simpler, (c) part geometries are generally more complex, (d) presses are oriented vertically rather than horizontally, and (e) shorter cycle times?

b and d

13.25 The two most common polymer foams are which of the following: (a) polyacetal, (b) polyethylene, (c) polystyrene, (d) polyurethane, and (e) polyvinylchloride?

c and d

13.17 Compression molding and transfer molding can be used on both thermosets and elastomers: (a) true or (b) false?

a

13.2 The die swell ratio for a polymer melt has a value that is never less than one: (a) true or (b) false?

a

13.23 Which one of the following thermoforming processes requires the most expensive mold: (a) mechanical thermoforming, (b) pressure thermoforming, or (c) vacuum thermoforming?

a

13.24 The term encapsulation refers to which one of the following plastics shaping processes: (a) casting, (b) compression molding, (c) extrusion of hollow forms, (d) injection molding in which a metal insert is encased in the molded part, or (e) vacuum thermoforming using a positive mold?

a

13.3 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: (a) true or (b) false?

a

13.8 Injection molding is a process in which a polymer is heated to a highly plastic state and forced to flow under high pressure into a mold cavity, where it solidifies and is then removed from the cavity: (a) true or (b) false?

a

13.12 A 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, (c) sprue does not solidify, and (d) stronger molded parts?

a and b

13.14 Which of the following are reasons why injection molding of thermosets is more difficult than injection molding of thermoplastics (two best answers): (a) allowances must be made for cross-linking of thermosets, (b) barrel temperatures must be hotter for thermosets, (c) cycle times are longer because of curing, (d) thermosets are denser, or (e) two injection units are required?

a and c

13.9 The principal components of an injection molding machine are which two of the following: (a) clamping unit, (b) hopper, (c) injection unit, (d) mold, and (e) part ejection unit?

a and c

13.1 A polymer melt exhibits which of the following properties and characteristics (three correct answers): (a) becomes less resistant to flow at high shear rates, (b) becomes more resistant to flow at high shear rates, (c) high viscosity, (d) low viscosity, (e) Newtonian fluid, and (f) viscoelasticity?

a,c, f

13.13 Which of the following defects are associated with injection molding (three correct answers): (a) bambooing, (b) die swell, (c) drag flow, (d) flash, (e) melt fracture, (f) short shots, or (g) sink marks?

d, f, and g

13.22 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, or (d) a three plate mold

(c).

13.10 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, or (d) where the two mold halves come together?

d

13.11 The function of the ejection system in injection molding 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, or (d) separate the part from the mold cavity after molding?

d

13.5 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 or (b) false?

(b). 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.

13.20 In rotational molding, centrifugal force is used to force the polymer melt against the surfaces of the mold cavity where solidification occurs: (a) true or (b) false?

(b). It is the force of gravity in the doubly rotating mold that forces the polymer against the mold surfaces.

13.26 In which of the following properties do plastic parts often compare favorably with metals (two best answers): (a) impact resistance, (b) resistance to ultraviolet radiation, (c) stiffness, (d) strength, (e) strength to weight ratio, and (f) temperature resistance? 13.27 Which of the following processes would be applicable to produce hulls for small boats (three best answers): (a) blow molding, (b) compression molding, (c) injection molding, (d) rotational molding, and (e) vacuum thermoforming? Answer. (a), (d), and (e).

a and e

13.7 Which of the following processes are used to produce plastic sheet and film (three correct answers): (a) blown film extrusion process, (b) calendering, (c) chill roll extrusion, (d) doctor blade method, (e) spinning, (f) thermoforming, and (g) transfer molding?

a, b, and c

13.27 Which of the following processes would be applicable to produce hulls for small boats (three best answers): (a) blow molding, (b) compression molding, (c) injection molding, (d) rotational molding, and (e) vacuum thermoforming?

a, d and e