CH.13

Toggle clamps and hydraulic clamps are the two basic types of clamping units. TRUE or FALSE

true

In the plastic extrusion process the feedback is in pellet or powder form and then melted down in an extrusion barrel. Then a rotating screw forces the polymer melt to flow through a die opening. TRUE or FALSE

false

The principal components of an injection molding machine are which of the following: A) clamping unit and injection unit B) hopper and mold C) extruder and part ejection unit

clamping unit and injection unit

Die swell, in extrusion, is where the hot plastic shrinks when exiting the die opening. TRUE or FALSE

true

For a Newtonian fluid, the viscosity is a constant at a given temperature, but polymer melt becomes thinner at higher rates of shear. TRUE or FALSE

true

Nearly all of the polymer products can now be produced by blow molding. TRUE or FALSE

true

Reaction injection molding involves chemical reactions among liquid ingredients solidifying in a mold. TRUE or FALSE

true

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

where the two mold halves come together

Which one is NOT one of the reasons why the plastic shaping processes are important? A) the variety of shaping processes, and the ease with which polymers can be processed B) processes allow an almost unlimited variety of part geometries to be formed C) further shaping is normally needed due to many plastic parts formed by bending and drawing D) less energy is required to form plastics due to lower processing temperatures than metal

further shaping is normally needed due to many plastic parts formed by bending and drawing

Which one is NOT one of the functions of the screen pack and breaker plate at the die end of the extruder barrel? A) it filters the contaminants and lumps B) it snaps the newly molded parts off the mold C) it builds pressure in the metering section D) it straightens the melt and removes the "memory" of the circular motion from the screw

it snaps the newly molded parts off the mold

Which is NOT one of the various forms of extruded shapes and corresponding die profiles? A) solid profiles B) hollow profiles C) wire and cable coating D) sheet and film E) multi-profiled dies F) filaments

multi-profiled dies

The study of the deformation and flow associated with physical properties of fluids is called: A) viscoelasticity B) non-newtonian C) rheology D) rod climbing

rheology

Use of 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

blow molding

An injection-molding machine is divided into three principal component: the plastic injection unit and the mold clamping unit and the die unit. TRUE or FALSE

false

In the injection molding process a polymer is heated to a highly plastic state and forced to flow under high pressure into a mold cavity, where is solidifies. TRUE or FALSE

false

Polymers have low thermal expansion coefficients. TRUE or FALSE

false

Viscosity is an important property of a polymer melt in plastics shaping processes. The parameters viscosity of polymer melt depends on are flow(or shear) rate, temperature and time. TRUE or FALSE

false

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

separate the part from the cavity after molding

_______________ is a variation of injection blow molding in which blowing rod stretches the soft parison for a more favorable stressing of polymer than conventional blow molding. A) two stage injection blow molding B) injection blow molding C) stretch blow molding D) continuous blow molding

stretch blow molding

The barrel and screw of an extruder are generally divided into three sections. Which one is NOT one of the sections? A) the feed section B) the compression section C) the flashing section D) the metering section

the flashing section