EMAE 160 LECTURE 8 EXAM
QUESTIONS AND ANSWERS
What is R.I.M ? For Thermoset. - ANSWER-Reactive Injection Molding.
a monomer and two more reactive fluids are forced at high speed into a mixing
chamber, then quickly into a mold cavity. chemical reactions take place rapidly,
creating heat for thermoset.
RIM polyurethane systems are composed of isocyanate and polyol that chemically
react to form plastic material in a mold.
Difference between transfer molding and compression molding? - ANSWER-
Transfer molding, unlike compression molding uses a closed mold, so smaller
tolerances and more intricate parts can be achieved. Transfer molding is the more
expensive process.
What is rotational molding? - ANSWER-A heated hollow mold filled with charge or
shot weight of material is rotated slowly causing the softened material to disperse
and stick to the walls of the mold.
Of the three polymer types, which is the most commercially important? - ANSWER-
Thermoplastic
Which of the three polymer types is not considered to be a plastic? - ANSWER-
Elastomer
What is the function of the ejection system in injection molding? - ANSWER-It
prevents chemical cross-linking that may occur (causing the screw and check valves
to seize and potentially damaging the injection molding machine)
What is a plasticizer? - ANSWER-Chemical added to a polymer to make it softer and
more flexible
What is structural foam molding? - ANSWER-Low pressure injection molding which
relies on the foaming action by nitrogen gas/chemical blowing agent.
used to make lightweight parts with high stiffness to weight ratio
Natural rubber is called ____ in its raw form and it is _____ in the winter and _____
in the summer. - ANSWER-latex, brittle and sticky
What is vulcanization? - ANSWER-a chemical process for converting
rubber/polymers into more durable materials by the addition of sulfur (or other
equivalent "curatives" or "accelerators")
List three differences between thermoset plastics and thermoplastics. - ANSWER-TS
= linear linked to cross linking, heat to set, brittle/stiff, permanent chemical change
TP = linear linked only, heat to flow, flexible, recyclable
QUESTIONS AND ANSWERS
What is R.I.M ? For Thermoset. - ANSWER-Reactive Injection Molding.
a monomer and two more reactive fluids are forced at high speed into a mixing
chamber, then quickly into a mold cavity. chemical reactions take place rapidly,
creating heat for thermoset.
RIM polyurethane systems are composed of isocyanate and polyol that chemically
react to form plastic material in a mold.
Difference between transfer molding and compression molding? - ANSWER-
Transfer molding, unlike compression molding uses a closed mold, so smaller
tolerances and more intricate parts can be achieved. Transfer molding is the more
expensive process.
What is rotational molding? - ANSWER-A heated hollow mold filled with charge or
shot weight of material is rotated slowly causing the softened material to disperse
and stick to the walls of the mold.
Of the three polymer types, which is the most commercially important? - ANSWER-
Thermoplastic
Which of the three polymer types is not considered to be a plastic? - ANSWER-
Elastomer
What is the function of the ejection system in injection molding? - ANSWER-It
prevents chemical cross-linking that may occur (causing the screw and check valves
to seize and potentially damaging the injection molding machine)
What is a plasticizer? - ANSWER-Chemical added to a polymer to make it softer and
more flexible
What is structural foam molding? - ANSWER-Low pressure injection molding which
relies on the foaming action by nitrogen gas/chemical blowing agent.
used to make lightweight parts with high stiffness to weight ratio
Natural rubber is called ____ in its raw form and it is _____ in the winter and _____
in the summer. - ANSWER-latex, brittle and sticky
What is vulcanization? - ANSWER-a chemical process for converting
rubber/polymers into more durable materials by the addition of sulfur (or other
equivalent "curatives" or "accelerators")
List three differences between thermoset plastics and thermoplastics. - ANSWER-TS
= linear linked to cross linking, heat to set, brittle/stiff, permanent chemical change
TP = linear linked only, heat to flow, flexible, recyclable
