MMET 281 EXAM 1 QUESTIONS AND
ANSWERS ALL CORRECT
What are the advantages of machining? - Answer- -no mold costs are needed
-components too large to be molded can be machined
-short lead times
-low volumes are economical
-can try a design before committing to tooling
What are the disadvantages of machining? - Answer- -limited to the more rigid plastics
-high scrap
-high costs of CNC machine time
-volume production requires robust jigs/fixtures
-some composite plastics produce dust
Why did modern plastics take so long to develop? - Answer- because they had an
unclear understanding of the chemical and structural nature
What global crisis spurred the development of the plastic industry? - Answer- WWII
What is the preferred polymers to use in order? - Answer- synthetic>modified natural
polymers>natural polymers
Why use an oversized tap when tapping? - Answer- to consider the elastic recovery
What is important to keep in mind when sanding and polishing? - Answer- plastics have
low thermal conductivity and tend to burn
What are some examples of mechanical adhesion? - Answer- thermoplastic resins,
thermosetting resins, elastomeric adhesion
What were the problems in using natural polymers? - Answer- supply, preparation,
properties
What are some examples of natural polymers? - Answer- horn, shell, hooves, shellac,
gutta percha
What is shellac/what is it made from? - Answer- a natural polymer made from the lac
insect
, What is the name of the natural polymer made from tree products? - Answer- Gutta
Percha
What is casein? - Answer- a milk curd product that is modified by formaldehyde
What was casein used for? - Answer- buttons, umbrella handles
What is rubber made from? - Answer- natural latex
How is vulcanized rubber made? - Answer- sulfur and heat are added
-more sulfur=harder rubber
What is celluloid? - Answer- plant product, modified natural polymers
What is bakelite? - Answer- an early, completely synthetic material
What is bakelite used for? - Answer- billiard balls, telephones, early automotive parts
Define Polymers - Answer- organic compounds that have at least 100 units (mers)
What is an elastomer? - Answer- a stretchable polymer, rubber
What are plastics? - Answer- formable polymers, plastic
What are the two types of plastic? - Answer- thermoplastic and thermoset
Define Resin - Answer- gumlike solid or semisolid used in making paints, varnishes and
plastics
What are the major plastic processing technologies? - Answer- -injection molding
-extrusion
-thermoforming
-blow molding
What is the main process for making plastic parts? - Answer- injection molding
What is injection molding used for? - Answer- complicated and simple shapes
What is extrusion used for? - Answer- continuous shapes-pipe, sheet
What is the most widely used form of thermoforming? - Answer- vacuum forming
What is thermoforming used for? - Answer- packaging
ANSWERS ALL CORRECT
What are the advantages of machining? - Answer- -no mold costs are needed
-components too large to be molded can be machined
-short lead times
-low volumes are economical
-can try a design before committing to tooling
What are the disadvantages of machining? - Answer- -limited to the more rigid plastics
-high scrap
-high costs of CNC machine time
-volume production requires robust jigs/fixtures
-some composite plastics produce dust
Why did modern plastics take so long to develop? - Answer- because they had an
unclear understanding of the chemical and structural nature
What global crisis spurred the development of the plastic industry? - Answer- WWII
What is the preferred polymers to use in order? - Answer- synthetic>modified natural
polymers>natural polymers
Why use an oversized tap when tapping? - Answer- to consider the elastic recovery
What is important to keep in mind when sanding and polishing? - Answer- plastics have
low thermal conductivity and tend to burn
What are some examples of mechanical adhesion? - Answer- thermoplastic resins,
thermosetting resins, elastomeric adhesion
What were the problems in using natural polymers? - Answer- supply, preparation,
properties
What are some examples of natural polymers? - Answer- horn, shell, hooves, shellac,
gutta percha
What is shellac/what is it made from? - Answer- a natural polymer made from the lac
insect
, What is the name of the natural polymer made from tree products? - Answer- Gutta
Percha
What is casein? - Answer- a milk curd product that is modified by formaldehyde
What was casein used for? - Answer- buttons, umbrella handles
What is rubber made from? - Answer- natural latex
How is vulcanized rubber made? - Answer- sulfur and heat are added
-more sulfur=harder rubber
What is celluloid? - Answer- plant product, modified natural polymers
What is bakelite? - Answer- an early, completely synthetic material
What is bakelite used for? - Answer- billiard balls, telephones, early automotive parts
Define Polymers - Answer- organic compounds that have at least 100 units (mers)
What is an elastomer? - Answer- a stretchable polymer, rubber
What are plastics? - Answer- formable polymers, plastic
What are the two types of plastic? - Answer- thermoplastic and thermoset
Define Resin - Answer- gumlike solid or semisolid used in making paints, varnishes and
plastics
What are the major plastic processing technologies? - Answer- -injection molding
-extrusion
-thermoforming
-blow molding
What is the main process for making plastic parts? - Answer- injection molding
What is injection molding used for? - Answer- complicated and simple shapes
What is extrusion used for? - Answer- continuous shapes-pipe, sheet
What is the most widely used form of thermoforming? - Answer- vacuum forming
What is thermoforming used for? - Answer- packaging
