Plastics Exam 2 Questions with Correctly Solved
Answers
What is the difference between thermoplastics and thermosets?
Thermoplastics can be melted and reshaped multiple times without undergoing chemical
changes. Thermosets undergo irreversible chemical reactions during curing, becoming
permanently hardened.
What does a plasticizer do?
It's an additive which increases flexibility and toughness
What are some examples of coatings?
Powder coating, painting, plating
Why are halogenated materials self-extinguishing?
The gas that is produced is denser than air which smothers the oxygen that feed a flame.
What are the three ways to increase surface free energy?
Physically (solvent/water), mechanically (media blasting), and chemically (plasma treatment)
Explain how a physical surface treatment increase SFE...
By cleaning the surface of the material with a solvent/water, you can remove bonded
contaminants
Explain how mechanical surface treatments increase SFE...
By abrading the surface of the material (ex. Media blasting) you clean it and increase surface
area
, Explain how chemical surface treatments increase SFE...
BY modifying the surface chemistry of the material (ex. Plasma treatment) you oxidize the
surface without impacting bulk properties
What are some examples of decorative coatings?
Pad printing, hot stamping, screen printing.
What are some types of secondary assembly operations?
Snap fits, ultrasonic welding, hot gas welding,
How is heat generated?
Vibration, spinning, heated tool/conduction, hot gas, laser, infrared, electric field, radio
frequency
What are the three steps of the assembly of thermoplastics using heat?
1. Gerate heat to melt a thermoplastic
2. Viscous substrate can flow and acts as adhesive
3. Clamping continues as substrate cools to a solid and forms a permanent bond
What is screen printing good/useful for?
1. Rapid, high-volume production
2. Complex color patterns
3. Only for simple, flat parts
Why should you use a hot stamper?
Answers
What is the difference between thermoplastics and thermosets?
Thermoplastics can be melted and reshaped multiple times without undergoing chemical
changes. Thermosets undergo irreversible chemical reactions during curing, becoming
permanently hardened.
What does a plasticizer do?
It's an additive which increases flexibility and toughness
What are some examples of coatings?
Powder coating, painting, plating
Why are halogenated materials self-extinguishing?
The gas that is produced is denser than air which smothers the oxygen that feed a flame.
What are the three ways to increase surface free energy?
Physically (solvent/water), mechanically (media blasting), and chemically (plasma treatment)
Explain how a physical surface treatment increase SFE...
By cleaning the surface of the material with a solvent/water, you can remove bonded
contaminants
Explain how mechanical surface treatments increase SFE...
By abrading the surface of the material (ex. Media blasting) you clean it and increase surface
area
, Explain how chemical surface treatments increase SFE...
BY modifying the surface chemistry of the material (ex. Plasma treatment) you oxidize the
surface without impacting bulk properties
What are some examples of decorative coatings?
Pad printing, hot stamping, screen printing.
What are some types of secondary assembly operations?
Snap fits, ultrasonic welding, hot gas welding,
How is heat generated?
Vibration, spinning, heated tool/conduction, hot gas, laser, infrared, electric field, radio
frequency
What are the three steps of the assembly of thermoplastics using heat?
1. Gerate heat to melt a thermoplastic
2. Viscous substrate can flow and acts as adhesive
3. Clamping continues as substrate cools to a solid and forms a permanent bond
What is screen printing good/useful for?
1. Rapid, high-volume production
2. Complex color patterns
3. Only for simple, flat parts
Why should you use a hot stamper?
