Materials Science 2 Study Guide
Lecture 1
Why do we design in plastic?
● Main reason: Possibility to integrate functions
● Prejudice:
○ Harmful
■ When extracting raw materials
■ When end up in nature
■ But:
● Weight reduction
● Natural polymers (wood/cotton/wool) exist
● Strong growth in bio-degradables
○ Inferior to metals
○ Look cheap
● Limitations:
○ Stress strain curve vs steel
■ Modulus 100x lower
■ Yield stress 10x lower
■ Elongation at break is higher
■ Temperature and time dependent
○
● Other reasons:
, ○ Weight reduction (again)
○ Resistant against corrosion: doesn’t need paint
○ Material is cheaper
○ Insulation (thermal and electric)
When to avoid plastic?
● Heat
● Strong forces
● Inflammable environment
● If mass is desired
● When tolerances are very tight
Applications:
● Without plastic:
○ Packaging weight x3
○ Packaging cost x3
○ Energy consumption x2
○ Waste volume x2
● Constructions:
○ Pipe lines
○ Windows/window frame
○ Paints
○ Floors
○ Household appli
○ Sports and toys (toys are 70% plastic)
What are polymers?
● Poly = many and meros = part
● Large molecules composed of many repeated subunits, also called macromolecules.
● Structure:
,● Origin
a. Natural : Wood, cotton, wool
b. Semi-synthetic: Cellophane, leather, rubber
c. Sythetic: Coal + petroleum = monomers (Molecular building blocks)
● Structures
a. Single chain (linear or branched)
■ Strongly entangled clusters of chains with weak intermolecular interactions
between the chains:
● Van der Waals, Dipolar, Hydrogen bonds = low stiffness due to weak
interactions
, b. Networks
1. Entanglements
■ When there’s sufficient chain length, a removable physical network is created.
The chains are connected through entanglements.
■ The “knots” are decisive for its mechanical properties such as strength and
stiffness.
2. Cross link: Chemical bond between chains (ex: rubbers)
○ Prevents flow/movement
○ Shape retaining!
So what are plastics?
● Plastics = polymer + additives
● Additive examples:
○ Improve processing: anti-oxidants, lubricants, sulfur, nucleating agents, blowing agents
Lecture 1
Why do we design in plastic?
● Main reason: Possibility to integrate functions
● Prejudice:
○ Harmful
■ When extracting raw materials
■ When end up in nature
■ But:
● Weight reduction
● Natural polymers (wood/cotton/wool) exist
● Strong growth in bio-degradables
○ Inferior to metals
○ Look cheap
● Limitations:
○ Stress strain curve vs steel
■ Modulus 100x lower
■ Yield stress 10x lower
■ Elongation at break is higher
■ Temperature and time dependent
○
● Other reasons:
, ○ Weight reduction (again)
○ Resistant against corrosion: doesn’t need paint
○ Material is cheaper
○ Insulation (thermal and electric)
When to avoid plastic?
● Heat
● Strong forces
● Inflammable environment
● If mass is desired
● When tolerances are very tight
Applications:
● Without plastic:
○ Packaging weight x3
○ Packaging cost x3
○ Energy consumption x2
○ Waste volume x2
● Constructions:
○ Pipe lines
○ Windows/window frame
○ Paints
○ Floors
○ Household appli
○ Sports and toys (toys are 70% plastic)
What are polymers?
● Poly = many and meros = part
● Large molecules composed of many repeated subunits, also called macromolecules.
● Structure:
,● Origin
a. Natural : Wood, cotton, wool
b. Semi-synthetic: Cellophane, leather, rubber
c. Sythetic: Coal + petroleum = monomers (Molecular building blocks)
● Structures
a. Single chain (linear or branched)
■ Strongly entangled clusters of chains with weak intermolecular interactions
between the chains:
● Van der Waals, Dipolar, Hydrogen bonds = low stiffness due to weak
interactions
, b. Networks
1. Entanglements
■ When there’s sufficient chain length, a removable physical network is created.
The chains are connected through entanglements.
■ The “knots” are decisive for its mechanical properties such as strength and
stiffness.
2. Cross link: Chemical bond between chains (ex: rubbers)
○ Prevents flow/movement
○ Shape retaining!
So what are plastics?
● Plastics = polymer + additives
● Additive examples:
○ Improve processing: anti-oxidants, lubricants, sulfur, nucleating agents, blowing agents
