Engineering Science 1021A/B Lecture Notes - Lecture 27: 3D Modeling, Repeat Unit, Polyethylene
17 May 2018
School
Department
Professor
Polymers are organic, chain molecules
Can vary in atom length
○
•
3 classes:
Thermoplastic
Flexible linear chains
§
○
Thermosetting
Rigid 3-D networks
§
○
Elastomeric
Linear cross linked chain
§
○
•
Structure
Polymers can be represented by:
•
3-D solid models
(a)
3-D space models(b)
2-D models(c)
Constrained only by 109.5 degree bond angle•
Next mer fits in a cone of possible orientations•
Molecules
Ethylene monomer:
○
Has an unsaturated bond (double bond can be broken to form 2 single
bonds)
○
•
Polyethylene molecule:
Polyethylene is built up from repeat units/mers
□
§
○
•
Functionally of a repeat unit: number of sites at which new molecules can be
attached
Functionality of ethylene is 2
○
•
Molecular Shape
Mechanical properties of a polymer are dictated by the shape of the chain•
Polymer chains are rarely straight
○
•
Carbon-Carbon bonds in simple polymers form angles of 109.5 degree
○
•
Molecular Structure
Mechanical properties are also governed by the structure of polymer chains•
Linear Branched
Cross-Linked 3-D Network
Molecular Configurations
Polymers that have more than one type of side atom or group can have a
variety of configurations:
○
•
Stereoisomerism: Head to Tail
○
Isotactic: all on the same side
§
○
Syndiotactic: alternating sides
§
○
Atactic: random
§
○
•
Geometrical isomerism is possible in mer units that contain a double bond
Cis structure:
§
○
Trans structure
§
○
•
Copolymers
Polymer chains do not have to comprised of the same mer•
Often beneficial to have 2 different mers in the same chain•
Random Alternating
Block Graft
Polymer Crystallinity
Thermoplastic polymers go through a series of changes with changes in
temperature
Similar to ceramic glasses
○
•
In their solid form they can be semi-crystalline or amorphous (glassy)•
Polymer Crystallinity
Similar to metals and ceramics, polymers can be made to exhibit some long-
range order (crystallize)
•
For polymers to crystallize, entire chains must be ordered•
•
•
Polymer Additives
In addition to basic mers, various other components can be added to alter their
properties
Fillers
○
Plasticizers
○
Stabilizers
○
Colorants
○
Flame retardants
○
•
Forming Polymers
Thermoplastics
Extrusion(a)
Blow molding(b)
Injection Molding(c)
Vacuum forming(d)
Calendaring
Liquid poured in the top
§
Rolls can be embossed
§
Floor tiles, shower curtains
§
(e)
Spinning(f)
Thermosets
Polymers
Polymers are organic, chain molecules
Can vary in atom length
○
•
3 classes:
Thermoplastic
Flexible linear chains
§
○
Thermosetting
Rigid 3-D networks
§
○
Elastomeric
Linear cross linked chain
§
○
•
Structure
Polymers can be represented by:•
3-D solid models(a)
3-D space models(b)
2-D models(c)
Constrained only by 109.5 degree bond angle•
Next mer fits in a cone of possible orientations•
Molecules
Ethylene monomer:
○
Has an unsaturated bond (double bond can be broken to form 2 single
bonds)
○
•
Polyethylene molecule:
Polyethylene is built up from repeat units/mers
□
§
○
•
Functionally of a repeat unit: number of sites at which new molecules can be
attached
Functionality of ethylene is 2
○
•
Molecular Shape
Mechanical properties of a polymer are dictated by the shape of the chain•
Polymer chains are rarely straight
○
•
Carbon-Carbon bonds in simple polymers form angles of 109.5 degree
○
•
Molecular Structure
Mechanical properties are also governed by the structure of polymer chains•
Linear Branched
Cross-Linked 3-D Network
Molecular Configurations
Polymers that have more than one type of side atom or group can have a
variety of configurations:
○
•
Stereoisomerism: Head to Tail
○
Isotactic: all on the same side
§
○
Syndiotactic: alternating sides
§
○
Atactic: random
§
○
•
Geometrical isomerism is possible in mer units that contain a double bond
Cis structure:
§
○
Trans structure
§
○
•
Copolymers
Polymer chains do not have to comprised of the same mer•
Often beneficial to have 2 different mers in the same chain•
Random Alternating
Block Graft
Polymer Crystallinity
Thermoplastic polymers go through a series of changes with changes in
temperature
Similar to ceramic glasses
○
•
In their solid form they can be semi-crystalline or amorphous (glassy)•
Polymer Crystallinity
Similar to metals and ceramics, polymers can be made to exhibit some long-
range order (crystallize)
•
For polymers to crystallize, entire chains must be ordered•
•
•
Polymer Additives
In addition to basic mers, various other components can be added to alter their
properties
Fillers
○
Plasticizers
○
Stabilizers
○
Colorants
○
Flame retardants
○
•
Forming Polymers
Thermoplastics
Extrusion(a)
Blow molding(b)
Injection Molding(c)
Vacuum forming(d)
Calendaring
Liquid poured in the top
§
Rolls can be embossed
§
Floor tiles, shower curtains
§
(e)
Spinning(f)
Thermosets
Polymers
Polymers are organic, chain molecules
Can vary in atom length
○
•
3 classes:
Thermoplastic
Flexible linear chains
§
○
Thermosetting
Rigid 3-D networks
§
○
Elastomeric
Linear cross linked chain
§
○
•
Structure
Polymers can be represented by:•
3-D solid models
(a)
3-D space models
(b)
2-D models
(c)
Constrained only by 109.5 degree bond angle
•
Next mer fits in a cone of possible orientations
•
Molecules
Ethylene monomer:
○
Has an unsaturated bond (double bond can be broken to form 2 single
bonds)
○
•
Polyethylene molecule:
Polyethylene is built up from repeat units/mers
□
§
○
•
Functionally of a repeat unit: number of sites at which new molecules can be
attached
Functionality of ethylene is 2
○
•
Molecular Shape
Mechanical properties of a polymer are dictated by the shape of the chain
•
Polymer chains are rarely straight
○
•
Carbon-Carbon bonds in simple polymers form angles of 109.5 degree
○
•
Molecular Structure
Mechanical properties are also governed by the structure of polymer chains•
Linear Branched
Cross-Linked 3-D Network
Molecular Configurations
Polymers that have more than one type of side atom or group can have a
variety of configurations:
○
•
Stereoisomerism: Head to Tail
○
Isotactic: all on the same side
§
○
Syndiotactic: alternating sides
§
○
Atactic: random
§
○
•
Geometrical isomerism is possible in mer units that contain a double bond
Cis structure:
§
○
Trans structure
§
○
•
Copolymers
Polymer chains do not have to comprised of the same mer•
Often beneficial to have 2 different mers in the same chain•
Random Alternating
Block Graft
Polymer Crystallinity
Thermoplastic polymers go through a series of changes with changes in
temperature
Similar to ceramic glasses
○
•
In their solid form they can be semi-crystalline or amorphous (glassy)•
Polymer Crystallinity
Similar to metals and ceramics, polymers can be made to exhibit some long-
range order (crystallize)
•
For polymers to crystallize, entire chains must be ordered•
•
•
Polymer Additives
In addition to basic mers, various other components can be added to alter their
properties
Fillers
○
Plasticizers
○
Stabilizers
○
Colorants
○
Flame retardants
○
•
Forming Polymers
Thermoplastics
Extrusion(a)
Blow molding(b)
Injection Molding(c)
Vacuum forming(d)
Calendaring
Liquid poured in the top
§
Rolls can be embossed
§
Floor tiles, shower curtains
§
(e)
Spinning(f)
Thermosets
Polymers
Document Summary
Next mer fits in a cone of possible orientations. Has an unsaturated bond (double bond can be broken to form 2 single bonds) Functionally of a repeat unit: number of sites at which new molecules can be attached. Mechanical properties of a polymer are dictated by the shape of the chain. Carbon-carbon bonds in simple polymers form angles of 109. 5 degree. Mechanical properties are also governed by the structure of polymer chains. Polymers that have more than one type of side atom or group can have a variety of configurations: variety of configurations: Geometrical isomerism is possible in mer units that contain a double bond. Polymer chains do not have to comprised of the same mer. Often beneficial to have 2 different mers in the same chain. Thermoplastic polymers go through a series of changes with changes in temperature. In their solid form they can be semi-crystalline or amorphous (glassy)
