Transcript Global Warming - University of Arizona

“The World We Create”
NATS 101
Section 6
Next Homework
To be posted in
D2L today!
03/25
UNIT 3:
New Materials,
To Build or to Waste?
What is ONE thing they all have in
common???
All of them are made of
POLYMERS!
Can you identify
all of the things
made of polymers
(plastics, fibers)
that allow this
game to be
played?
Our Focus: Polymers
What is a polymer?
What are
polymers
made of?
How do the
sub-units connect,
and how do polymers
align themselves?
How do polymer
structure determine
its properties?
Understanding their chemistry can
help us use them wisely!
PolymersPolymersPolymers
Polymers are made by very large molecules made up
from many smaller molecules joined together.
“mono” = single (individual)
“poly” = many
“mer” = part
Most polymers are made up of one or two
different types of monomers.
How the Monomers become Polymers?
Chemical bonds
are formed
between
monomers, and
a
NEW PRODUCT
IS MADE.
Polymer Properties
The properties of a polymer depend on
two main factors:
Chemical composition of the monomers;
Geometry of the polymer chains;
Let’s Explore Some Polymers!
Identify some physical properties of the
polymeric materials in your bag
PROPERTIES:
flexibility, elasticity, density etc.
Try to group the materials into 3 different
groups according to “similar” properties.
You Have 15 minutes
Let’s Explore Some Polymers!
Some
properties to
consider:
Materials
Properties
A
Styrofoam,
Plastic bottle,
Party cups
Somewhat Dense
Flexible
Semi-stretchable
B
Rubber band
Pantyhose
Socks
Low density
Somewhat Elastic
Stretchable
C
PVC pipe
Pen caps
Wood dowels
Density
Flexibility
Elasticity
Stretchable
Hardness
Very Dense
Hard
Brittle
Three Main Structures
Linear
chains
Branched
chains
Cross-Linked
chains
Which of these
polymer
structures would
lead to a more or
less dense
plastic?
Let’s talk more about
Structure Properties
How are the properties of a polymer
related to its structure?
Linear Structure
Due to minimal branching, the linear polymer
molecules can pack tightly, resulting in a strong,
rigid structure known as a high density polymer.
Linear Structure: Example
polymerizes
High Density
Linear Structure: Example
Nature has many examples of polymers. Cotton fibers
are made of sugar molecules that are repeated in a
chain-like manner. Hair, wool, and other natural fibers
are polymers. They are made by chaining one or two
substances one after another.
Branched Structure
Due to higher amounts of branching
(as compared to linear), the polymer structures
can’t pack tightly together, resulting in a softer,
more flexible polymer.
Branched Structure: Example
Ethylene
Ethylenemonomer
monomer
Polyethylene
Low
Density
Cross-Linked Structure
The presence of the cross-linking bonds keeps the
polymer elastic, but stronger than branched polymers
(ex: Natural rubber vs. “Goodyear” tires). However, a
higher concentration of cross-linking bonds can yield a
somewhat brittle polymer.
(ex: “Goodyear” tires vs. PVC pipe).
Cross-Linked: Example
Ethylene
monomer
Crosslinking is often accomplished
by adding substances that create
chemical bonds between chains
Ultra High Molecular Weight PolyEthylene
(composed of 160 to 215,000 ethylene monomers)
Cross-Linked: Example
A naturally occurring cross-linked polymer:
Let’s Create 3 different polymers
You will be given a pack of “bendaroos”
(Amazing Flexible Building Sticks)
Use them to build a model for the structure of the
polymeric materials needed to produce:
Water Pipes
Canoes
Plastic Gloves
You Have 10 minutes
Other Common Polymers
Polyethylene
terephthalate
Polyvinyl chloride
Other Common Polymers
Polypropylene
Polystyrene
Polymer Interactions
Because of the role of water in our world, determining
how polymers interact with H2O
is very important.
Water interacts more strongly with “water-like”
substances (compounds with oxygen attached to
hydrogen, for example)
Polyethylene
Starch
Strong
H
Weak
H
C
O
C
Acetone
The more
similar the
structure, the
stronger the
interactions
Let’s Predict and Observe
Consider these materials
Water
Acetone
Cellulose
Predict what should
happen when the
polymers interact with
water and acetone.
Polystyrene
You
have
3
minutes
Polymer Interactions
Whether a polymer gets wet or dissolves in a liquid
depends on its chemical composition and structure.
TEFLON
LAUNDRY
BAGS
PVA
Consider this scenario:
If you needed to buy new tires for your vehicle
and your choices were PVA or polyisoprene,
which would you choose and why?
OR
PolyVinyl Acetate
Polyisoprene
Our Focus: Polymers
What is a polymer?
What are
polymers
made of?
How do the
sub-units connect,
and how do polymers
align themselves?
How do polymer
structure determine
its properties?
Understanding their chemistry can
help us use them wisely!
What have you learned?
 If you were asked to create a bullet proof mask, which
polymer would you use to design the mask?
 Remember the shirt from last lecture that shrunk
when hot and expanded when cold. Which types of
polymers do you think were used in creating this
shrinkable and impermeable shirt?
 If asked to create an ink pen that was bendable, but
still was rigid enough to contain a water-based ink,
which type of polymer would you use?
As a team, write your answers on a piece of paper.
a) Justify your choices based on composition and
structure, and b) draw a molecular model of each material.