Transcript Polymers___Composites 1.3 MB

Polymers and Composites
by
Joseph A. Castellano, Ph.D.
RESEED Silicon Valley
Adapted from Focus on Physical Science, California Grade 8
Glencoe/McGraw-Hill, Columbus, Ohio (2007).
What Are Polymers and How Are They Made?
Polymers are very large molecules made of a chain of
many smaller molecules bonded together. The small
molecules that are used to create polymers are called
monomers.
Polymers are made of organic compounds that contain the
elements carbon and hydrogen, but may also include O, N,
P, S, and other elements.
Polymers form when chemical bonds link large numbers
of monomers together in a repeating pattern.
Polymers - 2
Polymer Classes
Think of polymers like chains of many paper clips connected
together. This is why chemists often call them “polymer
chains.” Each paper clip would represent a monomer molecule.
Monomer
When two different monomers combine, they form a copolymer
Monomer 1
(Green)
Monomer 2
(Red)
Polymers - 3
Polymer Types - Natural
 Polymers that occur in nature are called natural
polymers and include:
1.
Cellulose formed in trees, plants, fruits and
vegetables from small sugar molecules.
2.
Silk and wool produced by animals.
3.
Proteins created in the human body from
small molecules called amino acids such as:
Polymers - 4
Polymer Types - Synthetic
 Polymers that are man-made are called
synthetic polymers and include:
1. Plastics used in bottles, storage
bags, toys, automobiles, and
many other items.
2.
Fibers made into clothing and carpets.
3.
Adhesives used in glue
and even chewing gum.
Thousands of products made today use
one or more synthetic polymers
Polymers - 5
Types of Synthetic Polymers - Soft
 Soft Plastics are called thermoplastic because they
can be recycled by melting to a thick liquid and
reforming into a new item. Examples include:
1.
Polyethylene used in squeeze bottles, and toys.
2.
Nylon and polyesters used in clothing
3.
Polystyrene used in cups and packing material
4.
Teflon (Polytetrafluoroethylene) used for cooking
pans:
Polymers - 6
Types of Synthetic Polymers - Hard
 Hard Plastics are called thermosetting because
they cannot be remolded to form a new item.
One example is Bakelite used in electrical
equipment.
 Sometimes hard plastics are recycled by
grinding the material into small particles for
use in composites.
 Another hard plastic is polyvinyl chloride used
for plumbing pipes.
Polymers - 7
Comparing Polymers
 Synthetic polymers like polyester and nylon are
widely used to replace natural polymers like
wool, silk, and cotton for clothing.
 Some synthetic polymers have made possible
the creation of new products such as CDs,
DVDs, and cabinets for computer equipment.
Polymers - 8
History of Polymer Development
1839 – Charles Goodyear developed a process
called “vulcanization.” This converted natural,
soft rubber into a hard, stretchable polymer
that could be used to make tires for bicycles
and later automobiles.
In vulcanization, the long polymer chains are connected
together from their sides like a chain-link fence in a
process called “cross-linking.”
Polymers - 9
History of Polymer Development
1856 – Cellulose nitrate, known as “Celluloid,” was
created by Alexander Parkes from naturally
occurring cellulose. It was used to make the first
movie films.
1909 – Bakelite was the first all-synthetic polymer that
became a commercial success. Invented by Leo
Baekeland, it was made from phenol and
formaldehyde, two compounds derived from oil
and coal processing. It was used to make the first
telephones.
Polymers - 10
History of Polymer Development
1933 – Polyethylene was first synthesized in England
by chemists using high pressure.
By the early 1940s, many factories were
established in Europe and the United Sates to
make polyethylene for various applications
during the World War II years.
Polymers - 11
Formation of a Synthetic Polymer - Polyethylene
Polymers - 12
Formation of Polyethylene
Polymers - 13
History of Polymer Development
1934 – Nylon was synthesized at the DuPont
Corporation to form fibers that became a
substitute for silk. It is widely used today for
stockings, clothing, carpets and other products.
Nylon is a copolymer formed by adding one monomer
with two diamino (NH2) groups to a second monomer
with two carboxylic acid (COOH) groups in the presence
of a catalyst:
Polymers - 14
Nylon Product Examples
Gloves
Playhouse
Jackets
Rope
Polymers - 15
History of Polymer Development
1937 – First synthesized by Otto Bayer in Germany,
polyurethanes are widely used in flexible foam
seating, rigid foam insulation panels, seals,
gaskets, and adhesives.
Polyurethanes are copolymers formed by reacting one
monomer with two isocyanate (NCO) groups and
another monomer with two alcohol (OH) groups in the
presence of a catalyst.
Polymers - 16
Polyurethane Product Examples
Furniture
Insulation
Car Seats
Surfboards
Polymers - 17
History of Polymer Development
1946 to 1952
Many of the polymers we use today were
synthesized during the years following World
War II. Among these are:
 Polystyrene
 Dacron
 Orlon
 Polypropylene
 Polyvinyl Chloride
 Teflon
Polymers - 18
History of Polymer Development
1965 - Kevlar was developed by chemists at the DuPont
Company. Because it is five times stronger than steel,
Kevlar is used in bullet proof vests worn by police
officers. It is also used in protective clothing for fire
fighters due to its fire resistant properties.
Polymers - 19
History of Polymer Development
Today
Scientists are making displays with light emitting diodes
based on organic compounds and polymers. This has led to
light emitting displays for cell phones and small televisions
on flexible film instead of rigid surfaces.
Samsung Flexible Display
Sony Television Display
Polymers - 20
Composites
 A composite combines two or more materials to
form a new material that has different and
improved properties.
 Many composite materials contain one or more
polymers.
 Wood is a naturally occurring composite – it
consists of long fibers of cellulose, held together
by another plant polymer called lignin.
Together these two polymers form a very
strong tree trunk.
Polymers - 21
Composites in Today’s Products
 Fiberglass composites combine glass fibers
woven together and strengthened with a plastic
material. The resulting composite is so strong
and hard that it is widely used for automobile
bumpers and boat hulls.
Polymers - 22
Composites in Today’s Products
 Composites that combine synthetic polymers
with the graphite form of carbon are so strong
and flexible that they are used in golf clubs,
fishing rods, and tennis rackets.
Polymers - 23
This presentation was produced as a public service
to help middle school and high school science
teachers develop experiments, presentations and
demonstrations that can be used in their classes.
More science experiments and demonstrations are
available on the RESEED Silicon Valley web site:
www.reseed-sv.org.
RESEED (Retirees Enhancing Science Education
through Experiments and Demonstrations) is a
program aimed at stimulating greater interest in
science by middle school students.
Polymers - 24