Page 101 - Academic Press Encyclopedia of Physical Science and Technology 3rd Polymer

P1: GOX/LBD P2: GLQ Final Pages
Encyclopedia of Physical Science and Technology EN012K-587 July 26, 2001 10:35

Plastics Engineering 471

TABLE V Desirability Factors to be Maximized for Minimum the major manufacturers. In one of the most recent inno-
Cost Design (for Minimum Weight Replace should be ρC by vations, Chrysler produced a Composite Concept Vehicle
ρ)
(CCV),whichfeaturesanalmosttotallyplastic(reinforced
Minimize cost PET) body. Table VI shows some of the other plastics used
for given: by the automotive industry. And of course, when one looks
Ductile at high performance vehicles, such as Formula One racing
Mode of loading Stiffness strength cars or fighter aircraft, then there is a very high reliance
on fiber reinforced plastics.
E 1/2 σ y 1/2
Bending of plate
ρC ρC
B. Sporting Applications
Although sporting applications do not, in most cases, pre-
sent critical (life or death) problems for the designer, they
do make very stringent demands on the properties of
E 1/2 σ y 2/3 materials. For this reason, the plastics industry takes the
Bending of rods
ρC ρC sporting, and indeed the toy, industries very seriously.
and tubes
There is no doubt that any development that is good
enough for a sporting goods application is going to make
its mark in other fields also.
Composites, in particular, can be used to very good ef-
E 1/3
Buckling of plate — fect in sports and leisure goods. The racing yachts used
ρC
in the Americas Cup depend almost totally for their high
performance on fiber-reinforced plastics. Using these ma-
terials provides combinations of lightness, strength and
E 1/2
Buckling of — high modulus not available in any other materials. Mod-
ρC
slender column ern tennis rackets used by professionals are usually hollow
or tube molded structures utilizing fiber-reinforced plastic. The
height records that pole vaulters can achieve increased
dramatically with the introduction of the fiber-reinforced
plastic poles. The key property required in this application
E σ y is a high elastic limit. A fiberglass composite has an elastic
Tie
ρC ρC limit of 2–3%, whereas a high strength aluminium alloy is
less than 1%.The high elastic limit of thecomposite means
that it can bend into a radius of about 1 m without breaking,
and in doing so stores enough energy to propel the vaulter
over the bar, which is typically 6 m above the ground.
G σ y
Torsion tube
ρC ρC
C. Medical Applications
Plastics have been a major boon to the medical pro-
E σ y
Cylinder with fession. In North America the value of the industry
ρC ρC
internal pressure has been estimated to be over $4 billion. The pack-
aging of medical products, tubes, and pharmaceutical
closures are routine applications for plastic materials.
Their high impact and chemical resistance and ability
to be easily sterilized make them the first choice in
factors are pushing the increasing use of plastics in cars. many cases. Almost 80% of polymers used in the med-
Not least are the “green” or environmental issues that re- ical industry is represented by PVC, polypropylene, and
quire lighter vehicles (to minimize energy consumption polystyrene. The excellent resistance to steam exposure
and/or facilitate alternative energy sources for the ve- of some plastics (such as polyphenylsulfone) is used very
hicle) as well as the need for recycleability. Many car effectively in special applications such as microfiltration
manufacturers continue to strive for the all-plastic car and devices for immunoassays, reusable syringe injectors,
a number of prototypes have been made and tested by respirators, nebulizers, prosthesis packaging, sterilizer