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POLYOLEFINS (Polyethylene,
polypropylene, ethylene-vinyl acetate, ionomer, polyallomer, polybutylene,
polymethyl pentene).
All olefins have similar chemical and electrical properties and often
compete for the same applications. They differ from each other primarily
in their crystalline structure. However, since strength properties
vary with the type and degree of crystallinity, each polyolefin may
have quite different tensile, flexural, and impact strengths. Stress
crack resistance and useful temperature range also vary with crystalline
structure.
POLYETHYLENE The largest volume thermoplastic polymer used today,
is available in a wide variety of grades and formulations that have
an equally wide range of properties. Some polyethylenes are flexible,
others are rigid; some have poor impact strength, others are virtually
unbreakable; some have good clarity; others are opaque. Service temperatures
can range from -40 degrees to +200 degrees F. In general, however,
polyethylenes are characterized by toughness, excellent chemical resistnace
and electrical properties, low coefficient of friction, near-zero
moisture absorption, and ease of processing.
Although we stock only natural colored HDPE, LDPE is also available.
Both PEís are available in black.
UHMWPE Ultra High Molecular Weight Polyethylene was originally defined
as polyethylene whose average molecular weight, as measured by the
solution-viscosity method, is greater than 2,000,000, later changed
to not below 3,100,000.
UHMW has outstanding abrasion resistance and low coefficient of friction.
Impact strength is high, and chemical resistnace is excellent. |
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Recommended
maximum service temperature is about 200 degrees F, however,
because of a high coefficient of thermal expansion, with increasing
temperature, the material swells, friction increases causing
further temperature increase, and the melting temperature, and
the melting temperature is soon approached.
Applications include: conveyor wear strips, guide rails, paper
machine suction box covers, chute linings, snowmobile track
sporckets, bearings, parts of textile looms, pipe for distribution
of slurrry materials, and other components requiring maximum
abrasion resistance and impact strength and a low friction coefficient.
These plastics have outperformed other materials, including
metals, in these applications.
POLYPROPYLENE would be used in an application where resistances
to chemicals and acids is critical.
All olefins are available in many more sheet thickness sizes
than listed below and in rod and tubing and some other mill
shapes. |
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