P R O D U C T S , I N C
Urethane
Urethane is widely
used in applications requiring high strength and resistance to impact.
It has outstanding abrasion resistance and a reputation for toughness
and durability. Urethane's combination of high load bearing strength,
resistance to impact, abrasion and compression set make it the ideal
material on many applications where rubber will not hold up.
HARDNESS AND
RESILIENCE 
The hardness of urethane ranges between 25A and 75D. The D scale is
typically used to measure hardness greater than 95A. Urethane bridges
the gap between rubber and structural plastics. No other type of elastomers
offers unique properties over this hardness range.
Special formulations
can be prepared with resilience (bayshore rebound) values as low as
15 percent or as high as 80 percent. Urethane can maintain its resilience
with changes in temperatures (far greater than rubber) from 10°C to
107°C (-50°F to 225°F).
(Urethane
durometer key chains are available at Parkway Products Inc. Call for
a free sample #513-851-5550)
CASTABILITY
 |
Because Urethane
has the ability to be poured, it can be cast into simple molds.
Parkway Products is a leader in molding Urethane assembly pallets
and nest where quantities are generally under 500 pcs. Epoxy, aluminum
and rubber molds are typically used for casting urethane. |
| ABRASION
RESISTANCE
Urethane has
outstanding abrasion resistance, which has led to many important
applications where severe wear is a problem such as roller blades
wheels, snow truck blades, sand-blast mask, and coatings on aircraft
engine blades.
Urethane is
considered to have excellent sliding and abrasion resistance and
has out worn conventional rubber and plastics often by a factor
as much as 8 to 1.
|
 |
IMPACT RESISTANCE
Urethane has better impact resistance than structural plastics. Most
standard compounds of urethane have excellent low temperature impact
resistance and low brittle points. Although the coefficient of friction
decreases drastically with temperature, its properties still enable
it to be used on applications for snowmobile rollers and ski boots.
|
IMPACT
RESISTANCE IZOD, J/m (FT.-LB./IN)
|
| |
Nylon |
Acetal |
Acrylic |
Adiprene
Urethane |
| Hardness |
Rockwell
R108 |
Rockwell
R120 |
Rockwell
M103 |
Rockwell
R90
(Durometer 75D) |
Notched,
24°C
(75°F) |
106.8
(2.0) |
74.7
(1.4) |
16.0
(0.3) |
800.7
(15.0) |
Notched,
-40°C
(-40°F) |
26.7
(0.5) |
64.1
(1.2) |
16.0
(0.3) |
58.7
(1.1) |
The impact or shock
resistance of a material is measured in foot-pounds, with a swinging
pendulum (hammer). As you see in the drawing, urethane will flex and
bend on many applications where metal and/or plastic fracture. This
has lead to urethane being used as front grills on tractors and automobiles.
SHEAR
 |
Mounting and
suspension assemblies generally require the loading in shear. Elastomers
deflect more under a given load in shear than in compression. Since
shear is a combination of tensile and compression forces acting
at right angles to each other, the stress strain curve for an |
 |
| elastomer
in shear is similar to the tensile and compression stress strain
curves. Urethane's combination of properties (specifically in the
higher hardness range) make it the ideal material for high impact
/ shear applications. |
FLEX PROPERTIES
Urethane resists cracking under repeated flexure time after time,
as evident by its successful use in dynamic applications such as forklift
tires and boots used in earth compactor devices. Urethane is superior
to rubber on almost all accounts, as long as, the part is designed properly.
When subject to flexing, rubber products frequently fail due to the
development and propagation of cracks. Urethane's high cut and tear
resistance, usually surpasses the life of a rubber part by four times.
As with all elastomers,
its rate of cut growth under flexing may be reduced by decreasing the
thickness of the part. Unlike other elastomers, urethane can be practically
utilized in very thin sections because of its exceptional strength and
toughness. Design of the part to reduce localized concentration of the
stress or heat build up will improve flex life to obtain the ultimate
in flex life with urethanes, careful attention must be paid to part
design. Urethane has a wide hysteresis loop and thus absorbs more energy
(heat) then other elastomers. Parts undergoing high frequent flexing
should be designed to eliminate as much bulk as possible. Premature
failure of Urethane parts most often occurs due to heat (generated by
working the material). A simple method of determining this failure mode
is to feel the part. If it is hot to the touch the design needs to be
altered. Contact Parkway Products for design and engineering assistance.
ADHESION
Urethane can be adhered to metals, elastomers, and plastics. The adhesive
strength often exceeds the cohesive strength of the urethane itself.
The hardness and rigidity of urethane make it practical to apply to
rollers and wheels. Parkway has roll-grinding equipment up to 8ft. Long.
PHYSICAL PROPERTIES
|
Hardness,durometer
value
|
80A
|
90A
|
95A
|
75D
|
| Specific
gravity |
1.07
|
1.10
|
1.13 |
1.21 |
Tensile strength,
Mpa (psi) |
20.7 (3,000) |
31.0 (4,500) |
34.5 (5,000) |
62.0 (9,000) |
Impact
resistance,
Izod notched J/m
(ft.-lb./in.)
24°C (75°F)
-40°C (-40°F) |
Flexed
---
|
Flexed
--- |
Flexed
--- |
800.7 (15)
58.7 (1.1) |
Tear
strength split,
kN/m (pli.) |
12.2 (70) |
13.1 (75) |
26.2 (150) |
19.2 (110) |
(The above data
is supplied by Uniroyal Chemical Company. See Parkway's home page for
more information)
PROCESSING
Adiprene urethane can be modified to provide greater strength, maximum
ultraviolet resistance, specific hardness, or various other elastomeric
characteristics. However, modifying urethane to enhance one property
can result in sacrificing another property. Therefore, choosing the
right molder & supplier is very critical. Parkway Products, Inc. is
a leading molder of urethane in Northern America. Parkway has the technical
competence, state of the art facilities, equipment and knowledge to
engineer your complete design, material selection, mold making and secondary
machining. See Parkways home page for more information.
