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There are many factors to consider when choosing a composite material
for a specific application. We can’t explain all the variables
involved in material selection in this section. But presented below
are useful guidelines and terms for selecting a material. Please
visit the "Contact Us" page to contact an H&V representative
for more information:
There are different types of binder systems used in composite material
formulation. The two most popular types are NBR and SBR.
NBR: More compatible with many types of fluids, NBR binder is employed
in materials that provide better sealing for fuels, oils, and coolant.
NBR is a non-swell binder; materials using this type tend not to
swell or expand when exposed to different fluids. H&V material
grade names that begin with the letter "N" employ an NBR
binder system.
SBR: This binder is employed for increased sealing performance
with oils. SBR binders generally will cause a material to swell
or expand when in contact with oils. This property provides increased
sealing performance by allowing the material to seal potential leak
paths in an application. SBR materials offer better sealing performance
with less than ideal sealing flange surfaces, or between dissimilar
sealing surfaces, such as a stamped-pan sealing against a cast surface
area. H&V material grade names that begin with the letter "S"
use an SBR binder system.
Caliper is a measure of material thickness. It usually falls somewhere
between a range of .010" to .125".
LOW CALIPER: These materials tend to provide better sealing in
applications with high bolt torque and uniform sealing surfaces.
Flexibility is higher in lower caliper materials, with better torque
retention.
HIGH CALIPER: These materials are generally the better choice for
applications where higher rates of distortion may occur on the sealing
surfaces. Stamped steel pans or flanges are generally considered
high-distortion applications. While high caliper materials have
less torque retention capacity, they generally seal well at lower
clamping loads and conform better in situations with "less
than ideal" sealing surfaces.
Compression is a measurement of a material’s change in thickness
under a given load. This measurement is expressed on a data sheet
as a percentage for comparison with the material's original thickness.
DENSITY
Material density is generally expressed in pounds per cubic foot
or grams per cubic centimeter. Density can fall within a range from
45 to 105 lb./ft. cu.
LOW DENSITY: Low-density materials are generally very conformable
for any application. These materials are more fibrous in nature
and are used extensively in many types of aftermarket applications.
HIGH DENSITY: High-density materials are generally employed in
applications where surface distortion is low. These materials have
low compression rates and very good recovery rates, making them
ideal for thick flange applications. By contrast, these materials
are usually specialized in nature and typically are employed in
more demanding applications.
Recovery is a percentage measurement of the original versus compressed
thickness a material will regain after being compressed under load.
TEMPERATURE RATING
Temperature rating is expressed on a data sheet in degrees Fahrenheit
or Celsius and is a measure of resistance to thermal degradation
in a bolted flange. It is important to understand the application’s
operating temperature when selecting a material to assure optimum
material performance and service life.
TENSILE STRENGTH
Tensile strength, expressed in pounds per square inch (psi) on
a data sheet, is a measurement of the material’s machine cross-direction
yield strength. As a general rule, a minimum cross-direction tensile
strength of 400 psi is desirable for processing on automated machinery.
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