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Scientific
Furniture Tests and Their Relevance to Laboratory
Applications
By Mike Quackenbush, Durcon Technical Services
Chemical Resistance
These tests are reflective of the worksurface’s
resistance to the major chemical substance classifications
(acids, bases, and solvents). Because it is impossible
to be 100% sure of the top’s performance against
any unlisted substance, we recommend the customer check
using a sample and the actual material in question. It
should be noted that some materials stain the top rather
than chemically harming it. This group includes silver
nitrate and zinc chloride.
Rockwell
Hardness “M” Scale
This test measures the force needed to penetrate the
surface of the sample. It is generally related to scratch
and mar resistance. There are various Rockwell scales
and the correct letter designation for the specification
is critical.
Water Absorption ASTM D-570
This test measures the amount of water absorbed during
immersion in water. It is most relevant to applications
where high humidity or long term submersion in water
may be present as service conditions for the product.
The state of the material after it is removed from the
water (any separation of layers or swelling) should also
be taken into consideration when evaluating the test
results.
Fire Resistance ASTM D-635
This test measures the material’s response to being
subjected to an open flame. The sample is marked with
start and finish lines. The flame is applied for a set
period of time and then removed. The sample is judged
on the time it takes for the flame to travel between
the lines, or whether it ever gets to the starting line
after the flame is removed (if not it is self-extinguishing).
Heat Deflection ASTM D-648
This test reflects the temperature at which the material
bends under pressure and heat. It is most relevant to
high heat applications or very long term medium heat
conditions like an oven or high temperature bath that
is constantly operating.
Flex Strength and Flex Modulus ASTM D-790
The flex modulus refers to the rate at which a material
deflects (bends or sags) as weight is put on it.
The flex strength refers only to the breaking point.
If the material bends significantly before it breaks
(as epoxy tops do), the bending (modulus) data is more
relevant than the breaking data, because earlier bending
would be detected as distortion of the top before the
top ever broke. This is particularly true in shelf or
cantilever type applications.
For these reasons, in most design work, the flex modulus
should be considered more important than the flex strength.
Specific Gravity ASTM D-792
This can be compared to get an idea of the relative weights
of various products. The specific gravity is the ratio
of the weight of the material as compared to the weight
of the same volume of water. The density is the material’s
actual weight per unit of volume.
Compressive Strength ASTM D-695
The compressive strength test refers to the strength
of the material as it is squeezed across its thickness
(compressed). The compressive strength of epoxy material
is generally far greater than that of the casework below
it. It is so much greater that it is practically impossible
to apply enough weight to the casework/top assembly to
get the countertop to fail in a compression mode before
the load is too heavy for the casework to bear.
Tensile Strength ASTM D-638
Tensile strength is the strength of the material as it
is pulled from end to end like stretching a rubber band.
As with the compressive strength, this test reflects
the material behavior under conditions not reproducible
under normal conditions.
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Chemical
Resistance