volume ) are related to the buoyancy forces acting on the samples while submerged in water . The % volume change ( ΔV ) is computed by the equation :
Where , M1 is the initial mass of the sample in air , M2 is the initial mass of the sample in water , M3 is the mass of the sample in air after oil immersion , and M4
and the nominal cross-section prior to loading by the equation :
Where , Ff is the applied on the specimen at failure , and Ao is the initial cross-sectional area , computed by the width and thickness of the gauge region for each specimen .
Compression Set Samples were tested for resistance to permanent compressive deformation per ASTM D395 Method B , Rubber Property Compression Set Under Constant Deflection in Air . Nitrile disc specimens were compressed ~ 20 % ( varying by individual specimen ’ s post-exposure thickness ) in a polished steel , chrome plated compression rig separated by calibrated , hardened steel
Figure 1-3 Tensile testing to failure of nitrile samples performed with a TiraTest 26005 uniaxialload frame with pneumatic grips ( left ); Nitrile dogbone specimen after testing to failure ( right ).
is the mass of the sample in water after oil immersion . Tensile Strength Tensile strength of the nitrile was tested per ASTM D412 Tension test . Sample geometry of the nitrile samples were die-cuts ( ASTM D638 Type V ) from a ~ 2 mm nitrile slab using a hardened steel die in the shape of dog bone specimens with initial gauge crosssection width of 3.175 mm and thickness of ~ 2 mm . Samples were tested using a screw-driven uniaxial load frame fitted with pneumatic-actuated grips and a 0.5 kN load cell . After the cleaning process , samples were immediately gripped in an un-stressed position and load was applied using a crosshead rate of 500 mm / min as per ASTM D412 . A computer-controlled data acquisition system was used to control the experiment and to record the load and displacement data simultaneously at a 50 Hz sampling rate . Testing was completed after sample rupture which resulted in an immediate loss of load . Tensile strength ( St ) is computed from the force at failure
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