Hardness is determined by measuring the extent to which surface resists indentation by a standard indentor. It is an important property which has a relationship to modulus and tensile strength. Measurements are commonly made by Shore Durometer.
Tensile strength, in pounds per square inch, measures the load per unit area of the original cross section to cause rupture. Elongation measures rubberstretch. Usually “Ultimate” elongation, it expresses by percent the amount of increase over initial length at instant of rupture. Modulus, in pounds per square inch, is a measure of loading required to stretch a test specimen a standard amount, usually 100% to 300%.
A measure of the degree to which a test specimen under standard loading and time, “sets” or deforms, or does not rebound to original dimensions. Expressed in percent. Important in sealing applications, particularly for high pressure over extended periods.