Tensile Properties of plastic films can help characterize their suitability for use in medical packaging. The sample is pulled between two grips, and the force required to produce the deformation is measured using a load cell in an Instron® testing machine. A variety of tests can be performed on each sample tested. For example:
Yield Strength is the strain (deformation) below which the material will revert back to its original size when the stress (applied force) is released (elastic deformation) and the strain above which the sample will be permanently stretched (plastic deformation).
Ultimate Tensile Strength is the force per unit area required to break the sample.
Ultimate Elongation is the percentage increase in length before the sample breaks. High tensile strength and high elongation will indicate a tough film.