The processing of plastics changes their properties.

Testing is essential in order to be able to guarantee defined properties for the customer. A variety of mechanical, thermal, chemical, and optical methods are available for that purpose. For many of these methods, standards are in place that specify a precise procedure. This ensures that the data obtained are comparable.

Zwick/Roell Z010 tensile testing machine with optical (contactless) measurement of the strain and digital control and data capture

One of the most important test methods is the tensile test that is used to determine mechanical properties such as tensile strength, elongation at break, and modulus of elasticity.

Messoptik der Zugprüfmaschine Z010 und ein Normzugprüfstab im polarisierten Licht

The picture on the left shows the optical measuring system of the tensile testing machine. The camera (in the “black box” in the left picture) is directed at the standard test rod to be measured. Measuring marks are glued to the standard test rod (right picture) and the distance between them is measured by the
camera. During the test, the tension rod is stretched in a longitudinal direction. The measuring marks make this movement visible to the camera.

Plastics are often very sensitive to abrupt stress. This so-called “impact strength” is measured using a pendulum impact tester. The picture shows the impact strength measurement according to Izod.

Zwick/Roell HIT 5.5 P Pendulum impact tester
Zwick/Roell BMF-001 melt flow tester

The melt index measurement is used to determine the flowability of plastic melts. With a standardized weight, a defined volume of a plastic melt is extruded through a die at a specified temperature. The melt flow index (MFI) is calculated from the quotient of the mass of the extruded melt and the time. The MFI is an important parameter for plastics processing.