Tensile Properties

As defined in ISO 527-3 and ASTM D 882, the most current specimen type is the strip. It can easily be obtained by using a cutting press or with special film-cutting devices.

Dumbbell specimens (dogbone-shaped) are employed for quality control purposes, requiring an extensometer for exact elongation measurement.

Typical results of this tests are stress at yield, elongation at yield, maximum stress, and nominal elongation at break.

The results obtained for break elongation depend both on the specimen shape and on the type of clamping if strip specimens are used. We recommend that parallel clamping grip-types such as pneumatic or screw types be deployed. The jaw faces should offer a line contact to the specimen.

Puncture Properties

This test, described in EN 14477, is also known as the Parker pen test. The puncture resistance is important, if the film is to be used for packing materials for food or parts with sharp edges.

The specimen strip, which is clamped in the lower specimen holder, is penetrated by an exchangeable indentor. The puncture force is measured and evaluated.

Tear, Peel, and Adhesion Properties

Tear tests are often employed to characterize the remaining resistance of a film which has been damaged. The typical specimens are called angle specimens and trouser specimens. A slit of known dimensions is cut into the specimen, which is then tested.

Peel tests in 90° direction or in 180° direction are used, for example, to characterize adhesive forces between layers or of adhesive tapes. They are also utilized to characterize welded and glued surfaces.

Melt-Flow Tests

Melt-flow plastometers deliver standard values of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastic materials according to ISO 1133 and ASTM D 1238.

Zwick provides simple method A type plastometers for the incoming goods inspection as well as sophisticated machines for both method A and method B testing.

Method A

The main parts of the 4100 plastometer are a barrel that is exactly heated to the given test temperature, a die of standardized diameter, and a piston with a mass piece mounted on top. The material filled into the barrel is heated and then extruded through the die by the force exerted by the mass. The extrudate is automatically cut in constant time intervals and then weighed. The MFR result can be calculated as the mass extruded in 10 minutes, even though the testing time is normally much shorter.

Tensile Impact Tests

This procedure is set out in ISO 8256 as well as in ASTM D 1822, where two methods are available. For method A, the dumbbell-shaped specimen is clamped at one end to the base of the impact tester. A yoke is fixed to the other end of the specimen. During the test, the pendulum hammer strikes the yoke and the specimen is thus tensiled. A part of the nominal energy of the hammer is used to bring the yoke in motion. Another part is the energy consumed by the specimen. Results obtained with the same hammer–yoke combination are comparable.