To determine tear resistance (Elmendorf ), a sample is torn with the help of a pendulum device starting from a predetermined cut. The work required for a tear of a given length is measured. The test is described in ISO 1974 (1990).
Z-directional strength refers to the ability of paper or board to resist tensile load¬ing in a direction perpendicular to the plane of the paper (z-direction). After ex¬ceeding the z-directional strength of the paper, a break in the paper structure occurs in the sheet but not at its surface.
The z-directional strength is therefore not equivalent to the surface strength or linting tendency of the paper. Many test meth¬ods to measure z-directional strength of paper are available. Some methods have also been standardized, TAPPI UM 584, TAPPI UM 403, TAPPI UM 527, and TAPPI UM 528.
The z-directional strength (DIN 54 516, 2004) is determined by measuring the maximum force per unit sample width required to split the sample.