Full control of the internal bond strength, is particularly important in the production of multi-ply paper.

Low or unevenly distributed internal bond strength values, can cause problems in the layering of paper and boxboard in an offset press with sticky printing ink. If the values are too high it impedes the creasing of the boxboard, since the aim is that the material should delaminate in the score. High internal bond values also mean a waste of raw material and energy. In other words, the aim is to achieve an even strength

• within customer specifications
• across the entire web width.

Up to now, measuring internal bond strength has been a time-consuming and complex procedure. To meet production’s need for fast reporting of measured values, most rolls are only measured at 1 to 3 points, which makes it difficult to detect streaks with low/high internal bond strength.
Another problem with the Scott Bond method, for example, is that the handling of the instrument can affect both the level and the distribution of the measurement result.

Fast and accurate

L&W ZD Tensile Tester measures internal bond strength in paper and boxboard quickly, and with a high degree of accuracy.

The operator only needs to position the sample on the measurement table and press the start button. The rest is performed automatically by the instrument, including the application of tape to the sample. Measurement of a 1.5 metre strip in ten positions, takes only six minutes. The results are displayed immediately on the built-in and easy-to-read screen, and then stored in memory. The instrument displays a warning message if the results do not comply with the preset specifications. L&W ZD Tensile Tester can be connected to a PC for direct transfer of measurement data to production control.

Wide measurement range

Due to its interactive software, L&W ZD Tensile Tester is easy to configure. Up to 30 different test sequences can be pre-set and stored in memory.

The method suits most multi-ply paper types. Measurements are made in accordance with the SCAN P 80:98 and TAPPI T 541 standards.

The Z-directional tensile and Scott Bond method are different methods to measure the material’s strength in the thickness direction. The ZD- tensile measures the maximum force to split the sample at a low standardized test speed perpendicular to the test surface. The Scott Bond method measures the energy needed to split the sample at a speed several thousand times higher. The methods do not always react the same for changes in the papermaking process.