The S-Test is a performance measurement for containerboard fluting. The name comes from the test set-up, where the sample is held in S-shape during a compression test.
For corrugated cardboard manufacturers, it is critical to ensure that the box contents arrive unharmed. Usually, this harm comes from the box being crushed or damaged due to external pressure. To reduce the risk of damage, producers use standard test methods to evaluate how well packaging materials can withstand external forces that may damage the packaging and, ultimately, the contents. One of the key performance tests used by corrugated board producers is the BCT (Box Compression Test).
During the supply chain, paper, board and box performance can be compromised, for example during converting from paper to corrugated board or from board to box, typically due to damage to the flute profile. After box manufacture, performance loss can also occur during packing at the customer premises or on the packing line. This type of damage is typically characterized by a flute crush, which reduces box performance and can be measured by a lower BCT result. Reduced BCT can be observed through the FCT (Flat Crush Test), particularly the first peak of FCT, which indicates the board’s ability to resist crush.
Given the structure of the corrugated cardboard, the thickness of the fluting paper, the flute height and the integrity of the flute shape are directly related to the strength.
Historically, the performance of fluting paper has been assessed by measuring its CMT (Corrugating Medium Test), i.e. its ability to resist compression. A parallel can be drawn between board FCT, especially the first peak, and fluting paper.
The S-Test is one alternative that can be correlated with the first peak of FCT, and it can be measured using automatic bench equipment to provide paper performance data quickly to the paper machine production team as part of the regular quality control process.
To learn more about the S-Test, download the report below.