Crush tests on corrugated board and corrugated board raw paper
It is important for these tests, that the forces are applied exactly vertically to the specimen during the test. Precision guided compression plates provide an extremely high transverse stiffness. They insure the reproducible results of the crush characteristics in corrugated board raw paper and corrugated board.
The Corrugating medium test provides information about the behavior of a corrugated paper after it has been formed in a fluter. A section of corrugated paper is glued one-sided, to a carrier paper and then loaded in compression. The maximum load characterizes the behavior of the paper during the converting processing steps (punching, printing) after board production. A disadvantage of this method is that only the A-corrugation is tested.
For other types of corrugations, the behavior in compression mode must be mathematically calculated.
In addition, this method takes a lot of time and requires much skill in making the specimen. For these reasons, Zwick-fluters are delivered which include a „third hand". With its help, a specimen can be easily and quickly prepared.
ISO 7263 and TAPPI T 809 are standards for this test.
In the flat crush test, a single-flute corrugated board specimen is loaded perpendicular to its surface. The resistance this corrugated board presents to the force, gives an indication of its behavior in further processing and use.
Characteristic curve: according to the height of the individual flutes, the highest flutes break first, then the middle ones and then finally, the rest of the flutes.
If the corrugated board has leaning or crushed flutes, it has been pre-damaged, and the curve is fundamentally different. The crush energy and data curve, provide the user with valuable information about the degree of damage.
Modern miniature flutes tend to crush only at forces greater than 10 kN, requiring excessive lateral stiffness on the compression plates. For these applications, Zwick offers the suitable compression test rig, too.
Standards for this test are ISO 3035, EN 23035 and TAPPI T 825.
This test according to ISO 3037 or TAPPI T 811 gives information about the strength of corrugated board at standing flute orientation.
The edge crush resistance goes into the McKee formula that is so important for quality control in corrugated board factories. The specimen must have clean, parallel and perpendicular edges, and the material must be free of pre-damage.
A hinged scissors or a knife is not suitable for cutting. Good results have been achieved with a circular saw from Zwick.
The ring crush test is similar to the strip crush test in that the strength of liner or fluting is measured in the machine and cross directions.
The results in this test are highly dependent on proper specimen preparation. The specimen, as well as the test fixture must be parallel in order to insure an exact determination with the ring crush strength.
ISO 12192 and TAPPI T 822 are Standards for this type of test.
Since the ring crush test provides more information about the buckling behavior rather than about crush behavior, it is being replaced by the strip crush test.
The advantages:
- Light, precision guided compression plates prevent lateral yielding of the specimen during the test
- Suitable compression plates for miniature flute board in Zwick´s standard program
- Automatic recognition of breaking on all flutes prevents misinterpretation in the flat crush test
- Inserts for the ring crush test fit into the compression plates without a problem. Lateral yielding of the specimen is also prevented
- A data graph of the test run is standard with all tests
