ISO 16945 standard assesses the edge crush resistance of a corrugated material after laboratory corrugation. This process involves creating a corrugated structure in the material by passing it through heated rollers. This standard is essential for evaluating the potential compression strength that a corrugated cardboard box may have when the corrugated material is used in its manufacturing.
The standard describes two testing methods, including immediate crush testing after corrugation (procedure a) and crush testing after a post-corrugation conditioning period (procedure b). Generally, procedure a leads to higher edge crush resistance due to lower moisture content and therefore higher stiffness of the unconditioned corrugated material. Procedure b involves a conditioning period of 30 to 35 minutes after corrugation under standard laboratory conditions.
Test specimens used in this standard are prepared from corrugated material, cut into strips, conditioned, and then corrugated using a specific apparatus. They are subsequently subjected to an edge compression load in a compression testing machine, which increases gradually until the test specimen fails. The maximum force sustained by the test specimen per unit length before failure is considered the edge crush resistance.
Edge crush resistance is expressed in kilonewtons per meter (kN/m), and the edge crush resistance index, which is the edge crush resistance divided by the grammage of the corrugated material, is expressed in newton meters per gram (Nm/g). These calculations provide essential data on the performance of corrugated materials under compression load, informing manufacturing and design decisions in the production of corrugated cardboard.
It is important to note that the accuracy of this test depends on several factors, including the uniformity of the corrugated material, the precision of test specimen preparation, and the accuracy of corrugation and compression procedures. Therefore, repeated testing is recommended to obtain reliable and accurate results.