Compressive Standard
Standardized testing protocols from the Technical Association of the Pulp and Paper Industry define the procedure for measuring the ring crush resistance of paperboard with a thickness up to zero point fifty-one millimetres. In the quality control of packaging materials, tappi t 818 provides a reliable method for evaluating the edgewise compression strength of paper used for liners and fluting. This measurement helps mills predict the performance of the finished corrugated sheet.
The standard is specifically limited to thin paperboard, as thicker grades require different test fixtures.
Specimen Preparation
Specimen preparation requires cutting a rectangular specimen and forming it into a cylinder of precise diameter using a specialized holder. This cylindrical shape prevents the sample from buckling during the application of the compressive force.
Testing Procedure
Inserting the holder between the platens of a compression machine allows applying a uniform force at a specified speed until the paper specimen collapses. Recording the peak force required to crush the ring provides the value used to calculate the board strength. This value serves to verify that the pulp refining and sheet formation have met the required specifications.
The test remains a global benchmark for paper mills producing containerboard.
