Compression Resistance
Corrugated packaging depends entirely upon the perpendicular ability of combined board to withstand stacking loads during warehousing and distribution, which makes TAPPI T 839 the standardized testing protocol for measuring edge crush properties under controlled laboratory conditions. Heavy-duty shipping containers constructed from multiwall corrugated configurations require precise evaluation of this attribute to prevent catastrophic failure while units sit in high-bay vertical storage arrays. Technicians place a rectangular specimen cut from finished board between rigid compression platens, applying continuous force perpendicular to the flute tips until structural collapse occurs.
Force values recorded during the test establish the maximum load capacity per unit length, allowing packaging engineers to predict box compression performance reliably from raw component specifications.
Laboratory Procedure
Testing mechanics demand exact specimen preparation using specialized die cutters to guarantee clean, uncrushed edges that transmit applied loads uniformly across the cross section. Ambient temperature and relative humidity directly influence moisture content within the cellulose matrix, requiring conditioning periods inside standard atmospheric chambers before evaluation commences. Lower moisture levels increase rigidity while excess humidity softens the adhesive bonds between linerboards and the corrugated medium, shifting test outcomes significantly unless environmental parameters remain strictly controlled throughout the procedure.
Platen parallelism and constant crosshead displacement speeds further ensure that machine compliance does not distort the ultimate load readings captured by the load cell during the compression stroke.
Performance Correlation
Converted box plants translate laboratory edge crush values directly into commercial compression strength estimates using geometric formulas that factor in box perimeter, board thickness, and flute geometry. Corrugated boxes fabricated from low-grade recycled liners exhibit higher variability in edge crush performance compared to virgin kraft alternatives, necessitating higher safety factors during structural design calculations. Print converting operations must balance flute integrity against aesthetic requirements because excessive nip pressure during printing processes crushes the internal flutes prematurely, reducing the overall stacking capability measured by the standard.
Regulatory compliance and supply chain integrity depend upon these standardized measurements to ensure secondary packaging withstands compressive forces encountered in palletized shipping environments.
