Relationship between the edgewise compression strength of corrugated board and the compression strength of liner and fluting medium papers

The compression strength of a corrugated board box is a direct measure of its stacking strength. The edgewise compression strength of corrugated board is the major contributor to the box stacking strength. This relation can be further extended to the critical strength properties of paper substrates. It was, therefore, the aim of this study to establish predictive mathematical correlations between corrugated board and paper compression properties after exposure to certain climate conditions. This would allow packaging technologists in the field to select adequate paper substrates, with certain strength characteristics, to manufacture corrugated board with the necessary compression strength for achieving a desired carton performance for certain climate conditions. The results of this study were used to determine the linear regression constants in the Maltenfort model by correlating the measured board edgewise compression strength (ECT) with the predicted strength, using the paper components' compression strengths, measured with the short-span compression test (SCT) and the ring crush test (RCT) methods. The obtained predictive mathematical models were as follows: ECT = 0.6982 (SCTL1 + SCTL2 + SCTL3 + alpha 1SCTF1 + alpha 2SCTF2) and ECT = 1.028 (RCTL1 + RCTL2 + RCTL3 + alpha 1RCTF1 + alpha 2RCTF2). The obtained models showed very high coefficients of determination (R-SCT(2) = 0.9758, R-RCT(2) = 0.9625), which confirmed that they can be used successfully to predict the compression strength of corrugated board, using the measured paper compression strength (SCT or RCT) after exposure to constant climatic conditions. The results also indicated that the obtained plant-specific predictive mathematical models compared well to the overall linear models and that no major difference existed between the plants' capabilities to convert the paper compression strength into corrugated board edgewise crush strength. This suggested that a single set of predictive mathematical models can be utilised with a good degree of confidence in the South African corrugating industry.