Issue link: http://cp.revolio.com/i/586959
23 ista views • October 2015 • www.ista.org BCT Specification Model Assumptions The assumption that BCT specifications predict long term compression performance is built on a linear property assumption as shown in figure 7. Paper properties define corrugated board properties, which determine BCT. Environmental factors influence compression strength, which over time drives long term compression performance. A more accurate specification model would look like figure 8. Still present are the linear progression from paper to board to box properties, but paper and board properties also have a direct impact on long term box performance – BCT does not serve as a proxy for paper and board properties. Further, the effects of environmental factors on paper and board properties are also considered. One might reasonably ask why one would bother looking at paper and corrugated board properties, when the traditional Safety Factor ostensibly covers all of the "unknown" factors which degrade box compression strength over time. There are two reasons for this. First, if we can reduce variability in the response of component papers and/or corrugated board to environmental effects, we can reduce the variability of sensitivity of the complete box to environmental factors. Second, if we can identify, and properly manage, factors which reduce box strength, we should increase effective box life, without adding material usage or cost. If such management is sufficiently effective, we create the opportunity to reduce material usage and cost. If such principles could be widely used to reduce corrugated usage by 1% and cost by 0.5%, the opportunity applied to 2013 worldwide sales of $140b and 90m tonnes (Smithers-PIRA; 2014) would be $700m and 0.9m tonnes, a notable environmental achievement. When we consider that the compound annual grown rate (CAGR) for corrugated is projected to be greater than 4% per year (Smithers-PIRA; 2014) over the next five years, the opportunity will grow. Conclusions Mathematical modeling of BCT at a point in time is exceedingly difficult, and from a practical perspective requires simplification of known factors which affect BCT. Modeling of BCT over time, as multiple, dynamic environmental factors affect paper/board/box properties, is not currently feasible, and so mathematical prediction of useful box life for long and environmentally dynamic supply chains is not currently feasible. Environmental factors (particularly time, load, and temperature and humidity – steady state and cyclic) reduce box compression strength, driven by strain due to hygroexpansive effects of moisture. Cyclic humidity accelerates strain and loss of strength. Box Compression Test (BCT) specifications do not assure maximized long term compression performance. To improve long term compression performance, the focus should not be on BCT for new boxes, but rather on factors which are known or suspected to improve performance – including, but not limited to – flute crush control, outside liner coatings, box style, box manufacturing factors, paper properties, flute shape, unitizing methods, handholes, initial moisture content, fiber type, fiber alignment, various paper finishing variables, and last but far from least – reducing manufacturing variability. Figure 7: Typical Current BCT Specification Model Figure 8: Proposed, Improved BCT Specification Model > MORE ON PAGE 24