Virgin Softwood Pulp Ratio Verification in Technical Packaging Papers
Verifying virgin softwood content in packaging paper relies on fiber morphology analysis, ISO chemical pulp identification, and trace chemical markers
Burst Factor
Strength Evaluation
A physical index of paper strength represents the resistance of a sheet to rupture under pressure applied through a rubber diaphragm. Paperboard manufacturers utilize burst factor to determine how much pressure a sheet can withstand before failure. This parameter helps converting plants select appropriate linerboard grades for specific box designs.
The property depends on fiber bonding and the refining intensity of the pulp.
Material Calculation
Calculating this metric involves dividing the burst strength of the sheet by its grammage. The burst strength is measured in kilopascals using a Mullen tester, and the basis weight is expressed in grams per square meter. In practice, the resulting ratio, traditionally called burst factor, provides a normalized value that allows direct comparison of sheets of different weights.
For example, a heavy linerboard might exhibit high absolute rupture pressure but a low ratio if its weight is excessive. When testing a packaging grade with a grammage of one hundred and fifty grams per square meter and a burst pressure of three hundred kilopascals, the resulting value is exactly two. This calculation strips away the influence of sheet thickness, focusing purely on material quality.
Production Constraint
Manufacturing operations regulate pulp refining and starch addition to adjust this mechanical property. High levels of refining increase fiber bonding, which elevates the burst factor of the finished sheet. However, excessive refining can shorten fibers and reduce tear strength, creating a trade off that operators must manage.
Typical linerboard requirements specify minimum values to ensure that packages do not fail on high speed filling lines.