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
Cross-Direction Tear Index
Tear Strength Ratio
Measurement of the energy required to propagate a tear through a paper sheet in the direction perpendicular to the machine alignment. The cross-direction tear index normalizes the force needed to continue a rip by the basis weight of the material. Resistance to failures that originate from nicks or edge defects during high speed printing is quantified by this value.
Testing Protocol
Standard testing employs an Elmendorf-type pendulum to measure the work done in tearing a fixed length of the specimen. Calculation of the cross-direction tear index involves dividing the tearing force in millinewtons by the grammage of the sample. This result allows for a direct comparison of toughness across different paper grades regardless of their thickness.
High values indicate a dense interlocking of fibres across the grain.
Application Variable
Converting operations rely on this value to predict how a roll behaves when subjected to lateral tension on a folder gluer. Lower results for the cross-direction tear index often suggest that short hardwood fibres dominate the furnish or that internal bonding agents are insufficient. The parameter determines whether a corrugated liner can withstand the mechanical stresses of the scoring and folding process without rupturing.
Poor performance here leads to increased downtime and waste at the press.