Quantifying Micro Surface Burnishing in Overprint Varnishes under Sled Shear
Surface burnishing under sled shear converts diffuse reflectance to specular gloss through silica displacement, controlled by matrix crosslinking and particle size.
TAPPI T815
Coefficient Evaluation
Friction resistance defines the physical interface between two paper surfaces or between a paper surface and another material. TAPPI T815 measures the static coefficient of friction through the sled method where a weighted block rests upon a horizontal specimen. This laboratory procedure quantifies the force required to initiate movement when the test block is pulled across the surface at a constant rate.
Paper mills and packaging converters use the resulting data to predict how containers behave during automated handling on conveyor systems. A precise friction value prevents sliding accidents or jams during the palletizing of finished corrugated boxes.
Testing Apparatus
Specialized equipment consists of a motorized drive mechanism that advances a load cell connected to a sled. The weighted sled has a flat base of specified dimensions and weight to ensure uniform contact pressure across the substrate area. Technicians mount the bottom specimen onto a rigid horizontal plane and place the sled on top before activating the drive system.
Mechanical force recorded during the initial motion indicates the static friction threshold of the tested material.
Process Consequence
Surface coatings or sizing agents applied during manufacturing alter the slip properties of board stock significantly. High friction values impede flow through production machinery and lead to frequent machine stops. Lower values improve movement but create unstable unit loads that shift during transportation.
Correct calibration of these surface properties allows for the high speed filling and stacking of secondary packaging materials.