Dispersion Barrier Performance under Crease Compression in Folding Boxboard
Wide matrix channels and shallow penetration depth prevent polymer micro-fractures in dispersion-coated folding boxboard during creasing.
Gravimetric Dish Test
Moisture Permeation
Moisture permeation defines the physical transmission rate of water vapor molecules through a specific packaging substrate under controlled atmospheric conditions. The gravimetric dish test measures this exact barrier property by sealing a desiccant inside a standardized metal or polymer cup covered by the test film, then recording incremental weight gains over fixed time intervals on a laboratory balance. Precision balance calibration directly controls the accuracy of the resulting water vapor transmission rate value.
Converting operations rely on this measurement to prevent moisture ingress in sensitive pharmaceutical blisters and food packaging laminates. Substrate selection depends heavily on whether a fibre based barrier coating or an extruded polymer film achieves the required moisture vapor transmission limit. The physical boundary of the method sits at saturated humidity extremes where structural degradation of the adhesive layer compromises cup seal integrity.
Test Protocol
Atmospheric chambers maintain a constant temperature and relative humidity gradient across the mounted specimen surface during the measurement window. Technicians weigh the entire assembly periodically to establish a steady mass flow rate through the planar sheet. Relative humidity fluctuations inside the conditioning cabinet invalidate the calculated permeability coefficient within hours.
Converting plants adjust extrusion coating weights upward when baseline gravimetric dish test results exceed maximum contractual tolerances for tropical shipping lanes. Polyethylene extrusion layers must maintain uniform thickness across the web to prevent localized vapor transmission spikes that would ruin a commercial barrier claim.
Evaluation Standard
Packaging converters depend on standardized cup weights to verify material compliance before converting raw paperboard into finished cartons. Laboratory technicians calculate water vapor permeability from the linear slope of mass gain plotted against elapsed time. Fibre substrates treated with wax coatings exhibit variable moisture barrier performance compared to foil laminates due to microscopic pinholes in the applied layer.
Production lines reject paperboard reels whenever the gravimetric dish test reveals excessive moisture transfer under standard tropical stress conditions.