Polymer Barrier Coatings and Pulpability Test Standards
Polymer barrier paperboard compliance requires passing 0.15mm laboratory slot screening with under 15 percent reject mass to prevent EPR fee penalties.
Somerville Screening
Laboratory Fractionation
Standardized laboratory wet screening procedure separates non-defibered shives and flat contaminants from defibered pulp slurries. Executing Somerville screening utilizes a flat screen plate with calibrated 0.15 mm slots and a vibrating diaphragm to fractionate aqueous pulp samples. The mechanical vibration prevents screen mat formation, allowing well-separated cellulose fibers to pass through while retains collect on the plate surface.
Testing laboratories rely on this method to determine shive content and stickies contamination in raw pulp.
Contaminant Isolation
Equipment operation requires controlled water flow rates and calibrated stroke amplitude. Applying Somerville screening isolates plastic films and unpulped fiber bundles for quantitative mass yield analysis. The retained fraction is washed and oven-dried to determine the exact weight percentage of rejects in the pulp sample.
Inconsistent water pressure or improper diaphragm vibration alters fluid dynamics, leading to inaccurate reject fractions. Data generated from this test helps mills optimize pulp refining and cleaning operations.
Precision Limit
Test parameters set operational bounds for identifying unpulped residue levels in pulp stock. Highly contaminated samples clog screen slots, distorting fluid movement and invalidating test results. The screening test stops when fluid drainage ceases or when target sample volumes complete filtration.
Standardized fraction isolation ensures repeatable purity measurements across pulp testing facilities.