Characterizing Porous Absorption in Recycled Packaging Paper Grades
Characterizing porous absorption in recycled paper requires measuring dynamic capillary wicking and pore size distribution to control ink set times and glue bonds.
Testliner Grade 2
Recycled Linerboard
Multi-ply containerboard classification specifies a predominantly recycled linerboard grade manufactured primarily from recovered paper stock with controlled burst strength and surface finish. Testliner grade 2 designates a standardized commercial packaging grade that meets intermediate structural requirements beneath premium grade 1 testliners and virgin kraftliners. Standard specifications dictate minimum bursting strength values, typically measured by the Mullen test, alongside defined compression resistance metrics such as the short-span compression test.
The grade commonly features a two-ply or three-ply construction, frequently utilizing a top ply of selected recycled fibers or unbleached semi-chemical pulp to enhance surface printability. The classification terminates where virgin wood pulp content dominates the furnish, which shifts the material into the kraftliner designation.
Structural Construction
Multi-fourdrinier or multi-ply former paper machines produce testliner grade 2 by laminating distinct pulp slurries into a unified wet web. The base plies incorporate mixed recovered paper stock and old corrugated container pulp to provide sheet caliper and bulk compression performance. High-refining energy applied to the top layer improves fiber conformability, creating a smoother, denser surface for flexographic printing on corrugated packaging lines.
Starch addition via size press or surface spray units bonds the multi-ply structure and compensates for the reduced hydrogen bonding capacity of recycled fibers. Compressive strength along the machine direction provides the necessary stacking strength for finished corrugated shipping containers. Moisture profile control across the web width prevents sheet warp during corrugating operations where the liner bonds to fluting medium at elevated temperatures.
Application Standard
Corrugated board converters utilize testliner grade 2 for inner liners, double-wall board combinations, and outer packaging faces where moderate bursting strength suffices. The material delivers predictable die-cutting clean-out, dependable scoring without face cracking, and stable ink holdout for standardized logistics graphics.