Evaluation of Melamine Coating Integrity on Particleboards Containing Surface Bark Inclusions

Melamine-faced particleboards are widely used in interior applications; however, their performance is often limited by the near-surface structure, film adhesion, and edge damage that can be generated during machining and service impacts. Here, model particleboards were produced with 0%, 10%, 20%, and 40% bark content in the face layers and laminated with two melamine films (light and dark décor). Density profiles, mechanical properties (MOR, MOE, internal bond, IB), and laminate adhesion (pull-off) were determined. Edge integrity was evaluated under edge milling, quantified by cumulative tear-out length (ΣL) and the normalized damage index Li (mm/m) together with tear-out depth, and under edge impact using a 0.5 kg mass dropped from 0.20 m (damage length and indentation depth). All boards were characterized by a typical U-shaped density profile, while increasing bark share reduced surface-layer density differentiation. MOR and MOE decreased significantly only at 40% bark, whereas IB (0.54–0.74 N/mm2) remained unchanged. Bark content significantly affected adhesion (32.76% contribution), whereas film type was not a significant factor. Milling damage depended on laminate: for the dark laminate, bark-containing boards showed much higher Li (54.82–60.13 mm/m) than the reference (12.26 mm/m); for the light laminate, the lowest Li occurred at 10% bark (21.24 mm/m). Tear-out depth varied narrowly (≈0.69–1.02 mm), while impact damage length ranged from 6.96 to 8.58 mm.