Upscaling strategies for atmospheric‑pressure plasma treatment of recycled PET flakes for particleboard adhesion

Abstract

The intrinsically poor adhesion between recycled polyethylene terephthalate (PET) flakes and wood particles limits their use in particleboard manufacturing. This study investigates atmospheric‑pressure plasma activation as a scalable approach to enhance interfacial adhesion in PET–wood composites. Two continuous plasma systems—dielectric barrier discharge and gliding arc—were evaluated for their effect on bonding with urea‑formaldehyde (UF) and melamine‑urea‑formaldehyde (MUF) adhesives. Plasma treatment was calibrated by chemiluminescence and characterized by X‑ray photoelectron spectroscopy. Particleboards containing 15 wt.% PET were fabricated and mechanically tested. Lap‑shear strength increased significantly for UF adhesives (up to +0.51 MPa), while MUF showed only minor improvements (≤ +0.17 MPa). Enhanced adhesion led to recovery of internal bond strength from 0.36 MPa to 0.49–0.50 MPa, meeting EN 312 requirements. Thickness swelling of PET‑containing boards was reduced from 29.3% to 22.0% after 24 h immersion, indicating improved interphase integrity. XPS suggests that plasma‑introduced nitrogen functionalities promote bonding with UF resins. Both plasma systems achieved comparable adhesion performance at similar doses while enabling continuous processing with low energy demand (0.15–0.19 kWh·kg−1). Atmospheric-pressure plasma‑engineered surface modification thus provides an effective route to overcome adhesion limitations of recycled PET.