Modification of hardwood samples in the flowing afterglow of N2–O2 dielectric barrier discharges open to ambient air

Insights: Publications Modification of hardwood samples in the flowing afterglow of N2–O2 dielectric barrier discharges open to ambient air

Cellulose Volume 22, Issue 5, 3397-3408

August 20, 2015

The effect of O2 addition in the gas feed of an open-to-air N2–O2 dielectric barrier discharge (DBD) on the surface modification of sugar maple hardwood samples is reported. After treatment by N2–O2 plasma, an increase of the contact angle with water and a decrease of the contact angle with diiodomethane was observed. X-ray photoelectron spectroscopy and Fourier-transform infra-red analyses further reveal a decrease of the O/C as well as increase of the C=O peak and surface aromaticity. When O2 is added to the nominally pure N2 DBD, the discharge transits from a homogeneous regime to a filamentary regime with increased dissipated power and neutral gas temperature. As a result, surface modification by N2–O2 plasmas becomes similar to those occurring under a low-temperature heat treatment of wood surfaces. In such conditions, a mechanism involving the thermally-activated deacetylation and depolymerisation of hemicelluloses and cross-linking between lignin and furfural and hydroxylmethylfurfural, leading to the increase of wood hydrophobicity is proposed.