Airglow discharge plasma treatment affects the surface structure and physical properties of zein films

Airglow discharge plasma (ADP) was used to modify the surface properties of zein film, and the influence of plasma dosage was investigated by controlling treating time (from 0s to 120s). Fourier transform infrared spectrophotometry (FT-IR) results indicated that the ADP treatment partly destroyed the acylamino groups of zein film, and the X-ray photoelectron spectrometer (XPS) analysis proved that oxygen was introduced into the matrix of zein films during ADP treatment, with the content enhanced from 14.29% to 18.45%. The microstructure of zein film exhibited a more robust surface with longer treating time, corresponding to the X-ray diffraction (XRD) results that the crystal structure of zein film was destructed under ADP treatment. The contact angle changed from 78.3 degrees +/- 2.3 degrees to 62.1 degrees +/- 1.7 degrees under ADP treatment, representing higher wettability. Mechanical properties also showed desirable changes under ADP treatment, with the tensile strength increased from 12.25 +/- 1.23 MPa to 18.12 +/- 0.68 MPa. ADP treatment could be a promising approach to modify the surface properties of protein films.