Cold-plasma Assisted Hydrophobisation of Lignocellulosic Fibres

Cold-plasma-assisted treatment of additive-free hand sheet paper samples with styrene (ST), para-fluorostyrene (FST), parafluoro- α-methylstyrene (FMST), para-chloro-α-methylstyrene (ClMST) and para-bromo-styrene (BrST) was studied and it was established that eficiente grafting had occurred, using elemental analysis, contact angle measurement, and X-ray Photoelectron Spectroscopy (XPS). The contact angle value of a drop of water deposited at the surface of paper increased from 40° for unmodified substrate to 109, 99, 106, 100 and 107°, for ST-, FST- FMST-, ClMST- and BrST-treated samples, respectively, indicating that the surface was rendered totally hydrophobic. The treated surfaces became totally non polar, with the polar component of the surface energy decreasing from 25 mJ/m2, for pristine samples, to practically zero for the treated samples. The XPS spectra showed that the modification induced a significant decrease in the O/C ratio, as well as an increase in the intensity of the aliphatic carbon contribution to the C1s signal. Moreover, the presence of fluorine and chlorine atoms was also detected in the low resolution wide scan XPS spectra.