Creating cellulose fibres with excellent UV protective properties using moist CF₄ plasma and ZnO nanoparticles

Weakly ionised gaseous plasma created in a moist tetrafluoromethane gas at a low pressure with an electrodeless radiofrequency discharge was applied to modify the surface properties of cellulose fibres. The plasma was used to increase the adsorption of zinc oxide (ZnO) nanoparticles such that cellulose fibres with good ultraviolet (UV) protective properties could be created. The UV protection factor (UPF) values of the ZnO-functionalised fibres were determined as a function of the plasma treatment time. The chemical and physical surface properties of the plasma-treated fibres were examined using scanning electron microscopy, X-ray photoelectron spectroscopy, and wettability tests. The quantity of zinc on the fibres was determined using inductively coupled plasma mass spectroscopy. The results indicated that 30 s of plasma treatment resulted in ZnO-functionalised samples with lower UPF values than samples without plasma treatment due to the creation of fluorine-rich functional groups on cellulose fibres and the agglomeration of ZnO nanoparticles. The highest UPF values (50+) were obtained when samples were treated with plasma for 10 s. These high UPF values were a result of the increased adsorption of uniformly distributed ZnO nanoparticles caused by fibres surface functionalization and roughening upon plasma treatment. Furthermore, the mechanical properties of textiles treated with moist CF₄ plasma for 10 s were slightly improved.