Study of hydrophobic finishing of cellulosic substrate using He/1,3-butadiene plasma at atmospheric pressure

Atmospheric pressure glow plasma was created using He/1,3-butadiene (BD) mixture. Stable milky white glow He/BD plasma was confirmed by spike free smooth I–V waveform. Optical emission spectroscopy (OES) spectra of He/BD plasma showed fragmentation of BD inside the plasma zone into small species. OES analysis also showed that fragmentation of BD could be significantly increased by increasing the He to BD gas ratio from 12.5 to 50. The He/BD plasma was successfully utilized to impart a high degree of hydrophobic functionality to cellulosic (viscose rayon) fabric, which was durable to soap washing. Water absorbency time in the 12 min plasma treated sample increased to > 60 min and contact angle to 142° compared to < 1 s and ~ 0°, respectively, in the untreated sample. XPS, SIMS, SEM and AFM analyses showed that under suitable conditions, He/BD plasma resulted in nano-scale chemical modification of the textile substrate instead of weakly adhered physical deposition of condensates of BD on the surface. XPS analysis showed that after the He/BD plasma treatment, the surface carbon percentage increased with a corresponding decrease of O percentage. The increase in C percentage was mainly due to the incorporation of species containing CHx, such as CH2 and CH3, in cellulose and removal of OH bonds from the top layers of cellulosic fibre. Similar results were obtained from SIMS analysis. analysis of He/BD plasma exhaust gases revealed that mainly, two types of species were formed: based on dimer of 1,3-butadiene (110 and 108 amu) and species with seven carbon atoms (96 amu). These species have possibly replaced or substituted the oxygen containing sites in the cellulose resulting in durable hydrophobic functionality.