Plasma-induced surface modification of lignocellulosic and synthetic polymers

Surface modification of lignocellulosic (cellulose and lignin) and synthetic (PP, PET and PTFE) polymers has been studied using plasma technologies in this investigation. Various low pressure radio frequency (rf) plasmas were employed to modify the surface characteristics and adhesion of inks on US currency paper for improvement of printability and durability of the currency. Response surface methodology was used to evaluate the influence of external plasma processing parameters on the wettability of currency. Both O{dollar}sb2{dollar} and SiCl{dollar}sb4{dollar} plasma treatments led to a significant increase of the wettability, but SiCl{dollar}sb4{dollar} plasma treatment had a more complex influence due to surface functional group attachment mechanisms. Further investigation of argon plasma induced surface chemistry of cellulose with chemical derivatization techniques resulted in a purposed pyranosidic ring opening mechanism for cellulose under an rf discharge.; Surface functionalization of inert synthetic polymers was achieved through the incorporation of chemical functional groups dependent on the selected plasma feedgases. SiCl{dollar}sb4{dollar} plasma treated polypropylene (PP) and polytetrafluoroethylene (PTFE) exhibited high hydrophilicity, functional group stability and improved surface roughness as a consequence of the surface attachment of the silicon-containing functionalities. The first time use of a fluorocarbon C{dollar}sb6{dollar}F{dollar}sb6{dollar} plasma for surface fluorination of PP was found to greatly favor plasma induced deposition processes rather than ablation. The higher fluorine content on the C{dollar}sb6{dollar}F{dollar}sb6{dollar} plasma treated PP surfaces was attributed to the nature of the plasma induced fragmentation of the C{dollar}sb6{dollar}F{dollar}sb6{dollar} to give structural unsaturation, capable of initiating crosslinking reactions and less free fluorine production.; A novel dense medium plasma (DMP) treatment method was also utilized for the first time to modify the surface of lignin. A direct current SiCl{dollar}sb4{dollar} discharge under atmospheric pressure was used for this purpose. Up to 9% of silicon atomic concentration and an associated higher oxygen content were successfully attached to the lignin surface without altering the bulk structure. The high reactivity and accessibility of the plasma induced Si(OH){dollar}sb3{dollar} functionality on the lignin surface has been demonstrated by the success of subsequent conventional grafting reactions with the dichlorodimethylsilane (DCDMS) to form lignin-polydimethylsiloxane type structures. The resulting product showed greater thermal resistance than untreated lignin.