It can be seen that

It can be seen that the major contribution (>95%) of C1s component of untreated PP film surface exhibited C–C which decreased gradually with respect to gaseous plasma treatment in the order of UT < Ar < O2 < Air < Ar + O2, while the concentration polar function groups such as C–O, CO/O–C–O, O–CO–C increased in the same order of gaseous plasma treatment as shown in Fig. 4. The above changes may be attributed to argon plasma treatment which produces enormous amount of free radicals on the surface of PP film through breaking of hydrogen bonds in the polymer network. However, feeble amount of C–O groups are formed on the surface of PP film by the interaction of free radicals with oxygen species in the environment when exposed in air. In contrast, the mechanism of oxygen containing plasma effect differ exclusively from argon plasma treatment because oxygen plasma produces polar functional groups onto the surface without creation of much cross linked network which mean in situ surface AG 99 arises on the surface of PP films [37] and [38]. Furthermore, formation of polar functional groups on the surface of PP films by oxygen containing argon plasma (O2 + Ar) has involved different simultaneous processes which include both the cross linking and the surface oxidation. In this processes plasma particles are initially able to interact with the polymer surface which break the hydrogen bond and creates carbon radials on the surface and it is immediately reacted with neighboring polymer chain. Due to the interaction between the two carbon radicals from the adjacent chains, cross linked network is formed onto the PP film surface. At the same time, the free radicals also interact with oxygen atoms in the plasma leading to the formation of high dense of oxygen containing polar functional groups such as C–O, CO/O–C–O, O–CO/COO and O–CO–C on the polymer surface. Based on the above mechanism, Ar + O2 plasma treatment yield high dense of polar functional groups on the PP film surfaces [39]. In addition, similar mechanism occurred on the air plasma treated PP film surfaces. However, different oxygen and nitrogen species (NO, NO2, N2O) and charged species (NO+, O2+, O+) are involved to produce more amounts of polar functional groups on the surface of PP films during the air plasma treatment. Thus, our results clearly suggest the formation of polar functional groups such as C–O, CO/O–C–O, O–CO/COO, O–CO–C mainly depends upon the plasma forming gases. Air and Ar + O2 plasma treatment creates high dense of functional groups on the PP film surface compared with other plasma treatments [37] and [40].