ABSTRACT
Plasma is the most active state of matter after solid, liquid and gas. Using appropriate device and power source, it is possible to generate cold or hot plasma. For textile surface modification, plasma at room temperature (cold plasma) is more appropriate. The cold plasma comprises of electrons, ions, radicals, metastables and UV radiation. Cold plasma is also known as nonequilibrium plasma, where electron temperature used to be much higher in comparison to ion or neutral temperature. Since electrons are very small in size, therefore, effective energy transfer does not take place. Consequently the plasma remains at room temperature. In atmospheric pressure plasma, the electric field transmits energy to the gas electrons which are the most mobile-charged species. This electronic energy is then transmitted to the neutral species by collisions. These collisions can be divided in (i) elastic collisions, in this case there is no change in the internal energy of neutral species, however, their kinetic energy increases slightly; and (ii) inelastic collisions – when electronic energy is high enough, the collisions modify the electronic structure of the neutral species and result in the creation of excited species or ions. Most of the excited species have a very short lifetime and they come to ground state by emitting a photon; however, the excited ‘metastable species’ have a much long life. In helium plasma, large numbers of metastable species are formed. The metastable species interact with neutrals and results into penning ionization and dissociation. This plasma when interacts with polymer or textiles modifies their surface properties without altering the bulk properties of these materials. In the plasma, reactions occurs in gas phase as well as plasma species interact with the substrate surface. These reactions are given in Table 2.1 and plasma surface interactions are shown in Fig. 2.1.
