Polystyrene thin films treatment under DC pulsed discharges conditions in nitrogen

A systematic parameters study is performed in a DC pulsed glow discharge in nitrogen in order to improve the wettability of thin polystyrene layers. T he experimental parameters considered are the pressure P, the interelectrod e voltage V, the frequency nu of the pulsed power supply and the treatment time t(t). The wettability is characterized by the contact angle technic. T he (Theta (i) - Theta (f))/Theta (i) = Delta Theta/Theta (i) ratio is measu red, where Theta (i) and Theta (f) are respectively the initial and final c ontact angles. In the first part of the paper, the variations of Delta Thet a/Theta (i) as a function of the electrical energy E are investigated, the variations of E being obtained by modifying the parameters V, nu and/or t(t ). In the second part, the specific energy epsilon and the economical crite rion gamma are introduced to deduce the best running conditions through a c hemical engineering approach. Taking into account the weak duty factor of t he power supply (1%), it is shown that the polymer surface is treated with a minimum of energy.