Influence of dc Pulsed Atmospheric Pressure Plasma Jet Processing Conditions on Polymer Activation

Abstract

Plasma treatments are widely used to activate polymer surfaces prior to adhesive bonding. This study investigates the influence of plasma treatment conditions on the surface activation of a range of polymers using the PlasmaTreat (Open Air) system. In this study the effect of dc pulse plasma cycle time, compressed air flow rate and the plasma jet nozzle to substrate distance on the plasma discharge was examined. The influence that the dc pulse plasma cycle time parameter has on the activation of polypropylene, polystyrene and polycarbonate was also investigated. The level of polymer surface activation was evaluated based on the change in water contact angle after plasma treatment. The polymer surface properties were also monitored using AFM and XPS measurements. The heating effect of the plasma was monitored using both infrared thermographic camera and thermocouple measurements. Plasma diagnostics measurements were obtained using the photo‐diode and optical emission spectroscopy techniques. From this study it was concluded that for the PlasmaTreat system the level of plasma activation was closely correlated with the dc pulsed plasma cycle time, which is a measure of the plasma intensity. For example, the more intense plasma obtained with shorter cycle times gave higher levels of polymer activation. The optimized pulsed plasma cycle times were found to be specific for a given polymer type and related to their thermal properties. The pulsed cycle times were also found to correlate with both the substrate and plasma gas temperatures. magnified image

Diagnostics of an O2–He RF Atmospheric Plasma Discharge by Spectral Emission

“…11 • 12 ) The upper energy level of OH309 is 13 metasable with an energy of 4.17 eV. The ionization energy 14 of the OH molecule (13.18 eV) is just slightly lower than the 15 ionization energy of a neutral hydrogen (13.62 eV) and both 16 species (OH and H) are produced through H 2 0 dissociation. This OES study was carried out on the plasma jet formed 44 using the SurFx Atomflo™ 400L atmospheric plasma 45 system.…”

“…9 Analysis of these species spectral intensities will assist in the 10 development of optimised plasma processing parameters for 11 treatments such as polymer surface activation, the removal of 12 contaminates etc. 13 14 …”

“…Because of 8 this the quenching of resonate energy levels is negligible and 9 therefore an electron transition that ends on a resonate energy 10 level may be use for the monitoring of an atom's density in 11 its ground state. 12 13 14 Oxygen species were studied in the He plasma using 1s measurements of atomic (0 I) and molecular (02) spectral 16 emissions. All recorded atomic oxygen spectral lines are 11 triplets.…”

“…Thermal energy transfer 12 was in the range of 185-615 m W, at the conditions 13 investigated. 14 The SurFx unit can generate plasma using He-0 2 gas 1s mixtures (in the range of 100-200 W). The input variables for 1s this system are strictly limited by the equipment manufac-17 turer, i.e., helium gas needs to flow at a constant flow rate of 18 30 1/min, while oxygen gas input varies with plasma power.…”

“…Under-4 pinning that He706 emissions, detected in helium discharges s with a small concentration of impurities, can be used to r. indicate the presence of energetic electrons. The 0777 and 7 0845 cannot be created by a dissociative recombination with a the ground state 0 2 + because the rate is strongly peaked 9 toward low energy electrons 26 ) and there is insufficient 10 energy for these to produce the excited atoms of interest 11 since the difference between the ionization potential of 0 2 12 (12.07 eV) and the bond dissociative energy (5.09 eV) 27 ) is 13 substantially less than the atomic excitation energy (11 eV) 14 for the OCSP) and oeP) states. Another option for the creation 15 of 0777 and 0845 is the dissociative excitation of the 16 molecular oxygen.…”