Atmospheric pressure plasmas are commonly used to improve the wetting and adhesion properties of polymers. In spite of their use, the mechanisms for achieving these properties are unclear. In this regard, we report on a computational investigation of the gas phase and surface kinetics during humid-air corona treatment of polypropylene (PP) and the resulting modification of its surface properties while varying energy deposition, relative humidity (RH), web speed, and gas temperature. Using results from a global plasma chemistry model validated against experiments, we found that increasing energy deposition increased the densities of alcohol, carbonyl, acid, and peroxy radicals on the PP surface. In doing so, significant amounts of gas phase O 3 and N x O y are produced. Increasing the RH increased the production of peroxy and acid groups, while decreasing those of alcohol and carbonyl groups. Production of O 3 decreased while that of HNO 3 increased. Increasing the temperature decreased the concentrations of alcohol, carbonyl, and acid groups on PP while those of the peroxy radicals increased. For a given energy deposition, higher web speeds resulted in decreased concentrations of alcohols, peroxy radicals, carbonyl, and acid groups on PP.

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Dielectric barrier discharge ͑DBD͒ reactors are being investigated for plasma remediation of NO x from the exhaust of internal combustion engines and diesel emissions, in particular. In earlier works, it was found that unburned hydrocarbons ͑UHCs͒, inevitably present in exhausts, play a significant role in altering NO x remediation pathways and increasing the oxidation of NO. In this study, the DBD processing of NO x in simulated diesel exhausts with hydrocarbons ͓propane (C 3 H 8 ) and propene (C 3 H 6 )͔ has been investigated. In general, the presence of UHCs improved the energy efficiency of remediation. For example, at 56 J/L, NO x remediation improved from 12% without UHCs to 32% in the presence of 175 ppm propene. The W-values for NO remediation at 56 J/L decreased from 160 eV/molecule in the absence of UHCs to 96 eV/molecule with 175 ppm propene, though the majority of this improvement is a result of conversion to NO 2 . Temperature dependencies of NO x remediation were investigated and it was found that higher temperatures improve NO remediation whereas the effect on total NO x remediation is not significant, implying that NO remediation at higher temperatures results from increased NO 2 formation.

Dielectric barrier discharges (DBDs) are being investigated to remediate NO x from atmospheric gas streams. The interaction of species generated during previous pulses of repetitively pulsed devices, such as DBDs, make their operation fundamentally different from single pulse operation. To investigate these effects, the reaction chemistry of multiple pulses during NO x remediation was modelled. Reactions between radicals produced during a pulse with the products from previous pulses produce significantly different end products. For example, approximately 10 ppm of methyl nitrate (CH 3 ONO 2 ) was obtained by multiple pulsing whereas less than 1 ppm of it was produced with single discharge formats. Multiple pulsing has also been found to be more efficient for NO x remediation. W -values for NO x remediation decreased from 240 eV for a single pulse (58 J l −1 ) to 185 eV when the same energy was distributed over 20 pulses.

Plasma remediation is being investigated as a means to remove NOx from combustion effluent and from diesel exhausts in particular. Soot particles are inevitably present in actual exhausts and may, through heterogeneous chemistry, affect the remediation process. In this article, a computational investigation of the effect of soot on the plasma chemistry of NOx removal in a simulated diesel exhaust processed in a dielectric barrier discharge reactor is presented using a zero-dimensional global-kinetics simulation. A surface chemistry model is employed to describe soot oxidation by O and OH radicals, and soot-NOx interactions. The NOx chemistry may be substantially affected by the reactions at the soot surface. In particular, for soot particles having densities of 108 cm−3 and diameters of 100 nm, significant increases of NO are obtained when taking into account NO2→NO conversion on the soot surface. Heterogeneous reaction of NO2 also results in an increase in the gas-phase OH density which results in the increased formation of HNO2, thereby adding to the NOx remediation. NO2→NO heterogeneous conversion also results in an increase of CO and a subsequent reduction of the soot mass. The mechanism for soot-NOx interactions depends on the deactivation of active hydrocarbon radicals on the soot.