The surface activation of high‐density polyethylene powder using a remote plasma process at atmospheric pressure is investigated. The developed circulating fluidized bed plasma reactor enables to carry fine‐grained powder particles repetitively through the afterglow of 64 dielectric barrier discharges of argon with O2 and CO2 admixtures. The evolution of particle size distribution during conveying in the reactor is monitored by laser diffraction and reveals that only a small particle fraction is lost during the process. The contact angle of activated powder samples steadily decreases with increasing treatment time. The surface activation is most effective for O2 admixtures of 0.25 vol% and CO2 admixtures of above approximately 1 vol%, respectively.
This review provides a comprehensive overview of scientific research on plasma treatment of polymer powders over the last 40 years. The current state of the art is described with special focus on basic research in the laboratory and commercially available technologies in industrial applications. Different reactor systems with low‐pressure and atmospheric pressure plasma are presented. Then, numerous application examples of plasma‐treated polymer powders are presented together with a brief overview of the experimental test results. Furthermore, the effects of the process parameters on the final properties of the polymer powders are discussed. Attempts are made to determine similarity parameters and correlations between the generated surface functionalities. Finally, some suggestions for future research are given.
The consumption of fresh fruit and vegetable products has strongly increased during the past few decades. However, inherent to all minimally processed products is the short shelf life, and the risk of foodborne diseases, which have been increasingly related to such products in many parts of the world. Because of the favorable conditions for the growth of bacteria during the germination of seeds, sprouts are a frequent source for pathogenic bacteria, thus highlighting the need for seed decontamination to reduce the risk of foodborne illness. Consequently, this study focused on cold atmospheric pressure plasma (CAPP) treatment of artificially inoculated seeds in a diffuse coplanar surface barrier discharge to determine the inactivation efficiency for relevant foodborne pathogens and fungal spores. Plasma treatment of seeds resulted in a highly efficient reduction of microorganisms on the seed surface, while preserving the germination properties of seeds, at least for moderate treatment times. To characterize the mechanisms that contribute to microbial inactivation during plasma treatment, an experimental setup was developed to separate ultraviolet light (UV) and other plasma components. The combination of bacterial viability staining with confocal laser scanning microscopy was used to investigate the impact of ozone and other reactive species on the bacterial cells in comparison to UV. Further characterization of the effect of CAPP on bacterial cells by atomic force microscopy imaging of the same Escherichia coli cells before and after treatment revealed an increase in the surface roughness of treated E. coli cells and a decrease in the average height of the cells, which suggests physical damage to the cell envelope. In conclusion, CAPP shows potential for use as a decontamination technology in the production process of sprouts, which may contribute to food safety and prolonged shelf life of the product.
Polyethylene powder is treated in an atmospheric pressure circulating fluidized bed plasma reactor, in which powder particles pass the afterglow of 64 discharge channels multiple times. Contact angle drops with increasing treatment time and powder gradually becomes wettable with liquids of higher surface tensions. X‐ray photoelectron spectroscopy is used to prove particle surface functionalization induced by the afterglow process. Two different channel arrangements and geometries are studied and the influence of applied voltage and frequency on activation efficiency is investigated. Minimal surface aging is observed when samples are stored in air. However, when dispersed in water, particles maintain the engineered wettability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.