Atmospheric pressure plasma treatment of chitosan-acrylic acid blends

Abstract

This study explores the effect of atmospheric pressure plasma (APP) treatment on chitosan-acrylic acid (Cs-AA) blends. The experiment involves a custom-built APP setup used to modify a polymeric blend composed of natural (Cs) and synthetic (AA) polymers. Even with a low process temperature (<40  °C), reactive oxygen and nitrogen species (RONS) were observed in an air plasma plume. The interaction of plasma with the liquid surface was also observed. With de-ionized water as the test liquid, the operating parameters such as the treatment time and flow rate were shown to influence the pH and absorption spectrum of the liquid. The presence of RONS was investigated using optical emission spectroscopy coupled with principal component analysis. The analysis revealed that the air plasma contains the different N systems, NO, OH, H α, monatomic N, and monatomic O species. Varying the gas flow rate influences the production of NO and OH radicals while measuring plasma discharge in different conditions (ambient air, DI H 2O, Cs, and Cs-AA blend) affects the concentration of the N positive and negative systems. The effect of these RONS on the Cs-AA blends was also investigated by assessing the chemical structure, pH, and viscosity of the solution. In correlation with all of the findings, it was observed that plasma treatment could degrade pure Cs solution by dehydrogenation and glycosidic bond cleaving. However, the addition of AA reduces the degradation so that the AA radicals created by plasma form a complex with the Cs that reduces Cs fragmentation and chain entanglement, as observed in the reduction of viscosity. In summary, the rich reactive species created by plasma in the Cs-AA solution not only provided stable species but also introduced more Cs-AA complexes.