Atmospheric pressure plasma jet treatment of wheat straw for improved compatibility in epoxy composites

Abstract

ABSTRACTThe aim of this study was to investigate the effects of an atmospheric‐pressure gas plasma jet treatment on the interior and exterior surface characteristics of wheat straw and on the mechanical properties of epoxy composites reinforced with wheat straw. Dry air was used as the process gas in the plasma system. A distance between the nozzle and the substrate surface (DNSS) of 35 mm was determined as the most effective parameter enabling remarkable decreases in the (surface energy) values of both the interior and exterior surfaces of virgin wheat straw. Increased intensities of the peaks related to carbon‐rich species and 11% to 43% decreases in the oxygen/carbon ratios on the surfaces confirmed the more hydrophobic nature of the plasma‐treated wheat straw. A further increase in the DNSS decreased the effectiveness of the plasma treatment, while a decrease in the DNSS caused an inverse effect on the value, probably due to the etching effect of the plasma action, which was supported by the atomic force microscopy analysis. The overall results indicated that the increased hydrophobicity and valley‐like occurrences without sharp pits created by the plasma action improved the compatibility of the wheat straw with the epoxy matrix, which contributed to superior mechanical properties of the composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45828.