Hydrophobic surface treatments of sunflower pith using eco-friendly processes

The aim of the present paper is to report the reduction of the water uptake of sunflower pith, sustainable raw by-product without current added-value in oilseed crops production. The water-sensitivity is ascribed to its structure, because mainly constituted of carbohydrates, due to the formation of additional hydrogen bondings with water molecules. Two environmentally-friendly approaches were applied to provide a modified layer presenting water resistance in surface of sunflower pith in order to keep its low-density property. The first approach based on vegetable oil corresponds to thermal and photochemical treatments. A thin layer of virgin or acrylated epoxidized soybean oil was sprayed on the pith surface, and thereafter was thermally cured or photocured, respectively. The second approach consisted in a solventless chemical modification of the pith surface by a cold plasma treatment. Both approaches were successfully performed: water resistance of sunflower pith was clearly enhanced, especially with oil-based treatments; while maintaining its integrity. Developing new and promising ecological water-resistant products of low density from sunflower pith is thought of increasing interest with potential practical applications.