Effects of Heat Treatments on the Morphological, Chemical, and Thermal Properties of Biologically Degummed Okra Bast Fibers

Abstract

Lignocellulosic fibers produced from okra stems via biological degumming were subjected to environmentally-friendly heat treatments where neither chemicals nor water were consumed. The treatments were conducted under various temperatures (100-160 degrees C) for different durations (150-600 min). The effects of heat on the morphological, chemical, and thermal properties of okra bast fibers were scrutinized. Heat treatments resulted in fibrillation and separation of extracellulosic constituents. Exposure to 160 degrees C led to fiber color darkening due to starting of thermal degradation of fiber components. The applied thermal treatments led to change of cellulose structure from native cellulose I to cellulose II as suggested by FT-IR, XRD, and thermogravimetric analyses. Slight change in cellulose crystallinity was observed upon exposure to high temperatures. The heat treatments attenuated the effect of moisture on okra bast fiber's chemical properties and improved thermal stability. Okra bast fibers showed endurance in the studied temperature and duration ranges.