IMPACT OF CARBOXYMETHYLATION PRETREATMENT ON THE MORPHOLOGICAL AND THERMAL CHARACTERISTICS OF CELLULOSE MICROFIBRILS FROM OIL PALM FROND TOWARD SOLAR THERMAL BENEFITS

Abstract

The morphological and thermal characteristics of cellulose microfibril isolated from oil palm frond (OPF) waste, using carboxymethylation pretreatment, to benefit solar thermal application were explored. Following the pretreatments, 30 minutes of high-intensity ultrasonication (HIUS) at 20 kHz and 130 W output power were applied as a solvent-free fibrillation technique to produce cellulose microfibrils. The morphology of the isolated cellulose revealed that the consecutive techniques produced a long and uniform cellulose microfiber, with diameters ranging between 2 and 10 µm, the coefficient of variation of its morphology distribution data being of 44.4%. It also caused the microfiber structure to shift from cellulose I to cellulose II, with a moderately high crystallinity index. Carboxymethylation greatly affected the thermal stability of cellulose microfibrils, with maximum degradation temperature up to 281 °C, as evident from TGA and DSC analyses. The surface chemistry for the carboxymethylated microfibril sample indicated significant changes in the functional groups responsible for its properties.