Morphological and chemo-thermal changes of oven-heat treated oil palm empty fruit bunch fibers during dry disk milling

Abstract

Dry disk milling has been proven as a feasible mechanical process for obtaining finer particles. The milling was used to pulverize oven-heat untreated and treated oil palm empty fruit bunch (OPEFB) fibers into micro to nano-sized fibers. Scanning electron microscope, X-ray diffraction (XRD), particle size analyser, fourier transform-infrared spectroscopy, energy dispersive spectroscopy, and differential scanning calorimetry tests were performed for dry-milled OPEFB fibers with three different temperatures (unheated sample, 100 °C, and 190 °C for 15 min). The properties of oven-heat untreated and treated OPEFB fibers were noticeably shifted due to dry disk milling processes. Irregular cut-edge, unsmooth, uneven and damaged external structures with varied foldings and scars were found in the fibers. Dry disk milling was able to reduce the crystallinity index of oven-heat untreated and treated OPEFB fibers. The XRD spectra of the fibers were similar with JCPDS Card No: 46-1932. Median particle size of the fibers in the range of 100–1000 nm was successfully obtained by means of dry disk milling for 27 min at 2895 rpm. Dry milled fibers of both treated and untreated fibers contained of C (47.64–51.71%), O (43.33–46.09%), K (1.38–3.95%) and Si (0.37–1.70%). Cementing agents existed after the milling whereas silica bodies were tremendously removed. Thermal stability of dry-milled OPEFB fibers varied with dry disk milling assisted oven-heat treatments.