Structure of the right-handed helical crystal ribbon and multilevel fibrils in a tube fiber from a coir fiber

Abstract

A coir fiber is composed of many tube fibers with large hollows that align in parallel. SEM observation has shown that the tube fiber existing in a coir fiber is packed by a right-handed helix crystal ribbon, and its length/diameter ratio is lower than that of the crystal ribbon by 1–2 orders of magnitude. Based on the results of TEM, the diameter of protofibrils extracted from coir fibers is 6–10 nm, while that of the microfibrils is 20–40 nm, and the length/diameter ratios of protofibrils and microfibrils are 50–250 and 25–150, respectively. According to these observed results, the packing models of the right-handed helix crystal ribbon and its multilevel fibrils have been derived and further verified through the calculation and comparison of both the crystallinity in volume and whisker sizes obtained by means of X-ray diffraction analysis.