Strengthening and stiffening of ramie yarns by applying cyclic load treatment

Abstract

AbstractA cyclic load treatment was developed by applying a load on ramie yarns up to a proper value and then unloading for different number of cycles under high temperature or wet state. The results of tensile tests revealed that compared to the untreated yarns, a significant increase of around 20–50% in tensile strength was obtained for the cyclic load‐treated yarns. Young's modulus of cyclic load‐treated yarns was increased drastically, one to two times higher than the initial value. The number of cycles had an influence on improving the tensile properties of ramie yarns. After the individual heat or wet treatment without cyclic load, it was found that tensile strength of treated yarns remained unchanged as the original value while Young's modulus was decreased remarkably, which implies that the introduction of cyclic load to individual heat or wet treatment plays a crucial role in strengthening and stiffening of ramie yarns. It was considered that the improved effect was correlated with the decreased microfibrillar angle and the increased orientation of amorphous region in fiber microstructure because the crystallinity and crystalline orientation of ramie yarns calculated from X‐ray diffraction diagrams showed little change after cyclic load treatment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008