Effect of Growth Period and Sampling Section on the Chemical Composition and Microstructure of Raw Hemp Fibers

Abstract

Hemp fiber's origin has a large impact on the physical properties of degummed fibers. In this research, the effect of hemp fiber origin on the treated fibers was studied mainly by evaluation of chemical composition and microstructure, as well as by the evaluation of the degummed fiber's properties under a biochemical process. The samples were chosen from the stem with two different growth periods (an early and a late harvest time) and three different sections along the hemp stem (top, middle, and bottom). The results showed a vast variety of chemical compositions and microstructures for raw hemp fibers in different growth periods. The results of the chemical composition analysis indicated that the cellulose content in raw fibers ranged from 41.9±2.3% to 44.8±0.8% and that the lignin content ranged between 12.0±1.5% and 16.5±0.9%. Both the Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) results demonstrated the close relation of the raw fiber's character to the growth period and sampling section. The physical properties of degummed fibers with different origins were also tested, and large variations in length and linear density were found, which ranged from 42 mm to 67 mm for length and from 11.36±0.37 dtex to 21.55±0.54 dtex for linear density.

The Complex Interactions Between Flowering Behavior and Fiber Quality in Hemp

“…Around the onset of flowering, nutrient flow and carbon partitioning is shifted to the development of flowers and seeds, and less to the development of stems, leaves, and roots. In hemp, the transition from the vegetative to the adult phase can be recognized by a change in the leaf arrangement from opposite to alternate, the formation of inflorescences (Hall et al., 2012), a reduction in stem growth (Faux et al., 2013; Tang et al., 2016), and formation of secondary more lignified bast fibers from the bottom-upward in the stem (Keller et al., 2001; Mediavilla et al., 2001; Li et al., 2013; Liu et al., 2015, 2018). Furthermore, Liu et al.…”

“…Thus, the quality of the fibers is influenced by the developmental stage at harvest and it differs between different sections of the stem. Based on fiber quality measurements, the best quality fibers are obtained from the middle part of stems, harvested around flowering (Keller et al., 2001; Mediavilla et al., 2001; Li et al., 2013; Liu et al., 2018). In addition to this, the after-harvest process “field retting” is important for a good separation of bast fibers from the woody core (shives).…”

Novel scouring method of hemp fibers based on electrochemical techniques

“…Although there is great similarity in the spectra of the three samples, several differences for scoured hemp fibers both by traditional chemical methods and active water compared with raw hemp fibers are detected. Characteristic absorption bands at 2920 cm −1 and 2850 cm −1 relating to antisymmetric CH 2 stretching and symmetric CH 2 fluctuations, 26 , 27 which are viewable in the spectrum of raw hemp fibers, have disappeared in the two scoured hemp fibers, indicating removal of the wax component from the scoured hemp fibers. 28 The discovered band at 1735 cm −1 , attributed to valence C=O fluctuations, can specify presence of acid and/or ether pectins in hemp fibers.…”

“…10 The absorption at the band of 897 cm −1 , which is specific to the glucose ring stretching vibration of cellulose, appears a little increased when the hemp fiber is scoured either by traditional chemical method or active water, implying a decrement in the amorphous form of cellulose caused by scouring treatment. 26 , 30 All these spectrum changes reveal that active water is an effective scouring treatment for hemp fibers and has a similar effect on the removal of non-cellulosic substances compared with traditional chemical methods.…”