A Comparative Study of the Effect of Field Retting Time on the Properties of Hemp Fibres Harvested at Different Growth Stages

Abstract

In this study, the comparison of field retting of hemp fibres harvested at different growth stages (beginning and end of flowering, seed maturity) was studied. Regardless of the harvest period, identical evolution of the fibres’ properties was observed during retting. The main difference is the kinetics of this transformation, which depend on weather conditions and the initial state of the fibres after harvesting. Retting leads to a change in colour of the stems and fibres, an increase of the cellulose fraction and a gradual improvement of the fibres’ thermal stability, in relation with a decrease in the non-cellulosic materials. This process induces fibre bundle separation into elementary fibres. A long period (5 weeks) is required for getting the highest mechanical properties of fibres harvested at the beginning and the end of flowering. However, the retting of fibres harvested at seed maturity has to be performed in a short period (1 week) in order to avoid over-retting treatment. If the fibres are over-retted, their quality decreases in terms of structure and mechanical properties.

Extraction and Characterization of Bast Fiber from Xanthium Oriental plant

“…After the treatment of fibers by any of these methods, all treated fibers are washed away before drying [32][33][34][35][36][37]. The moisture content in fiber affects its quality, so proper drying is critical.…”

Hemp: From Field to Fiber—A Review

“…Nowadays, is possible to divide retting into four different categories: physical, semiphysical, chemical, and biological. In most cases, the retting process combines two or more of these categories to achieve a higher fiber quality [9,38]. The choice of retting method depends on factors like fiber quality, processing time, and environmental impact.…”

“…Dew retting is the most used treatment, due to the fact that it has a lower cost and is simple to apply [38]. This type of treatment consists after harvest to lay down the stems in piles for 2 to 3 weeks [35,41].…”

“…This type of treatment consists after harvest to lay down the stems in piles for 2 to 3 weeks [35,41]. Throughout this period, the action of the weather conditions, dew, precipitation, and sunlight, combined with the colonization of microorganisms, leads to a gradual degradation of the nonessential components [35,37,38]. Consequently, microorganisms develop on the plant's surface, degrading the superficial tissue by the release of specific enzymes, mainly pectinase, but also hemicellulases and cellulases [32,35,38,41].…”

Physicochemical and Mechanical Characterization of Raffia vinifera Pith

“…Waste management in recent years has led researchers to take an interest in the development of biodegradable materials for the emergence of biodegradable composites based on natural fibers [1][2][3]. Indeed, works have been carried out on plant fibers through treatments to replace synthetic fibers in composites materials [4].…”