Toward the cottonization of hemp fibers by steam explosion. Flame-retardant fibers

• Published in: Industrial crops and products Vol. 151; p. 112242
• Main Authors: Moussa, Maria, El Hage, Roland, Sonnier, Rodolphe, Chrusciel, Laurent, Ziegler-Devin, Isabelle, Brosse, Nicolas
• Format: Journal Article
• Language: English
• Published: Elsevier 01.09.2020
• Subjects: aqueous solutions; calorimetry; carbon; Chemical and Process Engineering; Chemical Sciences; Engineering Sciences; flame retardants; hemp; Materials; nitrogen content; nuclear magnetic resonance spectroscopy; Organic chemistry; phosphorus; phosphorus content; Polymers; scanning electron microscopy; stable isotopes; synergism; thermal stability; thermogravimetry; urea; Thermal grafting; Hemp fibers; Steam explosion; HEDP/urea
• ISSN: 0926-6690
• DOI: 10.1016/j.indcrop.2020.112242

The goal is to produce cottonized hemp fibers with improved thermal stability. It was first found that the fine hemp fibers produced from technical non-retted hemp fibers by steam explosion exhibited an enhanced thermal stability. An efficient and low-cost process was developed using a mixture of urea/etidronic acid in aqueous solution in order to achieve a high phosphorus content and produce flame retardant fibers by chemical grafting. ICP, ³¹P and ¹³C NMR, SEM, thermogravimetric, Pyrolysis-Combustion Flow Calorimetry analyses and a flame test were used to characterize the grafted fibers. Fibers modified with relatively high P and N contents have been produced (≈ 6 wt % and ≈ 4 wt % respectively) but lower grafting rates (P ≈ 0.5 % and N ≈ 0.35 %) are sufficient to produce non-flammable fibers. A synergistic effect between N and P has been proposed to induce the formation of a stable char.