Kinetic assessment of the thermal decomposition of hemp fiber and the impact of pretreatments

Motivated by green building applications (bio-composite and insulation materials), thermogravimetric and kinetic analysis is applied to investigate the thermal degradation of cleaned hemp fibers (F), obtained after water retting and mechanical decortication of dioecious plant stalks, and technical fiber (TF), obtained after field retting of monoecious plant stalks. Celluloses (microcrystalline PH105 cellulose and cotton linter cellulose) are used for comparison. F and TF dynamic curves are well described by a four-step scheme. The dominant one concerns pseudo-cellulose decomposition with the release of 70 and 54 mass% volatile matter, respectively. The corresponding activation energies are in the range of typical cellulose values (223 and 211 KJ mol−1). Fiber pretreatments (water washing, mild torrefaction, mercerization) modify the pseudo-cellulose content (release of 73–80 mass% volatile matter) and properties, as testified by the higher activation energies (229–248 kJ mol−1) of the decomposition process. The decortication method also contributes remarkably to the characteristics of the fiber cellulose