Thermal and thermomechanical behavior of Moroccan Boufeggous variety date seeds

Abstract

In this work, the physicochemical and thermomechanical characteristics of date seeds were examined during their pyrolysis under inert atmosphere from room temperature to 600 °C. We first discuss the thermal analysis characterization including TG/DTG, DTA, and DSC analyses and then the thermomechanical aspects related to fixed bed heat treatments, dimensional variations measurements, and SEM characterizations. TG allowed us to delimit the different zones of the pyrolysis of date seeds. Thus, an active pyrolysis zone between 120 and 410 °C is related hemicelluloses decomposition, followed by the degradation of cellulose. Lignin decomposes slowly throughout all the temperature range. All these degradations and reactions are suggested by the different peaks of the mass loss derivative. The DTA and DSC analyses indicate that the thermal stress of date seeds is exothermic. This exothermicity is related to the internal frictions representative of the thermomechanical behavior of the thermally stressed material. Dimensional variation measurements show that the material generally shrinks with slight increases in volume. These phenomena are well evidenced by the characterization by SEM indicating the development of a plastic phase by crazing and shear mainly in volume and the formation of cracks on surface. The development of this phase occurred mainly during the first warming of the material by DSC.