Valorization of bean agricultural wastes for the production of polymeric composites

Abstract

The objective of this study is to evaluate the characteristics of polymeric composites containing different bean residue levels for polymer replacement. To this end, agricultural residues were first reduced to particles and characterized "in natura" through tests for moisture content, bulk density, content of extractives, lignin and ash and by thermogravimetry technique. Then, particles of both materials were dried and selected based on their granulometric fractions to make low-density polyethylene (LDPE) composites with substitution levels of 0, 10, 20, 30 and 40% bean residues. The polymeric material and the bean stem and pod particles were hot-extruded to obtain strands and then pellets; the resulting materials were then molded and hot-pressed. After fabrication, the specimens were subjected to physical testing for humidity, density, water absorption, and flammability and to mechanical testing for tensile strength. Scanning electron microscopy (SEM) was performed to evaluate the fracture regions of the specimens that were broken during mechanical testing. The results indicated that the physical–mechanical properties of the composites were negatively affected by the characteristics of the lignocellulosic material and by the increased number of pores caused by the presence of the waste material.