By: Pavon, Alcoy, Miguel, Cristina, Juan, José Miguel
In this study, recycled cardboard sheets were produced by incorporating 30 wt% micronized filler obtained from three biomass residues: artichoke bagasse, Malva arborea (tree mallow) stems, and corn cob. The objective was to evaluate the potential of Malva arborea, introduced here for the first time as a non-wood filler in recycled cardboard, and to compare its performance with two commonly studied agro-residues. Mechanical tests (n = 5 per formulation), conducted under controlled laboratory conditions of 23 °C and 50% relative humidity, showed that the incorporation of fillers decreased the tensile strength and stiffness relative to the unfilled control. Tree mallow reduced tensile strength to 56%, while artichoke and corn cob retained 52–55% of the original value. Chemical composition analysis (Chasson–Datta method), which quantifies the structural fractions relevant to pulping behavior (hemicellulose, cellulose, and lignin), revealed that Malva arborea contains high hemicellulose (71.4%) and low lignin (11.9%), contributing to its early thermal degradation observed in TGA. Artichoke bagasse presented the highest cellulose content (23.1%), while corn cob showed the largest lignin fraction (28.2%). FTIR spectra confirmed the presence of characteristic lignocellulosic functional groups. Although Malva arborea exhibited the lowest reinforcement capability due to its fragmented morphology and high hemicellulose content, its low lignin content and ease of processing make it a promising sustainable filler for light-duty recycled cardboard applications. These findings support the valorization of biomass residues as alternative raw materials in circular bio-based packaging.
