Primary Sludge from Paper Processing as Filler in Poly(lactic acid) Composite: Physical, Thermal and Mechanical Properties

This article characterizes and evaluates the use of primary sludge from the paper industry as a filler in poly(lactic acid) polymer. To improve the matrix/filler interaction, chemical treatments were carried out in the primary sludge, using alkaline sodium hydroxide solution, nitric acid solution and citric pectin. The composites were made with 1, 3 and 5% (wt/wt%). The composites were characterized by thermogravimetry (TGA) and differential scanning calorimetry (DSC), X-ray diffraction (XRD), vibrational infrared spectroscopic analysis (FTIR), scanning electron microscopy (SEM) and mechanical tensile and flexure tests. Thermal analyzes indicate a reduction of up to 8.35% in the decomposition temperature of the composite. FTIR analysis indicated that there was no molecular interaction between polymer and filler. The morphological analyzes using SEM, demonstrated a better interfacial adhesion of the filler with the polymer in the sludge treated with pectin. The mechanical tensile tests showed an improvement in the maximum tensile stress of up to 1.77% and 5.48% in the modulus of elasticity. The maximum flexural strength had an increase of up to 5.76% in relation to the unloaded PLA and the flexural modulus had an increase of up to 10.42%.