LODO PRIMÁRIO DO PROCESSAMENTO DE PAPEL COMO CARGA EM COMPÓSITO DE POLI(ÁCIDO LÁTICO): OBTENÇÃO E CARACTERIZAÇÃO

Abstract

The present work aimed to characterize and evaluate the use of primary sludge discarded from the pulp and paper industry as a filler with the poly(lactic acid) polymer, seeking to study the effects of the matrix/filler interaction. Primary sludge has in its composition a large amount of cellulose fibers and minerals such as calcite and kaolinite, which, even being a non-hazardous waste, with low potential for environmental contamination, it is not inert, therefore, disposal in landfills. This option is not economically viable, so it becomes interesting to reuse it. In order to improve the interfacial adhesion between the filler and the polymer, some chemical treatments were studied in the primary sludge, using alkaline sodium hydroxide solution, nitric acid solution and citric pectin. The composite processing was carried out using the thermomechanical mixing technique, making it similar to the industrial process of mechanical extrusion of polymers. The composites were made with 1%, 3% and 5% weight/weight ratio. The primary sludge was characterized using thermogravimetry, differential scanning calorimetry, X-ray diffraction, infrared vibrational spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. The polymer and composites obtained were characterized by the following techniques: thermogravimetry and differential scanning calorimetry, X-ray diffraction, infrared vibrational spectroscopy, scanning electron microscopy and three-point tensile and bending mechanical tests. The X-ray diffraction results obtained indicate the presence of two crystalline phases in the primary paper sludge, being formed by calcite, together with kaolinite, energy dispersive spectroscopy analyzes indicate a greater presence of calcium carbonate (calcite) in the sludge composition in relation to kaolinite. Thermal analysis of the composites indicated a decrease in the decomposition temperature of all samples. Infrared vibrational spectroscopy analysis of the composites indicated that there was no molecular interaction between polymer and filler. The morphological analyzes using scanning electron microscopy of the composites demonstrate a better interfacial adhesion of the filler with the polymer in the sludge with treatment performed with pectin. The mechanical tensile tests showed an improvement in the maximum tensile stress of 1.77% in the composite with 1% (wt/wt) sludge with acid treatment and 5.48% in the modulus of elasticity of the composite with 1% (wt/wt) of sludge without treatment. The maximum flexural strength had an increase of 5.76% in relation to PLA without load, in the composite with 3% (wt/wt) sludge treated with pectin and the flexural modulus had an increase of 10.42% in the sample with 5% (wt/wt) of sludge treated with pectin. The work demonstrates that the primary sludge can be used as filler in a composite with PLA matrix, however, a deepening in the improvement of the adhesion between filler and matrix should be studied.