In this work muscovite was ultrasonically treated to obtain composites with post-industrial wood plastic residues. The muscovite was ultrasonicated for 30 or 60 min and mixed with the polymeric matrix at a constant level of 15% (weight percentage). The composites were prepared in a single-screw extruder and formed into flat films for characterization. SEM images of the ultrasonicated muscovite revealed the occurrence of delamination, while the particle size distribution results suggested a decrease in size with longer sonication time. FTIR spectra also indicated the occurrence of delamination of the material. The composites exhibited a slight increase in density and a large increase in impact resistance of the samples with ultrasonicated muscovite. The XRD of the composites suggested the occurrence of alignment of the mineral in the matrix. The results indicate that ultrasonication is an effective method to improve the interaction and dispersion of muscovite with wood plastic waste to obtain composites.

Abstract Composites based on recycled high-density polyethylene (rHDPE) and muscovite mica, with different rHDE/mica ratios (100/0, 95/5, 90/10, 85/15 and 80/20, weight percentage) were prepared in an internal mixer with roller-type rotors at temperature of 170 ºC for 10 minutes. The materials obtained were characterized by tests of density, Shore hardness D and melt-flow index, along with infrared spectroscopy, thermogravimetry, differential scanning calorimetry and scanning electron microscopy. The hardness analysis confirmed the action of mica as a reinforcing load in the matrix, but this effect stabilized at around 15%. The TG analysis showed that the 85/15 composite presented slightly better performance than the 80/20, indicating that mica, up to 15%, caused disorganization of the polymer structure instead of reinforcing it. The DSC results revealed that the composites had slightly lower melting temperatures than the matrix. The FTIR spectrum indicated there was no chemical interaction between the rHDPE and mica.

Abstract Mining activities worldwide are subject to serious geotechnical accidents involving tailings dams. Therefore, many studies have focused on tailings dewatering before their deposition. This article studies the rheological properties of flocculated and thickened nickel tailings in order to determine the effect of the initial solid concentration and type of rheology modifying agents (two anionic polymeric flocculants) on their stability for disposal in dams. The sediment was submitted to rheological tests, with the vane technique, and slump tests, to obtain information about static and dynamic yield stress and slump height, respectively. The results showed a strong influence of the initial solid concentration and the polymeric flocculant on the particle aggregation. Both particle cohesion and yield stress of the sediment increased, reaching static yield stress of around 1,400 Pa. Both flocculants were efficient in thickening by batch sedimentation, allowing water recycling in the range of 70-90% with turbidity less than 100 NTU and the production of sediment with static yield stress much higher than specified for mineral paste.