This article presents a comprehensive study on the physical, mechanical, thermal, and chemical properties of polypropylene (PP) composites reinforced with hemp fibers (HF) and compatibilized with maleic anhydride (MAPP). The composites were processed using a twin-screw extruder, followed by hot compression at 190 °C. Subsequently, the composites were analyzed using Izod impact and Shore D hardness tests to evaluate their mechanical properties. Thermal properties were investigated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), while X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) were employed to study their chemical properties. Additionally, a statistical analysis was conducted to compare the average results of the impact and hardness tests. XRD analysis revealed that the addition of HF and MAPP led to the disappearance of peaks corresponding to the beta phase in pure PP. Hemp fibers exhibited an impressive crystallinity of 82.10%, surpassing other natural fibers, and had a significant molecular orientation angle (MFA) of 6.06°, making them highly desirable for engineering applications. The crystallite size was observed to be relatively large, at 32.49 nm. FTIR analysis demonstrated strong interactions between the fiber, compatibilizing agent, and polymer matrix. TGA tests showed that the addition of 5 and 10 wt.% MAPP resulted in complete degradation of the composites, similar to pure PP. DSC analyses indicated a reduction in crystallinity (Xc) due to the incorporation of HF and MAPP. Shore D hardness tests revealed an increase in hardness with the addition of 5 wt.% MAPP, while a steep decline in this property was observed with 10 wt.% MAPP. In terms of impact resistance, fractions of 3 and 5 wt.% MAPP in the composites exhibited improved performance compared to the pure polymer. Analysis of variance (ANOVA) was employed to ensure the statistical reliability of the mechanical test results. This comprehensive study sheds light on the diverse properties of PP composites reinforced with hemp fibers and compatibilized with MAPP, emphasizing their potential as sustainable materials for engineering applications. The results contribute to the understanding of the structural and functional aspects of these composites, guiding future research and developments in the field.

Neste trabalho foram avaliadas as alterações no comportamento reológico e na capacidade absorvedora da radiação eletromagnética de tinta acrílica comercial modificada com goma xantana (GX) e negro de fumo condutor. A metodologia do planejamento fatorial de experimentos foi utilizada em dois níveis experimentais para GX e negro de fumo para otimização do estudo. O modelo reológico de Herschel-Bulkley foi empregado para determinação dos principais parâmetros reológicos. A GX exerceu maior influencia na tensão limite de escoamento (t0) em relação ao negro de fumo. As variações nos valores de t0 foram de 1000 % entre as formulações estudadas. Os resultados de blindagem eletromagnética confirmaram a melhor dispersão do negro de fumo, em formulações com baixas concentrações de goma xantana. As tintas aditivadas aumentam a energia de ativação e as constantes C1 e C2 da lei WLF para o ensaio de superposição tempo-temperatura. O ensaio de tixotropia, realizado pela metodologia de três intervalos de deformação, corrobora com os valores obtidos da tensão limite de escoamento. A reestruturação da tinta é mais pronunciada em baixa concentração de GX.

No abstract