Compósitos de polietileno verde de baixa densidade com reforços celulósicos isolados a partir do bambu

Abstract

The study explored the use of bamboo, cellulose, and cellulose nanocrystals (CNCs) as reinforcements in nanocomposites with low-density green polyethylene (LDPE). Chemical treatments were performed to obtain cellulose and CNCs. Cellulose was characterized according to TAPPI standards, and its structural, thermal, and morphological properties were investigated using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD results revealed a crystallinity value of 72.24% after the removal of amorphous components. FTIR results confirmed the preservation of cellulose structure, as well as the presence of hydroxyl groups in CNCs. TGA and DSC analyses demonstrated the thermal stability of CNCs, which can be attributed to their high surface area, making them promising reinforcements in polymeric nanocomposites. SEM images showed changes in the fiber surface after chemical treatments. TEM analysis revealed that CNCs have nanometric dimensions with diameters of 10-20 nm. After obtaining the fillers, composites reinforced with bamboo and cellulose fibers and also nanocomposites reinforced with CNCs were prepared using extrusion and injection molding processes. The samples were characterized for their mechanical, thermal, structural, morphological, and accelerated aging properties. The reinforcement concentrations used were 5% and 10% for bamboo and cellulose fibers and 1% and 1.5% for CNCs. In addition to these blends, systems using maleic anhydride-grafted polyethylene with the compatibilizing agent were also prepared, using mass ratios of 1% and 3%. Tensile tests showed that the addition of reinforcements, such as cellulose and CNCs, increased the materials' elasticity modulus, with a more pronounced increase for compatibilized samples. However, particle agglomerates affected the tensile strength in some cases. CNC containing nanocomposites exhibited higher strain at break. All compositions studied did not undergo fracture in impact resistance tests, characterizing them as non-break materials. TGA and DSC analyses demonstrated that the incorporation of CNCs improved the thermal stability of the nanocomposites, while bamboo and cellulose fibers had minimal influence on crystallinity. The presence of PE-g-MA strengthened the interface without affecting the crystalline structure. SEM analysis revealed ductile fractures in LDPE with inadequate adhesion but improved adhesion in uniformly dispersed nanocomposites. However, in uniformly dispersed nanocomposites, the results pointed to a significant improvement in adhesion quality. XRD analysis showed an increase in crystallinity mainly for the nanocomposites. CNC-containing nanocomposites exhibited high resistance to aging, attributed to their interaction with the matrix and thermal stability, amplified by the PE-g-MA agent.