Search

We developed polyurethane foams (PU) filled with eucalyptus charcoal residue (ECR) (5, 10, 20, and 30% by wt) for diesel sorption from seawater. The PU foams were characterized by FTIR, FT-Raman, SEM, density, TGA, contact angle, diesel S500 and S10 sorption, and recyclability. The ECR addition altered PU chemical structure, inducing new chemical bonds and probably altering cross-linking ability of the foams, as indicated by FTIR. FT-Raman spectra of PU-ECR foams showed shifts associated with filler dispersion and interaction with the matrix; besides, its addition decreased the foam pore size and density. The ECR addition did not significantly change the thermal behavior of PU foam and increased hydrophilicity in low ECR content and hydrophobicity in high ECR content samples. Experimental results showed adequate oil sorption capacity, and the optimal amount was 30% (by wt) ECR, which enhanced the diesel sorption from 4.1 and 5.9 g.g−1 to 9.6 and 8.8 g.g−1 for diesel S500 and S10, respectively. The Langmuir sorption isotherm was the best-fitting model to describe oil sorption. Reusability of the PU + 30% ECR was examined through 34 and 39 cycles for diesel S500 and S10, and about 50% of the initial sorption capacity remained at the end. The results indicated the success of developing a sustainable material and demonstrating feasibility in practical applications of PU-ECR foam for spilled oil removal from seawater or treatment of oily effluents.

Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) is a biodegradable, biocompatible, and non-toxic biopolymer. The biopolymer properties can be improved using cellulosic-based materials, often derived from agro-industrial residues, and promoting reuse/re-significance of a by-product for bone tissue engineering applications. Biocomposites of PHBV filled with bleached fibers of palm residues (BFPR) (0–10 % wt/wt) for 3D-printing were prepared. The scaffolds were obtained by additive manufacturing (fused deposition modeling (FDM)). The samples were characterized by stereomicroscopy, SEM, TGA, nanohardness, wettability, FTIR, and biocompatibility. Biocomposites filaments revealed homogeneous diameters, suitable for FDM. Composite filaments had thermal stability at 100–250 °C (processing did not degrade the material). The -OH groups of cellulose (enhanced by bleaching treatment) BFPR added to PHBV had advantages: optimal cell viability, wettability improvement, and slight nanohardness increase. PHBV/BFPR1 % scaffolds had an interconnected porous structure with a pore size of ~900 µm and 60 % filling.

Macadamia is a nut widely used globally in food, personal hygiene products, and human health. After removing the nut, high amounts of the shell residual, which is an underutilized material with high economic interest. This work presents a sustainable alternative to revalorize the macadamia nutshell residues (MR) developing the green composites. Polypropylene (PP) composites were prepared using different MR content (5, 10, 15, 20, 25, and 30 wt%) as a filler. The samples were investigated by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis, scanning electron microscopy (SEM), mechanical tests (tensile and flexure) before and after water absorption tests, and Life Cycle Assessment (LCA). FTIR results indicated that the MR acted only by physical impediments, without chemical interactions between the filler and matrix. Thermal analysis showed a significant increase (~ 20 °C) in PP thermal stability after MR addition, probably due to the filler high lignin content, and SEM photomicrographs indicate that high MR contents resulted in little cracks and voids in the interface. However, the defects did not influence the mechanical performance, and the green composites showed superior elastic modulus (2401 MPa) than the pristine PP (1516 MPa) and similar tensile strength (~ 30 MPa), confirmed by the statistical analysis and corroborating with the theoretical percolation network (25 wt%). The composites showed low water absorption (up to 0.3%), reflecting in downward variations in the wet samples' mechanical behavior. It evidences the possibility to use these samples for water applications. LCA indicated that higher MR contents promoted lower environmental impacts than the classical handling of this residue, and the results indicated that 30 wt% MR is the better environmental option. However, the PP/MR-25% showed reduced environmental impacts and associated with other properties improvements, considered the better sample. This work shows the MR revalorization as a sustainable approach to expand green composites applications.

Fused deposition modeling (FDM) has been a widely applied technology as one of the most practical tools of additive manufacturing in terms of industry 4.0. Biopolymer filaments obtained by extrusion can be a promising material for scaffold manufacturing by FDM 3D printers. In this work, composite filaments of polyhydroxybutyrate-cohydroxyvalerate (PHBV) reinforced with ZrO2·nH2O particles were obtained (1–10% wt/wt.) and characterized aiming the production of scaffolds by FDM process. ZrO2·nH2O particles were prepared and mixed to the PHBV in a mini-extruder. The pristine PHBV and composite filaments (PHBV/ZrO2) were characterized by stereomicroscopy, scanning electron microscopy (particle analysis), thermogravimetric analysis (TGA and DSC), X-ray diffractometry, Fourier transformed infrared spectroscopy , Vickers microhardness test (HV), and relative density. The addition of ZrO2·nH2O particles altered the behavior of the PHBV matrix: increased the number of ZrO2·nH2O particles in the composite filament surface, enhanced the amorphous phase and the relative density. The PHBV/7.5%ZrO2 sample presented higher microhardness. It was possible to print the filaments by FDM and the appearance of the scaffolds obtained was a cylindrical structure with rounded inner pores, contributing to the future application in regenerative medicine.

Polymer nanocomposites are a promising area of research due to quite superior to the conventional composites. However, obtaining a homogeneous distribution of the nanoparticles in the matrix has been a great challenge. Standard processing techniques of nanocomposites are non-practical, requiring longer periods and can affect both mechanical and thermal properties of the final product. The thermokinectic mixer is an interesting alternative due to its high-speed rotation leading to a better dispersion of the nanoparticle without compromising the polymer properties. This paper reports for the first time a nanocomposite of high-density polyethylene (HDPE)/Al2O3 processed by the thermokinetic mixer. The addition of Al2O3 nanoparticle (0 to 4% wt) to the HDPE led to an increase in both the melting and crystallization temperature. It was also observed an improvement of the mechanical properties due to the increase in the crystallinity degree, which is a consequence of the multiple nucleation sites of Al2O3 nanoparticles. An optimal composition was obtained at 4% wt of Al2O3. Thus, the nanocomposites processed by the thermokinetic mixer demonstrated a significant enhancement of the mechanical and thermal properties.

Surface modification of palm fibers has been made by different methods. This work, cellulose fibers from palm were bleached and modified by zirconium oxychloride. Cellulose fibers were coated with ZrO2·nH2O particles with different amount of zirconium oxychloride in acidic medium in the presence of cellulose fibers using ammonium hydroxide as the precipitating agent. The coating of hydrous zirconium oxide on cellulose fibers was carried out by scanning electron microscopy, X-ray diffraction, themogravimetric analysis, attenuated total reflectance Fourier transform infrared spectroscopy and atomic emission spectrometry with inductively coupled plasma were also techniques used to characterize the materials. Dichromate ion was adsorbed on the Cell/ZrO2·nH2O by immersing this solid in an aqueous solution of potassium dichromate. The analyses to determine the concentration after the adsorption were made using UV–Vis spectrum, in a wavelength of 349 nm. The results were satisfactory showing that the Cell/ZrO2·nH2O materials obtained presented good adsorption capacity. Results showed that the amount ZrO2·nH2O particles coated on cellulose fibers influenced in the sorption capacity of dichromate ions.