In this study, the dependence on the morphology and mechanical properties was analyzed when different amounts of polylactic acid are added to the polyethylene terephthalate polymer matrix using single-screw extrusion. Thermograms of the polymer blends obtained by differential scanning calorimetry couple to thermal gravimetric analysis show a displacement in the glass transition temperature with the amount of polylactic acid (1, 2.5, 5, and 7.5 wt%) added to the polymer matrix. Scanning electron microscopy and atomic force microscopy images showed two different kinds of morphology, both characteristics of miscible and partially miscible polymer blends. Fourier transform infrared spectroscopy measurements confirmed a physical interaction by hydrogen bond in the polymer blends. The impact resistance and tensile strength are reduced with the polylactic acid addition and are influenced by the fraction of segments of hydrogen bonded in the polyethylene terephthalate/polylactic acid blends as well as their miscibility. GRAPHICAL ABSTRACT

In this work, the optimal conditions of synthesizing and purifying carbon nanotubes (CNTs) from ferrocene were selected at the first stage, where decomposition time, argon fluxes, precursor amounts, decomposition temperature (at 1023 K and 1123 K), and purification process (HNO₃ + H₂SO₄ or HCl + H₂O₂), were modulated through chemical vapor deposition (CVD) and compared to commercial CNTs. The processing temperature at 1123 K and the treatment with HCl + H₂O₂ were key parameters influencing the purity, crystallinity, stability, and optical/electrical properties of bamboo-like morphology CNTs. Selected multiwalled CNTs (MWCNTs), from 1 to 20 wt%, were electropolymerized through in-situ polarization with conductive polymers (CPs), poly(aniline) (PANI) and poly(pyrrole) (PPy), for obtaining composites. In terms of structural stability and electrical properties, MWCNTs obtained by CVD were found to be better than commercial ones for producing CPs composites. The CNTs addition in both polymeric matrixes was of 6.5 wt%. In both systems, crystallinity degree, related to the alignment of PC chains on MWCNTs surface, was improved. Electrical conductivity, in terms of the carrier density and mobility, was adequately enhanced with CVD CNTs, which were even better than the evaluated commercial CNTs. The findings of this study demonstrate that synergistic effects among the hydrogen bonds, stability, and conductivity are better in PANI/MWCNTs than in PPy/MWCNTs composites, which open a promissory route to prepare materials for different technological applications.

Microalgae, including cyanobacteria, represent a valuable source of natural compounds that have remarkable bioactive properties. Each microalga species produces a mixture of antioxidants with different amounts of each compound. Three aspects are important in the production of bioactive compounds: the microalga species, the medium composition including light supplied and the photobioreactor design, and operation characteristics. In this study, the antioxidant content and productivity performance of four microalgae were assessed in batch and continuous cultures. Biomass productivity by the four microalgae was substantially enhanced under continuous cultivation by 5.9 to 6.3 times in comparison with batch cultures. The energetic yield, under the experimental conditions studied, ranged from 0.03 to 0.041 g biomass kJ⁻¹. Phenols, terpenoids, and alkaloids were produced by Spirulinaplatensis, Isochrysisgalbana, and Tetraselmissuecica, whereas tocopherols and carotenoids were produced by the four microalgae, except for phycocyanin and allophycocyanin, which were only produced by S. platensis and Porphyridiumcruentum. The findings demonstrate that the continuous cultivation of microalgae in photobioreactors is a convenient method of efficiently producing antioxidants.