Evaluation of CNTs and SiC Whiskers Effect on the Rheology and Mechanical Performance of Metakaolin-Based Geopolymers.

Despite geopolymers having emerged as a more sustainable alternative to Portland cement, their rheological properties still need to be thoroughly investigated, aiming at the material's applicability. Additionally, studies that evaluated the fresh state of geopolymer composites with nanomaterials are scarce. Thus, two metakaolin-based geopolymer systems were reinforced with nanomaterials with a similar geometry: carbon nanotubes (CNT) and silicon carbide whiskers (SCW). The nanomaterials incorporation was assessed by rotational rheometry (conducted up to 110 min), isothermal calorimetry, compressive strength after 7 and 28 days, and the microstructure was investigated using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). CNT and SCW incorporation (0.20 wt.%) did not significantly affect the yield stress and viscosity of the R2-group (based on metakaolin type 2), while increasing the rheological parameters up to 56.0% for the R1-group (based on metakaolin type 1). Both additions modified the reaction kinetics. Increments of up to 40.7% were observed in the compressive strength of geopolymer pastes with the incorporation of a SCW content of 0.2 wt.%. XRD and FTIR results suggest similar structural modifications between precursors. Nevertheless, R2 showed substantial transformations while the R1 group exhibited anhydrous material that can react over time. Overall, incorporating CNT and SCW contributed to higher mechanical increments on systems with average mechanical strength (R1) compared to systems with higher potential mechanical performance (R2).

Thermal and Rheological Characterization of Recycled PET/Virgin HDPE Blend Compatibilized with PE-g-MA and an Epoxy Chain Extender.

In this work, recycled poly(ethylene terephthalate) (PETR) was blended with virgin high-density polyethylene (HDPE) in an internal mixer in an attempt to obtain a material with improved properties. A compatibilizer (PE-g-MA) and a chain extender (Joncryl) were added to the PETR/HDPE blend and the rheological and thermal properties of the modified and unmodified blends as well as those of virgin PET with virgin HDPE (PETV/HDPE). All the blends were characterized by torque rheometry, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The data obtained indicate that the incorporation of either the chain extender or the compatibilizer agent led to increases in torque (and hence in viscosity) of the blend compared to that of the neat polymers. The joint incorporation of the chain extender and compatibilizer further increased the viscosity of the systems. Their effect on the crystallinity parameters of HDPE was minimal, but they reduced the crystallinity and crystallization temperature of virgin and recycled PET in the blends. The thermal stability of the PETR/HDPE blend was similar to that of the PETV/HDPE blend, and it was not affected by the incorporation of the chain extender and/or compatibilizer.

Valorization of Artichoke Industrial By-Products Using Green Extraction Technologies: Formulation of Hydrogels in Combination with Paulownia Extracts.

The integral valorization of artichoke bracts generated during industrial canning of artichoke was assessed. The extraction of bioactive compounds was addressed with pressurized hot water under subcritical conditions. The performance of this stage on the extraction of phenolics with antioxidant properties and the saccharidic fraction using conventional and microwave heating was compared. The microwave assisted process was more efficient than the conventional one regarding extraction yields of total solubles, and glucose and fructose oligomers and phenolics, because lower operational temperatures and shorter times were needed. Degradation of fructose oligomers was observed at temperatures higher than 160 °C, whereas the maximal phenolic content occurred at 220 °C. Both the extracts and the residual solids, obtained at conditions leading to maximum phenolics yields, were evaluated for the production of starch-based hydrogels, supplemented with Paulownia leaves' aqueous extracts.

Thermoreversible mucoadhesive polymer-drug dispersion for sustained local delivery of budesonide to treat inflammatory disorders of the GI tract.

Mucoadhesive drug formulations have been studied and used as alternatives to conventional formulations in order to achieve prolonged retention at the intended site. In addition to providing a controlled drug release, several drugs and disease conditions might benefit from mucoadhesive formulations, contributing to better therapeutic outcomes. Here, we describe the development and the in vitro/in vivo characterization of a mucoadhesive in situ gellifying formulation using PF127, a thermo reversible polymer, entrapping budesonide (BUD), a potent corticosteroid used for the treatment of a wide range of inflammatory diseases, including those affecting mucosas, such as in the GI tract. PF127 formulations (15-17%) were successfully prepared by a cold method as a thermo reversible in situ gelling dispersion for mucosal drug delivery, as confirmed by DSC. Sol-gel temperatures of PF127 formulations (25-39 °C) were observed by dynamic gelation and determined by microrheology and oscillatory rheometry. X-ray diffractograms and TEM images showed that BUD was completely solubilized within the polymeric micelles. In vitro, the gels showed 5-14 g force of mucoadhesion, and the ex vivo studies confirmed that the formulation efficiently adhered to the mucosa. Histopathological analysis combined with fluorescence images and ex vivo intestinal permeation confirmed that the formulation remained on the TGI mucosa for at least 4 h after administration. In vivo studies conducted in a murine model of intestinal mucositis demonstrated that the 16% PF127 BUD formulation was able to resolve the inflammatory injury in the intestinal mucosa. Results demonstrate that fine-tuning of PF127 formulations along with adequate selection of the drug agent, thorough characterization of the dispersions and their interactions with biological interfaces leads to the development of effective controlled drug delivery systems targeted to GI inflammatory diseases.

Dispersion of reduced graphene oxide within thermoplastic starch/poly(lactic acid) blends investigated by small-angle X-ray scattering.

Reduced graphene oxide (rGO) was incorporated into plasticized cornstarch (TPS), poly(lactic acid) (PLA) and their blends. Small-angle X-ray scattering (SAXS) was used to investigate rGO dispersion within the materials. For the TPS/PLA blend at 70:30 composition, the incorporation of rGO led to a larger fraction of small-sized rGO sheets, which at 5.0 mass% content developed stable fractal structures and domains of correlated sheets. The formation of fractal structures resulted in substantial enhancements in macroscopic properties. For these hybrids, the electrical conductivity, melt viscosity, storage moduli and biodegradation rates presented enhancements in relation to the neat blend. For the TPS/PLA blend at 30:70 composition, SAXS results indicated the formation of smaller fractions of well-dispersed rGO sheets and of segregated larger rGO sheets. With rGO at 5 mass% content, less expressive increases in electrical conductivity, melt viscosity, storage moduli and biodegradation rates were observed.