Search

The work evaluated the nucleating effect of nanometric zirconia (Zr-NP), obtained by the green sol-gel synthesis route using Euclea natalensis root extract as a reductant, in the low-density polyethylene (LDPE). The Zr-NP was characterized with x-ray diffraction (XRD) and transmission electron microscopy (TEM) which confirmed the presence of Zr-NP in the cubic crystalline phase with an average particle size of 6.73 nm. The Zr-NP was incorporated into the polymeric matrix by solubilization in concentrations ranging between 0 wt% and 6 wt%. Non-isothermal DSC analyzes demonstrated that a small addition of 1 wt% changes the degree of crystallinity from ~23% to ~56%, an increase of ~137%. The addition of Zr-NP also caused a small increase in crystallization and melting temperatures, and a large increase in the total crystallization time of LDPE.

The Montmorillonite-Erucamide nanocomposite (MMT-EU) can be used to reduce and to control the values of coefficient of friction of low-density polyethylene films (LDPE), widely used by the food industry. In this work, the effect of the addition of 5 wt% and 10 wt% of MMT-EU on the mechanical properties of LLDPE films involving the weld region was investigated. The MMT-EU concentration range was defined considering its possible technological application as an additive to stabilize the friction coefficient of polymeric films. The result shows a significant improvement in the values of stiffness, strength and ductility of polymeric films. In addition, it did not change the coefficient of friction, but the brightness of the LLDPE films decreased and the opacity increased, due to the increase in the crystallinity degree of the LLDPE polymer promoted by MMT-EU, not being a problem for the application of these films.

This research was aimed to obtain biodegradable polymeric films with antifungal action against Aspergillus niger, through the addition of copper oxide nanoparticles (CuO-NPs) in the commercial polymer (Ecoflex®) and to evaluate its mechanical, morphological, biodegradation, and copper release properties. The microbiological results showed that the films with 4 wt% CuO-NPs inhibited 97.57% the growth of the fungus growth of 1×105 spores·mL-1 compared to the control. The morphological characterization revealed that the CuO-NPs presented irregular form with particles size of 50 to 400 nm and the XRD showed characteristic peaks of copper oxide. The addition of CuO-NPs to Ecoflex® provided increased maximum and rupture tension, strain, and elasticity modulus the obtained films with 1 wt% CuO-NPs and did not alter the biodegradability of the films. It can be said that, through the addition of CuO-NPs to Ecoflex®, it was possible to add antifungal activity for Aspergillus niger without compromising its biodegradability, meeting the safety standards established by legislation regarding the release of copper.

Ionic polymer-metal composites (IPMC) are typical electromechanical transducing materials suitable for use as soft actuators, bioinspired artificial muscles and sensors. However, IPMC produced with platinum films has the great disadvantage of the large number of cracks and wrinkles, which reduce the performance of the electrode. Polyaniline (PANI) is a promising conductive polymer that can address this issue, especially when it is electropolymerized on the platinum surface. An IPMC/PANI actuator was developed by potentiostatic electropolymerization of PANI at 0.9 V in 0.1 M and 0.3 M aniline solution. The characterization revealed that PANI is preferentially electropolymerized in the platinum film cracks and improve the electronic conduction mechanisms, which is not reported so far. The maximum tip displacement of the IPMC/PANI under 5 V was 8.3 mm, while for the IPMC was equal 5.2 mm. These results provide a simple and effective method to repair IPMCs and enhance their electromechanical performances.

Composites based on green high-density polyethylene (G-HDPE) and hydroxyapatite (HA) compatibilized with maleic anhydride grafted high-density polyethylene (HDPE-g-MAH) were developed in this work. The main objective was to evaluate the effects of HA and HDPE-g-MAH contents on the mechanical and thermal properties and hydrolytic degradation of composites through design of experiments and statistical analysis, as well as to evaluate the hemolytic stability. Hydroxyapatite acts as a reinforcing agent for the G-HDPE matrix while the HDPE-g-MAH acts as a compatibilizing agent, improving the dispersion of the HA particles in the polymer matrix and thus increasing the mechanical properties. The crystallization temperature and the degree of crystallinity of the polymer matrix were increased with the addition of HA, suggesting the filler acts as a heterogeneous nucleating agent. Hemolysis tests performed on a composite sample with best mechanical performance did not indicate significant hydrolytic degradation, which suggests this composite is a promising material to be used in bone tissue engineering, for application in implants and bone grafts.

Tetracycline is used to treat various diseases in animals and humans, so its high use causes this substance to be frequently found in effluents and in potable water reservoirs, causing serious problems for human health and the environment. Many processes are applied and evaluated in an attempt to removal tetracycline found in environment, such as adsorption. The application of iron-carbon nanoparticles with core-shell structure (Fe3O4@C) as adsorbent, can be an alternative to removal of these contaminants. In the present study Fe3O4@C nanoparticles were synthesized and used to adsorb tetracycline in aqueous solutions. The core-shell characterization was performed using X-ray diffraction techniques, infrared spectroscopy, surface area, chemical analysis and morphology, and adsorption capacity through isotherms. The results indicated that Fe3O4@C nanoparticles presented good tetracycline removal capability, 73.3%, when applied an initial concentration of antibiotic of the 30 mg L-1 and 0.5 g of adsorbent.

Zinc is an important chemical element in many metabolic mechanisms at low concentrations, but can be toxic when administrated in doses higher than 500 µg·g-1 or 3 mg·L-1. This metal has been detected in many aquatic environments due to several industry activities and swine manure effluents. Thus, the contaminant removal of water and wastewater has been a major challenge. Many processes are applied and evaluated in an attempt to removal zinc found in environment, such as adsorption. In the present study Fe3O4@C core-shell nanoparticles were synthesized and used to adsorb ionic zinc species in aqueous solutions. The core-shell nanoparticles exhibited excellent zinc removal capacity, with a maximum efficiency equal 65% where applied in an aqueous solution containing 10 mg·l-1 of this ionic metal.