Resumo em Inglês:

Abstract This manuscript explored film production for food packaging using Ecovio® and natural additives (Babassu, Castor, and Cotton Vegetable Oil), emphasizing the oil’s maleinization to optimize compatibility with the polymer. The thermogravimetric analysis revealed variations in the maximum thermal decomposition temperature of maleinized vegetable oils (Thermal event II; natural oil to maleinized oil): from 402 to 338 °C (Babassu), 441 to 446 °C (Castor), and 413 to 430 °C (Cotton). The films were produced by casting, resulting in average thicknesses varying between 0.047 and 0.065 mm, and presented low surface defects. Optical micrographs showed that films with maleinized vegetable oil were more homogeneous due to maleic anhydride. Infrared spectroscopy showed that unsaturated fatty acid bonds affected the matrix and oil interaction. The presence of oils impacted the thermal stability, moisture content, and mechanical properties. This research promotes the use of renewable resources, contributing to the development of sustainable packaging.

Resumo em Inglês:

Abstract Rheo-optical studies allow the monitoring of rheological properties by indirect measurements of optical properties. For pure polymeric fluids, flow birefringence can be used to quantify the molecular orientation level by the application of shear strain rates. In this work, flow birefringence experiments were carried out with a pure polystyrene under different shear rates, shear cycles, and temperature conditions, in a polarized light optical microscope under controlled shear. The level of orientation and its correlation with the dynamics of uncoil/recoil and disentanglement were analyzed. The expected increase in the orientation level as a function of the increase in the shear rate due to the chain uncoiling was confirmed. Following, the chain orientation level reduces over time, associated with chain disentanglement and its subsequent recoiling. Disentanglement behaves irreversibly, while uncoiling and recoiling are reversible processes. A model is proposed to represent these dynamics.

Resumo em Inglês:

Abstract Composites of polyamide 6.6 (PA 6.6) reinforced with glass fibers exhibit strong mechanical properties; however, the hygroscopic nature of PA 6.6 introduces variability due to water absorption, which can affect these properties. This study aimed to develop a statistical model to assess the impact of hydration on the mechanical properties of PA 6.6/glass fiber composites. A 23 factorial design was employed to analyze the effects of time, temperature, and glass fiber content on tensile strength, impact resistance, and flexural properties. Characterization of the composites using scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) revealed excellent fiber-matrix adhesion and an increased degree of crystallinity, which contributed to enhanced Young’s modulus. The analysis showed that time and temperature were the primary factors influencing water absorption. A statistical model was created to predict the mechanical properties of the composites, incorporating the effects of hydration directly into the predictions.

Resumo em Inglês:

Abstract Recycling polyvinyl chloride (PVC) is a significant challenge for the footwear industry due to its short lifecycle and environmental impact. This study focused on recycling thermoplastic polyvinyl chloride (rPVC) from used sports shoes, sourced from a recycling company. The rPVC and thermoplastic polyurethane (TPU) were melt-blended and prepared using industrial injection molding with varying compositions. These polymer blends were then characterized morphologically, thermally, and mechanically. The recycled polymer blends demonstrated improved properties compared to the virgin polymers. Blending TPU with rPVC resulted in a material with notable hardness and enhanced abrasion resistance, with TPU/rPVC blends (67/33 and 50/50 wt.%) showing double the abrasion resistance of pure PVC. Additionally, the rPVC blend exhibited a rupture strength of 14.73 MPa, 1.6 times greater than virgin PVC. The TPU/rPVC blend (50/50 wt.%) also offered higher deformation resistance, indicating a more entangled and tensile structure. These advancements support the development of environmentally friendly footwear.

Resumo em Inglês:

Abstract The coating of microparticles obtained by ionic gelation with protein is a strategy adopted to increase the oxidative stability of different oils. In this work, the effect of different concentrations of alginate and calcium on the production of microparticles and the oxidative stability of microencapsulated sacha inchi oil coated with ovalbumin was evaluated. The sacha inchi oil demonstrated to be a source of polyunsaturated fatty acids, especially linolenic and linoleic acids. The obtained coated and uncoated microparticle showed spherical morphology with continuous walls, encapsulation efficiency about 72%, and the average size of 239 µm and 309 µm, respectively. The higher size of coated microparticle is due to high amounts of ovalbumin adsorbed, which ranged from 51.8 to 70.9%. The Oxidative stability evaluation showed that the presence of ovalbumin adsorption contributed to the stability of sacha inchi oil, when compared to the oil present in particles without protein coating.

Resumo em Inglês:

Abstract Gamma radiation effects on extrinsically electrical semiconducting polymer nanocomposite films of poly(vinyl alcohol) (PVA) and 0.5 wt% histidine-modified reduced graphene oxide (H-RGO) filler were evaluated. Thermogravimetric analysis showed thermal degradation stages of the films and UV-Vis analysis allowed the study of optical parameters. Optical band gap energy (Eg) of PVA was shifted from 6.20 to 3.76 eV with the addition of H-RGO filler into the polymer matrix, while the electrical conductivity changed from 10-11 (isolator) to 10-6 (semiconductor) S/cm and PVA/H-RGO nanocomposite reached 10-4 S/cm at 25 kGy gamma-radiation dose. PVA/H-RGO nanocomposite films are promising in a wide range of potential applications, such as bio and chemical sensors, catalysis, and active layers for optoelectronic devices.