Abstract in English:Abstract Currently there is a great trend towards cleaner, more sustainable and green production, based on a circular economy. Therefore, in the present work the study of the effect of the concentration of potato starch, aloe vera and graphene on the mechanical properties, water vapor permeability, biodegradability and structural properties of bioplastics is reported. These bioplastics could replace conventional synthetic plastics that currently produce high environmental pollution. According to the statistical analysis of a 2˄3 factorial design, a biodegradable bioplastic with improved mechanical properties was obtained, with a high maximum stress of 2.49 ± 0.28 MPa at high concentration levels of starch, aloe vera and graphene (10% w/w starch, 24% w/w of aloe and 0.045% w/w of graphene). A minimum value of permeance and permeability to water vapor of 5.35 kg/h.kPa.m2 and 0.001839 kg/h.kPa.m, respectively, was found at a graphene concentration of 0.005%; aloe concentration, 24%; and starch concentration, 10%.
Abstract in English:Abstract Solid residues from agroindustry often accumulate and cause environmental imbalance. An alternative to this is to use this residue as a reinforcement in polymers. The achievement of this work was to characterize a composite with a polystyrene matrix reinforced with Brazil nut shells residues. The residues were cleaned and ground to then produce the samples via injection molding with the proportions of 0%, 2.5% and 5% of load. The specimens were characterized using mechanical tensile testing and thermogravimetric analysis (TGA). The mechanical test showed that the composite with 2.5% of filler had greater stiffness and strength was improved by 5%. Thermal analysis showed an increase in the temperature for the beginning of the degradation of the M2.5 composite. The results confirm a potential application in the automotive industry for the polystyrene composite reinforced with Brazil nut shells.
Abstract in English:Abstract In this study, the hybrid Entropy-TOPSIS method is applied to the problem of selecting an optimal impregnation material with maximum performance requirements. Swelling, shrinkage, bending strength, modulus of elasticity, compressive strength and shock strength values were used to rank the impregnation materials. Barite, boric acid, borax and their mixture were used to impregnation material. The impregnation materials used in the study generally increased the physical and mechanical properties of the spruce specimens, except swelling. The impregnation materials reduced the swelling of the specimens. According to the entropy method, the most important factor affecting the success of the impregnation process was the modulus of elasticity. According to the TOPSIS method, the most successful impregnation material was a mixture of barite and boric acid. Moreover, the proposed method was compared with other Multi-Criteria Decision-Making (MCDM) approaches and it can be used to ranking of impregnation materials with reliable accuracy.
Abstract in English:Abstract To analyze the surface topography and mechanical properties of a polyurethane derived from castor oil reinforced with hydroxyapatite (PU–HA) for bone fixation. The surface analysis was performed by Scanning Electron Microscopy (SEM) and the mechanical properties by Vickers microhardness and tensile tests. The SEM images showed that the PU surface presented important characteristics for materials intended for bone fixation, such as an irregular and porous surface. The analysis showed a surface with alternating areas with depressions and elevations of approximately 80±100 µm, presence of pores of 12 µm in size. The microhardness analysis showed values of 0.42±1.01 HV for PU–HA plates, lower in relation to the poly lactic-co-glycolic acid (PLGA) plate (control group). The elastic modulus and ultimate tensile strength of 317.4 MPa, and 35.57 MPa for PLGA sample, 1.187 MPa, and 0.29 MPa for PU–HA sample. The PU produced showed good surface properties, however demands better mechanical properties.
Abstract in English:Abstract This analysis studied the effects modification on the properties of starch-based polymer grafted with acrylonitrile (copolymers). Starch was extracted from bitter yam. The starch was modified by heating the solution above 70 °C and then esterified with phthalic anhydride to produce a pregelatinized phthalated derivative. Acrylonitrile was grafted onto natural and pregelatinized phthalated starch at 120 °C using calcium oxide from snail shell as the initiator. The grafting reaction of starch with poly(acrylonitrile) and the phthalation of the starch were both confirmed by Fourier transform infrared (FTIR). Scanning electron microscopy analysis revealed changes in the morphology of the pregelatinized phthalated grafted copolymers. The X-ray diffractogram showed that native starch grafted copolymer displayed broad diffraction peaks (amorphous), but the phthalated bitter yam starch grafted with acrylonitrile had prominent diffraction peaks (crystalline). Thermogravimetry analysis revealed that the phthalated grafted copolymer has better thermal stability than the native grafted copolymer.
Abstract in English:Abstract This systematic review investigates evidence concerning antioxidant migration from polyethylene packaging to food. The review protocol was based on the Preferred Reporting Items for Systematic Reviews guidelines. Several electronic databases were consulted for relevant studies, as well as references in eligible studies. Of the 44 eligible studies, only two did not indicate antioxidant migration. The reported migrations were influenced by numerous factors, the most important comprising the fatty contents of food and/or fat simulants, with higher fat amounts resulting in higher migration rates. Migrated antioxidant values ranged from 3.42 mg kg-1 to 231.70 mg kg-1, far above the maximum permissible amounts established by the current legislation regarding foods in contact with plastic resins.