Abstract in English:Abstract Epoxidized sunflower oil (ESO) and epoxidized sunflower oil methyl ester (ESOME) were synthetized and employed as secondary bio based plasticizers and combined with primary natural plasticizers. As such, di-esters isosorbide (DEI) and acetyl tributyl citrate (ATBC) used in Poly Vinyl Chloride (PVC) as compared to di-(2-ethylhexyl) phthalate (DEHP). PVC Sheets were obtained by processed the polymer and its additives on two-roll mill. The effect of the plasticizers combination on flexible sheets properties, including stabilization, migration, fusion rheological properties and light transmission have been discussed, Results have shown that ESO and ESOME have improved PVC formulations thermal stability, the weight loss by volatility has decreased in the formulations which contained ESO or ESOME. Mixtures of plasticizers have lower migration rates. Plastograph test has indicated a better compatibility of PVC with these plasticizer mixtures. The light transmission rate through PVC sheets plasticized by bio-based plasticizers mixtures is more than those containing DEHP.
Abstract in English:Abstract In this work, a ternary composite of epoxy filled with ND and MS was produced for abrasive applications. Surfactants (oleic acid (OA), sodium dodecyl sulfate (SDS) and Triton TX-100 (TX-100)) were used to improve the particle dispersion and, consequently, the composite properties. The elastic modulus increased up to 76% for the sample with 1 wt% ND and 5 wt% ND using TX-100 (1ND5MS-TX100). Regardless of the filler concentration, the particles did not modify the thermal degradation behavior of the epoxy. Thermogravimetric (TGA) and dynamic mechanical (DMA) analyses suggest a strong particle-matrix interface, also evidenced in scanning electron microscope (SEM) micrographs. The composites presented superior tribological performance. 1ND5MS-TX100 presented a wear rate of 2.19 x 10-3 mm3.Nm-1, 61.3% lower than the epoxy. Also, all composites significantly reduced the roughness of the marble, being proportional to the abrasives concentration. Overall, composites with TX-100 presented improved wear behavior.
Abstract in English:Abstract The aim of this investigation was to assess the effects of gamma radiation on nanocomposite films (NC films) formed by PCL (polycaprolactone) with MCM-48 nanoparticles (PCL/MCM-48) and PCL with MCM-48 NPs modified with (3-aminopropyl)triethoxysilane (APTES) (PCL/MCM-48-NH2). The nanocomposite films were obtained using the solvent casting method. After preparing the films, they were irradiated at 25 kGy in the presence of air and analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), transmission electronic microscopy (TEM), as well as for their mechanical properties. The exposure of NC films to gamma radiation at 25 kGy did not cause major changes in either thermal or mechanical properties such as tensile strength and modulus of elasticity. The results revealed that gamma radiation was a successful choice for the sterilization of these materials.
Abstract in English:Abstract The literature reports several potential applications of polymers prepared with high internal phase emulsions (HIPEs). However, the evaluation of these materials as supports for antimicrobial agents has not been explored. In this work, silver composites based on polyHIPEs were prepared. Initial studies indicated that these materials can be efficient to prevent biofilm formation. The silver composites were prepared in three steps. First, HIPEs based on styrene-divinylbenzene were polymerized by aqueous suspension polymerization. These particles showed surface areas of 18 and 48 m2/g. These polyHIPEs were sulfonated with concentrated sulfuric acid or acetyl sulfate and showed cation exchange capacities of 4.03 and 5.07 meq/g respectively. The sulfonated material was impregnated with silver ions, followed by reduction of the ions to prepare silver composites. These composites showed inhibition halos against E. coli and P. aeruginosa. and did not present adhesion of bacterial cells of K. variicola and S. aureus on their surface.
Abstract in English:Abstract The effect of adding ionomer as a compatibilizing agent in ABS/recycled PCTG blend was the objective of this study. Design of experiments using extreme vertices was used, to obtain a mathematical equation to predict the result of the impact resistance of blends, within a pre-established interval. The sample that obtained the highest impact resistance was the 79/20/1 (ABS/PCTG/Ionomer) and was analyzed by DSC and SEM. The results showed partial compatibility. Through the analysis of the fracture surface of the Charpy test specimen, it was verified that the PCTG, as a dispersed phase, presented itself in the form of fibers and the ionomer acted as an emulsifier. All results showed that it is possible to reuse PCTG industrial waste by mixing it with ABS and Ionomer as compatibilizing agent.
Abstract in English:Abstract This article aimed to evaluate some mechanical and chemical properties of acrylic thermoactivated resins by microwave energy, varying the condition and type of plaster. The groups were divided into Lucitone and Vipi-Wave groups, with or without previous treatment (drying) of type III and IV plasters. It was evaluated flexural strength, microhardness, roughness, porosity, residual monomer, and also, time and temperature relationship of plaster and acrylic resin during the polymerization cycles. The data were analyzed using Analysis of Variance (ANOVA) 5%, followed by Tukey's test. The results showed that the drying of the plaster influenced the results and the groups with dry plaster maintained a higher temperature permanence. Therefore, changes in the water condition contained in the inclusion plaster showed effects on the final properties of the acrylic resin, which may be a technical indicator for laboratory procedures in the manufacture of prosthetic devices.
Abstract in English:Abstract The accumulation of polymeric residues has been one of the most impacting environmental problems in recent human history, coming, above all, from disposable artefacts, such as plastic bags. Processing polyolefins with pro-oxidant additives is an alternative to favour the abiotic degradation process of macromolecules, including thermooxidation, so that the oxygenated fragments produced can be assimilated by microorganisms. The objective of this work was to evaluate the process of thermomechanical oxidative degradation of polyethylene (PE) during tubular extrusion of HDPE/LDPE films, without and with 1% of two different pro-oxidants, d2wTM and benzoin. The results of viscosimetric and MFI analyses indicated smaller chain sizes in the additivated films. The FTIR spectra and contact angles indicate a higher presence of polar functional groups in the samples with pro-oxidants. The surface morphological analysis by SEM indicated difference of PE homogeneity in the films. Benzoin, however, proved to be a better pro-oxidant than d2wTM.
Abstract in English:Abstract The reuse of plastic polymers is one of the ways to reduce the negative environmental impact caused by these products. This work presents a study of mechanical and morphological properties of ABS and PCTG residue blend using SBS as compatibilizing agent to make copolyester recycling process feasible. It was observed that the incorporation of SBS in the mixture decreased the stiffness and increased the impact resistance compared to the results obtained in the non-compatible mixture, indicating that the SBS acted as a toughening agent in the mixture. Additionally, according to the results obtained by DSC and SEM, the blends obtained can be considered partially miscible, since two glass transition temperatures were evidenced shifted by a few degrees from neat components. Micrograph suggests that there are SBS small domain inclusions dispersed in the PCTG matrix and partial compatibility occurred by partial interaction of the SBS in the interface.
Abstract in English:Abstract This study evaluated the influence of cellulose nanocrystals (CNC) content on the properties of epoxy nanocomposites. The CNC were obtained from microcrystalline cellulose by acid hydrolysis. 4.0, 5.5 and 7.0% of untreated CNC were incorporated into epoxy resin. Sonication was used to disperse the CNC in the resin. The thermal stability, the glass transition temperature and the degree of conversion were reduced as observed by Thermogravimetry and Differential Scanning Calorimetry, respectively. The tensile and bending modulus showed no significant improvement and the impact resistance showed a slight reduction due to the non-uniform dispersion of the CNCs, as observed by Transmission Electron Microscopy. Analysis of Scanning Electron Microscopy showed a change of the fracture mechanism of the epoxy resin: the CNCs increased the elastic modulus by reinforcement, but accelerated the fracture by acting as defects. The Halpin-Tsai model was applied to predict the elastic modulus of the epoxy/CNC system.
Abstract in English:Abstract Thin a-C:H:Si:O:N films were deposited from plasmas fed hexamethyldisiloxane, oxygen and nitrogen, and characterized as a function of the partial pressure of oxygen in the feed, Rox. Deposition rates varied from 10 to 27 nm min-1. Surface roughness was independent of Rox, being around 10 nm. The films contain C=C and C=O, and also Si-C and Si-O-Si groups. Lower [C] and [N] but greater [O] and [Si] were measured in the films as Rox was increased. Refractive indices of ~ 1.5 and optical energy gaps which fell from ~ 3.3 to ~2.3 eV were observed with increasing Rox. The Urbach energy fell with increasing optical gap, which is characteristic of amorphous materials. Such materials have potential as transparent barrier coatings.
Abstract in English:Abstract In the present study, catalytic activity of dense, porous, electrospun membranes of polysulfone (PSF) and polysulfone with sulfonated polystyrene (PSF_PSS) have been evaluated in reactions of esterification of oleic acid with methanol, in times that varied from 10 to 480 minutes. Conversion to biodiesel has been confirmed by FTIR and quantified through gas chromatography. The results showed the catalysts used were effective in the esterification reaction studied and the PSF_PSS electrospun membrane has presented the best conversion to methyl oleate, reaching 70.5% in a 10-minute reaction and 95.8% in a 240-minute reaction, when methanol:oleic acid molar ratio of 10:1, 5% of catalyst and temperature of 100 °C were used. Considering the performance of solid catalysts described in literature, mainly related to reaction times and conversion of the process, this study reveals a promising feasibility of using electrospun membranes of PSF_PSS for developing a heterogeneous acid catalyst aimed to biodiesel synthesis.
Abstract in English:Abstract The aim of this study was to incorporate tucuma oil (Astrocaryum vulgare) into PolyCaprolactone (PCL) electrospun fibers and evaluate its physicochemical properties and cell viability. FTIR and DRX confirmed that tucuma oil (TO) does not affect the chemical properties of PCL and that the oil was loaded into the PCL microstructure, while TGA analysis showed that the oil increased the thermal stability of the polymeric fibers. SEM showed that the addition of the oil modified fibers structure by reducing the average fiber size from 5.5 μm to 1.7 μm for TO loaded samples. Cell viability assay demonstrated an increment on cell proliferation from 80% of pure PCL to 100% for samples containing TO. Therefore, it can be concluded that tucuma oil can be incorporated into PCL to form fibers by electrospinning, without meaningful changes in its physicochemical properties and increasing its biocompatibility.