Caio Marcio Paranhos

Method for the production of acrylonitrile–butadiene–styrene (ABS) and polycarbonate (PC)/ABS standards for direct Sb determination in plastics from e-waste using laser-induced breakdown spectroscopy

This study presents a procedure for direct Sb determination in solid e-waste samples (polymers). Polymer standards (acrylonitrile–butadiene–styrene (ABS) and polycarbonate (PC)/ABS) were mixed with dichloromethane solution for homogenization and then dried, milled and sieved. The obtained powder was mixed with Sb2O3 and pressed in a thermopress. A calibration curve (Sb: 0 to 2.6% w/w) was prepared and analysed using LIBS (laser-induced breakdown spectroscopy) and more than 10 000 spectra were obtained. Carbon (247.856 nm) and Sb (259.805 nm) signals were recorded and normalized by their individual norm values. The best results were obtained when using C as the internal standard and the Sb concentration observed in the samples ranged from 0.15 to 0.68% (w/w). Standard addition tests were performed and the recoveries ranged from 63 to 83%.

Use of laser-induced breakdown spectroscopy for the determination of polycarbonate (PC) and acrylonitrile-butadiene-styrene (ABS) concentrations in PC/ABS plastics from e-waste

Due to the continual increase in waste generated from electronic devices, the management of plastics, which represents between 10 and 30% by weight of waste electrical and electronic equipment (WEEE or e-waste), becomes indispensable in terms of environmental and economic impacts. Considering the importance of acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), and their blends in the electronics and other industries, this study presents a new application of laser-induced breakdown spectroscopy (LIBS) for the fast and direct determination of PC and ABS concentrations in blends of these plastics obtained from samples of e-waste. From the LIBS spectra acquired for the PC/ABS blend, multivariate calibration models were built using partial least squares (PLS) regression. In general, it was possible to infer that the relative errors between the theoretical or reference and predicted values for the spiked samples were lower than 10%.

PA6/NBR blends: improvement of processability and mechanical properties

Abstract This work deals with the study of the processability of blends based on PA6 and NBR. The aim is to achieve reduced PA 6 melting temperatures in order to avoid degradation of the NBR phase during processing. The effect of different additives in PA has been studied. For this purpose PA6 was blended with nonylphenol, EVA 18, EVA 33 and EVAMA. Among several masterbatches based on PA6; the sample containing 5% of EVAMA presented the best combination of processability and mechanical properties. The influence of additives in the processing behavior, crystallinity of the PA6 phase, mechanical and physicochemical properties are discussed in the present work.

Creep Behavior of PA6/NBR TPVs

The influence of compatibilizers and other additives in PA6/NBR blends is evaluated in terms of creep resistance. The results obtained are correlated with density, selective solvent extraction, tensile strength, DMA analysis, and scanning electron microscopy. Our studies show an enhancement of dimensional stability of samples with the presence of EVAMA in the PA6 master batch. On the other hand, better elastomeric behavior is achieved with the compatibilization process, oxazoline-modified NBR being the best compatibilizer. Also, the possibility of evaluating a material in conditions near to final applications, through a shot-time test, with minimal material waste is shown.

Dynamic and structural correlations in nanocomposites of silica with modified surface and carboxylated nitrile rubber

Distinct affinities between the organic and inorganic phases were observed in nanocomposites prepared through a colloidal route with carboxylated nitrile rubber and modified silica nanoparticles, which resulted in variable mechanical properties and improved thermal stability. Nanoparticles with modified surface affected the macromolecular arrangements of the elastomeric matrix, changing the final mechanical behavior of the nanocomposite, which could be predicted by the spin-lattice relaxation time measured by solid-state NMR. It was also possible to identify how each different nanoparticle affected the molecular dynamic of nanocomposite, correlating the dynamic-mechanical analysis with the NMR data of the saturated carbons of the elastomer.

Hybrids membranes with potential use in fuel cells - part 1: sulphonated poly (etherimide) nanocomposites

Fuel Cells based in polymeric membranes are an alternative for the conventional energetic matrices based on fossil fuel and generation of energy with minimum environmental impact. However, polymeric membranes available nowadays for this specific use have some disadvantages, like low efficiency and cell durability. The aim of this work was to prepare and to characterize hybrid polymeric membranes for application as hydrogen fuel cell electrolytes. Membranes based in poly(ether imide) were chemically modified with sulfur groups to increase their ionic conductivity. The incorporation of mineral clay in nanometric scale aims to increase their mechanical and thermal properties. The membranes were evaluated by FTIR, DSC, TGA, DMA, density, hot water uptake, water vapor transmission and ionic migration resistance. The results leaded to a better structure versus properties balance, aiming the high performance of the obtained membranes.

THERMAL PROTECTION OF POLYAMIDE 6/ACRYLONITRILE–BUTADIENE RUBBER THERMOPLASTIC-VULCANIZATES: INFLUENCE OF TYPE AND CONTENT ON BLEND PROPERTIES

ABSTRACT Polyamide 6 (PA6)/NBR blends are interesting because of their supposed properties at elevated temperatures. The blend, however, has a critical problem in terms of processing stability, as a result of the thermal degradation of the NBR phase. We evaluate a system of dissimilar addition of antioxidant in each phase (a combination of Irganox®/Irgafos® for the PA phase, and Naugard 445® for the NBR phase) and study the influence of these antioxidants on the properties of the blend. The evaluation was performed through tensile strength, differential scanning calorimetry (DSC), thermogravimetric analysis, and X-ray diffraction analysis. The influence of the antioxidant system on the crystallization process of the PA phase was evaluated through isothermal DSC analysis. Results showed the best combination of antioxidant addition in master batches and during processing.

Hybrids membranes with potential for fuel cells – Part 3: extruded films of nanocomposites based on sepiolite and PC/sulfonated PC blends

Fuel Cells based in polymers are an alternative for the conventional energetic matrices. However, materials currently available still present disadvantages to overcome. Membranes of polycarbonate (PC)/sulfonated polycarbonate (PCs) blend/sepiolite nanocomposites have previously been studied by the authors, resulting in good mechanical properties and promising properties of vapor transmission and ionic migration resistance. However, their production in large scale is still a challenge. The aim of this work was the development further the formulation and processing of the previously studied material. Films of PC/PCs blends (50/50 wt%) with different content of sepiolite clay, with and without chemical modification, have been prepared in an extruder and evaluated by FTIR, XRD, DSC, TGA, DMA, tension strength and water vapor transmission (WVT). Even after two processing steps, the blend-based nanocomposites keep good thermal and mechanical properties. However, changes in WVT were observed with respect to data obtained in previous studies.