Adhemar C. Ruvolo Filho

Despolimerização do poli (tereftalato de etileno) - PET: efeitos de tensoativos e excesso de solução alcalina

The depolymerization of waste polyethylene terephthalate (PET) in aqueous solutions 7.5 M of sodium hydroxide was tested at 100 °C and 1 atm, in order to obtain the terephthalic acid monomers (TPA). The effect from surfactants and concentration of sodium hydroxide (NaOH) on the reaction extent of depolymerization was studied quantitatively by gravimetric and thermal measurements. Excess of alkaline solution catalyze the reaction and doubled the reaction rate with larger particle size PET. The surfactants DDS and Tween are efficient in catalyzing larger particle size PET under equimolar conditions, but do not affect the reactions under excess of alkaline solution.

Análise termodinâmica do comportamento mecânico na região elástica de blendas de poli (tereftalato de etileno) reciclado e poliolefinas recicladas

This work describes the study using mechanical tests with the blend of recycled poly(ethylene terephthalate) (PET) and recycled polyolefin with and without the addition of polypropylene grafted with maleic anhydride and poly(ethylene-co-octene-1). A thermodynamic approach based on the Helmholtz work function was applied in the analysis of mechanical tests, correlating the effects of energy storage and from the compatibilizer on the elastic region of the materials. For the system studied, the polyolefin-rich region shows higher storage of elastic energy corroborating the morphology images obtained from SEM analysis. The thermodynamic analysis seems a useful tool to evaluate the compatibilizer effect in polymeric immiscible blends. In this work, more specifically, this method was used to analyze the mechanical behavior of different compositions of recycled polymeric commodity materials.

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.

Estudo do efeito do envelhecimento sob radiação UV no transporte de água em filmes de PET reciclados de bebidas carbonatadas

This work describes a study about the UV ageing effect on water transport through PET film sheets recycled from beverage bottles. Using a thermodynamic formalism based on the Eyring relationship and results of water permeability coefficient, it is possible to determine the entropy and enthalpy of activation for the water transport process. These functions were correlated using the compensation thermodynamic plot and correlations were made between the degradation of the PET samples, measured by FTIR, and transport properties. Also, possible effects from the presence of stabilizers, pigments and processing history were analyzed.

Correlation among volumetric conductivity, electrical threshold field and compensation plots by oxidation induction time on LDPE/CB composites

The thermodynamic compensation effect plot derived from Eyring rate process theory was applied to the thermal and UV ageing of LDPE/Carbon Black composites containing commercial carbon black (CB) and carbon black surface oxidized with nitric acid. Correlations were tested among compensation effect, electrical threshold field and volumetric electrical conductivity. Compensation plots from OIT measurements correlate with thermal and UV ageing effect on activation ΔS and ΔH values, giving a good linear correlation for all samples studied. The relative changes in dc conductivity and electrical threshold field are consistent with the OIT compensation plot, demonstrating that this analysis can be used to monitor LDPE/CB composite degradation under thermal or UV ageing. It can also be used to evaluate, quite accurately, the effect of oxidizing the surface of the CB on the electrical properties (dc conductivity and electrical threshold field) of the LDPE/CB composites.

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.

NANOCOMPÓSITOS DE MATRIZ POLIMÉRICA E ARGILA LAMELAR

Os nanocompositos polimericos compreendem uma classe de materiais formados por pelo menos uma fase finamente dispersa com dimensoes nanometricas, tais como argila lamelar, nanotubos de carbono e silica, entre outros, em uma matriz polimerica. Esses materiais destacam-se uma vez que apresentam grande potencial de incrementos significativos nas propriedades termicas, mecânicas e de barreira a gases em comparacao com as propriedades dos polimeros puros ou modificados com aditivos convencionais. Dentre as diferentes substâncias inorgânicas utilizadas, as argilas lamelares, como a montmorilonita, destacam-se por proporcionarem significativa melhora principalmente nas propriedades mecânicas e na reducao de permeabilidade. Neste capitulo sao abordados os principais temas referentes aos metodos de obtencao, estruturas formadas, compatibilizacao e propriedades de nanocompositos de matriz polimerica e argila lamelar. Os nanocompositos foram divididos em dois grandes grupos: matriz polar e matriz apolar, em que sao discutidos aspectos relevantes para a preparacao desses nanocompositos, com formacao de diferentes tipos de estrutura e avaliacao de propriedades mecânicas e de permeabilidade.

Avaliação das propriedades mecânicas de material polimérico utilizado na confecção de caixas de medição de energia elétrica.

The mechanical properties of polymeric materials depend strongly on the processing. In this work, blends of Poly(phenylene oxide)/polystyrene (PPO/PS) and polycarbonates used in electrical cabinet boxes have been studied. A comparison was made of the mechanical properties of samples injected in the form of test specimens, according to the standard practice ASTM D638, with test specimens removed from the boxes. From the results of impact Izod test, a great variability in the values was verified before and after ageing in water, for all the boxes. This is due to the different internal tensions in each region of the box arising from the processing. A large difference was observed among the values found for resistance to the impact Izod test of the removed test specimens of the lower part of the boxes compared with the values found for the respective injected materials. This indicates a significant influence from the parameters of injection processing, in the boxes as well as in the injected test specimens. Overall, the values of tensile strength in the point of maximum elastic deformation do not differ significantly among the test specimens injected and the removed from the boxes of the same material; however, it was observed that this variation is significant in the values of elongation at break, demonstrating that this property must be considered in the evaluations of the mechanical behavior of the polymeric materials.