Abstract In this study, the influence of carbon black (CB) trimodal mixture, with different medium particle sizes, on the colorimetric and rheological properties of polyethylene was evaluated. Three different types of CB were selected, with particle sizes of 15nm (S), 38nm (M), and 75nm (L) and combined, generating a Design of Experiments (DOE) with 19 formulations to be dispersed at 30% in low density polyethylene (LDPE) in twin screw extruder. Such formulations were evaluated in performance and process properties, such as Tint Strength, Melt Flow Index (MFI), and Total Transmittance (TT). It was observed that the mixtures between small (S) and medium (M) particles developed greater tinting strength and lower viscosity, demonstrating the synergy of the mixture, which was superior in the performance of the mixture containing only a particular of 15nm (S) that would have greater potential for results.

Abstract In this work, the influence of Specific Mechanical Energy (SME) to disperse a trimodal distribution of carbon black (CB) by extrusion was studied to evaluating the effect on LDPE films properties (colorimetric and rheological). Three types of CB were previously evaluated (PART1) and determined that the best formulation was the combination between small (S) and medium (M) particles (F18 and F13), obtaining greater tinting strength with lower viscosity. In this work (PART2), these formulations were processed with different SME levels by varying the extrusion parameters, like screw rotation speed (N) and feed rate (Q), modulate the SME. The result of each process was evaluated by Tinting Strength, MFI, Total Transmittance and it was determined that the process with 600 rpm and 10 kg/h feed rate, generating a SME of 0.29 kWh/kg for F18-P03, developed the best results, mainly in the Tinting Strength, from 126.7% to 133.2% related to F18 (PART1).

Abstract The (de)hydrogenation properties of a TiFe intermetallic compound (IMC) alloy activated by cold rolling inside a glovebox at ambient temperature were investigated by kinetic measurements, x-ray powder diffraction (XRD), and transmission electron microscopy (TEM). Rate-limiting steps were identified by testing kinetic models on hydrogen absorption and desorption curves. To prevent surface poisoning during air exposure, the TiFe IMC was also cold rolled with polytetrafluoroethylene (PTFE) and ultra-high molecular weight polyethylene (UHMWPE). The addition of either PTFE or UHMWPE to nanostructured TiFe by cold rolling did not produce a polymer-metal composite with O2 poisoning resistance, regardless of the polymer-mixing way adopted. This occurred because large surfaces of the particles were not adequately coated with polymer. The results identify challenges to the TiFe IMC polymer-covered material that must be overcome before a methodology can significantly contribute to the formation of nanostructured TiFe-polymer composites with enhanced hydrogen storage properties. The diffusion-controlled reactions in the cold-rolled TiFe IMC without polymer were prevalent in all cases, as predicted by the Jander three-dimensional diffusion model. The main contribution of this work regards estimation of the amount of hydrogen released, which was 0.60% after 6 min and reproducible for the three subsequent cycles.

Abstract 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.

In this work, polyaniline (PANI) in emeraldine-base form, synthesized by chemical oxidation polymerization, was protonated with hydrochloric acid (HCl). Composites based on high-density polyethylene (HDPE) and linear-low density polyethylene (LLDPE) blends with PANI were prepared in molten condition using a torque rheometer. The effect of compatibilizer agent (maleic anhydride-grafted high density polyethylene, HDPE-g-MA) and different contents of PANI on the blends-based composites was also investigated. Thermal, mechanical, and electromagnetic (electric permittivity) measurements and morphological aspects of the composites were evaluated. The addition of PANI content in the composites decreases the degree of crystallinity of HDPE and LLDPE blends, which implies that PANI particles make it difficult for co-crystallization to occur in the HDPE and LLDPE, respectively. On the other hand, the addition of compatibilizer agent in the HDPE and LLDPE blends increased the degree of crystallinity. The complex parameters of permittivity in the frequency range of 8.2 to 12.4 GHz varied as a function of the PANI content in the blend. It was also observed that the compatibilizer agent increased the composite stiffness and decreased the electric permittivity values. This result shows that the increasing rigidity of the molecular structure of the polyethylene matrix hindered the dissipation of the electromagnetic energy in the sample.

Epoxy/CNT and epoxy/CNT/calcium carbonate nanocomposites were produced via in situ polymerization assisted by ultrasonication without solvent and electrical, mechanical, thermal and thermomechanical properties of nanocomposites were evaluated. Epoxy/CNT presented very low percolation threshold, near 0.05 wt % and nanocomposites with higher contents of CNT presented further increase in electrical conductivity. The addition of calcium carbonate in epoxy/CNT nanocomposites increased the electrical conductivity, due to volume exclusion phenomena. Regarding thermal properties, due to the low content of the CNT and calcium carbonate no changes in glass transition (Tg) were observed. DMA results showed no significant changes in thermomechanical properties, once the contents of CNT and calcium carbonate are below stiffness threshold, however an increase of flexural modulus by adding CNT and calcium carbonate was observed.

Blends of ultra-high molecular weight polyethylene (UHMWPE) and different contents (0, 10, 20 and 30 wt%) of linear low-density polyethylene (LLDPE) with and without maleic anhydride-grafted LLDPE (LLDPE-g-MA) were prepared by melt blending and aging resistance, thermal and mechanical properties were evaluated. The degree of crystallinity increases with the content of LLDPE in the blends. On the other hand, the addition of compatibilizer agent modifies the crystallinity and the crystallite size. Non-compatibilized blends have excellent impact resistance properties and the addition of LLDPE-g-MA aids processing but decrease the impact resistance of the blends. Thermal and mechanical properties were greatly affected by thermal and water aging. The thermal aging leads to an increase in the degree of crystallinity and consequent a decrease in impact resistance.

The effect of maleic anhydride (MA) content on morphological, thermal, thermomechanical and mechanical properties of PA6/AES/MMA-MA (66.5/28.5/5 wt%) system was investigated. In general, the simple incorporation of MMA-MA to PA6/AES system is responsible for enhancements in mechanical performance. PA6/AES/MMA-MA3% and PA6/AES/MMA5% exhibited similar morphology and final properties, indicating no MA content effect on the studied system. On the other hand, PA6/AES/MMA-MA10% exhibited a quite different morphology and lower mechanical performance compared to the other compatibilized blends. Such unexpected behavior was not attributed to the effective maleic anhydride content in this composition, but to the reduced molar mass resulted from the excess of non-reacted MA monomer during the synthesis procedure.

Poly(ethylene terephthalate)/organically modified montmorillonite (PET/o-Mt) nanocomposites were prepared via melt intercalation in a twin-screw extruder using a polyester ionomer (PETi) as compatibilizer. The o-Mt content used was 0, 1, 3 or 5 wt% and the compatibilizer/o-Mt mass ratio was 0/1, 1/1 or 3/1. The main objective was to study the effects of the addition of o-Mt and compatibilizer on the barrier properties of PET/o-Mt nanocomposites. The nanocomposites showed a significant reduction in CO2 permeability of up to 50% when compared to the neat PET, without significant change in the CO2 solubility revealing the importance of the diffusional path imputed by the organoclay on the overall permeation process. Water vapor permeability was reduced for all nanocomposites, achieving up to 30% reduction for the nanocomposite containing a compatibilizer/o-Mt mass ratio of 1/1. Overall, the nanocomposite containing 5 wt% of organoclay and compatibilizer/o-Mt mass ratio of 1/1 showed the best barrier properties.

To understand the processing influence in an intermeshing corotating twin-screw extrusion (ICTSE) on the morphology and impact properties of the uncompatibilized PBT/ABS (70/30) blend, it was submitted to different processing parameters. In this way both morphology and impact properties (resistance and ductile brittle transition temperature (DBTT) would be a function of processing only, because there would be no influence of a compatibilizer. The rotation speed of the screws influenced both impact resistance and Ductile Brittle Transition Temperature (DBTT) of the PBT/ABS blends. Blends prepared with higher rotation speed (240 rpm) did not present toughness at room temperature, whereas the blends prepared at lower speed showed high impact strength at room temperature and DBTT near to 5 °C. The angle between the kneading blocks discs also influenced the impact properties, because blends processed with screw with 90º angle between kneading block disks, for two different feed rates, showed lower DBTT than the blends processed with 45º angle. The morphological analysis by TEM showed that blends processed at low rotation speed of the screws presented a higher dispersion degree than those processed at high rotation speed. Blends processed in screws where the angle between the disks was 90º showed a higher dispersion degree than the blends processed in disks with a 45º angle. These results are in agreement with the impact properties, confirming that high dispersion of the ABS particles improves the impact properties of the blend.

Abstract Polymer/clay nanocomposites are a new class of composites with polymer matrices where the disperse phase is a silicate with elementary particles that have at least one of dimensions in nanometer order. Polyamide 6/Brazilian organoclay nanocomposites were prepared by melt intercalation, and the mechanical, thermal and thermomechanical properties were studied. The structure and morphology of the nanocomposites were evaluated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was verified by XRD and TEM analysis that all systems presented exfoliated structure predominantly. By thermogravimetry (TG), nanocomposites showed higher stabilities in relation to pure polymer. It was observed that the nanocomposites showed better mechanical properties compared to the properties of polyamide 6. The heat deflection temperature (HDT) values of the nanocomposites showed a significant increase in relation to pure polymer.

Mixed matrix membranes are promising options for improving gas separation processes. Zeolitic imidazolate frameworks (ZIFs) have a porous structure similar to conventional zeolites, being capable in principle of separating gases based on their differences in kinetic diameter while offering the advantage of having a partial organic character. This partial organic nature improves the compatibility between the sieve and the polymer, and a combination of the mentioned characteristics makes these hybrid materials interesting for the preparation of mixed matrix gas separation membranes. In this context the present work reports the preparation of Ultem®/ZIF-8 mixed matrix membranes and their permeabilities to pure CO2, N2 and CH4gases. A significant increase in permeability with increase in CO2/N2 selectivity was observed for the mixed matrix systems as compared to the properties of the neat Ultem®. Sorption results allowed to speculate that the ZIF-8 framework is not completely stable dimensionally, what influences the separation process by allowing gases with higher kinetic diameter than its nominal aperture to be sorbed and to diffuse through the crystal. Sorption and diffusion selectivities indicate that the higher separation performance of the mixed matrix membranes is governed by the diffusion process associated with the influence of gas molecule's geometry.

O efeito da organofilização da argila no comportamento mecânico, morfológico e termo-mecânico de nanocompósitos baseados em blendas de poliamida 6 )/acrilonitrila-EPDM-estireno foi estudado. Três nanoargilas foram utilizadas para a preparação dos nanocompósitos: duas montmorilonitas comerciais modificadas organicamente (Cloisite®30B and Cloisite® 20A) e uma montmorilonita sódica não modificada (Cloisite®Na+). Difração de raios-X em alto ângulo, microscopia eletrônica de transmissão e testes de tração e resistência ao impacto foram utilizados para avaliar o efeito da organofilização da nanoargila na morfologia e propriedades mecânicas dos materiais. As propriedades termo-mecânicas foram avaliadas por análise dinâmico mecânica e temperatura de deflexão térmica. Os resultados mostraram que a modificação da nanocarga afeta simultaneamente o grau de reforço da matriz, dispersão das lamelas de argila na blenda e tamanho da fase dispersa AES. A adição das diferentes nanoargilas aumenta o módulo elástico de todos os nanocompósitos ternários em relação à blenda pura sem argila. Por outro lado, um aumento na tenacidade foi obtido apenas para os sistemas com Cloisite®Na+. Um aumento significativo no módulo de armazenamento e HDT foi observado pela incorporação da Cloisite®30B na blenda.

The effect of clay organophilization on mechanical, morphological and thermo-mechanical behavior of polyamide-6/acrylonitrile-EPDM (ethylene/propylene/diene elastomer)-styrene blends was studied. Three nanoclays were used for the preparation of nanocomposites: two commercial organically modified montmorillonites (Cloisite®30B and Cloisite® 20A) and an unmodified sodium montmorillonite (Cloisite®Na+). We used wide angle X-ray scattering, transmission electron microscopy and mechanical tests to evaluate the effect of clay modification on the morphology and mechanical properties of the nanocomposites. The thermo-mechanical properties were characterized using dynamic mechanical analysis and heat distortion temperature (HDT). The results show that the modification of clay affected simultaneously the degree of PA6 matrix reinforcement, dispersion of the clay lamellas in the blend and size of the dispersed phase AES. The incorporation of different nanoclays increase the elastic modulus of all the ternary nanocomposites compared to the neat blend. An increase in the toughness is obtained only for systems with Cloisite®Na+. A significant increment in the storages modulus and HDT was observed by the incorporation of Cloisite®30B in the PA6/AES blends.

Scrap tires are considered a type of waste that litters landfills and the environment in general. Due to its chemically cross-linked structure, this material cannot be recycled by conventional processes because it does not melt. This work examined the production of polymeric composites using high density polyethylene (HDPE) filled with rubber tire powder (RTP). Ethylene-octene-1 copolymer (C2C8), an elastomeric material, was also added to improve the mechanical properties. Morphological analysis showed a good interfacial adhesion when C2C8 is added to the mixture. Raman spectroscopy coupled to optical microscopy revealed that the HDPE phase encapsulated the rubber tire particles. The mixtures containing C2C8 and RTP presented lower ultimate tensile strength and elastic modulus, but the impact strength of the binary and ternary mixtures was much higher than that of neat HDPE.