Abstract This paper describes the effects of adding organic montmorillonite clays (MMT) with different polarities (one polar and one non-polar) in recycled poly (ethylene terephthalate) (PET) and polypropylene (PP) blends. Styrene-Ethylene/Butylene-Styrene-maleic anhydride-graft (SEBS-g-MA) was used as a compatibilizer. MMT polarity was chosen based on the expected specific interaction of each clay with PET and PP. Samples were evaluated by wide angle X-ray diffraction, scanning electronic microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, dynamic mechanical analysis and mechanical tests. The clays caused no statistical change in the mechanical properties high-concentration PET blends, but increased Young’s modulus and decreased the elongation at break, tensile strength and impact strength of high-concentration PP blends. The different interactions between PET and SEBS-g-MA and the level of MMT exfoliation in each polymer-rich phase explained the results.

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 The compatibilization of recycled PP/PET blend with high and low concentration (20 and 5 phr) of elastomer functionalized by maleic anhydride (SEBS-g-MA) was achieved. Recycled polypropylene from plastic industry and recycled PET from post-consumer bottles was used. PP/PET blends: 80:20 w/w, 50:50 w/w and 20:80 w/w were prepared in an internal mixer for mechanical properties, thermal properties, morphology and rheological properties. SEBS-g-MA promoted compatibilization of the PP/PET blends and improved their properties. With an increasing compatibilization level, the refinement of morphology was observed in the PET rich blend. Compatibilized blends showed negative deviation in the PET glass transition temperature related to neat PET, demonstrating that compatibilization was very successful. PET crystallization was accelerated in the blends due to PP presence that enhanced nucleation. It was found that the 50/50/20 blend showed huge potential for textile fiber application and that of 80/20/20 showed more intermediary properties than neat polymers.

The effect of clay hydrophobicity on the cold crystallization and rheological properties of nanocomposites of poly(D,L-lactic acid) (PDLLA) was investigated. Crystallization was evaluated by DSC for isothermal and non-isothermal conditions. The clay modified with a hydrophilic surfactant acts as a nucleating agent, while the clay modified with a hydrophobic surfactant acts in an opposite way. The Avrami and Ozawa parameters showed a three-dimensional spherulitic growth for all samples and the activation energy increased for the hydrophobic clay and decrease for the hydrophilic one. The equilibrium melting point for the PDLLA was found at 161ºC, being slightly altered as function of the surfactant polarity. The rheological behavior was investigated in terms of Isothermal Flow-Induced Crystallization and Structural Recovery. The hydrophobic clay showed to reduce the mobility of chains and retard the chain relaxation, which is attributed to the formation of a network, while the hydrophilic clay increased the chain mobility.

Abstract This study evaluated the modification effects of adding ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMGMA) in the presence of polyphosphoric acid (PPA) to an asphalt binder graded as 50/70 (0.1mm) in the Brazilian penetration grade specification (AC 50/70). The EMGMA terpolymer has been presented as a new alternative to modify asphalt binders properties, as scientific literature is scarce on its usage in this context and also on the role of PPA when used in combination with reactive polymers. The characteristics of the modified binder were analyzed by standard and rheological testing, including Multiple Stress Creep Recovery test (MSCR) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The MSCR test showed that the modified binder presented lower values of non-recoverable compliances (Jnr) and a higher percent recovery, when compared to the conventional binder. This behavior indicates that addition of EMGMA and PPA in asphalt binders could enhance the resistance to rutting of asphalt mixtures. The statistical evaluation showed that EMGMA had greater influence on the studied properties of Jnr (0.1kPa), MSCR recovery, softening point and elastic recovery at 25°C and that the PPA had also significant influence on these properties. FTIR analysis showed that chemical reactions occurred between the asphalt binder and EMGMA, forming a three-dimensional polymeric network, which promotes improved characteristics.

Modeling electrical conductivity of polymer composites with conductive fillers has great applicability to predict conductive materials behavior. In this study, the electrical behavior of simple and hybrid systems prepared from Carbon Black (CB) and Carbon Nanotubes (CNT) was studied. There have been few advances reported in the literature regarding the modeling of hybrid systems, which motivated the development of this study. More specifically, a program was developed with the intention to describe the electric percolation threshold and the effect of synergism between the conductive fillers. Simulation was performed using the Monte Carlo method and Fortran programming language, considering concentration and geometry of conductive fillers to the system in two dimensions. Finally, simulation results were compared with the experimental results and this method proved to be effective in predicting the systems percolation threshold, being an important contribution to predict material behavior, which allows reducing the number of samples to be prepared in an experimental study.

Resumo O presente artigo apresenta a aplicação e adequação dos modelos de percolação elétrica em trabalhos experimentais e teóricos da literatura para compósitos poliméricos condutores. Foi realizado um levantamento das publicações referentes aos modelos estudados para os diferentes tipos de cargas condutoras mais aplicadas na preparação destes compósitos, tais como pós metálicos, grafite, negro de fumo, nanofibras e nanotubos de carbono. A discussão está apresentada quanto à adequação dos modelos ao comportamento dos compósitos na influência das cargas nas propriedades elétricas de matrizes poliméricas.

Abstract This paper presents the application and adjustment of electrical percolation models in conductive polymer composites. Different models have been proposed for different types of conductive fillers applied in composites preparation, such as metal powders, graphite, black carbon, carbon nanotubes and nanofibers. The discussion was carried out considering the consistency of the model on the behavior of these fillers and their influence on the electrical properties of polymer matrices.

O copolímero Etileno Acetato de Vinila (EVA) é uma poliolefina utilizada principalmente em filmes para embalagens, onde a sua flexibilidade, tenacidade, elasticidade e transparência são atributos desejáveis. As propriedades mecânicas, térmicas e de barreira do EVA podem ser melhoradas pela incorporação de cargas inorgânicas. O EVA apresenta polaridade variável de acordo com o teor de Acetato de Vinila, o que promove a viabilidade para obtenção de nanocompósitos com argilas organicamente modificadas, tornando desnecessária a adição de agentes compatibilizantes. Neste trabalho foram preparados nanocompósitos de EVA e montmorilonita organofílica comercial pelo método de intercalação do fundido em um reômetro de torque, com rotores tipo roller, a 150°C durante 10minutos, com monitoramento do torque em função do tempo. A fim de investigar a influência da polaridade do EVA, da concentração da argila e das condições de processamento nas características dos nanocompósitos, variou-se a concentração de Acetato de Vinila (19% e 28%), o teor de argila (2% e 5%) e a velocidade de rotores (60 rpm e 100 rpm). Foram avaliadas a estrutura da argila, a estabilidade térmica e as propriedades mecânicas e de barreira dos nanocompósitos, mediante as técnicas de difração de raios X, análise termogravimétrica, ensaio de tração e análises de taxa de permeabilidade ao oxigênio e ao vapor d’água. A partir dos dados de permeabilidade foi aplicado o modelo de Nielsen para avaliar o grau de esfoliação da argila. Dentre os principais resultados com o planejamento fatorial destacam-se: (a) o aumento da polaridade do EVA aumentou a permeabilidade ao oxigênio e ao vapor d’água dos materiais; (b) o teor de argila não modificou a estabilidade térmica dos nanocompósitos e a estrutura da argila; (c) o aumento da concentração da argila aumentou o módulo elástico, reduziu a deformação de ruptura e reduziu significativamente o coeficiente de permeabilidade ao oxigênio e ao vapor d’água; (d) o fator rotação não implicou em alterações significativas em nenhuma das respostas avaliadas.

The copolymer Ethylene Vinyl Acetate (EVA) is a polyolefin used mainly in packaging films, where its flexibility, toughness, elasticity and transparency are desirable attributes. The mechanical, thermal and barrier properties of EVA can be improved by the incorporation of inorganic fillers. Its polarity varies according to the content of Vinyl Acetate, which allows for nanocomposites to be obtained with organically modified clay, with no need to add compatibilizing agents. In this work nanocomposites of EVA and commercial organophilic montmorillonite were prepared by melt intercalation in a torque rheometer with rotors roller type, at 150°C for 10 minutes, monitoring the torque versus time. The concentration of Vinyl Acetate (19% and 28%), clay content (2% to 5%) and the rotors rotation (60 rpm to 100 rpm) were varied in order to investigate their influence on the characteristics of the nanocomposites. The clay structure, thermal stability, mechanical and barrier properties of the nanocomposites were evaluated by X-ray diffraction, thermal analysis, tensile testing, oxygen and water vapor transmission rates. Based on the permeability data, Nielsen´s model was applied to assess the degree of clay exfoliation. The main results obtained from the factorial design are: (a) increasing the polarity of EVA led to an increase in the permeability to oxygen and water vapor of the material, (b) the clay content did not change the clay structure or the thermal stability of the nanocomposites, (c) increasing the concentration of clay increased the elastic modulus, decreased the elongation at break and significantly reduced the coefficient of permeability for oxygen and water vapor, (d) the rotation factor did not result in significant changes in any of the evaluated responses.

Nanocomposites of poly (methyl methacrylate) (PMMA) and carbon nanotubes have a high potential for applications where conductivity and low specific weight are required. This piece of work concerns investigations of the level of dispersion and morphology on the electrical properties of in situ polymerized nanocomposites in different concentrations of multi-walled carbon nanotubes (MWCNT) in a PMMA matrix. The electrical conductivity was measured by the four point probe. The morphology and dispersion was analyzed by Transmission Electron Microscopy (TEM) and Small Angle X-ray Scattering (SAXS). The correlation between electrical conductivity and the MWCNT amount, presented a typical percolation behavior, whose electrical percolation threshold determined by power law relationship was 0.2 vol. (%) The exponent t from the percolation power law indicated the formation of a 3D network of randomly arranged MWCNT. SAXS detected that the structures are intermediate to disks or spheres indicating fractal geometry for the MWCNT aggregates instead of isolated rods. HR-TEM images allowed us to observe the MWCNT individually dispersed into the matrix, revealing their distribution without preferential space orientation and absence of significant damage to the walls. The combined results of SAXS and HR-TEM suggest that MWCNT into the polymeric matrix might present interconnected aggregates and some dispersed single structures.

Neste estudo, foram preparados, pelo método de intercalação do fundido, nanocompósitos de PLA com as argilas organofílicas Cloisite 20A e Cloisite 30B. A influência das argilas no processo de biodegradação do PLA foi avaliada com base no método de respirometria. A incorporação da argila Cloisite 20A praticamente não alterou a curva de mineralização do PLA. O nanocompósito com Cloisite 30B, por sua vez, apresentou um comportamento distinto, indicando um atraso no processo de biodegradação do polímero neste material. As amostras foram caracterizadas pelas técnicas de Difração de Raios X, Análise Termogravimétrica e Calorimetria Diferencial Exploratória. A caracterização dos materiais indicou uma estrutura possivelmente intercalada dos nanocompósitos, bem como a redução da estabilidade térmica e um pequeno aumento no grau de cristalinidade, em relação ao polímero puro.

In this study nanocomposites of PLA and organoclays Cloisite 20A and Cloisite 30B were prepared by melt intercalation. The influence from the organoclays on the biodegradation of PLA was evaluated based on the respirometry method. The incorporation of clay Cloisite 20A did not change the mineralization curve of PLA. The nanocomposite with Cloisite 30B, on the other hand, presented a different behavior, indicating a delay in the polymer biodegradation. The materials were characterized by X-ray Diffraction, Thermogravimetric Analysis and Differential Scanning Calorimetry. The materials characterization indicated nanocomposites with an intercalated structure as well as reduced thermal stability and a slight increase in the degree of crystallinity compared to the pure polymer.

O poliácido lático (PLA) é, dentre os polímeros biodegradáveis, o que apresenta o maior potencial para substituição aos polímeros derivados do petróleo na indústria de embalagens. No entanto uma de suas principais limitações está na baixa estabilidade térmica dimensional. O presente trabalho apresenta um estudo da influência da utilização de dois aditivos: modificador térmico (nucleante) e modificador de impacto, na Temperatura de Distorção Térmica (HDT), no Ponto de Amolecimento Vicat (Vicat) e nas propriedades mecânicas do PLA. Os mecanismos de atuação destes aditivos foram estudados por alterações na temperatura de transição vítrea (Tg) e na cristalinidade medidas por calorimetria diferencial exploratória (DSC) em corpos de prova injetados sem e com tratamento de recozimento. Aplicou-se um planejamento experimental para tratamento estatístico dos dados. Os valores de HDT e de Vicat foram pouco alterados pela presença dos aditivos, embora tenha sido observado aumento nos valores do módulo elástico de tração. O tratamento de recozimento foi responsável pelo aumento tanto na HDT como na Vicat devido ao aumento no grau de cristalinidade. As curvas de DSC mostraram uma grande complexidade no comportamento térmico do PLA, sendo fortemente influenciado pelas condições de tratamento térmico.

Poly(lactic acid) (PLA) is the biodegradable polymer with greatest potential to replace petroleum-based polymers for the packaging industry. However one of its major limitations is the poor thermal dimensional stability. This paper presents a study of the influence of two additives: thermal modifier (nucleating) and impact modifier on the Heat Distortion Temperature (HDT), Vicat Softening Temperature (Vicat) and mechanical properties of PLA. The mechanism of these additives was evaluated by analyzing the glass transition temperature (Tg) and degree of crystallinity by Differential Scanning Calorimetry (DSC) in the samples with and without annealing treatment. An experimental design was applied for the statistical treatment of the data. The values of HDT and Vicat were slightly altered by the presence of additives, although the tensile elastic modulus increased. Annealing was responsible for the increase in HDT as well as in Vicat due to an increased degree of crystallinity. DSC curves showed a great complexity in the thermal behavior of PLA, being strongly influenced by the conditions of heat treatment.

Blendas imiscíveis de poliamida 6 e polietileno de baixa densidade foram preparadas com e sem a presença de polietileno enxertado com anidrido maleico como compatibilizante. Montmorilonita organofílica foi incorporada nas blendas por intercalação do fundido. Análises morfológicas e estruturais apresentaram boa dispersão da argila, com a obtenção de estruturas intercaladas e esfoliadas. A separação de fases foi observada nas amostras, e tanto o compatibilizante como a argila causaram redução no tamanho dos domínios. Esta estrutura proporcionou uma melhora significativa nas propriedades mecânicas das blendas, revelando o efeito de reforço causado pela argila. O módulo elástico e a tensão máxima aumentaram em até 300% e 100%, respectivamente. O efeito da compatibilização da argila foi positivo. Pelas análises de DSC pode-se observar o surgimento de um pico na região de fusão da PA6 atribuído à formação de uma nova fase cristalina devido à presença de argila.

Immiscible blends of polyamide 6 and low density polyethylene were prepared with and without maleic anhydride grafted polyethylene used as a compatibilizer. Organophilic montmorillonite was incorporated in the blends by melt intercalation. Morphological and structural analysis showed good clay dispersion with partially exfoliated and intercalated structures. Phase separation was observed and domains size reduction was induced by the clay and the compatibilizer. Improvement on mechanical properties of compounds was observed, showing the reinforcing effect caused by the clay. Elastic modulus and tensile strength have increased up to 300% and 100%, respectively. The clay showed a positive effect on compatibilization. DSC analysis revealed a new melting peak for PA6 assigned to a new crystalline phase due the clay effect.