Summary Dispersions of 10% wt hydrotalcite were prepared by mixing using an ultrasound probe and then incorporated into NBR latex for the purpose of evaluating the influence of the surfactant presence and dispersion stability of the hydrotalcite, both in water and in latex. The surfactant used was Pluronic F‐127 and its influence was determined on the size of the agglomerates, the degree of sedimentation and the viscosity of water/LDH dispersions and latex/LDH suspensions. Preliminary results showed the efficiency of the surfactant in promoting dispersion of water/LDH, presenting lower agglomerate diameter values and increased stability of the dispersion. For the latex/LDH suspension, the viscosity of the system containing surfactant was significantly greater due to a better dispersion of LDH. After coagulation, the systems were examined in detail using X‐ray diffraction (XRD) and the results did not show differences in the degree of intercalation, but XRD pattern of LDH was not observed, indicating the breakdown of crystallinity and ordering of the clay crystallites. The ash content showed that the presence of surfactant was an important factor to optimize the incorporation of the clay during coagulation. The estimation of Payne effect from shear modulus indicated a better filler dispersion in NBR matrix when using Pluronic F‐127, this behavior was also confirmed by FESEM micrographs.
Resumo: Neste trabalho foram obtidos nanocompósitos de elastômeros termoplásticos à base de PP/EPDM/argila organofílica pela técnica de intercalação no estado fundido em câmara interna de mistura. Foram preparados concentrados de PP-MA (agente interfacial) e Claytone 40 (argila organofílica) nas proporções de 1:1, 2:1 e 3:1 que posteriormente foram adicionados na matriz PP/EPDM, previamente preparada, mantendo o teor de argila fixo em 5% (em massa). Foram investigadas as propriedades mecânicas de módulo elástico, tração e alongamento na ruptura, reologia e morfologia, a fim de estabelecer a influência da razão PP-MA/argila organofílica no comportamento dos nanocompósitos. Os resultados mostraram que a adição de teores crescentes de PP-MA melhorou a dispersão da argila organofílica na matriz de PP/EPDM. Conforme revelado pela difração de raio X e confirmados pela reometria foram obtidos nanocompósitos com estruturas mistas intercaladas e esfoliadas, que resultaram em maiores valores de módulo e deformação na ruptura. Palavras-chave: Nanocompósito, elastômero termoplástico, argila organofílica, PP-MA. Influence from the Concentration of Interfacial Agent on the Properties of PP/EPDM/Organoclay NanocompositesAbstract: In this work, nanocomposites were prepared with PP/EPDM thermoplastic elastomer and organoclay by melt intercalation in an internal mixture chamber. Masterbatches composed of PP-MA/organoclay in proportions of 1:1, 2:1 and 3:1 were prepared and further added to a PP/EPDM thermoplastic elastomer, keeping the clay content fixed at 5% (by weight). The tensile properties, rheology and the morphology (organoclay dispersion, crystalline structure and crystallinity degree) of nanocomposites were studied to establish the influence of the PP-MA/Organoclay ratio in the system. The results showed that the addition of increasing levels of PP-MA improved the dispersion of organoclay in the PP/EPDM matrix. As revealed in x-ray diffraction and confirmed by rheology measurements nanocomposites were obtained with mixed intercalated and exfoliated structures, resulting in higher tensile modulus and elongation at break. Keywords: Nanocomposite, thermoplastic elastomers, organoclay, PP-MA. IntroduçãoElastômeros termoplásticos (TPE) à base de polipropileno (PP) e de terpolímero de etileno-propileno-dieno (EPDM) ganharam notoriedade pela facilidade de preparação de compósitos e pela combinação das altas deformações de um elastômero e do processamento de um termoplástico [1] . A adição de cargas em escala nanométrica a essas matrizes poliméricas, tem sido um atrativo potencial em função das características que a carga inorgânica pode apresentar quando bem dispersa no polímero orgânico. Esses materiais inorgânicos utilizados como nanocarga (geralmente silicatos em camadas), além de apresentarem elevada razão de aspecto, são suscetíveis a intercalação de macromoléculas e são os mais utilizados em função da fácil disponibilidade e tratamento de superfície [2] . A utilização de baixos teores de organo-argila (≤5%) [3][4][5] é e...
The use of biodegradable polymers to produce nanocomposites with mineral fillers leads to the production of new materials with low cost and reduced environmental impact, combined with improvements in mechanical and thermal properties. Nanocomposites based on poly(butylene adipate-co-terephthalate) and starch blend (Ecobras) and vermiculite (VMT) modified with hexadecyltributylphosphonium bromide (P-VMT) were prepared by melt intercalation in a mixing chamber at 140 C, keeping the amount of clay at 4%wt. The intercalation of P-VMT in Ecobras was characterized by X-ray diffraction (XRD) and infrared spectroscopy (FTIR). VMT organophilization was confirmed by the appearance of FTIR bands characteristic of the long alkyl chain of the phosphonium salt used and also by displacement of the basal peak towards lower 2u values in the diffractogram compared to pure vermiculite. The thermal properties of Ecobras and its compositions were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The addition of VMT and P-VMT in Ecobras increased the crystallization temperature (T c ) and crystalline melting temperature (T m ), as observed by DSC analysis. The result of the thermogravimetric analysis showed that the addition of P-VMT in Ecobras improved thermal stability of the nanocomposite. The Young's modulus of the composite with 4 wt% of P-VMT indicated an increase in stiffness compared to the pure matrix.
O presente trabalho objetivou discutir a relação da liberdade de expressão e seus limites no discurso de ódio. A análise do tema baseia-se no estudo da previsão constitucional acerca da liberdade de expressão nos ordenamentos jurídicos americano e europeu, e no estudo da jurisprudência atual brasileira, passando-se então à análise dos princípios da ponderação e proporcionalidade como meios do qual se é possível solucionar conflitos de normas fundamentais caso a caso. Por fim, fez-se o estudo de um caso concreto: RHC 146.303/RJ, caso do pastor Tupirani da Hora Lores, no qual o Supremo Tribunal Federal decidiu por conferir à liberdade de expressão um caráter não absoluto.
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