A rheological method to compare the degree of exfoliation of nanocomposites

Wagener, Reinhard; Reisinger, T.

doi:10.1016/j.polymer.2003.01.001

Cited by 382 publications

(264 citation statements)

References 12 publications

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“…The high viscosity at low shear rates points to strong interactions between the delaminated clay platelets and the polymer chains or, alternatively, the formation of network structures by clay particle interactions. Pronounced shear thinning indicates extensive clay exfoliation in a given system [30][31][32]. The nanocomposites internal structure is retained at low shear rates but at high shear rates the clay network structures break down and the platelets tend to orient in the flow direction.…”

Section: Composites Characterizationmentioning

confidence: 99%

Surfactant-free dimer fatty acid polyamide/montmorillonite bio-nanocomposites

Macheca

Gnanasekaran²,

Focke³

2013

Colloid Polym Sci

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Polyamide bio-nanocomposites were successfully prepared using a surfactant-free approach. The clay morphology was fixed by dispersing the ammonium ion-exchanged clay in acetic acid. This was mixed wi th an aceti c aci d sol uti on of the polyamide and the composite was recovered by precipitation with water. The composites featured a mixed morphology containing some exfoliated clay sheets together with nano-sized clay tactoids.Bio-nanocomposites containing as much as 27.5 wt.% clay were obtained. At this filler level, and depending on the temperature, the modulus was up to nine times higher than that of the parent polymer. Addition of clay also increased the glass transition temperature by as much as 5°C. This indicates that the high interfacial surface area, presented by the clay platelets dispersed in the matrix, significantly impaired the polymer chain mobility.

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Section: Composites Characterizationmentioning

confidence: 99%

Surfactant-free dimer fatty acid polyamide/montmorillonite bio-nanocomposites

Macheca

Gnanasekaran²,

Focke³

2013

Colloid Polym Sci

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“…Os polímeros de maneira geral seguem a Regra de Cox-Merz, porém essa regra não é válida para nanocompósitos, uma vez que quando submetidos a fluxos elongacionais as lamelas tendem a se alinhar de maneira perpendicular ao fluxo [10,28] . Estudos com nanocompósitos de poli(butileno tereftalato) com argila [29] concluíram que é possível correlacionar o valor do índice da Lei das Potências, n, com o grau de dispersão da nanoargila na matriz Estes resultados corroboram com os resultados obtidos por difração de raio X, e evidencia a importância do estudo da sequência de mistura na busca de maiores interações entre a matriz orgânica e a carga inorgânica.…”

Section: Caracterização Estruturalunclassified

Caracterização estrutural de nanocompósitos de blendas HDPE/LLDPE e OMMT obtidos por diferentes sequências de mistura

2012

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de cinco sequências de mistura na formação da microestrutura dos nanocompósitos foi estudado. A caracterização estrutural foi realizada por análises de difração de raio X de alto ângulo (WAXD), microscopia eletrônica de transmissão (MET) e comportamento reológico em regime permanente de deformação. Os resultados mostraram que a formação da microestrutura depende da ordem de mistura dos componentes e a utilização de mistura de dois agentes compatibilizantes miscíveis com os constituintes da matriz auxiliou na distribuição da polaridade, facilitando a dispersão das nanoargilas por toda a matriz. Dentre as sequências estudadas, as que a nanoargila foi primeiramente misturada com componentes de menor viscosidade e cristalinidade (LLDPE e/ou LLDPE-g-MA) apresentaram melhor dispersão e distribuição da nanoargila na blenda polimérica. Palavras-chave: Nanocompósitos, HDPE/LLDPE, sequência de mistura. Structural Characterization of HDPE/LLDPE and OMMT Blend-Based Nanocomposites Obtained by Different Blending SequencesAbstract: High density polyethylene/linear low density polyethylene (HDPE/LLDPE) blend-based nanocomposites were prepared in a torque rheometer, using a mixture of HDPE-g-MA and LLDPE-g-MA both containing 1% of maleic anhydride as compatibilizer system. The effect from five blending sequences on the microstructure of the nanocomposites was investigated. The structural characterization was performed through wide angle X-ray diffraction (WAXD), transmission electron microscopy (TEM) and rheological properties. The results showed that the formation of morphology is dependent on the sequence of nanocomposite preparation and that the use of a mixture of two compatibilizer agents, miscible with both components of the blend matrix, facilitated the dispersion of the nanoclay throughout the matrix. The blending sequence where the nanoclay was first mixed with components of lower viscosity and crystallinity (LLDPE and/or LLDPE-g-MA) yielded better distribution and dispersion of nanoclay in the polymer blend. Keywords: Nanocomposites, HDPE/LLDPE, blend sequence. IntroduçãoPoliolefinas, como polietilenos e polipropileno, são amplamente utilizadas em aplicações para embalagens, no setor automotivo e elétrico, onde as propriedades de resistência térmica, mecânica e de permeação a gases possuem grande importância. As propriedades finais dos produtos obtidos a partir de poliolefinas estão intimamente relacionadas à morfologia desses materiais desenvolvida durante o processamento. A grande versatilidade de uso e baixo custo das poliolefinas têm gerado grande interesse tecnológico e científico, principalmente na obtenção de blendas HDPE/LLDPE [1][2][3][4][5][6] . O processamento de HDPE com baixo índice de fluidez é dificultado devido a elevada viscosidade do fundido. A adição de um material com estrutura química semelhante como o LLDPE, com alto índice de fluidez, auxilia no processamento, reduzindo a viscosidade do fundido.Dentre as alternativas utilizadas para melhorar o desempenho mecânico e de barreira das poliolefinas, ...

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“…Storage moduli of the molten nanocomposites are sensitive to nanocomposites structural changes [47]; slopes at low frequency (where the response of the nanocomposites are rather dominated by the polymer/filler interactions) were therefore determined. The latter is considered as a semi-quantitative measure of the degree of exfoliation of the mineral filler [48]. Mechanical properties were evaluated in dynamic and static modes.…”

Section: Nanocomposites Processing and Moldingmentioning

confidence: 99%

Efficient one-step melt-compounding of copolyetheramide/pristine clay nanocomposites using water-injection as intercalating/exfoliating aid

Touchaleaume¹,

Soulestin²,

Sclavons³

et al. 2011

Express Polym. Lett.

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Abstract. Polyether-block-amide (PEBA) /clay nanocomposites were prepared water-assisted by twin-screw extrusion. Both organomodified and pristine (i.e. purified but non-modified) montmorillonite clays were used. A high-pressure differential scanning calorimetry analysis carried out in the processing conditions demonstrated that PEBA/water blend exhibits some miscibility and that amide blocks and water behave as a single phase. In addition to a significant decrease of the melting temperature, water injected into the melt plays a key role among the filler dispersion and prevents the matrix from degradation during melt-extrusion. This process enables the compounding of pristine clay-based nanocomposites whose dispersion state is high enough for the resulting mechanical performances in tension to be at least equivalent to what is reached with organomodified clay. Effects of the nanofiller dispersion onto the macromolecules' mobility are detailed and fracture mechanisms are identified for the various structures.

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A rheological method to compare the degree of exfoliation of nanocomposites

Cited by 382 publications

References 12 publications

Surfactant-free dimer fatty acid polyamide/montmorillonite bio-nanocomposites

Surfactant-free dimer fatty acid polyamide/montmorillonite bio-nanocomposites

Caracterização estrutural de nanocompósitos de blendas HDPE/LLDPE e OMMT obtidos por diferentes sequências de mistura

Efficient one-step melt-compounding of copolyetheramide/pristine clay nanocomposites using water-injection as intercalating/exfoliating aid

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