Effect of melt processing conditions on the extent of exfoliation in organoclay-based nanocomposites

Dennis, Hugh; Hunter, Dan; Chang, Donghoon; Kim, S.; White, James L.; Cho, J. W.; Paul, Donald R

doi:10.1016/s0032-3861(01)00473-6

Cited by 934 publications

(718 citation statements)

References 17 publications

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“…The strength of the flow field does not affect the kinetics of the dispersion process. These results are similar to those obtained by Dennis et al [32,33], Cho and Paul [34], and Fornes et al [35] for the exfoliation of nanoclay in PA-6 matrix. The process of erosion is similar to the peeling mechanism proposed by Cho and Paul [34] and Fornes et al [35].…”

Section: Breaking Clay Particles Into Tactoids and Plateletssupporting

confidence: 92%

“…Dennis et al [32,33], Cho and Paul [34], and Fornes et al [35] demonstrated the importance of processing conditions in the preparation of nanocomposites by melt compounding. They proposed two mechanisms for the exfoliation of clay platelets: (i) the height of the stacks of platelets is reduced by sliding platelets apart from each other; this process requires shear intensity and (ii) the polymer chains enter the clay galleries, thus pushing the ends of the platelets apart; this pathway does not require high shear intensity but involves diffusion of polymer into the clay galleries, which is driven by physical or chemical affinity of the polymer for the organoclay surface.…”

Section: The Role Of Intercalation and Diffusionmentioning

confidence: 99%

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Estimation of stresses required for exfoliation of clay particles in polymer nanocomposites

Borse¹,

Kamal²

2008

Polymer Engineering & Sci

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The dispersion of clay in a polymer matrix is influenced by two factors: the choice of organic treatment for the clay and the processing or mixing method. Maximum benefits are achieved when the platelets are well dispersed or exfoliated. Exfoliated nanocomposites are formed when the individual clay layers break off the agglomerated particles or tactoids and are either randomly dispersed in the polymer (a disordered nanocomposite) or left in an ordered array. It is suggested that size reduction of clay particles and platelet delamination occur by erosion or surface peeling. A model based on the classical theories of interparticle interactions was formulated for the exfoliation of the clay platelets in a polymer matrix. The model involves the estimation of the binding energy and the adhesive force between the platelets in a clay particle, which indicate the forces required for breaking apart or delamination of clay particles. Then, the shear force required for breakup or delamination of the tactoids is estimated and compared to the hydrodynamic shear forces available during processing. POLYM INTRODUCTIONPolymer/clay nanocomposites are materials composed of a polymer matrix and nanometer size clay particles. They exhibit significant improvements in tensile modulus and strength and reduced permeability to gases and liquids, in comparison with the pure polymer. These property improvements can be realized, while retaining clarity of the material with a little increase in density, since the typical clay loading is 2-5 wt%. It is well known that some polymers interact with montmorillonite and that the clay surface can act as an initiator for polymerization [1,2]. However, clay/polyamide-6 (PA-6) nanocomposites were commercialized mainly after practical methods were developed for appropriate dispersion of the clays at the nanometer scale [3].The first step in achieving nanoscale dispersion of clays in polymers is to expand the galleries and to match the polarity of the polymer or monomer, so that it will intercalate between the layers [4]. This is done by exchanging an inorganic cation, generally sodium cation present in the clay, with an organic cation of a quaternary ammonium compound. The larger organic cations swell the layers and increase the hydrophobic (or organophilic) properties of the clay [5], resulting in an organically modified clay. The organically modified clay can then be intercalated with polymer by several routes. Highly polar polymers, such as polyamides and polyimides, are more easily intercalated than nonpolar polymers, such as polypropylene and polyethylene [6,7]. Melt intercalation involves mixing the clay and polymer melt, with or without shear. Nanocomposites can have several structures. Intercalated nanocomposites usually appear as tactoids with expanded interlayer spacing, but the clay basal spacing remains in the few nanometer range. Exfoliated nanocomposites are formed when the individual clay layers break off the tactoid and are either randomly dispersed in the polymer (a disordered nanocom...

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Section: Breaking Clay Particles Into Tactoids and Plateletssupporting

confidence: 92%

Section: The Role Of Intercalation and Diffusionmentioning

confidence: 99%

Estimation of stresses required for exfoliation of clay particles in polymer nanocomposites

Borse¹,

Kamal²

2008

Polymer Engineering & Sci

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“…Less work has been done to date on the role of processing on the polymer/clay structure [23][24][25]. Cho and Paul [23] examined PA6/clay nanocomposites prepared via melt compounding using a Haake intermeshing corotating twin screw extruder.…”

Section: Introductionmentioning

confidence: 99%

Nylon 66/clay nanocomposite structure development in a twin screw extruder

Lin

Thümen

Heim

et al. 2009

Polymer Engineering & Sci

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Nylon 66/clay nanocomposites were prepared in a Berstorff ZE25A UTX Ultra-glide corotating twin screw extruder at 2708C. Two types of extruder configurations with different mixing sections were used. One comprised two kneading block sections in the screws (KB only) and the other had a combination of a multiprocess-element (MPE) section and a kneading block section. Samples at eight different locations along the extruder screw were obtained and analyzed using scanning electron microscope and transmission electron microscope to examine the morphology development of clay inside nylon down the length of the extruder. It is found that the clay aggregates are quickly broken into smaller tactoids (micron size) and then even much smaller clay bundles (nanometer size) and single clay platelets in the first mixing section. The structure changes in the second mixing section are much less significant. X-ray diffraction (XRD) analysis of the nanocomposite products showed small, or disappearance of, characteristic XRD (001) peaks, which indicates partial exfoliation, or complete exfoliation,

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“…This pathway is so industrially favoured and has been used in this study. However it is to notice that in such processing, the conditions used play a very important role 10 . The nature of the clay, the organic cation selected as surfactant to compatibilize the clay with the matrix 11 , the characteristics of the polymer such as the molecular weight 12 strongly affect the dispersion of the clay.…”

Section: Introductionmentioning

confidence: 99%

Crossed characterisation of polymer-layered silicate (PLS) nanocomposite morphology: TEM, X-ray diffraction, rheology and solid-state nuclear magnetic resonance measurements

Samyn

Bourbigot

Jama

et al. 2008

European Polymer Journal

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ArticleCrossed characterisation of polymer layered silicate (PLS) nanocomposite morphology: TEM, X ray diffraction, rheology and solid state nuclear magnetic resonance measurements SAMYN, F, BOURBIGOT, S, JAMA, C, BELLAYER, S, NAZARE, S, Hull, T Richard, CASTROVINCI, A, FINA, A and CAMINO, G Available at http://clok.uclan.ac.uk/1134/ SAMYN, F, BOURBIGOT, S, JAMA, C, BELLAYER, S, NAZARE, S, Hull, T Richard, CASTROVINCI, A, FINA, A and CAMINO, G (2008) Abstract:As the nanocomposite properties dramatically depend on the dispersion state of the filler in the matrix, it is essential to develop technical methods to characterise the nanodispersion both qualitatively and quantitatively. In this study, complete characterisations of the nanodispersion of organomodified clays in polyamide 6, polypropylene and poly(butylene terephtalate) are presented and discussed using different analytical tools including X-ray diffraction and transmission electron spectroscopy and more original and quantitative measurements like rheology and solid state NMR measurements.

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Effect of melt processing conditions on the extent of exfoliation in organoclay-based nanocomposites

Cited by 934 publications

References 17 publications

Estimation of stresses required for exfoliation of clay particles in polymer nanocomposites

Estimation of stresses required for exfoliation of clay particles in polymer nanocomposites

Nylon 66/clay nanocomposite structure development in a twin screw extruder

Crossed characterisation of polymer-layered silicate (PLS) nanocomposite morphology: TEM, X-ray diffraction, rheology and solid-state nuclear magnetic resonance measurements

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