Polymer/layered silicate nanocomposites: a review from preparation to processing

Single-walled carbon nanotube (SWNT)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared via our coagulation method providing uniform dispersion of the nanotubes in the polymer matrix. Optical microscopy, Raman imaging, and SEM were employed to determine the dispersion of nanotube at different length scales. The linear viscoelastic behavior and electrical conductivity of these nanocomposites were investigated. At low frequencies, G‘ becomes almost independent of the frequency as nanotube loading increases, suggesting an onset of solidlike behavior in these nanocomposites. By plotting G‘ vs nanotube loading and fitting with a power law function, the rheological threshold of these nanocomposites is ∼0.12 wt %. This rheological threshold is smaller than the percolation threshold of electrical conductivity, ∼0.39 wt %. This difference in the percolation threshold is understood in terms of the smaller nanotube−nanotube distance required for electrical conductivity as compared to that required to impe...

Nanotube Networks in Polymer Nanocomposites: Rheology and Electrical Conductivity

Reḿi Auvergne,† Sylvain Caillol,† Ghislain David,*,† Bernard Boutevin,† and Jean-Pierre Pascault‡,§ †Institut Charles Gerhardt UMR CNRS 5253 Laboratoire Ingeńierie et Architecture Macromolećulaire, Ecole Nationale Supeŕieure de Chimie de Montpellier, 8 rue de l’Ecole Normale, 34296 Montpellier Cedex 05, France ‡INSA-Lyon, IMP, UMR5223, F-69621, Villeurbanne, France Universite ́ de Lyon, F-69622, Lyon, France

Biobased thermosetting epoxy: present and future.

Vegetable oils are excellent but very heterogeneous renewable raw materials for polyols and polyurethanes. This review discusses the specific nature of vegetable oils and the effect of their structures on the structure of polyols and polyurethanes. One section is dedicated to polyols for rigid and flexible foams and methods of their preparation such as direct oxidation of oils, epoxidation followed by ring opening, hydroformylation, ozonolysis, and transesterification. The next section deals with preparation and structure‐property relationships in polyurethanes from different groups of polyols, different isocyanates, and different degrees of crosslinking. The final section covers the environmental aspects of bio‐based polyurethanes, i.e., thermal stability, hydrolytic stability, and some aspects of biodegradability.

Polyurethanes from Vegetable Oils

https://cyberleninka.org/article/n/397502.pdf

Melt rheology of organoclay and fumed silica nanocomposites

A correlation between morphology development and rheology of polystyrene nanocomposites based upon organophilic layered silicates (organoclay) such as fluoromicas was found as a function of the silicate modification Organoclay was obtained by means of ion exchange of clay with protonated amine-terminated polystyrenes with molar mass of Mn = 121 and 5 800 g/mol Only when applying shear forces during melt compounding of organoclay modified with high molar mass polystyrene (PS), individual silicate platelets of 1 nm diameter and 600 nm length were obtained Dispersions of such in-situ formed nanoparticles with aspect ratio of 600 accounted for unique elastic properties observed in the low frequency range of the dynamic modulus, whereas organoclay modified with low molecular PS did not exfoliate and exhibited rheological behavior very similar to that of conventional fillers

Morphology and rheology of polystyrene nanocomposites based upon organoclay

A wide variety of polymer nanocomposites exhibiting novel property combinations were obtained via in-situ formation of silicate nanofillers during polymerization and processing. Key intermediates were tailor-made silicates which were rendered organophilic by means of cation exchange and exfoliated upon applying shear forces. As a function of organophilic modification, interfacial coupling, and processing conditions it was possible to control nanostructure formation and to improve thermal and mechanical properties such as toughness/stiffness balance, heat distortion temperature, and flame retardency. Basic structure/property correlations were established for nanocomposites based upon in-situ nanofillers and polymers such as polystyrene, polyamide 12, polypropylene, polymethylmethacrylate, polyurethane, and epoxy resins.

Nanofillers based upon organophilic layered silicates

Novel families of flexible, semiflexible and rigid crosslinked polyesters were prepared from modified natural oils such as soybean, rape-seed and linseed oil. Maleinated oils were used as anhydride-functional curing agents of epoxy resins such as bisphenol-A-diglycidylether and epoxidized natural oils. A new class of unsaturated polyester resins was based upon maleic anhydride, epoxidized natural oils and styrene. The resulting thermosetting polyesters were reinforced with natural fibers such as hemp and flax fibers. The influence of molecular architectures, curing conditions and formulations on thermal, mechanical and morphological properties were investigated.



Aus modifizierten Pflanzenolen, wie Sojabohnen-, Raps- und Leinol, wurden neue Familien flexibler, semiflexibler und starrer Polyesternetzwerke hergestellt. Maleinierte Ole wurden als anhydridfunktionelle Harter von Epoxyharzen wie Bisphenol-A-diglycidylether und epoxidierter Pflanzenole eingesetzt. Eine neue Klasse ungesattigter Polyesterharze (UP) basiert auf Maleinsaureanhydrid, epoxidierten Pflanzenolen und Styrol. Die hergestellten Polyesterduromeren wurden mit naturlichen Fasern wie Flachs und Hanf verstarkt. Untersucht wurde der Einflus von molekularem Aufbau, Hartungsbedingungen und Formulierungen auf die thermischen, mechanischen und morphologischen Eigenschaften.

Polyester networks based upon epoxidized and maleinated natural oils

Nanocomposites based on polystyrene (PS) and organophilic layered silicates (organoclays) were prepared and characterised with respect to their morphological and rheological properties. The organoclays were obtained by means of ion exchange of clay with protonated, amine-terminated PS. Two different exchange agents - a high (M w = 5 800 g/mol) molecular mass amine functionalised PS, and 2-phenylethylamine - were used to study the influence of their molecular weight on morphological and rheological properties of corresponding composites. Wide-angle X-ray scattering measurements show a significant increase in the interlayer spacing upon the ion exchange. Composites of organoclay prepared from the high molecular mass amine-terminated PS and PS-matrix polymer reveal a fine and stable dispersion of exfoliated silicate layers in the PS matrix if the compounding time in a conical twin screw extruder exceeds 180 s at a temperature of 200°C. This composite, i.e. nanocomposite, shows unique elastic properties which can be understood quantitatively if one assumes that above a characteristic concentration of about 1 vol.-% percolating strands of platelets are present in the material. Composites of PS and organoclay prepared from 2-phenylethylamine did not exfoliate and consequently exhibited the rheological behaviour of a conventional composite. Qualitatively all morphological and rheological features of the PS nanocomposite can be entirely understood if one considers this material as a mixture of hairy platelets dispersed in an entangled PS matrix.

Viscoelastic Properties of Polystyrene Nanocomposites Based on Layered Silicates

This contribution is concerned with the unique rheological properties of blends of liquid crystalline polymers (LCP) dispersed in thermoplastic matrices. The materials under investigation were rigid rod polyesters solution blended with poly(e-caprolactone), polypropene, polystyrene or poly(methyl methacrylate) as matrix polymers. Oscillatory measurements of these melted blends revealed that LCP contents of only 1 wt.-% cause the dynamic shear moduli to increase at low frequencies by a factor of several magnitudes compared to the neat matrices. The extraordinary effect is primarily governed by a spatial arrangement of the LCP molecules forming a network as shown by microscopy. The different strength of this effect in different matrices is explained by the interaction between matrix and LCP.

Botho Hoffmann

Papers

Morphology and rheology of polystyrene nanocomposites based upon organoclay

Nanofillers based upon organophilic layered silicates

Polyester networks based upon epoxidized and maleinated natural oils

Viscoelastic Properties of Polystyrene Nanocomposites Based on Layered Silicates

Rheological and Morphological Properties of Various Blends Containing Liquid Crystalline Polyesters