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

A review on polymer–layered silicate nanocomposites

Recently, polymer nanocomposites reinforced with lower volume fraction of nanoceramics and carbon nanotubes have attracted steadily growing interest due to their peculiar and fascinating properties as well as their unique applications in commercial sectors. The incorporation of nanoceramics such as layered silicate clays, calcium carbonate or silica nanoparticles arranged on the nanometer scale with a high aspect ratio and/or an extremely large surface area into polymers improves their mechanical performances significantly. The properties of nanocomposites depend greatly on the chemistry of polymer matrices, nature of nanofillers, and the way in which they are prepared. The uniform dispersion of nanofillers in the polymer matrices is a general prerequisite for achieving desired mechanical and physical characteristics. In this review article, current development on the processing, structure, and mechanical properties of polymer nanocomposites reinforced with respective layered silicates, ceramic nanoparticles and carbon nanotubes will be addressed. Particular attention is paid on the structure–property relationship of such novel high-performance polymer nanocomposites.

Structural and mechanical properties of polymer nanocomposites

A new epoxy-based ink is reported, which enables 3D printing of lightweight cellular composites with controlled alignment of multiscale, high-aspectratio fiber reinforcement to create hierarchical structures inspired by balsa wood. Young's modulus values up to 10 times higher than existing commercially available 3D-printed polymers are attainable, while comparable strength values are maintained.

3D-Printing of Lightweight Cellular Composites

Biobased plastics and bionanocomposites: Current status and future opportunities

Intercalated nanocomposites of modified montmorillonite clays in a glassy epoxy were prepared by crosslinking with commercially available aliphatic diamine curing agents. These materials are shown to have improved Young's modulus but corresponding reductions in ultimate strength and strain to failure. The results were consistent with most particulate-filled systems. The macroscopic compressive behavior was unchanged, although the failure mechanisms in compression varied from the unmodified samples. The fracture toughness of these materials was investigated and improvements in toughness values of 100% over unmodified resin were demonstrated. The fracture-surface topology was examined using scanning electron and tapping-mode atomic force microscopies and shown to be related to the clay morphology of the system. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1137–1146, 2001

Intercalated clay nanocomposites: Morphology, mechanics, and fracture behavior

PMMA-layered silicate intercalated nanocomposites are synthesized using supercritical carbon dioxide (scCO2) to produce ordered materials with significant levels of reinforcement. The scCO2 is used to homogeneously distribute monomer as well as act as a low-viscosity solvent for MMA polymerization. This route allows for synthesis of nanocomposites containing significant levels of organically modified layered silicates (OMLS). Below 40 wt % OMLS, the intercalated nanocomposites exhibit a d spacing commensurate with dimensions of the fully extended surfactant chains. Above 40 wt % OMLS, the composite volume is saturated with inorganic material, and the d spacing decreases to homogeneously distribute the polymer volume. A model for estimating this transition concentration is presented. At concentrations approaching the homogeneously intercalated morphology, the basic mechanical and physical properties of the composite are investigated.

Highly concentrated, intercalated silicate nanocomposites: Synthesis and characterization

Amine-cured epoxy resins are prepared containing an aliphatic phosphonate additive which aids in the processing of the epoxy by reducing the viscosity of the resin mixture. The additive also acts as an antiplasticizer in the cured epoxy by increasing the modulus and yield strength under uniaxial tension and compression. Additionally, phosphonates are known to behave as flame retardants and dimethyl methyl phosphonate (DMMP) demonstrates a reduction in the rate of thermal degradation and the heat-release rate upon pyrolysis. Addition of the antiplasticizer reduces the Tg and suppressed β-relaxations, while effectively increasing the density of the material. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 302–309, 2002; DOI 10.1002/app.10329

Organophosphorous additive for fortification, processibility, and flame retardance of epoxy resins

Intercalated nanocomposites of modified montmorillonite clays in a glassy epoxy were prepared by crosslinking with commercially available aliphatic diamine curing agents. These materials are shown to have improved Young’s modulus but corresponding reductions in ultimate strength and strain to failure. These results are consistent with most particulate filled systems, The macroscopic compressive behavior is unchanged, although the failure mechanism in compression varies from the unmodified samples. The fracture toughness of these materials is investigated and improvements in toughness values of 200% over unmodified resis are demonstrated. The fracture surface topology is examined using SEM and tappin-mode AFM and showm to be related to the clay morphology of the system.

Intercalated clay nanocomposites: Morphology, mechanics and fracture behavior

A new class of molecular additives is investigated for epoxy-based crosslinked polymers. These additives are shown to increase modulus and yield stress in the cured networks. In order to elucidate the mechanisms for reinforcement of epoxy thermosets, the effects of additive chemistry and network architecture are considered. Both model and commercial epoxy networks are studied, thereby probing the effect of molecular weight between crosslinks, Mc, on reinforcement. Additionally, the family of phosphates being studied ranges in molecular weight, solubility parameter and density. These parameters are demonstrated to strongly influence the degree of reinforcement and correlate with the ability of the additive to reduce mobility of the polymer network. Mechanisms of reinforcement are discussed. Polym. Eng. Sci. 44:2125–2133, 2004. © 2004 Society of Plastics Engineers.

Adam S. Zerda

Papers

Intercalated clay nanocomposites: Morphology, mechanics, and fracture behavior

Highly concentrated, intercalated silicate nanocomposites: Synthesis and characterization

Organophosphorous additive for fortification, processibility, and flame retardance of epoxy resins

Intercalated clay nanocomposites: Morphology, mechanics and fracture behavior

Characteristics of antiplasticized thermosets: Effects of network architecture and additive chemistry on mechanical fortification