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

http://staff.ulsu.ru/moliver/ref/polymers/pott11.pdf

Graphene-based polymer nanocomposites

A review on polymer–layered silicate nanocomposites

https://cyberleninka.org/article/n/768408.pdf

Mechanical properties of graphene and graphene-based 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

This study shows the importance of nanoparticle (NP) spatial arrangement on the nucleation, morphology, and properties of nanocomposite foams. It probes CO2 blown PMMA with three types of nanosilica structures with exactly the same chemical composition: aggregates, chain bound clusters, and individually dispersed NPs. A systematic but nontrivial scaling of morphology, glass transition temperature, static and impact mechanical properties, and thermal conductivity is discussed with special regard to the combined nanoconfinement by soft and stiff inclusions. The presented results suggest a limited potential of simultaneous toughening by nanoreinforcement and shear banding, which can draw significant implications for both the fundamental science and industrial practice dealing with nanoreinforced cellular materials. 

Revealing the Combined Nanoconfinement Effect by Soft and Stiff Inclusions in PMMA/Silica CO
 2
 Blown Foams

An alternative route to prepare polymer-clay nanocomposites using supercritical carbon dioxide (scCO2) is described. The presence of clay nanoparticles significantly influences the morphology, foaming process and crystallization of a polymer when processed in scCO2. Intercalated structures are successfully produced in the presence of scCO2 even when favorable interactions between the polymer and the clay are not present. The effect of scCO2 on the intercalation process is analyzed for a variety of polymer systems both with modified and unmodified clays. By controlling the hydrophilicity of the polymer and clay systems, specific understanding of the effect of scCO2 on the structure and morphology of the nanocomposites is obtained. Experimental results show significant increases in the clays d-spacings for scCO2-treated samples. This behavior is consistent regardless of the nature of the polymer, showing significant amounts of intercalation even in purely hydrophobic polymers.

Intercalated polymer nanocomposites prepared in supercritical carbon dioxide.

Combining Mechanical Fortification and Ultralow Flammability in Epoxy Networks

The drawing behavior and mechanical properties of as-spun and highly oriented nylon 66 fibers drawn in supercritical carbon dioxide (SCCO2) were investigated. Conditions including different temperatures, CO2 pressures, and plasticizers with different polarity were systematically studied. Results indicate that CO2 is an efficient plasticizer for as-spun nylon 66 fibers as shown by decreases in the draw stress. In contrast, CO2 shows only a slight influence on the drawability of highly oriented nylon 66 fiber. The effect of other plasticizers such as water, methanol, and ethanol on the drawability of nylon 66 fibers is very similar to that of CO2. Tenacity and modulus of one-stage drawn fibers were less than 0.8 and 5.0 GPa, respectively. Fibers with the highest tenacity and modulus, 0.96/5.04 and 1.06/5.04 GPa, were obtained by two-stage drawing in SCCO2 from as-spun and drawn nylon 66 fibers, respectively. The main reason for the extremely low draw ratios (<6.0) of nylon 66 fibers was the presence of hydrogen bonds in the crystalline phase. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2282–2288, 2004

Influence of interchain forces and supermolecular structure on the drawing behavior of nylon 66 fibers in the presence of supercritical carbon dioxide

In certain fire situations, a structural or load-bearing polymer matrix composite (PMC) may be exposed to excessive thermal loads that degrade the matrix. In this paper, we report the results of a study to assess the utility of ultrasonic spectroscopy as a means of assessing the residual physical and mechanical characteristics of PMCs exposed to excessive thermal loads. We show that the measured power spectra of ultrasonic energy correlates with performance of graphite fiber epoxy matrix composites exposed to thermal degradation. Unidirectional composites were exposed to short term-high intensity thermal loads at one end of the specimen. Thus, inducing a thermal gradient along the length of the specimen. Simultaneous thermogravimetric analysis - differential scanning calorimetry (TGA/DSC) and Fourier transform infrared spectroscopy (FTIR) analysis of the aged specimens revealed a gradient in thermal degradation. The thermal loads induced substantial degradation of the composite. However, the amplitude of the power spectra is observed to increase gradually then sharply prior to its complete attenuation due to delaminations. Mode I fracture toughness tests correlate with the observed changes in the ultrasonic spectra. FTIR, TGA/ DSC, fracture toughness, and ultrasonic spectral analysis all indicate the same critical temperature at which thermally induced damage sharply increased.

Alan J. Lesser

Papers

Revealing the Combined Nanoconfinement Effect by Soft and Stiff Inclusions in PMMA/Silica CO 2 Blown Foams

Intercalated polymer nanocomposites prepared in supercritical carbon dioxide.

Combining Mechanical Fortification and Ultralow Flammability in Epoxy Networks

Influence of interchain forces and supermolecular structure on the drawing behavior of nylon 66 fibers in the presence of supercritical carbon dioxide

Evaluation of short term-high intensity thermal degradation of graphite fiber reinforced laminates via ultrasonic spectroscopy