Properties Of Nanocomposite Foams Research Articles

Revealing the Combined Nanoconfinement Effect by Soft and Stiff Inclusions in PMMA/Silica CO2 Blown Foams

AbstractThis 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.

Rheology and foaming behaviour of styrene–ethylene–butylene–styrene nanocomposites

The dependence of the foaming behaviour of a polymeric material on its material characteristics and foaming temperature gives rise to the research question that how the degree of dispersion/distribution of nanoparticles and the resulting viscosity changes affect the foaming behaviour and properties of nanocomposite foams. In the study reported here, styrene–ethylene–butylene–styrene was selected as a model polymer, because of its complex microstructure and its commercial importance. Styrene–ethylene–butylene–styrene nanocomposites, with different nanoclay loadings, were processed in a twin-screw extruder. The nanocomposite structure was correlated with the rheological properties to evaluate the batch-foaming performance of nanocomposite using carbon dioxide at different temperatures. At 35 °C, selective foaming of the elastomeric phase, hindered by the stiff polystyrene phase, resulted in foams with more than 74% shrinkage. At 80 °C, higher viscosities and moduli resulted in foams with higher volume expansion ratios. Increases in the degree of delamination of silicate layers in nanocomposites resulted in cell sizes up to 41% and 75% lower than that of neat polymer foams produced at 35 °C and 80 °C, respectively. Dynamic mechanical analysis results suggest heterogeneous nucleation and the presence of nanoclay in both phases. The study results show that the nanocomposite structure plays an important role in the production of thermoplastic elastomer foams of superior morphology and low shrinkage.

Using the Mass Method to Produce PVC/Clay Nanocomposite Foams: The Effect of Nano-clay and Foaming Conditions on Density and Cell size

Nanocomposite foams contain very fine cells because of the fillers in nano scale. Due to the limited size of the cells, the mechanical and physical properties of nanocomposite foams are improved compared to polymer foams. In this study PVC/clay nanocomposite foams containing various concentrations of nano-clay (1, 3 and 5 phr) were successfully prepared. The samples were placed under CO2 gas pressure at 5 MPa, by immersing in glycerin bath at 60, 70, 80 °C and 20, 30, 40 s, respectively, to form foams. The density and the cell size as a factor of nano-clay content, foaming time and temperature were investigated using Archimedes method and scanning electron microscopy, respectively. The minimum density was obtained in the sample containing 1 phr nanoclay prepared at 80 °C and 40 s. The minimum cell size was related to the sample containing 5 phr nanoclay at 60 °C and 20 s.

Probing Nanodispersions of Clays for Reactive Foaming

Nanodispersions of clays in polyurethane components have been prepared. Nanoclays (both natural and organically modified) of various aspect ratios are used. The fillers are dispersed separately in polyurethane components, viz., polyol and polyisocyanate. The nanodispersions are characterized by the combined use of solution rheology, X-ray scattering, cryo-electron microscopy, and IR spectroscopy. Reactive foaming of these nanodispersions is carried out to make polyurethane nanocomposite foams. The status of the dispersion of fillers in components and in foams has been compared to investigate the effect of the foaming process in exfoliation. Interpretation of the results from different characterization techniques describes the state of the dispersion of fillers in components and in foam. The rheological and physicochemical behaviors of nanodispersions are shown to have a significant influence on the properties of nanocomposite foams.