Effect of nanoclay dispersion on the properties of a commercial glass ionomer cement

Abstract

Objective. The reinforcement effect of polymer-grade montmorillonite (PGV and PGN nanoclay) on Fuji-IX glass ionomer cement was investigated. Materials and Method. PGV and PGV nanoclays (2.0 wt%) were dispersed in the liquid portion of Fuji-IX. Fourier-transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) were used to quantify acid-base reaction and the liquid portion of GIC. The mechanical properties (CS, DTS, FS, and E f ) of cements (n = 20) were measured at 1 hour, 1 day, and 1 month. The microstructure was examined by cryo-SEM and TEM. Results. FTIR shows that the setting reaction involves the neutralisation of PAA by the glass powder which was linked with the formation of calcium and aluminium salt-complexes. The experimental GICs (C-V and C-N) exhibited mechanical properties in compliance to ISO standard requirement have higher values than Fuji-IX cement. There was no significant correlation of mechanical properties was found between C-V and C-N. The average Mw of Fuji-IX was 15,700 and the refractive index chromatogram peak area was 33,800. TEM observation confirmed that nanoclays were mostly exfoliated and dispersed in the matrix of GIC. Conclusion. The reinforcement of nanoclays in GICs may potentially produce cements with better mechanical properties without compromising the nature of polyacid neutralisation.

Figure 1

The custom made Wilson's oscillating rheometer.

Figure 2

FTIR spectra of Fuji-IX liquid (FL) and solutions formed after dispersion of 2 wt% PGV and PGN nanoclays in FL.

Figure 3

Real time FTIR analysis of the setting reaction of F-IX cement (a) and C-V cement (b) at different time intervals for one hour.

Figure 4

GPC plot showing the molecular weight distribution of FL.

Figure 5

Cryo-SEM micrographs of the fractured surface of GIC at various magnifications demonstrating (a) micrograph at lowest magnification (×250) showing the absence of the cracks and ((b), (c), (d)) micrographs at high magnifications (×1998 and ×3997) indicating the presence of pores, glass particles, and the matrix phase of GIC.

Figure 6

TEM micrographs of Fuji-IX cement after the dispersion of 2% nanoclay in liquid portion (C-N) showing the interaction of nanoclays within GIC system, ((a) and (b)) at lower magnification and (c) at higher magnification indicating remnant glass core (G), nanoclay (N), siliceous hydrogel layers around the periphery of glass filler core (H), cement matrix (M), and fully reacted hydrogel within the matrix (white bold arrow).