METHODS: To develop a better understanding of the nanoclay dispersion mechanism in poly-acrylic acid (PAA), XRD, XPS, FTIR and Raman spectroscopy were performed. The mechanical properties of the new cements namely compressive-strength (CS), diametral-tensile strength (DTS), flexural-strength (FS), flexural modulus (Ef) and Vickers Hardness (HV) were determined. Wear studies were performed using reciprocation wear test and OHSU wear simulator.
RESULTS: The interlayer space of nanoclays (d001) increased to 18.83Å indicating exfoliation of nanoclays in PAA. XPS showed that Si-O-Al linkages can be identified. Furthermore, the lack of the Na peak confirmed the Na ions interactions with PAA. ANOVA and t-test of CS, DTS and FS data were not statistically different (P>0.05) than the control but average values for CS, DTS and FS of 1% and 2% nanoclay containing cements were higher. The HV of cements were calculated around 62-89 HV. OHSU wear test suggested a significant difference (P<0.013) of total wear volume and total wear depth (P<0.019) of cements with 4% nanoclay content, however 1% and 2% nanoclay containing cements were not different from the control (P>0.05).
CONCLUSIONS: Inclusion of clays can improve the GIC system. In most cases 1% of nanoclay content was enough to improve CS, DTS and FS, however the improvement was not as much as expected suggesting that exfoliation of nanoclays in the polymer liquid does not result in significant improvement of the mechanical properties. The wear resistance on the other hand was also not improved by the addition of nanoclays but the 1% nanoclay containing cements showed not significant changes compared to the control samples.