In-Vitro Wear Determination & Mechanical Properties of Glass-Ionomer Clay Nanocomposites

OBJECTIVES:  The dispersion of nanoclays in poly(acrylic acid) has been employed to achieve novel formulations of glass-ionomer clay nanocomposites with enhanced properties. This paper presents the wear rates, hardness data and mechanical properties of experimental and a commercial GIC.

METHODS:  Polymer solutions were prepared by dispersing nanoclays (0%, 1%, 2% and 4% w/w) in water and adding 40% w/w of poly(acrylic acid) powder via a consistent heating and stirring process. The experimental cements were prepared using HiFi glass-powder. Fuji-IX was the reference cement.  A reciprocating wear tester (ASTM G133-02) used to produce a wear-facet, which was examined with optical and scanning electron microscope.  The hardness of cements was quantified by a Vickers-hardness test (HV03).  20 specimens from each type of cements were tested for Compressive-strength (CS), Diametral-tensile strength (DTS) and Flexural-strength (FS) at 1hr, 1day, 1week and 1month.  

RESULTS:  A comparison of wear rate of cements is presented in Figure1, although no significant differences in terms of the wear rate after clay exfoliation were observed. However, 1% and 2% nanoclay addition indicates an improvement in wear for all cements. The microhardness of cements shown in Table 1 is calculated between 62-89 HV. ANOVA and t-test at a level of (P<.005) was used for statistical significance of CS, DTS and FS data and the highest values were found for the specimens with 1% and 2% nanoclays (162 MPa for CS, 19.5 MPa for DTS and 32 MPa for FS) for different time periods and were statistically higher than the control and reference group.

CONCLUSIONS: The use of nanoclays offers the potential to improve the properties of conventional glass-ionomer systems, however  in order to achieve more remarkable improvement further studies need to be carried out towards an understanding of the dispersion mechanism and optimization of the novel system.

Figure-1

Table-1