Influence of clay type on exfoliation, cure and physical properties of in situ polymerised poly(methyl methacrylate) nanocomposites

The nature of the dispersion of clay platelets in a resin composite will play an important role in the process of enhancement of the physical properties of that material. This paper examines how different modifiers and the quantity of surface treatment for the Cloisite range of organically modified clays affect properties in situ polymerised poly(methyl methacrylate). Another clay which is a mixture of rod- and platelet-like minerals is also investigated to understand how the shape of the clay particles can affect the polymer properties. Five different clays, including Cloisite 30B and Cloisite 15A, were dispersed using ultrasound and the cure of the samples was monitored using the Strathclyde Rheometer. Rheology, transmission electron microscopy and X-ray diffraction were used to determine that a good level of clay dispersion was achieved. The mixed mineral formed the most stable dispersion seen from settling tests. The cure accelerated in the presence of organo clay, although the affect was less pronounced at higher temperatures. The glass transition temperature was increased by 20 ◦C with only a few weight percent of clay and water uptake was not adversely affected.