Polymethylmethacrylate–montmorillonite composites: preparation, characterization and properties

The objective of this work was directed to solve a problem of polymerization shrinkage in acrylic resin polymethylmethacrylate (PMMA) material. Organophilic montmorillonite (claytone) was added up to 1% by weight to one commercial type of PMMA powder to form PMMA–MMT composite. Acrylic specimens were processed by the conventional heat curing method following manufacturerʹs instructions. Thermogravimetric analysis data indicates that polymer–clay composites exhibit significant increase in thermal stability with very small amount of inorganic content. The morphology of the composites was verified using scanning electron microscopy revealing the absence of large mineral aggregates. Interlamellar spacing was measured from wide angle X-ray diffraction. The d(001) spacing of clay was expanded to 18 Å in claytone and the intensity of the peaks is progressively reduced with increasing the concentration of polymer in the composites samples. Warpage and linear dimensional change measurements were achieved using ‘traveling microscope’ and one way analysis of variance was employed to compare results. The results indicated that there was a significant decrease of warpage and linear dimensional changes between PMMA specimens and that of PMMA–MMT composite materials.