Investigation of the stiffness and yield behaviour of melt-intercalated poly(methyl methacrylate)/organoclay nanocomposites: characterisation and modelling.

The elastic modulus and yield stress behaviour of a melt intercalated Poly(methylmethacrylate)/ organoclay (PMMA/C30B and PMMA/C20A) were studied using uniaxial tensile tests at different temperatures and different strain rate. The stress-strain response was obtained for different loading rates and different test temperature. Both the stiffness and the yield stress were then clearly identified as function of strain rate and temperature. Our experimental results show that the yield stress and modulus of both PMMA/C20A and PMMA/C30B organoclay nanocomposites are very sensitive to clay concentration, strain rate and temperature. A micromechanically-based composite approach was used to predict the yield stress of both PMMA/C20A and PMMA/C30B organoclay nanocomposites. The results obtained from the model are in good agreement with our experimental results. As expected, the activation enthalpy of cooperative model increased slightly while the activation volume decreases slightly with the clay concentration.

Preparation, structural characterization, and thermomechanical properties of poly(methyl methacrylate)/organoclay nanocomposites by melt intercalation.

Poly(methyl methacrylate) (PMMA) based nanocomposites were synthesized by melt intercalation technique using organoclays (Cloisite 30B and Cloisite 20A) as fillers. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to determine the dispersion and the morphology of the nanocomposites obtained. Thermomechanical tests including tensile test and dynamic mechanical analysis (DMA) were used to evaluate the Young's modulus, storage modulus and the glass transition temperature. Thermogravimetric analysis (TGA) is conducted on the poly(methyl methacrylate) based nanocomposites to determine their thermal stability. The effect of filler content is studied by considering samples with filler contents varying from 1 to 5 wt%. The mechanical properties obtained from the tensile tests show an increase in the Young's modulus and a decrease in the strain to failure as function of the nanoclays concentration. Relative to the pure poly(methyl methacrylate), the dynamic mechanical analyses show an increase in the storage modulus and the glass transition temperature of both nanocomposites. The thermogravimetric analysis shows an increase of the thermal stability of both nanocomposites.