Dynamic rheological study of paraffin wax and its organoclay nanocomposites

Dynamic rheological data for paraffin wax and its organoclay nanocomposites are reported. Dynamic mechanical analysis of paraffin wax for temperatures ranging from -40 to 55°C showed a decrease of several orders of magnitude in the dynamic moduli and a significant shift toward viscous behavior, which resulted from the occurrence of two solid-solid phase transitions. In both the crystalline and mesophase regions, the dispersion of organoclay platelets in paraffin wax via ultrasonication increased the storage modulus, whereas the effect on the loss modulus was temperature-dependent. The melt rheology data of the wax-clay nanocomposites at 70°C showed that the complex viscosities increased monotonically with clay addition and demonstrated shear-thinning behavior for frequencies between 0.1 and 100 rad/s. The complex viscosity versus angular frequency data were well fit by a power-law function for which the shear-thinning exponent provides a gauge for the extent of clay exfoliation. The nanocomposites exhibited low-frequency solid behavior, which indicated good exfoliation of the organoclay in the wax matrix.