Effect of TiO2 on extrusion stability

The residence time of an extrusion coating formula in an extruder causes degradation of the material as shown by changes in its molecular weight (Mn and Mw) values and in its molecular weight distribution(MWD). Fillers (TiO2, etc) enhance these changes. To follow these changes by conventional Gel Permeation Chromatography (GPC) analysis is both time consuming and costly (columns and refractive index detectors are quickly damaged by fillers). The changes can be followed by rheological measurements: namely the crossover point between the Loss Modulus (G '') and the Storage Modulus (G') and the variation in the complex viscosity vs. frequency curves seen in the Rotational Mechanical Spectrometer (RMS) curves, the variations in the viscosity vs. shear rate curves seen in the Capillary Extrusion Rheometer (ICER) curves, and by the shifts in the Dynamic Mechanical Thermal (DMTA) curves.