Measurement and Correlation of Rheological Properties of Molten Plastics and Their Blends
The non-Newtonian rheological properties of plastic melts are critical for regulating plastic processing, molding, and recycling processes, ensuring processing stability and product performance. However, rheological data for commonly used plastics and their blends remain incomplete. This study combined experimental testing and theoretical modeling to investigate the rheological behaviors of four pure plastics—polypropylene (PP), polyethylene (PE), polystyrene (PS), and acrylonitrile-butadiene-styrene copolymer (ABS)—and three binary blend systems: PE/ABS, PP/ABS, and PS/ABS. Rheological tests were conducted using a rheometer over a shear rate range of 0.1–100 s⁻¹ and temperatures from 180°C to 250°C. Results showed that the flow behavior index n was less than 1 for all samples, and apparent viscosity decreased significantly with increasing shear rate, indicating clear shear-thinning behavior. The consistency coefficient K followed the Arrhenius relationship with temperature, and melt viscosity decreased as temperature increased. The study quantitatively characterized the relationship between the mass fraction m (0.5 < m ≤ 1) of the main component in binary blends and melt viscosity. Based on experimental data, a component correction term was introduced into the traditional power-law model to construct a constitutive equation that simultaneously describes the effects of shear rate, temperature, and component fraction on melt viscosity. The average relative error between model predictions and experimental values was only 5.90%. These rheological data and the modified constitutive equation provide important theoretical support and data reference for optimizing process parameters in waste plastic recycling and injection molding.