Assessment of Mixing Efficiency of Intermeshing Rotor Mixers on Morphological and Mechanical Properties and Crosslink Density of Dynamically Vulcanized EPDM/PP Blends

The mixing efficiency of intermeshing rotor internal batch mixers for the preparation of rubber-rich thermoplastic vulcanizates (TPV) based on ethylene propylene diene terpolymer (EPDM) and polypropylene (PP) blends was investigated. Two laboratory scale mixers, namely intensive batch mixer (INS) and kneader batch mixer (KND), were used. The mixer choice at controlled mixing conditions was investigated to determine its effects on morphological and mechanical properties and crosslink density of the prepared EPDM/PP TPVs. Such effects were found on the degradation of the polymer, on the distribution of the EPDM phase in the blend morphology, particularly the size of EPDM inclusion, and on the crosslink density of the EPDM phase. In summary, the different mixing efficiencies of INS and KND type mixers affect the EPDM/PP TPVs and their properties. Also, the INS mixer has higher mixing efficiency than the KND mixer.

ANALYSIS AND MODELING OF AN EXPERIMENTAL DEVICE BY FINITE-TIME LYAPUNOV EXPONENT METHOD

In this paper, we investigate the transport and mixing process of the batch mixers with two different configurations, the centered-blade and offset-blade mixers, by using a dynamical system approach. The 2-D velocity fields of the mixers measured using Particle Image Velocimetry (PIV) are used to identify the Lagrangian coherent structures (LCSs). The results show that the LCSs separate the physical space into two portions. In the case of the center-blade mixer the portion bounded inside the LCS experiences a relatively slow mixing relative to the portion outside of the LCS boundary. However, when the blade position is located near the wall, the LCS becomes more complicated but it still separates regions of fast mixing from a slower one. We develop a heuristic dynamical system model of our mixers to understand how the vorticity strength at the blade tips influences the variation of the LCSs. Finally, we define an appropriate notion of mixing to study the mixing rate of our mixing devices.

Analysis of Power Requirements and Dispersion Quality in Batch Compounding Using a Dispersion Model for Single Agglomerates

The extent of dispersion and torque requirements vary with processing time during the compounding of filled polymers in batch mixers. Starting with a model for the erosion of single agglomerates under simple shear flow conditions, equations have been developed that enable correlation and prediction of the evolution of both dispersion quality and mixing torque during the course of processing. There was an excellent agreement between the shape of predicted dimensionless torque curves and experimental results for silica-silicone rubber premixes. The model was also found useful in correlating results reported in the literature for the quality of dispersion of carbon black into natural rubber.