Quantification Limits of Phase Inversion Boundaries in Recycled Olefin Compound Fractions
Phase inversion boundaries in recycled olefin fractions shift with shear rate, necessitating combined dynamic rheology and thermal analysis for domain sizing.
Palierne Viscoelastic Model
Meaning
Mathematical descriptions of the viscoelastic properties of multi-phase polymer melts relate the macroscopic flow behaviour to the microscopic droplet geometry. For immiscible polymer blends, the Palierne viscoelastic model predicts the dynamic storage and loss moduli based on the properties of the individual components and the interfacial tension. This approach treats the melt as an emulsion of deformable droplets dispersed within a continuous matrix.
Model Equation
Rheological measurements at low frequencies show a characteristic relaxation peak that corresponds to the shape recovery of deformed droplets. Through the Palierne viscoelastic model, compounding engineers can estimate the average droplet size by analyzing this relaxation behaviour. This calculation utilizes the shear moduli of the matrix and the dispersed phase alongside the interfacial tension.
Compounding Application
Tuning the dispersion of recycled polymer blends requires a reliable method for evaluating interface quality. The Palierne viscoelastic model helps in determining the effectiveness of added compatibilizers, which reduce the interfacial tension and stabilize the morphology. This modeling enables the optimization of mixing times during the melt extrusion process.
Prediction Limitation
Theoretical predictions of melt behavior often assume a narrow droplet size distribution and small deformations. The Palierne viscoelastic model holds true only when the strain amplitude is kept low enough to remain within the linear viscoelastic region. When the blend exhibits high concentrations of the dispersed phase or a co-continuous structure, the model loses its predictive accuracy.
Users must apply alternative rheological models to analyze these highly concentrated polymer systems.