Meaning
Constitutive equation used in rheology to describe the viscoelastic behavior of polymer melts under complex flow conditions. The extended phan-thien-tanner model accounts for the non-linear relationship between stress and strain rate, which is common in branched polymers. It provides a mathematical framework for predicting how a material will flow through a die or into a mold cavity.
Flow Prediction
Simulation software utilizes this model to identify potential areas of melt instability or high shear stress. By characterizing the relaxation times and viscosity of a resin, the model helps engineers design tooling that minimizes internal stresses. Predicted flow patterns allow for the adjustment of cooling channels to prevent warping in the final part.
Engineers rely on these results to optimize the gate placement in complex injection molds.
Design Optimization
Accuracy in predicting die swell is one of the primary benefits of using this specific rheological description. It allows for the precise sizing of extrusion dies to achieve the target profile dimensions. Fewer tool iterations are required to reach a final part geometry.
Rheological Precision
Parameters within the equation are derived from experimental data such as shear and extensional viscosity measurements. Unlike simpler models, the physics of chain disentanglement and stretching are captured. Detailed calculations are necessary for high-precision molding where dimensional tolerances are tight.
