TY - ADVS

T1 - THE IMPORTANCE OF VISCOELASTICITY AND PRESSURE DEPENDENCE OF VISCOSITY FOR SIMULATION OF MELT FLOW IN INJECTION MOLDING AND CAPILLARY RHEOMETRY

AU - Friesenbichler, Walter

AU - Neunhäuserer, Andreas

AU - Fasching, Michael Andreas

AU - Mitsoulis, Evan

N1 - Conference code: 11

PY - 2017/4

Y1 - 2017/4

N2 - To establish closed-loop control of the injection molding process with regard to a self-optimizing process,quality models derived from injection molding simulations acc. to DoE are of crucial importance. Qualityfunctions derived from simulation linking the process parameters with desired part quality (part weight,dimensions) allows running the production within the allowed process window realizing a robust injectionmolding process. It is well known that viscoelasticity of polymer melts [1,2] and pressure dependence ofviscosity [3] play a major role in processing. Nevertheless these effects are commonly neglected in simulationof polymer melts resulting in remarkable deviations between the real pressure demand and the prediction viasimulation. The effects increase strongly with raising pressure level for processing.The aim of this study was to compare measured data for the pressure demand in capillary rheometry as wellas in injection molding with calculated values based on simulations. Particular emphasis had been given onviscoelasticity and the pressure-dependence of viscosity. The results from viscous calculations for differentconical dies having different diameters, D, and length-to-diameter L/D ratios, were compared with those fromviscoelastic modeling and viscoelastic modeling taking into account the pressure effect. Four injection moldingnozzle geometries had been also used to reach apparent shear rates up to 800,000 s-1. Using oscillatory andcapillary rheometry a full rheological characterization had been carried out for both a polypropylene-fillednanocomposite and a rubber compound (SBR).It was found that only the viscoelastic simulations were capable of reproducing the measured pressure dropvery well [4], while any viscous modeling always strongly underestimates the pressures, especially at the higherapparent shear rates and L/D ratios. The experimental data have been fitted both with a viscous model (Cross)and a viscoelastic one (the Kaye - Bernstein, Kearsley, Zapas / Papanastasiou, Scriven, Macosko or KBKZ/PSM model).The data for pressure dependence of viscosity were measured on an injection moldingmachine rheometer with the help of a special rheological mold. Experimental data are evaluated taking intoaccount the melt temperature rise due to dissipative heating.In addition the importance of pressure-dependence of viscosity for injection molding simulations of practicalparts is shown for different thermoplastics (ABS, PS, isotactic PS) and a rubber compound (NBR) comparingmeasured pressures in the screw antechamber or the cavity with simulated pressure values. For pressures higherthan 100 MPa the pressure-dependence of viscosity should be taken into account.

AB - To establish closed-loop control of the injection molding process with regard to a self-optimizing process,quality models derived from injection molding simulations acc. to DoE are of crucial importance. Qualityfunctions derived from simulation linking the process parameters with desired part quality (part weight,dimensions) allows running the production within the allowed process window realizing a robust injectionmolding process. It is well known that viscoelasticity of polymer melts [1,2] and pressure dependence ofviscosity [3] play a major role in processing. Nevertheless these effects are commonly neglected in simulationof polymer melts resulting in remarkable deviations between the real pressure demand and the prediction viasimulation. The effects increase strongly with raising pressure level for processing.The aim of this study was to compare measured data for the pressure demand in capillary rheometry as wellas in injection molding with calculated values based on simulations. Particular emphasis had been given onviscoelasticity and the pressure-dependence of viscosity. The results from viscous calculations for differentconical dies having different diameters, D, and length-to-diameter L/D ratios, were compared with those fromviscoelastic modeling and viscoelastic modeling taking into account the pressure effect. Four injection moldingnozzle geometries had been also used to reach apparent shear rates up to 800,000 s-1. Using oscillatory andcapillary rheometry a full rheological characterization had been carried out for both a polypropylene-fillednanocomposite and a rubber compound (SBR).It was found that only the viscoelastic simulations were capable of reproducing the measured pressure dropvery well [4], while any viscous modeling always strongly underestimates the pressures, especially at the higherapparent shear rates and L/D ratios. The experimental data have been fitted both with a viscous model (Cross)and a viscoelastic one (the Kaye - Bernstein, Kearsley, Zapas / Papanastasiou, Scriven, Macosko or KBKZ/PSM model).The data for pressure dependence of viscosity were measured on an injection moldingmachine rheometer with the help of a special rheological mold. Experimental data are evaluated taking intoaccount the melt temperature rise due to dissipative heating.In addition the importance of pressure-dependence of viscosity for injection molding simulations of practicalparts is shown for different thermoplastics (ABS, PS, isotactic PS) and a rubber compound (NBR) comparingmeasured pressures in the screw antechamber or the cavity with simulated pressure values. For pressures higherthan 100 MPa the pressure-dependence of viscosity should be taken into account.

M3 - Digital or Visual Products

CY - Slowenien

T2 - International Conference on Industrial Tools and Advance Processing Technologies

Y2 - 24 April 2017 through 26 April 2017

ER -