TY - THES

T1 - Experimental study and numerical simulation on rheological properties of PA66GF30 and ABS under pressure

AU - Gao, Fangxuan

N1 - embargoed until null

PY - 2021

Y1 - 2021

N2 - The flow and deformation of the polymeric melt are necessary for the molding process of polymer materials. Theoretical analysis and experimental research help to understand the rheological behavior and characterizing the properties of the melts. It is the foundation for the rational selection of molding processes, optimization of processing equipment, and simulation of processing processes. Mold filling during injection molding takes place via pressure flow. However, the influence of pressure on the rheological properties of the polymer melt is often ignored when simulating polymer flow. On the other hand, the study of the pressure dependence of the rheological properties is limited by the complexity of the characterization process and has therefore often been omitted. Moreover, the current researches on pressure-dependent rheological properties mainly focus on unfilled polymers, and the highly filled polymer compounds are hardly studied. In order to investigate the rheological properties of polymer melts and their highly filled compounds in the pressure range, the following studies were carried out in this work: Through theoretical considerations and experimental studies, the shear viscosity of the polymer melt was analyzed in terms of its pressure dependence for the two polymer types acrylonitrile-butadiene-styrene copolymer (ABS) and polyamide 66 with 30 wt.% glass fibers (PA66GF30). Studies have shown that the rheological properties of polymer melts are significantly affected by the pressure in the pressure field. Therefore, the pressure dependence of viscosity is an important part of the analysis of the rheological behavior of the polymer melt. The experiment was based on the modified high-pressure capillary rheometer, with a back-pressure chamber at the end of the die. By stepwise increase of the average pressure in the capillary, the pressure dependence of the shear viscosity of the polymer melt was achieved as a function of the shear rate. Two different calculation methods were used to calculate the viscosity pressure sensitivity coefficient of the material. Experiments on two different materials found that under the same shear rate and pressure, as the stiffness of the polymer main chain increased, the pressure dependence decreased accordingly, and the addition of reinforcing materials also reduced the pressure dependence. At the same time, the study found that the viscosity pressure sensitivity coefficient of PA66GF30 first decreased and then increased with the increase of temperature. This was attributed to the fact that the polarity of strongly polar materials dominates at lower temperatures, while the effect is lower at high temperatures. Finally, the flow in the capillary rheometer was simulated in Sigmasoft®, and the actual pressure curve was compared with the simulation result to verify the calculation method. The verification result was shown that the pressure obtained from the simulation was 1%-7% lower than the actual measured pressure, explaining that the calculation method could be used to simulate the melt flow in the pressure field.

AB - The flow and deformation of the polymeric melt are necessary for the molding process of polymer materials. Theoretical analysis and experimental research help to understand the rheological behavior and characterizing the properties of the melts. It is the foundation for the rational selection of molding processes, optimization of processing equipment, and simulation of processing processes. Mold filling during injection molding takes place via pressure flow. However, the influence of pressure on the rheological properties of the polymer melt is often ignored when simulating polymer flow. On the other hand, the study of the pressure dependence of the rheological properties is limited by the complexity of the characterization process and has therefore often been omitted. Moreover, the current researches on pressure-dependent rheological properties mainly focus on unfilled polymers, and the highly filled polymer compounds are hardly studied. In order to investigate the rheological properties of polymer melts and their highly filled compounds in the pressure range, the following studies were carried out in this work: Through theoretical considerations and experimental studies, the shear viscosity of the polymer melt was analyzed in terms of its pressure dependence for the two polymer types acrylonitrile-butadiene-styrene copolymer (ABS) and polyamide 66 with 30 wt.% glass fibers (PA66GF30). Studies have shown that the rheological properties of polymer melts are significantly affected by the pressure in the pressure field. Therefore, the pressure dependence of viscosity is an important part of the analysis of the rheological behavior of the polymer melt. The experiment was based on the modified high-pressure capillary rheometer, with a back-pressure chamber at the end of the die. By stepwise increase of the average pressure in the capillary, the pressure dependence of the shear viscosity of the polymer melt was achieved as a function of the shear rate. Two different calculation methods were used to calculate the viscosity pressure sensitivity coefficient of the material. Experiments on two different materials found that under the same shear rate and pressure, as the stiffness of the polymer main chain increased, the pressure dependence decreased accordingly, and the addition of reinforcing materials also reduced the pressure dependence. At the same time, the study found that the viscosity pressure sensitivity coefficient of PA66GF30 first decreased and then increased with the increase of temperature. This was attributed to the fact that the polarity of strongly polar materials dominates at lower temperatures, while the effect is lower at high temperatures. Finally, the flow in the capillary rheometer was simulated in Sigmasoft®, and the actual pressure curve was compared with the simulation result to verify the calculation method. The verification result was shown that the pressure obtained from the simulation was 1%-7% lower than the actual measured pressure, explaining that the calculation method could be used to simulate the melt flow in the pressure field.

KW - ABS

KW - Polyamid 66

KW - Viskosität

KW - Druckabhängigkeit

KW - Fließsimulation

KW - ABS

KW - polyamide 66

KW - viscosity

KW - pressure dependence

KW - flow simulation

M3 - Master's Thesis

ER -