TY - THES

T1 - Comparison of different measuring methods for thermo-mechanical characterization of polymer powders

AU - Tröscher, Thomas

N1 - no embargo

PY - 2023

Y1 - 2023

N2 - Polymer powders play a vital role in the current industry and are used in various applications. A few examples are the fabrication of abrasives, printing a prototype via additive manufacturing and coating metal surfaces. Polymer powders became the feedstock of choice for several polymer types. Commonly used Polyvinylchloride, as well as the more specialized Polytetrafluoroethylene, are fed to processing machines as powders. Critically evaluating the thermal dependency of properties, relevant for production and application is a key requirement. Properties like the flowability, cohesion and effective angle of internal friction appear to be connected to the thermo mechanical state of powders. Therefore, determining transition temperatures like the glass transition temperature or second order relaxation temperatures is of utmost importance. The aim of this master thesis is the determination of thermomechanical properties of different types of polymer powders and compare them to conventional testing methods, such as Differential scanning calorimetry and Dynamic Mechanical Analysis (DMA) of solid samples. Polymer powders were tested via DMA, here a special container (¿Powder Pocket¿) allowed for a measurement in a Dual Cantilever setup. A second characterization method evaluated was connected to powder rheological properties. Over the course of this thesis, the sample preparation and the conduct of the measurement were optimized. For this purpose, several different parameters were evaluated such as, the tightening torque, the sample volume and distribution, the material of the Powder Pocket and a compression step before measuring. The metal of the Powder Pocket and the sample volume had the biggest influence on the measurement. The sensitivity regarding the measurement is comparable with DSC. However, with powder DMA, additional transition temperatures could be detected in PA12 and the low temperature range of PTFE. Powder rheological methods could only roughly determine the transition temperature of powders. Nonetheless, the connection of process relevant properties and their change at transition temperatures was observed.

AB - Polymer powders play a vital role in the current industry and are used in various applications. A few examples are the fabrication of abrasives, printing a prototype via additive manufacturing and coating metal surfaces. Polymer powders became the feedstock of choice for several polymer types. Commonly used Polyvinylchloride, as well as the more specialized Polytetrafluoroethylene, are fed to processing machines as powders. Critically evaluating the thermal dependency of properties, relevant for production and application is a key requirement. Properties like the flowability, cohesion and effective angle of internal friction appear to be connected to the thermo mechanical state of powders. Therefore, determining transition temperatures like the glass transition temperature or second order relaxation temperatures is of utmost importance. The aim of this master thesis is the determination of thermomechanical properties of different types of polymer powders and compare them to conventional testing methods, such as Differential scanning calorimetry and Dynamic Mechanical Analysis (DMA) of solid samples. Polymer powders were tested via DMA, here a special container (¿Powder Pocket¿) allowed for a measurement in a Dual Cantilever setup. A second characterization method evaluated was connected to powder rheological properties. Over the course of this thesis, the sample preparation and the conduct of the measurement were optimized. For this purpose, several different parameters were evaluated such as, the tightening torque, the sample volume and distribution, the material of the Powder Pocket and a compression step before measuring. The metal of the Powder Pocket and the sample volume had the biggest influence on the measurement. The sensitivity regarding the measurement is comparable with DSC. However, with powder DMA, additional transition temperatures could be detected in PA12 and the low temperature range of PTFE. Powder rheological methods could only roughly determine the transition temperature of powders. Nonetheless, the connection of process relevant properties and their change at transition temperatures was observed.

KW - thermo-mechanical characterization

KW - polymer powder

KW - dynamic mechanical analysis

KW - powder rheology

KW - shearcell

KW - Thermomechanische Charakterisierung

KW - Polymerpulver

KW - Dynamisch mechanische Analyse

KW - Pulverrheologie

KW - Scherzelle

U2 - 10.34901/mul.pub.2023.150

DO - 10.34901/mul.pub.2023.150

M3 - Master's Thesis

ER -