TY - THES

T1 - Influence of the Processing conditions on morphology and fracture mechanical properties of unfilled polyoxymethylene (POM)

AU - Halb, Marita

N1 - embargoed until null

PY - 2016

Y1 - 2016

N2 - Polyoxymethylene (POM) is an engineering thermoplastic with a high degree of crystallinity. It is used for applications with high requirements with regard to the mechanical properties. Mechanical properties are strongly dependent on the morphological structure of the material. Through processing, additives, etc. this structure can be strongly influenced. Especially the processing conditions can vary the mechanical properties significantly. The aim of this thesis was to find a correlation between processing conditions, morphological structure and mechanical properties for two different POM resins (Delrin and Tenac). For this purpose plates of both materials were produced using compression molding (CM) and injection molding (IM) with three different mold temperatures. The plates were analyzed concerning their morphological structure and their fracture mechanical properties. The morphological structure was determined using X-ray radiation methods, polarized light microscopy (PLM) and differential scanning calorimetry (DSC). The X-ray tests used can be subdivided into small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD). Additionally, the SAXS profiles were analyzed using two different methods: the so-called 1D correlation and a curve fitting procedure based on a 3-component model. A further aim of this thesis was the practical implementation of both, SAXS and WAXD and the evaluation of the SAXS data analysis methods (1D correlation and 3-component model) because they were not well investigated for POM. For the characterization of the fracture mechanical behavior fatigue fracture tests were performed on compact tension (CT-) specimens. Fatigue fracture curves were used for the comparison of the differently processed material plates. The curves were generated by testing at four different load levels. The CM plates showed the highest degree of crystallinity of all plates for most test methods used. Their morphology was very homogenous even though there were big differences between the two POM resins. In the fracture mechanical tests they also revealed the best performance. The IM plates were more diverse. Low mold temperatures lead to a lower degree of crystallinity and slightly worse results in the fracture mechanical tests. The morphological structures observed using PLM varied strongly with the mold temperature and the sample position on the plate. For the X-ray tests the WAXD technique worked quite well while the results obtained from the two different SAXS analysis methods were less satisfying.

AB - Polyoxymethylene (POM) is an engineering thermoplastic with a high degree of crystallinity. It is used for applications with high requirements with regard to the mechanical properties. Mechanical properties are strongly dependent on the morphological structure of the material. Through processing, additives, etc. this structure can be strongly influenced. Especially the processing conditions can vary the mechanical properties significantly. The aim of this thesis was to find a correlation between processing conditions, morphological structure and mechanical properties for two different POM resins (Delrin and Tenac). For this purpose plates of both materials were produced using compression molding (CM) and injection molding (IM) with three different mold temperatures. The plates were analyzed concerning their morphological structure and their fracture mechanical properties. The morphological structure was determined using X-ray radiation methods, polarized light microscopy (PLM) and differential scanning calorimetry (DSC). The X-ray tests used can be subdivided into small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD). Additionally, the SAXS profiles were analyzed using two different methods: the so-called 1D correlation and a curve fitting procedure based on a 3-component model. A further aim of this thesis was the practical implementation of both, SAXS and WAXD and the evaluation of the SAXS data analysis methods (1D correlation and 3-component model) because they were not well investigated for POM. For the characterization of the fracture mechanical behavior fatigue fracture tests were performed on compact tension (CT-) specimens. Fatigue fracture curves were used for the comparison of the differently processed material plates. The curves were generated by testing at four different load levels. The CM plates showed the highest degree of crystallinity of all plates for most test methods used. Their morphology was very homogenous even though there were big differences between the two POM resins. In the fracture mechanical tests they also revealed the best performance. The IM plates were more diverse. Low mold temperatures lead to a lower degree of crystallinity and slightly worse results in the fracture mechanical tests. The morphological structures observed using PLM varied strongly with the mold temperature and the sample position on the plate. For the X-ray tests the WAXD technique worked quite well while the results obtained from the two different SAXS analysis methods were less satisfying.

KW - POM

KW - processing conditions

KW - morphology

KW - fracture mechanical properties

KW - SAXS

KW - WAXD

KW - DSC

KW - polarized light microscopy

KW - fracture mechanical fatigue curves

KW - POM

KW - Verarbeitung

KW - Morphologie

KW - bruchmechanische Eigenschaften

KW - SAXS

KW - WAXD

KW - DSC

KW - Polarisationslichtmikroskopie

KW - bruchmechanische Ermüdungskurven

M3 - Master's Thesis

ER -