dc.description.abstract | This study’s aim is to investigate manipulating the compression molding manufacturing
process to influence morphology and mechanical properties of thick wall and tall advanced
performance thermoplastic polymers, as well as to highlight the mechanisms that cause property
deterioration in those products. Two advanced performance polymer systems, neat
poly(etheretherketone) (PEEK) and its composite (CF/PEEK), were considered as model systems
to fundamentally understand structure-property relationships in thick wall advanced polymeric
materials.
An instrumented compression molding setting with thermal control and 3D embedded
thermocouples is designed and fabricated to produce thick polymer parts and investigate how
altering processing procedures influences properties. A novel hybrid sealing method is invented to
enhance compression molding quality and avoid leaking issues associated with this process.
The temperature distribution profiles throughout the compression molding and the bushing
are collected during heating and cooling processes. The resultant temperature profiles are analyzed
to further understand the compression molding process behavior, and thus adjust the processing
procedure to enhance products morphology and properties.
Crystal structure formation is controlled via templating material manufacturing cooling
process. The influence of holding temperature at the crystallization temperature while increasing
the hold time is examined by characterizing samples throughout bushings processed using various
strategies. Manipulating the cooling is expected to guide the polymer amorphous arrangement
toward a uniform crystal structure and grow this structure equivalently throughout the thick cross-section
and the extended length of the final product. Remarkable crystallinity improvement with
adequate consistency was achieved throughout thick wall and tall compression molded PEEK
bushing that improved the compression molding product properties. Carbon fiber reinforcement’s
influence on crystal morphology and mechanical properties of thick products is addressed in this
dissertation.
Different techniques and tests are used to investigate the bushings produced using different
processing strategies such as dynamic scanning calorimetry (DSC), dynamic mechanical analysis
(DMA), scanning electron microscopy (SEM), wide angle x-ray scattering (WAXS), polarized
optical microscopy (POM), compression test, and 3-point bending test. Those techniques assisted
in establishing correlation between the morphology modification and the material properties
response.
Predictive numerical models are developed to simulate the compression molding heating
process. Experimental validations provide beneficial tools to predict the heating time required for
various thick compression molded materials. The predictive models established in this study can
substitute building an expensive thermal control system and performing compression molding with
embedded thermocouples to estimate material processing time. These models can provide a great
assist for industrial applications.
This study highlights an intelligible processing procedure for developing thick
compression molding bushing with consistent crystallinity and enhanced mechanical properties.
The processing protocol introduced in this study acquired based on analyzing compression
molding temperature profiles and studying the possibility of using different methods to control the
process during the cooling stage to produce neat and composite polymers with better properties.
The produced products can be used for many applications such as aerospace, biomedical,
automotive, food processing, oil and gas industry, etc. | en |