Semi-crystalline polyolefins in fused deposition modeling
Hämäläinen, Janne Petteri (2017)
Hämäläinen, Janne Petteri
2017
Materiaalitekniikka
Teknisten tieteiden tiedekunta - Faculty of Engineering Sciences
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Hyväksymispäivämäärä
2017-09-06
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201708241800
https://urn.fi/URN:NBN:fi:tty-201708241800
Tiivistelmä
Keywords: polyolefin, polypropylene, polyethylene, fused deposition modeling, 3D printing, shrinkage, warping
With the continuous developments, FDM has surpassed the status as rapid prototyping method, and matured to the point where it is widely applied in direct manufacturing of various end-use products. However, the end-use applications are partly limited due to most current feedstock materials being prone to degradation in high-temperature, humid and chemically aggressive environments. The goal of this thesis was to evaluate the per-formance of polypropylene (PP) and polyethylene (PE) as alternative feedstock materi-als in the FDM process. PP and PE are prevalent polyolefin plastics and their principal value lies in the attractive balance of physical properties in the solid state and chemical inertness, and for the same reasons, they represent attractive FDM feedstock materials for the environmentally challenging conditions. However, as highly semi-crystalline plastics they show substantial solidification shrinkage upon cooling, and the shrinkage induced contractile stresses can deform the deposited parts.
In this work, the performance of PP and PE as feedstock materials in FDM was evaluat-ed through several deposition experiments. The entire manufacturing chain from fila-ment fabrication to deposition of specimens was controlled. Bonding quality between deposited filament strands at varying deposition conditions was assessed by preparing and testing tensile specimens, and comparing the results to injection molded counter-parts. The effects of deposition conditions on the shrinkage and warp deformation were studied by depositing specimens with different geometrical features.
Based on the results, FDM of PP and PE feedstock materials is feasible and holds a great potential, but requires special arrangements and awareness of the inherent chal-lenges. Bonding quality was highest at high temperature deposition conditions, and only roughly 10% loss in yield strength was observed when compared to injection molded counterparts. All specimens, regardless of deposition conditions, showed poor ductility and little to no correlation was found between the elongation and deposition tempera-tures. Excessive heat flow to the specimen during deposition caused substantial shrink-age due to prolonged cooling of the deposited plastic, and consequently the most di-mensionally stable specimens were produced by limiting the deposition temperatures or increasing interlayer cooling time. Specimens with sharp protruding features showed higher tendency to peel off from the build platform than circular specimens did, due to differences in contractile stress distributions. Warp deformation became also more prom-inent when feature thickness was reduced. Nevertheless, the deposition performance under optimal conditions was for the most parts on par with many traditional feedstock materials.
With the continuous developments, FDM has surpassed the status as rapid prototyping method, and matured to the point where it is widely applied in direct manufacturing of various end-use products. However, the end-use applications are partly limited due to most current feedstock materials being prone to degradation in high-temperature, humid and chemically aggressive environments. The goal of this thesis was to evaluate the per-formance of polypropylene (PP) and polyethylene (PE) as alternative feedstock materi-als in the FDM process. PP and PE are prevalent polyolefin plastics and their principal value lies in the attractive balance of physical properties in the solid state and chemical inertness, and for the same reasons, they represent attractive FDM feedstock materials for the environmentally challenging conditions. However, as highly semi-crystalline plastics they show substantial solidification shrinkage upon cooling, and the shrinkage induced contractile stresses can deform the deposited parts.
In this work, the performance of PP and PE as feedstock materials in FDM was evaluat-ed through several deposition experiments. The entire manufacturing chain from fila-ment fabrication to deposition of specimens was controlled. Bonding quality between deposited filament strands at varying deposition conditions was assessed by preparing and testing tensile specimens, and comparing the results to injection molded counter-parts. The effects of deposition conditions on the shrinkage and warp deformation were studied by depositing specimens with different geometrical features.
Based on the results, FDM of PP and PE feedstock materials is feasible and holds a great potential, but requires special arrangements and awareness of the inherent chal-lenges. Bonding quality was highest at high temperature deposition conditions, and only roughly 10% loss in yield strength was observed when compared to injection molded counterparts. All specimens, regardless of deposition conditions, showed poor ductility and little to no correlation was found between the elongation and deposition tempera-tures. Excessive heat flow to the specimen during deposition caused substantial shrink-age due to prolonged cooling of the deposited plastic, and consequently the most di-mensionally stable specimens were produced by limiting the deposition temperatures or increasing interlayer cooling time. Specimens with sharp protruding features showed higher tendency to peel off from the build platform than circular specimens did, due to differences in contractile stress distributions. Warp deformation became also more prom-inent when feature thickness was reduced. Nevertheless, the deposition performance under optimal conditions was for the most parts on par with many traditional feedstock materials.