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Title: Investigation into the use of polypropylene in high speed sintering
Author: Fox, Luke
ISNI:       0000 0004 7970 2530
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2019
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Additive Manufacturing (AM) is becoming increasingly popular for production of end-use parts, partly due to their potential for mass customisation as well as costs reducing, for production to be feasible. High Speed Sintering (HSS) is a polymer AM technique developed to provide the production speeds needed to compete with Injection Moulding. There is increasing interest in the use of HSS from Fast Moving Consumer Goods (FMCG) companies, but the current range of materials is unsuitable due to high costs and limited material properties. There is therefore a need to identify more suitable HSS materials for FMCGs, and this will be addressed in this research. A comprehensive material selection process was carried out to identify possible materials for the use of FMCGs manufactured via HSS. Processing compatibility, chemical compatibility and cost were considered in order to identify the most suitable polymer for investigation. This selection process identified polypropylene (PP) as the most likely to be suitable for production of FMCGs through the HSS process; this material was therefore chosen for investigation in this thesis. The ability to process three separate grades of PP in the HSS process was investigated here, in order to identify any factors which lead to differences in processability and properties of parts manufactured. The three different grades of PP tested (CP22 PP, XX00199PP and AdSint PP) demonstrated different levels of processability, with the base material type and the presence of flow additives identified as key reasons for this. The best performing grade was found to have a significantly different melt temperature and crystallinity, which is likely due to the polymer being a copolymer polypropylene, and led to increased mechanical properties. The ability to reuse unsintered material from the build area was seen to be possible, with indications that the levels of reusability may be greater than those for other HSS materials. Key processing parameters (bed temperature, grey level and sinter speed) were found to be critical in the processing of the PP powder into part. The range at which build bed temperature could be varied was found to be material-dependent, and fell within a small window. Increasing grey level was generally found to lead to poorer mechanical properties, and sinter speed was found to affect the mechanical properties of parts, but again this relationship was dependent on the material used. AdSint PP has been identified as the best choice of material currently for the production of FMCGs via HSS, partly through its higher mechanical properties (Ultimate Tensile Strength of 23.39 MPa, Elongation at Break of 59.33 % and Youngs's Modulus of 977 MPa), and partly due to its greater ease of processing.
Supervisor: Majewski, Candice ; Hopkinson, Neil Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available