Characterisation of polypropylene (PP) polymers in laser sintering (LS)
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- Tez No: 916331
- Danışmanlar: PROF. OANA GHİTA
- Tez Türü: Yüksek Lisans
- Konular: Makine Mühendisliği, Mechanical Engineering
- Anahtar Kelimeler: Laser sintering (LS), polypropylene (PP), powder flowability, thermal properties, particle shape analysis, flow agents
- Yıl: 2019
- Dil: İngilizce
- Üniversite: Unıversıty Of Exeter
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Makine Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
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Özet (Çeviri)
Additive manufacturing (AM) has been improving quite quickly over the last three decades. Laser sintering (LS) is one of the techniques used in AM, and it has the capability to produce prototypes and components from computer aided design (CAD) data. LS is a powder-based process. It has many advantages for small to medium-sized products. The LS process happens in a narrow temperature window that is called the sintering window. There are limitations in terms of the materials used in this process. LS materials are mostly polyamide (PA) materials. This limitation of material variety causes many drawbacks in some industries. There is an aim to increase the variety of materials, which is crucial for LS. The new materials are polypropylene (PP), poly (ether ether) ketone (PEEK), polyetherketone (PEK), polyethylene (PE), as well as several others. Plastic production includes a high amount of PP among thermoplastics. In this project, PP powder is used to increase the suitability of LS materials, and attempts are made to find out the powder and part characterisation properties. Based on the sintered parts, the thermal properties are analysed. Also, the powder spreading problems experienced with virgin PP and PP blend with different flow agents are evaluated. Powder and particle properties are examined with a Scanning Electron Microscope (SEM). The powder and particle morphologies are examined with SEM, particle shape analysis of the images is analysed by using ImageJ software to reveal roundness, circularity, solidity, and aspect ratio (AR) of the powder. Furthermore, in the powder analysis, it is shown that all powders have a special angle for measuring flowability, which is called the angle of repose (AOR). This angle has been found for virgin PP powder and blended PP powder with additives, and four flow agents used for increasing flowability by decreasing AOR are used. Flow agents have a positive effect on the flowability of virgin PP powder. They have been mixed in small amounts, and different trials are used to produce new PP parts using LS. Flowability and temperature problems have been encountered in the LS process. Heated powder beds and subsequent layers show the better features of LS, but when the number of powder layers increases there are problems with cold powders being spread on a heated powder bed, and this is called a thermal gradient. Also, there have been problems with curling on LS process. It has been recognised that these sintered parts are not suitable for mechanical tests.
Benzer Tezler
- Characterisation of Polypropylene (PP) Polymers in Laser Sintering (LS)
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Yüksek Lisans
İngilizce
2019
Makine MühendisliğiUnıversıty Of ExeterMakine Mühendisliği Ana Bilim Dalı
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