| Fused deposition modeling(FDM) is the rapidly developed 3D printing rapid prototyping technology in recent years. And it is very suitable for office working environment due to its simple operation, low cost, safety and environment protection. In the FDM process, hollow parts and cantilever parts cannot be printed without support materials. So it has important significance in improving the molding precision of the FDM process by developing water-soluble support material. Polyvinyl alcohol(PVA) is a water-soluble and biodegradable polymer material, and it is very suitable for FDM process as the support material. However, since the thermal decomposition temperature of PVA is very close to its melting temperature, the melting process of PVA is difficult.In this paper, PVA was chosen as the water-soluble support material in the FDM process, by adding plasticizer and heat stabilizer, PVA was modified and melting process of PVA had realized. The performances of the modified PVA were studied by DSC test, melt index test, mechanical property test and other means. The results showed that with the addition of compound plasticizer which is mixed glycerol and PEG200, the melting temperature and crystallinity of PVA decreased, and the processing flowability of PVA improved. And glycerol was more effectively than PEG200 to reduce the melting temperature and crystallinity of the modified PVA, when the total mass portion of the compound plasticizer was 15, the ratio of glycerol and PEG200 was 3:2, the melt processing temperature of the modified PVA was the lowest, and the synergistic effect of glycerol and PEG200 was best. Increasing the amount of the compound plasticizer can significantly improve the processing flowability of modified PVA, but the mechanical properties of the modified PVA reduced. The effects of thermal stabilizer magnesium hydroxide for modified PVA was studied, the results showed that magnesium hydroxide can significantly improve the appearance of the modified PVA, and eliminate acidic gases produced by melting process of PVA, and reduce the processing flowability of PVA. When the amount of magnesium hydroxide was 5 mass portion, the thermal stability of the modified PVA was the best, and the appearance and odor of the sample were also satisfied with requirements.PVA water-soluble filament satisfied with FDM process was prepared by extrusion molding. Because of its water solubility, PVA filament cannot be cooled with water in the extrusion molding process. In this paper, the cooling effect of liquid cooling and air-cooled cooling was studied. The results showed that the liquid cooling had a better control the appearance and diameter precision of PVA filament, and it was simple to operate and has good cooling effect, but it was difficult to balance safety and cost. While air-cooled cooling had lower cost and higher safety, but the suitable formulation system and equipment with higher requirement were needed.Yellowing index of different formulations of PVA filament under printing nozzle was contrasted, and the suitable formulation system was picked out. The printing performance of PVA filament was investigated by printing temperature and printing speed, the results showed that when the printing temperature was 200 ℃, the comprehensive printing performance of modified PVA filament was best. Water-soluble test results showed that the modified PVA filament can completely dissolve in water in 6 hours, and the water solubility can meet the requirement of water soluble support filament for FDM process.Integrating the analysis of the whole thesis, when the mass portion of glycerol, PEG200, magnesium hydroxide was respectively 9, 6, 5, the melting process properties of modified PVA was best. The industrialization of PVA filament had realized by using air-cooled cooling, and the performance of PVA filament was satisfied with FDM process. |
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