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The Influence of Shear History on Crystallization Behavior of iPP Melt

Author: WangFei
Tutor: ChenJingBo;ShenChangYu
School: Zhengzhou University
Course: Materials Processing Engineering
Keywords: Polypropylene β crystal Rheological behavior Heat treatment process Isothermal crystallization
CLC: TQ325.14
Type: Master's thesis
Year: 2009
Downloads: 35
Quote: 1
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Abstract


Polypropylene is a crystalline polymer material one of the most widely used industrial applications, and the production process by the shear tensile will change its crystalline structure of the crystal, and eventually lead to a variation of the performance of the product structure. In many of its crystalline form of β-crystal phase of special hexagonal lattice structure determines its excellent mechanical properties, such as: having a superior toughening effect and the higher the elongation at break, good tensile toughness and Extension and so on. The β crystal formation mechanism of the process by adjusting the parameters to improve the structure and performance of the products, providing a way. In this experiment, the first to adopt the melt rate of the unit to simulate the extrusion process, the shear history of the the iPP melt crystallization behavior. Extrusion conditions, the heat treatment process of the crystal morphology, crystal structure and the distribution of the degree of crystallinity and the β-crystal content, to provide theoretical guidance for the regulation of polymer morphology in the molding and PLM, WAXD and DSC characterization methods experimental basis. Specific work as follows: 1, extrusion conditions on the the the iPP melt rheological behavior of the impact, and draw the relationship between temperature and load and sampling time, shearing time and shear rate. PLM and WAXD study load on the the extrusion specimen crystal morphology, crystal structure, and distribution of the coexistence of α and β crystal beta crystal along the α row columnar crystals of nuclear generated, and the distribution of β crystal with the increase of the load tends to the surface layer of the extrudate: Quantitative study of the impact of extrusion conditions on the degree of crystallinity and the content of β crystal by DSC and found that the content of the β crystal is more sensitive than the crystallization degree of load and temperature, and on this basis easy-processing window is formed by the β crystal. Given by different heat treatment processes different sample heat engine history, to study the impact of different heat treatment process of the formation of β-iPP, the study showed that: extrusion before the holding time of the raw material in the barrel, raw materials not eliminate heat engine history, the melt shear history of the sample tempering process on the content of β-crystal significant impact: load and extruded insulation time also affects the extruded isothermal crystallization process of the formation of β-crystal content. 4, homo and copolymer PP and different molecular weight homopolymerization of PP on the β crystal formation, and found that homopolymerization of PP single monomer structure easier the formation of the β crystal, and the β-crystal content increases with its molecular weight .

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CLC: > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > Polymer resin and plastic > Polyolefin plastic > Polypropylene
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