第7课 塑料在包装中的应用 (NXPowerLite).ppt

文档介绍：Plastic in Packaging
Lesson 7
第7课塑料在包装中的应用
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1. What elements are in the molecule?
2. What size (molecular weight) is the molecule?
3. Is the molecule polar or non-polar?
4. What shape is the molecule?
5. What is its thermal history?
6. What is its mechanical history?
Polymer Properties Depend On:
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Deformation and Thermal History
Room temperature deformation is permanent.
Plastics stretched at about Tg and cooled
slowly are heat stable.
Plastics stretched at about Tg and cooled quickly
have “memory” and will shrink if reheated.
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Plasticating Extruder
Fig.
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Cast Film and Sheet Extrusion

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Three-Layer Coextrusion

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Extrusion Cast Film Line Layout

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Machine Direction Orientation

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Cross Direction Orientation

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Blown-film Die Cross-Section

The die is often rotated to prevent gauge bands
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