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Home Work _8

Home Work _8

Q Q1. True or False Questions (put “T” or “F” below for each questions, each 5 pts, 50 pts) 1.___ The shrinkage of injection molded parts must lead to the part warpage. 2.Generally speaking, as the part thickness increases, the shrinkage of injection molded parts increases. 3.Shrinkage of plastic components is driven by the volumetric change of the material as it cools from the melt state to solid state. 4.___ PVT diagram for polymers provides important information to injection molders. At the same temperature, if the pressure increases, then the specific volume increases. 5./__ For injection molded crystalline parts, if the part cooling rate decreases, the part shrinkage will increase because the slower cooling promotes the crystal growth and increases the crystallinity. 6.Orientation will cause the plastic to shrink by different amounts parallel and perpendicular to flow. 7.Usually oriented material will tend to relax, giving a lower shrinkage in the direction of flow than across the flow.

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1. _F___ The shrinkage of injection molded parts must lead to the part warpage. 2. _T___ Generally speaking, as the part thickness increases, the shrinkage of injection molded parts increases. 3. __T___Shrinkage of plastic components is driven by the volumetric change of the material as it cools from the melt state to solid state. 4. _F___ PVT diagram for polymers provides important information to injection molders. At the same temperature, if the pressure increases, then the specific volume increases.