Today's KNOWLEDGE Share: Larger gate when molding amorphous polymers

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Today's KNOWLEDGE Share

Why would you choose a larger gate when molding amorphous polymers ?


This is often mentioned and linked to the typically higher viscosity of amorphous polymers that do not undergo the sharp melting transition with associated dramatic drop of viscosity.

But one major aspect to consider is packing. Due to the already mentioned pressure effect on viscosity and no-flow temperature for this class of polymers a larger gate, with its longer freeze-off time, will allow you to pack for longer, and thus use a lower packing pressure, avoiding the aforementioned pressure dependent problems altogether.


Keep in mind that a longer freeze-off time creates a higher risk of differential shrinkage (gate area overpack), to be addressed with the proper packing pressure profiling.


Source:Vito Leo

Visit MY BLOG http://polymerguru.blogspot.com


#plastics #polymerindustry #injectionmolding #shrinkage #gate


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