MW vs. MWD…

I was discussing polymers with a technician and was asked this question:

I understand how molecular weight affects the process, but how does molecular weight distribution affect the process?

My Response
Polymer chain mobility is highly dependent on the length, or molecular weight, of the polymer chain. If most of the polymer chains have a similar molecular weight, or smaller distribution, then they are all more likely to soften at similar temperatures typically resulting in a more narrow temperature range at which the polymer can be processed.
Adversely, a broad molecular weight distribution often results in a wider processing window due to the mobility of some polymer chains while other chains remain highly entangled.
Additional Thoughts
Semi-crystalline polymers with a narrow molecular weight distribution can often achieve a higher degree of crystallinity than polymers with a wide distribution. 

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