tolerances MFI

[campp]

Hello,

Does anyone know which is the permissible tolerances for MVR to ensure that the material is not degraded during the injection process?
I know that the values of MVR is influenced by process conditions, humidity of polymers and storage.
How can evaluate the degradation level of material using the MVR values?
Which should be the difference between raw material and injected part regarding MVR?
If the specification is 15÷40 cm3/10min and I found 46, can I say that the material is degraded?
Is a 50% increase is too much for a molded part compared to raw material?

Thank you!

 

[Pud]

What polymer are you finding the problem? I would have thought 50% was an indication of severe degradation.



Politicians like to panic, they need activity. It is their substitute for achievement.

 

[campp]

It's about PBT GF10.
Raw material have 32 - 33cm3/10min, while the parts have 46 - 49cm3/10min.
This variation is enough to consider that the parts are degraded during the injection process?
Generally, what would be the allowed limits for the parts to consider them Ok in relation to the raw materials? These limits differ depending on the polymer family?

Thank you!

 

[Pud]

I would suggest that the PBT was not dried correctly prior to moulding.
The stuff is very hygroscopic, and requires a very low moisture content. It moulds nicely when not dry. Nice surface finish, melt looks good etc. Parts are severely weakened though.


Politicians like to panic, they need activity. It is their substitute for achievement.