posted April 14, 2003 05:09 PM               

quote:

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Originally posted by burak dincel:
Can anyone answer the following ?

I understand that heavy materials of dry blend(powder) compound such as titanium dioxide, fillers ,etc,separates from other parts,such as pvc-resin due to transportation related vibration hence causing problem unless re-mixed prior to extrusion.Is this true ? Also what happens if dry-blend is effected by moisture during transportation? Is the simple answer not to deal with transported dry blend?Your valuable comments/assistance would be very much appreciated.
Regards - Burak

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Generally speaking, anything over one gram per pound of dry colorant or additive does not get absorbed by the pellets. That is to say that once the pellets are coated, you will have excess additive floating around in the mix. It is that excess that settles to the bottom.

Of course that depends on the S.G. of the additive.

As to moisture affecting the blend, yes, that could be a problem with some additives. In my humble opinion though, the moisture would only help the particles stick to the pellet. The real problem there is how does the plastic perform when run wet?

posted April 14, 2003 05:29 PM               

For myself I usually make a small sample blend (1-2 lbs) in a clear plastic bag. I will bounce the bag lightly up and down on a table a dozen times or so. Then I visually and physically inspect the blend for separation problems.

I you do find separation in this test, then usually the separation will cause problems somehow and somewhere. Solutions are varied ... however I can't give away all of my income earning potential.

Moisture is usually not a problem unless storage will be extended, 6 months +, or shipping overseas. There are also solutions to these problems, but they is some expense in implementation.

Tom C