Floppy parts

[Joel JS]

Help!

I am running a substrate that gets overmolded with a tpe... the substrate was previously more rigid and now is floppy and flashes easily in the overmold. (The substrate looks like a book end.)

The Substrate material is Lucent PP TPP-0320QU BK2072 , which is a 20% Talc filled Copolymer Propylene, with a UV stabilizer.

I am trying to pinpoint this issue to a material lot change, but not 100% sure as yet,...... in the meantime has anyone seen this as being a possible processing effect?

Thanks,
Joel

[rickbatey]

Are you sure that you are running the same resin? Maybe the talc content is on the low end when you've been getting it at the high end of the spec?
Excessive temperature and residence time will kill resins with UV and FR stabilizers in them. Is the part weight still the same? Could you have a cracked NRV, worn screw/barrel allowing the melt to stay in the barrel too long?
Rick

[Joel JS]

Thanks Rick!....... :-)

Yes same resin, different lot, but did not see change immediately upon lot change (if our paperwork is right.)...... I am thinking Talc too, too little yeah. Part weight is the same, residence time is suitable and has not changed.... I was able to increase stiffness a bit with higher water temps, not much else... Let's see what else comes about.

Thanks again for your reply.
Joel

[back4more]

See if durometer number has changed on this lot/batch