3 replies to this topic

[AlpanaNew]

Hello and good day to all.

Our production making hot cast Polyurethanes tubes for seals making by injection molding. Lately we faced the problem: Polyurethane material after mixing in mold and subsequent curing has different surface hardness (difference from down to top part can vary between ShA 90 to ShA 80). As far as seals are used in machinery with high requirements for physical and mechanical characteristics, the hardness should vary for 1 or 2 units max.

Probably someone can suggest solutions to this problem?

We have already trued rheology/thixotropy agents to make the polyurethane system more gomogeneous. Also we tried various catalysts to reduce curing time. Nothing has helped so far.

[Pilesar]

I suspect uneven temperature. Can you rotate the mold or the tubes while curing?

[latexman]

Lately we faced the problem

 

What changed?  RMs, suppliers, mixing, heat transfer, equipment, instrumentation, batch instructions, etc?  It sounds like everything was fine for some time, then much different surface hardnesses started appearring.  Something in the process must have changed.  Did the much different surface hardnesses appear suddenly, or gradually?

[breizh]

Hi,

I'm with Latexman, for sure something has changed over the time. Go back to your production when the quality was OK and check for the changes, if any. Review all the process parameters, the MOC on the equipment, the raw materials.

 

Note:

I've in mind a change of Raw mat supplier who affected the quality of the final product for months. Sometimes people want to save $ through competition and create big losses.

 

I cannot offer more, outside my expertise.

Good luck,

Breizh