Jump to content

Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

Vertical Tank Selection

New Blog Entry

Low Flow in Pipes- posted in Ankur's blog


Hardness In Hot Cast Polyurethane System

hot cast polyurethane

3 replies to this topic
Share this topic:
| More

#1 AlpanaNew


    Brand New Member

  • Members
  • 1 posts

Posted 12 September 2023 - 01:25 AM

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.

#2 Pilesar


    Gold Member

  • Members
  • 1,251 posts

Posted 12 September 2023 - 05:59 AM

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

#3 latexman


    Gold Member

  • Admin
  • 1,593 posts

Posted 12 September 2023 - 06:48 AM

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?

#4 breizh


    Gold Member

  • Admin
  • 6,075 posts

Posted 14 September 2023 - 01:15 AM


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.



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,


Similar Topics