Epoxy vs Polyurethane resins

[Calvin]

Hi,
I need to reproduce some small pieces I made (basically 54mm accessories and 80mm heads) with a silicon mould, so I would like to know what is the difference between epoxy and polyurethane resins and what is the best for this kind of work.
Thanks, Luca

 

[btavis]

Resin is the best for casting as it is a liquid that can be poured to fill all of the mold cavity.

 

[Calvin]

Hi Bob, sorry for my poor english, but I was referring to epoxy resin vs polyurethane resin.
There are two products, from a well known brand here in Spain, the epoxy resin and the polyurethane resin.
For what I know, the epoxy resin needs more time to set and is more dense, while the polyurethane resin is more liquid and with a reduced working time, so I would like to know what is the best medium for the very little pieces I need to reproduce and what kind of product you are using.
Thanks, Luca

 

[btavis]

It depends on what it is you are trying to cast and the type of mold. For a two part mold with a lot of detail and large cavity the less viscose polyeurethane is probably the best. You really do not need a lot of working time and the mixture can be measured, mixed and poured within two minutes. Ensure you have probper vent holes in the mold to allow for the resin to fill every part of the mold cavity. Unless of course if you have a vacuum or prssure chamber then the vacuum or pressure will force the resin into the cavity.

I have experimented with at least half dozen different types of resin and the each have their own characteristics. The best thing is to experiment and develop an understanding of your own with whatever materials you have selected.