Polyurethane Casting Resins FAQ

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1. I find I get bubbles in my clear casting resins; why is this?

Even after vacuuming, once the resin is poured into the mould it can extract air from the mould itself, particularly as the temperature rises as it starts to cure (the exotherm increases). We would always suggest that the way to avoid this is to preheat the mould for 1-2hours at 40-50 degrees C. -

2. What if my urethane shows low tensile strength?

In thinner sections, they can be brittle: this would generally be the result of poor mixing or wrong ratio. This can be counteracted to some degree by post curing, which will improve the properties -

3. At what temperature should they be used?

Most need to be used at room temp)25 degrees C), but there are some that require an elevated temperature for curing. -

4. How can I determine which Pu I should use?

There are several criteria you can sort by: Thin/thick section casting Quick setting Filled resins Water white/clear castings Heat resistance High impact resistance Thermoplastic appearance Room temperature curing -