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Jack, you’re good. Both terms work. But if you want to be persnickety about it.

Urethane is the correct term for the monomer, the building block of the system chemically. Polyurethane is the term used when the monomer (urethane) has been stimulated either by heat or a catalyst to link together the individual monomer molecules into longer chains of molecules.

The chemistry of the catalyst is adjusted to control how long the chains become, and how much cross linking they form with other chains. The longer the chain the more elastic the polymer(elasticity), the more cross linking the more stiffness (modulus) the polymer will have.


The two part castable resins range from about 20a to 90a durometer. The catalyst chemistry is the controlling factor in the hardness of the part. These are designed for the chemical reaction to work at room temperature. They can take up to a week to fully cure into their final properties.

The injectable urethanes contain a heat activated catalyst. The reaction goes quickly and the part is ready to go as soon as it cools. These are not for the DYI guy.

Sorry you mentioned it right. Retired Chemical Engineer who spent his work life in polymer based industries couldn’t resist the explanation.

 
Thanks for the info Richard, this stuff is Greek to me, glad for your info. The one video I was watching shows him baking the parts in his wife’s oven after he casts them, guess that is your cross linking? He did it while his wife was away! I have a small toaster oven that I think will be perfect for this.