I'm looking for an elastic material (e.g., a rubber), whose tangential elastic modulus E is lower than 1 MPa (0.5 MPa would be enough). Anyone has an idea of which kind of rubber could fit this specification? I need a tube (16-25 mm diameter, and 1-4 mm wall thickness) of this material to simulate an artery (e.g., aorta) in a biomedical engineering application at room temperature. Unfortunately, arteries have a very low Young Modulus and it is very difficult to find a material with characteristics as close as possible to the ones of an artery. Thank you for any helpful information.
Silicone gels can be this soft.
Your requirement is quite extreme, so you are unlikely to find a ready tube. But you can find a solution, that will harden in a required shape.
So, I suggest to look for liquid silicone gels, that harden when mixed with hardener, like epoxy. An example, that is probably too soft, 0.2 MPa, but gives an idea: https://www.wacker.com/h/de-se/medias/6982-EN.pdf
It seems tupical silicone is too tough for your use, as it is about 5 MPa, and tupical silicone gel is too soft for your use, it is about 0.01 MPa. So look for tough silicone gel. I think it is easier to make silicone gel harder, than silicone softer.