In 3dsMax I assigned the left arm a separate material from the rest of the the body. How do I use the two different materials in Unity?
You need to use submeshes in order to use multiple materials in Unity, where each material is applied to a different submesh. I don’t know how Max works, but in Blender you can make submeshes by assigning different textures to different parts of the mesh.
I have word about it in past with our 3D artist. they are used Polygon Map to used multiple material in a single mesh and every part take texture from different martial.
please talk with your 3D Max Artist about Polygon map.