Answer:
Poly-m-phenylene isophthalamide (Nomex)
Step-by-step explanation:
Nomex is a highly-resistant material used as a heat-resistant fiber and can be used as an insulating material or a protecting coat for a hot mitt.
It is a poly-m-phenylene isophthalamide that has multiple advantages for this use such as high flexibility, great insulating properties, good absorption of moisture, and is known to have a high level of comfort - which is also important in mitts. Moreover, it exhibits very low flammability, self-estinguish, and high durability.
Therefore, I would choose the meta-aramid Nomex as an insulating substance for a hot mitt.