Hi 1whitehorse1,
No … it would be “sock” that surrounds the interior components of the mattress and then the cover goes over this.
While it’s certainly a synthetic material (the same material that is used in bulletproof vests) I wouldn’t consider it to be toxic no. There is more about “safe” fire barriers in post #2 here and post #4 here and in post #13 here.
There is also an MSDS for kevlar here.
They don’t specify any further details about their fire barrier or whether it is all kevlar or just contains kevlar and includes other materials as well.
I share the same thoughts as well.
Phoenix