Fire blanket construction

Does anyone know what the "fire retardant inner layer" in a fire blanket is made from ? For example, the top two blankets on this page '&ispcb180
A search using Google didn't turn up anything specific.
I was hoping to use one as a cheap source of fibreglass for a epoxy fibreglass repair job, but it may not be suitable unless I can separate the fibreglass layers from the retardant.
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