Not sure I have answer. I will tell you that I have tried stitch witchery (iron-on fabric adhesive) on felt, and it 'melted' the felt.
I saw this on J's website: Ultrahold Iron-On adheisve is a paper backled sheet of solid heat activated adhesive. It uses a low temperature & short pressing time so it allows for a wider range of materials that can be bonded. Use with fabric, foil, lame, denium, felt, suede, leather, wood and cardboard. Machine washable. There is no steam or pressing cloth needed. It will not lift or pucker after washing. It's no-sew bond is three times stronger than any other traditional fusible web.