What would be the best solution for attaching polyurethane foam to a lycra sheet of material. I was thinking a chain or pad stitch or possibly glue, but not sure if sewing would be the best alternative or another approach might work better to secure firmly these two types of materials together?
Or alternative, how to bond polyurethane foam with a leather sheet?
Sewing may work, depending on the context, the problem here is that the stitches are quite likely to tear through the foam and may well work loose over time through friction causing the thread to effectively saw through it.
Adhesive may be the most effective solution, this will be easier with something like leather as there is less likelihood of it soaking through to the surface of the fabric. Here something like a latex based contact adhesive should work reasonably well.
For more porous textiles you could look at bonding a lining of something like canvas or calico to the foam first and then stitching into that or using double sided tape or Velcro.
In all cases I would advise doing some tests with small samples to get a feel for how different methods will perform.
I think your best bet is to provide a far more porous "interface": sew on a strip or whatever other shape you need of a porous cloth - cotton, flax, etc, then glue that to polyurethane - even using spray-on PUR foam - either as glue, or just as the foam, shaping it as needed in a cast.
