UL pillow

Edward, just as a starting point for you; the Black Diamond Hot Forge Jacket uses 70% DWR-treated goose down and 30% PrimaLoft synthetic fibers in the body. I tried one of these jackets on and the instant warm-up was amazing. A cold weather pillow, mittens or booties would be a great application if you can shred/separate the fibers and mix with the down (if that is how BD does it).
Steofan M.

The properties that make Apex good clothing insulation aren’t so good for a pillow

Pillow insulation should be less compressible

But, can’t hurt to try it and see how you like it

I agree with Jerry… you are talking about making a big fluffy pillow, right up until the moment you put your head on it.  Then, the insulation will collapse and you’ll have a thick blanket under your head.

Have you tried an inflatable UL pillow?

The stuffing in seat cushions is good.  You could buy a seat cushion and scavenge.  Or they probably sell something at local fabric store.

That is what Wiggys bags are stuffed with.

Well it wasn’t a success, as predicted the APEX plus down is simply too soft to give enough support, I did add some stiff fibre pulled from a scrap of wall batt polyester insulation and that improved it , but of course it now won’t compact enough to be staffable. I’ll keep it and it will go with the base camp/car camping stuff.

I can see me sewing up a slip cover with this mixture in and using it over a blow-up pillow such as the S2S

I’ve found that Kapok fiber excels in this–good balance between some compression and resistance of same. I have some left over, and can send you some for free if you’d like?  Just take the pillow you already have, open up the seam on one end, take out the heavy, thick poly fill, and stuff the Kapok in. Of course it won’t pack down like Down, or even Primaloft or Apex, but it’s density is similar to lower quality duck down (like 550).

The side benefit, with enough Kapok, your pillow will also float.  But seriously, this stuff is great for mittens and boots/sock insulation as well as pillows. Warm, lightweight, highly hydrophobic, floats in water (thick, durable wax coating on hollow, sealed fibers), and has reasonable compressive potential for smaller items.

NOT so good for quilts or the like, too bulky compared to Down and Apex. Keep it away from fire though, highly, highly flammable (that same thick wax coating + cellulose. Loose stuff is great for tinder).