I knitted some chemocaps for myself.. and I used a soft yarn, 50 % cotton and 50 % acryl. Very nice. I used the Odessa pattern from Grumperina. I also knitted the Shedir hat from Knitty, and used the yarn in the pattern. I love that cap too.
I friend gave me a Odessa knitted with silcalpaca, it was quite scratchy before I washed it. Afterwards soft as the softest thing!
I wish your friend good luck!
One of mine Odessas
Pattern Odessa: www.magknits.com/feb06/patterns/odessa.htm
My Shedir: http://virtuella.blogdrive.com/archive/488.html
Pattern Shedir: http://www.knitty.com/issuefall04/knittyF04surp.pdf