There's a great DIY forum at
www.thebabywearer.com where you could get more info on good materials for DIY wraps.
www.mamatoto.org has info, too.
Not only is there the concern about the grippiness of the knot, but also you want a fabric that a) will be supportive enough and b) will hold up to washing. I was just reading a thread at the Babywearer about single-layer silk ring slings starting to tear

after repeated use/washing, because the fabric just had too much wear and tear. So knowing how the fabric will respond to usage and to washing is v. important.