When making fake dreads it's absolutely essential to use Kanekalon type fake-hair!
You *might* get lucky with other types, but chances are slim, as "KK" is the only hair that "melts" together good enough for the dreads to stick together.
Actually, I have been making dreads for over a year and a half, and for me, I don't think the KK works as well as the cheap synthetic braid. I am probably the ONLY person who believes this, but I also iron my dreads rather than steam or hairdry them. I like smooth, melted, skinny dreads, so the reaction of synthetic to my iron is perfect. If you're looking for a more natural, hairy finish, Scarab is right: KK is better for you.
Some recent projects for me, just so this isn't text only:
Double ended synthetic dreads in flamingo pink and lime, made from the synthetic.
And a single black and flamingo pink fall with swirls made for Rachel of Agent-Designs corsetry.