Use an ionic flat iron. It will not curl back easly.
Solia makes a Tourmaline Ceramic Ionic Flat Iron.
According to the Solia flat iron website, "tourmaline,
a precious stone, is used to generate up to 6 times more
negative ions than traditional ceramic irons".( $75/85)

* Solia Hairstyling - how to style & straighten hair
http://homebeautytips.blogspot.com/2007/01/solia-hair-styling-guide-to-solia-flat.html