African American Hair and Straightening Techniques?

My hair is unmanageable at times. I cut off all the processed hair about two years ago and it has done extremely well. Unfortunately, it has gotten so long, I cannot put on a wig when I want straight hair and my curl is getting too curly when I want to wear that. I looked into the thermal reconditioning, bio ionic treatment, and the Brazilian keratin treatment thinking these would not damage my hair... They all seem harsh in their own right. So, have any ladies of African descent had any positive experiences with any of these treatments? And, ladies offering an opinion about acquiescence to the European culture and/or intentional imilation, I am not interested.