editing a jacket accessory

hi, i was wondering if anyone can tell me how to change a jacket accessory so that it doesn't follow and morph to the sim in game? So that it acts as if it were an actual accessory. In blender I've managed to get it to act like an 'object' that you can pose and animate with, but in game it morphs to the body of the sim. (I'm not familiar with blender) 

thanks in advance.