how do you make an nparticle explosion?
 

Hi i have nparticle water filling a sphere. At a certain frame i have turned off the collide so the particles begin to escape. but for the life of me i can't figure out how to make the nparticles explode outwards. I've tried adding a vortex field but can't get it too explode fast enough. Also texture wise i have a mia chrome material on the nparticle (which has been converted to a polygon mesh) but maya keeps telling me either there is no uv set or the mesh has no faces it alternates between those two messages. any help would be appreciated.