When I was trying to create hair from particles, this is what I did:
First, create the scalp by selecting faces on a 3D character's head. Select Shift+D to Duplicate those faces, then type "P" and Click on "Selection" to separate those duped faces to make its own object.
Then (I'm think this was an addon) click on Object>QUick Effects>Quick Fur. From here, you can look at the Particles tab (wherever you have it set up in the interface), and select the number of parent hairs, their length, and how many children you want those parent hairs to spawn (ok...that sounds disturbing.) From here, once the hairs become visible, you can switch from Object Mode to Particle Mode, and style your hair particles as you wish.
When happy with final style, go back to Object Mode, click on the Modifiers (Wrench) tab, and select "Convert". This will convert the particles of hair into a mesh...but it doesn't stop there. You actually have to convert the "mesh" into "Curves". Object>Convert to>Curves From Mesh/Text. Once this is done, deselect everything, and add a bezier circle (Add>Curve>Bezier Circle) to the canvas. (Be sure to translate the circle away from your build so that you can easily select and manipulate it). Switch to the Curves Tab. Select your hair, and then click on the eye-dropper in the Bevel Object button. This will now add geometry to your hair curves, and those curves are influenced by the size and shape of the Bezier Circle. Reduce the Bezier circle so that the individual hairs reduce in witdh to something to your liking. Now, while still in Edit Mode, type A to select all the hair curves, then type P and click on Separate. This will duplicate those curves, but those duplications will now be separated from the Scalp Mesh. The hair sources that are still on the Scalp Mesh are STILL in Particle mode. You can then delete the Scalp Mesh, (or move it to another layer) leaving only the hair curves.
Once that is done, Select Object>Convert To>Mesh from Curve/Meta/Surf/Text. Now your hair has become an mesh that you can export as a .obj. HEADS UP (no pun intended): This is extremely dense in terms of face count, and I do believe that when you do the conversion from Curves to Mesh, it does so in quads...so this may be about as low poly as you can get. You can use the Decimate modifier to try and reduce the face count, but there will be a lower limit, so the reduction might not be so much as to greatly effect a reduction in memory. Caveat Emptor!
I hope this helps. :)