Charge

Although charges are normally arranged in a way so that they are evenly (neutrally) distributed, they can be redistributed. Thereby, different substances have got a certain susceptibility to charge. In case of many substances it is very difficult to change the neutral charge distribution. Plastic material on the other hand very easily absorbs negative charges so that can easily be charged negatively. Glass, amber or your hair deliver electrons quite quickly so that they can easily be charged positively.

So strictly speaking charge is not generated by rubbing. Instead of that existing charge particles of bodies are redistributed.
If you rub an air balloon on your hair, negative charges are released from your hair and accumulate in the balloon. Consequently, the balloon is charged negatively and your hair is charged positively then.