  We use the HIPSE (Heavy-Ion Phase-Space Exploration) Model to discuss the
origin of the bimodality in charge asymmetry observed in nuclear reactions
around the Fermi energy. We show that it may be related to the important
angular momentum (spin) transferred into the quasi-projectile before secondary
decay. As the spin overcomes the critical value, a sudden opening of decay
channels is induced and leads to a bimodal distribution for the charge
asymmetry. In the model, it is not assigned to a liquid-gas phase transition
but to specific instabilities in nuclei with high spin. Therefore, we propose
to use these reactions to study instabilities in rotating nuclear droplets.
