Tibolone polymorphic forms I (monoclinic) and II (triclinic) have been prepared by recrystallization from acetone and toluene,
respectively, and characterized by different techniques sensitive to changes in solid state, such as polarized light microscopy,
X-ray powder diffractometry, thermal analysis (TG/DTG/DSC), and vibrational spectroscopy (FTIR and Raman microscopy). The
nonisothermal decomposition kinetics of the obtained polymorphs were studied using thermogravimetry. The activation energies
were calculated through the Ozawa’s method for the first step of decomposition, the triclinic form showed a lower Ea (91 kJ mol−1) than the monoclinic one (95 kJ mol−1). Furthermore, Raman microscopy and DSC at low heating rates were used to identify and follow the thermal decomposition of
the triclinic form, showing the existence of three thermal events before the first mass loss.