Differential scanning calorimeter (DSC) was performed on DSC-XP-10 unit . Samples between 5 and 20 mg were placed in platinum pans and were heated from 25 to 120 °C at a heating rate of 10 °C min -1 and cooled at a cooling rate of 10 °C min -1 to -80 °C. After that, samples were heated again to 120 °C and subsequently cooled to 25 °C. Decomposition temperatures were determined visually using Melting Point System MP90 apparatus (Mettler Toledo, USA).