In the temperature range of about 50-120 ºC, a clear endothermic effect can be observed, characteristic of the melting of semi-crystalline domains originating from the so-called 'hard segment' of the polymer chain (PBS block) . The melting effect recorded has a bimodal distribution in all cases, indicating the presence of two types of crystallites in the system. This fact is not directly related to the presence of HAp particles in the system, as it can also be observed in the reference sample coPBS. This phenomenon can be the subject of separate studies. The melting point Tm was determined as the maximum of the predominant peak and differs slightly for all materials and is in the range of 106.9 ºC -107.7 ºC. It should also be noted that such a wide melting range of the material can lead to instability of the material properties already from about 40 ºC for some samples. Calculations of the degree of crystallinity showed no significant influence of the hydroxyapatite filler on the crystallinity of the copolymer.