## 3 Results and Discussion
### Mechanical Properties
However, in the case of a filling with more than 10%, a significant growth in its value is observed. The M\({}_{\rm f}\) value of the composite containing 20% HF is over two times greater than the modulus of pristine PCL. This knowledge has significant importance on the eventual suitable range of application for these types of composites. Irradiation of PCL/HF composites affects their M\({}_{\rm f}\) values. When the radiation dose is 10 kGy, a significant increase in the M\({}_{\rm f}\) value is observed. Higher doses do not have a considerable influence on the further growth of modulus values. Differences in M\({}_{\rm f}\) values of composites irradiated with doses of 20, 40 or 60 kGy do not differ notably from each other (Table 2). An exception to this is the case of when the CF20 composite is irradiated with 90 kGy and its M\({}_{\rm f}\) value decreases slightly. This may be due to degradation of both composite phases and, in particular, the HF phase. We can assume this because no decrease in the M\({}_{\rm f}\) value was observed for lower fiber contents. The impact strength (a\({}_{\rm cN}\)) of PCL shown in Figure 7 decreases significantly as the radiation dose increases. The maximum decrease in the PCL's impact strength, 56%, occurs upon irradiation of the polymer with 90 kGy. This may result from the formation of a branched or partially crosslinked structure of PCL macromolecules that hinders their conformational changes. This, in turn, limits the amount of energy absorbed by the irradiated PCL. Possible limitations for the rotation of macromolecular fragments can also affect other mechanical properties, including M\({}_{\text{f}}\) or \(\epsilon_{\text{B}}\), which were presented earlier. The PCL/HF composites are also characterised by significantly reduced impact strength. It is also worth noting that the highest impact strength of non-irradiated composite (sample CF2.5) is considerably lower than the lowest impact strength value of irradiated PCL. By introducing the amount of just 2.5% of fibers (sample CF2.5) into the polymer matrix causes a reduction in impact strength by 60% and the addition of 20% fibers (sample CF20) reduces its value by 78%. Therefore, it can be concluded that the impact strength of PCL is more significantly influenced by even a minimal amount (2.5 wt%) of fibers introduced into the polymer matrix than by electron radiation with the highest applied dose (90 kGy). In the case of irradiated PCL/HF composites, further decreases in impact strength are observed. However, while present, the changes in impact strength of the composite after irradiation are less significant. For example, the impact strength of the CF2.5 composite after irradiation with the maximum dose (90 kGy) decreases by a maximum of 83% compared to the impact strength of pristine PCL. Thus, irradiation decreases the impact strength of PCL by an additional 23% compared to the non-irradiated CF2.5 composite. In turn, the impact strength of the composite containing the maximum amount of fibers (sample CF20) and irradiated with the maximum dose (90 kGy) decreases by a maximum of 88% compared to the impact strength of pristine PCL. For this composite (CF20), irradiation decreases the impact strength of PCL by an additional 10% compared to the non-irradiated CF20 composite. The data in Table 2 indicates that large relative changes occur in the impact strength values for individual composites after irradiation. For example, doses of 10 and 90 kGy led to a decrease in the impact strength of the CF2.5 composite by 24% and 57%, respectively. Moreover, an increase in the HF weight fraction in the PCL matrix causes a decrease in the relative differences in impact strength for composites after irradiation. For example, the doses of 10 and 90 kGy decreases the impact strength of CF20 composite by 19% and 48%, respectively.