## 1 Introduction  
One of the most important biodegradable polymers, produced from petroleum resources, is poly(\(\varepsilon\)-caprolactone) (PCL) [1; 2; 3; 4; 5]. Its physico-chemical properties are generally beneficial and the material may play a key role in many branches of the economy (both in specialised and mass applications). However, the PCL properties need to be modified for some applications. It concerns, for example, properties such as its thermal resistance due to low melt temperatures (58-60 \({}^{\circ}\)C) or its barrier properties for some gases [6; 7; 8]. PCL mechanical properties can also be modified with the use of mineral or vegetable fillers that simultaneously lower the price of the polymer. It is important because PCL in its pristine form is generally more expensive than conventional polymers and even some biodegradable ones such as PLA [9; 10; 11; 12; 13] or TPS [14; 15; 16; 17]. PCL properties can be modified by different methods. Various types of PCL polymer blends as well as composites and nanocomposites are most often obtained. The most well known PCL blends are: (i) PCL/TPS [18; 19; 20], (ii) PLA/PCL [21; 22; 23; 24] or (iii) PCL/PBAT [25]. PCL blends containing non-biodegradable polymers also exist, e.g., PCL/PVC [26] or PCL/PBT [27]. Another significant group is PCL composites with natural fillers, including plant fibers [28; 29; 30; 31; 32; 33; 34; 35]. Other known methods of PCL property modification refers to processes such as copolymerization, grafting and crosslinking [36; 37; 38; 39; 40; 41]. In this study, we proposed a combination of two methods to modify PCL properties. The first method refers to obtaining PCL composites with hemp fibers (HF) and the second method is related to irradiation of such obtained composites with the use of electron radiation. Our literature review revealed only a few studies on PCL/HF composites. For example, the experimental work carried out by [PERSON] et al. [42] investigated the reinforcement efficiency of hemp fibers with different fiber aspect ratios on PCL-based biocomposites and compared the influence of these aspect ratios on moisture absorption behavior along with the tensile, flexural and impact properties of hemp fiber/PCL biocomposites. In another study by this author [43], the effects of variable mean hemp fiber content on nano-mechanical (hardness, modulus, elasticity and plasticity), surface and thermal properties of hemp fiber/polycaprolactone biocomposites were studied. [PERSON] et al. [44] presented some test results of PCL/HF composites and compared them to the results of similar composites, i.e., those containing date palm fibers. Studies on PCL/HF composites have also been carried out by [PERSON] et al. [45], who examined, among other parameters, the effect of processing conditions on defibration and mechanical properties. Many more studies on PCL composites with other types of natural fibers have been conducted. Examples of such studies are presented in a review publication by [PERSON] et al. [46]. The authors of this publication concluded that green composites with enhanced mechanical properties can be successfully prepared. They also showed that natural fibers reduce the price of these composites and expand their application areas, which in turn could attract public interest. Key studies on the modification of PCL properties also concern its radiation modification, especially in cases of modified PCL to be applied in medicine or tissue engineering. Studies in this area were conducted mainly with the use of gamma radiation or electron radiation [47; 48; 49]. These studies indicated that PCL, when subjected solely to irradiation, does not form a significant amount of gel fraction and the degradation processes are not dominant at the same periods of time. Good crosslinking of PCL may be successfully carried out by using crosslinking agents such as triallyl isocyanurate (TAIC) [49; 50; 51]. Then, with the appropriately selected irradiation conditions, PCL can be completely crosslinked.