# Structural Features and Properties' Characterization of
## 2 Materials and Methods  
In our research, we used Ingeo 4043D extrusion PLA by NatureWorks (Blair, NE, USA), of 1.24 g/cm\({}^{3}\) density. SMRCV60 natural rubber (Barena Group, Kuala Lumpur, Malaysia) was also used. A total of 200C epoxidized soybean oil was obtained from Galata Chemicals (Southbury, CT, USA).  
Before mixing, pre-treatment of the polymers was as follows: the PLA was vacuum-dried for 8 hours at 80 \({}^{\circ}\)C, and NR was plasticized on a two-roll mill at ambient temperature for 15 min. This operation improves the processability of NR. The components were mixed in a closed double-rotor mixer for 30 min at 160 \({}^{\circ}\)C and 60 RPM. Based on the previously published recommendations [24; 25] the PLA/NR ratio was 60/40. The ESO in-polymer content varied at 5, 10, 15 and 20 ppb (the samples were tagged M0--no oil; M5, M10, M15, M20, respectively. The number is the ESO content). Samples for physical and mechanical tests were injection molded at 170 \({}^{\circ}\)C.  
To run the physical and mechanical tests, the Autograph AG-X 5 kN tensile testing machine by [PERSON] (Kyoto, Japan) was used at room temperature. The upper clamp moved at 100 mm/min. All samples were tested 5 times.  
The scanning electron microscopy of the obtained samples' structure was carried out on a JSM-6510 scanning electron microscope by JEOL (Akishima City, Japan). To make the samples brittle, they were cooled in liquid nitrogen and then broken, thus giving a fresh cleavage. Following that, to improve the quality and clarity of photographs, a layer of platinum was deposited upon the surface at 4 Pa pressure. The thickness of the deposited layer was 8 nm.  
Differential scanning calorimetry (DSC) was used to determine the compounds' thermophysical properties. The DSC curves were recorded on a DSC-60 calorimeter by [PERSON] (Kyoto, Japan). The samples were heated in aluminum crucibles. The reference sample was aluminum oxide. The tests were run in a nitrogen atmosphere at 50 mL/min flow rate; the temperature range varied from room temperature to 180 \({}^{\circ}\)C; and the heating rate was 10 K/min. The instrument was calibrated against indium, tin, and lead. The samples inside the crucible weighed about 5 mg. To eliminate the samples' thermal history, they were heated up to 180 \({}^{\circ}\)C for 5 min, cooled to room temperature, and then reheated to record the final DSC curve. All samples were tested 3 times.  
The study of the thermal stability of materials was carried out on a DTG-60 synchronous thermal analyzer by Shimadzu (Kyoto, Japan). The samples were heated in platinum crucibles. The reference sample was aluminum oxide. The tests were run in an air atmosphere at 150 mL/min flow rate; the temperature range varied from room temperature to 600 \({}^{\circ}\)C; and the heating rate was 10 K/min. The instrument was calibrated against indium, tin, and lead. The samples inside the crucible weighed about 7 mg.  
The rheological properties tests were run on the StressTech multifunctional rheometer by REOLOGAC Instruments AB (Lund, Sweden) at 170 \({}^{\circ}\)C. The melts' dynamic characteristics (G', G'', \(\eta\)) were measured in the 0.01-10 Hz frequency range. The design of the test cell was that of two parallel surfaces (25 mm in work diameter).