## 3 Results and Discussion
### Tensile Test of Extruded PVB Filament  
Tensile testing was performed on a specific device, TestometricX350-5, Testometric Company Ltd., Oldham, UK according to standard DIN 527-1. The diameter of the produced filament yams corresponds to 1.75 mm. A total of five groups of measurements were taken, and every group consisted of six specimens as stripes. Tensile testing was performed to specify which extrusion temperature is optimal for the best material characteristics of filament yams [17; 29]. The TestometricX350-5 device is a tabletop, two-column, computer-controlled universal testing machine for testing materials in tension, compression, bending, cyclic loading, adhesion, shear, hardness, and spring testing. A modern and functional design, the latest control electronics, and high-quality processing characterize the machine. The electronics are placed on silent blocks for protection against impact during tests. The machine is controlled using the modern Wintest Analysis software running on the Windows operating system [27]. The software is fully configurable and allows for the setup of simple and more complex multi-step test methods. WinTest Analysis software, EC 6.2.5 is a complex system working on the Windows operating system. It is fully integrated and fully customizable software that supports the creation of test programs according to ISO, EN, ASTM, CSN, STN, DIN, BS, and other standards, including internal procedures and researchers' own specifications for testing materials [28; 30]. With the help of this software, it is possible to perform all the aforementioned tests on the machine. The software allows for the setup of simple tests for normal material testing. For development or research needs, there is a possibility of setting up multi-stage loading. The used device, Testometric X350-S, measured mechanical properties more precisely for performing a mechanical tensile test [31]. The load capacity is 5 kN, the feed rate is from 0.00001 to 2000 mm/min, the height (without jaws) is 1100 mm, the width is 320 mm, and the measuring range is from 0.4% to 100% of the nominal value of the load [32]. The tested samples were made in a stabilized environment; each sample had a constant length of 160 mm and a diameter of 1.75 mm. Standard jaws equipped with preparation for the possibility of attaching the fiber were used for the tests [33]. A sample of PVB filament with a diameter of 1.75 mm at a temperature of 140 \({}^{\circ}\)C is clamped in the jaws of a Testometric X350-5 tearing machine (Figure 10). A tensile test was used to evaluate the material's tensile strength [34]. The test's principle stressed the test body until the sample ruptured. The test sample was clamped in the jaws of the tearing machine [35]. Due to the constant speed, it was stretched [29]. Along with the increasing deformation, the force needed to maintain a continuous speed of the displacement of the jaws of the tearing machine also increased [36]. Parts of the sample are still attached in the jaws of the tearing machine, which are taken out after loosening the screws that hold the sample. Figure 10: Clamping a 1.75 mm filament sample in the jaws of a Testometric X350-5 tearing machine. The tensile test of the tested samples from recycled polyvinyl butyral (Table 3) took place at a room temperature of 23 \({}^{\circ}\)C and a humidity of 60%, according to DIN EN ISO 527-1. The following graphic representation (Figure 11) shows the measurement progress of a PVB filament with a diameter of 1.75 mm. The tensile test works on the principle of stressing the test sample until it breaks [21]. The tested PVB filament sample is clamped in the jaws of the tearing machine and gradually stretched at a constant speed [37]. As the deformation increases, the strength increases. Elongation at break is measured in % (% of elongation vs. initial size when a break occurs) [38]. The maximum elongation at the break (Emax) is also called \"strain to failure\". The force is required to maintain a continuous displacement speed of the jaws of the shredding machine.