## 4 Analysis of the Automotive Lamp Reflector Application Test
### Analysis of the Reflector Temperature Distribution Test  
To measure the temperature difference between the reflectors due to the material change, a system was constructed as shown in Figure 6. Polycarbonate (PC) chambers were constructed to conduct the test in environments with conditions similar to the enclosed conditions wherein the reflector is mounted and used in a vehicle, and the fabricated PBT and PA6 (60) reflectors were set, respectively. The temperature measurement time was set to 50 min at which the temperature converged in a preliminary test, and the temperature of the reflector surface was measured after 50 min. A fog lamp h8 of 12 V and 35 W was used as the target lamp, and 12 V was applied using a power supply (SPS-2415). K-type thermocouples were attached to measure the temperature distributions of the reflectors. They were attached to three internal positions and three external positions above the lamp where the highest temperatures were predicted in the simulation [42]. This position was found to be the highest temperature, similar to the results predicted by infrared thermal camera (FLIR T620). A thermocouple was used for more accurate temperature measurement. Figure 7 shows the results of measuring the temperature of the reflector surface using a thermal imaging camera. The results obtained by the thermal imaging camera were not well defined for the accurate measurement of the temperature. This was due to the curvature offered by the reflector surface and the reflection of the surface itself; however, the trend of the overall temperature of the reflector surface was confirmed. Figure 6: Experimental setup for reflector temperature measurement, (**a**) reflector temperature measurement positions; (**b**) device setup. Figure 8 shows the temperature measurement results of the reflectors made of PBT (0) and PA6 (60). The measurement started simultaneously when the bulbs were turned on, and the measurement speed was set to 2 s. It was found that the temperature stabilized approximately 20 min after the start of the test. Figure 9 shows the temperatures of the reflectors made of PBT (0) and PA6 (60). FT2 in Figure 9a is the position closest to the lamp and, thus, it is the hottest position. The maximum temperature of the PBT reflector was 95.6 \({}^{\circ}\)C and that of the PA6 (60) reflector was 88.7 \({}^{\circ}\)C, which confirms the temperature of the reflector made of conventional PBT was approximately 7 \({}^{\circ}\)C higher. This is the result caused by the difference in heat transfer between the materials. Moreover, it was found that PA6 exhibited relatively higher temperatures at FT1 and FT3. Figure 8: Reflector temperature measurement results over time: (**a**) temperature distribution of the PBT reflector, (**b**) temperature distribution of the reflector made of PA6-based composites. Figure 7: Temperature distribution on reflector surface measured using a thermal imaging camera. As PA6 (60) has higher thermal conductivity than PBT, it can be estimated that more heat transfer from FT2 increased the temperatures. While the difference between the maximum and minimum temperatures was approximately 32 \({}^{\circ}\)C for PBT, it was approximately 23 \({}^{\circ}\)C for PA6 (60). Figure 9b shows the temperatures measured at three points outside the reflectors. The maximum temperature was observed at the position of BT2, and the value was 74.4 \({}^{\circ}\)C for the PBT reflector and 77 \({}^{\circ}\)C for the PA6 (60) reflector. Among the temperatures behind the PBT reflector, those of BT1 and BT3 were 55.1 and 54.8 \({}^{\circ}\)C, respectively, indicating no significant temperature change. In the case of the PA6 (60) reflector, however, the temperatures rose to 60 and 64.8 \({}^{\circ}\)C, respectively. This appears to be because the temperature of the bulb was well transferred to the back of the reflector owing to the thermal conductivity of the material applied to the reflector. Therefore, the PA6 (60) reflector exhibited higher temperatures at all three points behind the reflector.