polymer materials will inevitably be affected by thermal oxygen aging during processing, storage and use, and thus change. In terms of appearance, such as: the material becomes sticky, pulverized, brittle, deformation, and color changes; in terms of mechanical properties, such as: tensile, bending, impact and other properties, such as: breakdown voltage, resistivity and other properties, and in terms of flame retardant properties, such as: flame retardant grade decreases. After polymer materials are affected by thermal oxygen aging, the service life of the product will be shortened, which greatly affects the economicality and environmental protection of products, thereby limiting the scope of use of the product. Therefore, it is of great significance to the study of factors affecting thermal oxygen aging. In recent years, research on thermal oxygen aging of polymer materials has mainly focused on in product , while there are few researches on the impact of thermal oxygen aging equipment on material aging performance. This paper comprehensively studies the configuration of the oven exhaust duct, the temperature difference in different areas of the oven, the impact on the thermal oxygen aging performance of polypropylene materials, and whether to lay the foundation for the influence of thermal insulation material on the thermal oxygen aging performance of polypropylene materials.
. Experiment
.1 Instrument
Hot oxygen aging oven; thermocouple FRUKE; Nine-point temperature equalization rack and temperature monitor FRUKE; Polypropylene (PP) made by the company.
.2 Experiment
.2.1 Analysis on the impact of adding a cover at the oven exhaust duct on the oven parameters
Analysis of the temperature equalization data of the oven at nine o'clock when the cover is in the upper, middle and lower part of the exhaust duct. The specific data are shown in Table 1, Table 2, and Table 3:
html ml1 In addition, when the exhaust duct is located at the upper, middle and lower ends of the cover, the corresponding ventilation rate data is measured, see Table 4:
According to the above results, it can be seen that the nine-point average temperature of the oven and the power meter were used to confirm the ventilation rate of the oven. It was found that the nine-point average temperature setting temperature deviation and the maximum temperature change did not change significantly when the exhaust duct is located at different positions of the cover. When the exhaust duct is located at the upper end of the cover, the ventilation rate is the largest. This is mainly because when the exhaust duct is located at the upper end of the cover, the gas inside the oven is subjected to a greater suction force, which leads to a larger ventilation rate.
.2.2 The difference in temperatures in different areas of the oven and its impact on sample performance
The oven is divided into three upper, middle and lower layers, each layer is divided into four areas, and the temperature collector is used to detect the temperature of the surface of the sample in 12 areas in real time. After aging at 150°C for 500 hours, the tensile performance of the PP sample was tested.The thermocouple line monitors the temperature of 12 areas, and the schematic diagram is shown in Figure 1;
Figure 1 Temperature monitoring diagram of different locations of the oven
2 areas of the sample surface is shown in Table 5;
Results show that the temperature of the sample surface in the oven is detected in real time by using the temperature collector, and the results show that the temperature of the sample surface in the oven is passed through the thermocouple. The temperature detection found that there was a certain difference in the temperatures of the 12 areas. The highest temperature was the first area of the third layer, the lowest temperature appeared in the fourth area of the third layer, and the lowest temperature difference was 1.7℃;
Tensile performance was tested for PP samples placed in the 12 areas after aging for 500 hours. The results are shown in Table 6;
According to the data in the above table, it can be seen that the tensile performance is not a symmetrical change pattern with the aging temperature, and the maximum value appears in the first area of the first layer and the second area of the second layer. , whether the minimum value appears in the third area of the second layer. Whether it is related to the oxygen content in the area, this issue still needs to be verified further;
.2.3 Effect of thermal insulation material on thermal oxygen aging performance
Use pad insulation material and no padding material to test the mechanical properties of PP samples after aging for 500 hours. The pictures of pad insulation material and no padding insulation material are shown in 2;
Figure 2 The tensile performance test results of the padding insulation material and the non-painting insulation material
unpainting material sample are shown in Table 7; the tensile performance test results of the
unpainting material sample are shown in Table 8; the tensile performance test results of the
According to the above results, it can be seen that the sample performance of the pad insulation material after 500 hours is slightly better than that of the sample after aging without any material; this is mainly because after laying the pad insulation material, the bottom heat at the sample is worse than that of the without padding material, which causes the sample to age slowly and maintain better performance; the reason for the poor performance of the aging sample without laying the thermal insulation material may be related to the direct contact of the sample in the sample and the metal catalytic degradation of polymer materials at high temperatures.
. Conclusion
This paper studies the impact of three different situations on the thermal oxygen aging performance of polypropylene materials from the perspective of the equipment itself and auxiliary facilities. According to the experimental results, it can be seen that: (1) The configuration of the exhaust duct has no significant impact on the set temperature deviation of the oven and the maximum temperature change, but it has a certain impact on the ventilation rate of the oven; (2) There are certain temperature differences in different areas of the oven, but there is no significant difference in the tensile properties of the polypropylene material after 500 hours of thermal oxygen aging in different areas; (3) After 500 hours of thermal oxygen aging, the tensile properties of the polypropylene that lays the insulation material is better than those without laying any materials.
