"Detailed Explanation of Aging Test Technology of Polymer Materials Laboratory" mainly introduces the common artificial accelerated aging test methods, including fluorescent ultraviolet lamp aging, carbon arc lamp aging, xenon lamp aging, metal halide lamp aging and other test methods, and introduces The spectral energy distribution of various commonly used light sources and their respective advantages and disadvantages, as well as common light aging Test Chambers and common test standards for various light sources. The following extracts part of the article and introduces several different aging test methods.
1. Fluorescent UV aging test
The ultraviolet aging Test Chamber uses fluorescent ultraviolet lamps as the light source, and conducts accelerated weather resistance tests on materials by simulating ultraviolet radiation and condensation in natural sunlight to obtain the results of material weather resistance. The fluorescent ultraviolet test can simulate natural environmental conditions such as ultraviolet light, rain, high temperature, high humidity, condensation, darkness, etc., and carry out aging tests by reproducing these conditions and cycling them. At present, the commonly used ultraviolet light sources are divided into two categories: long-wave ultraviolet light source (UVA lamp) and short-wave ultraviolet light source (UVB lamp). There are four types of light sources in total, and their spectral energy distribution is shown in Figure 1 [1] .
1.1 Long wave ultraviolet light source
Long-wave UV lamps are especially useful for comparing the UV resistance of different types of polymers. Because the spectrum of UVA lamps does not contain ultraviolet light below 295nm, which is the same as the wavelength cut-off point of outdoor sunlight, it is usually not as fast as short-wave ultraviolet rays destroy materials, but they are closer to real outdoor aging. Commonly used light sources include:
(1) UVA-340 light source is closer to the spectrum of sunlight in the ultraviolet band of 295nm to 365nm, and its radiation peak is at 340nm, which is currently the ultraviolet light source closer to outdoor sunlight;
(2) UVA-351 light source, which simulates the ultraviolet part of sunlight filtered by window glass, it is suitable for indoor environment applications. Used to test the aging properties of materials in indoor environments such as inks and polymers near windows.
1.2 Short-wave ultraviolet light source
The spectrum of the short-wave ultraviolet light source includes ultraviolet rays from 280nm to 400nm. Among them, the ultraviolet rays from 280nm to 295nm, which reach the surface of the earth, do not include this part of ultraviolet rays, but this part of ultraviolet energy is relatively strong, and it is easy to make polymer materials Aging occurs, which sometimes causes distortion in the aging results, that is, it is different from the actual outdoor use. At present, the application of this light source is less and less, and it is often used to quickly screen materials and study the UV resistance of materials. The current UVB light tube also includes two types, they have the same spectral distribution, but the total amount of ultraviolet light emitted is different. One is UVB-313 light source, and the other is FS-40 light source. At present, the application of these two light sources is less and less, and there is a tendency to be gradually eliminated.
1.3 Fluorescent UV Test Chamber
Currently popular UV Test Chambers on the market include Q-Lab’s Q-spray series Test Chambers and ATLAS’ QUV2000 series of Test Chambers. Simultaneously control the irradiance and the temperature of the blackboard to realize conditions such as condensation and spraying; however, the current domestically produced UV Test Chambers cannot control the irradiance, and often fail to meet the requirements of the standard. Currently commonly used standards for testing include ASTM G154, ISO4892-3, SAE J2020, GB/T16422.3, GB/T 14522, etc.
2. Carbon arc lamp aging test
At present, carbon arc and other aging tests mainly include two types, one is a closed carbon arc lamp, and the other is a sunlight carbon arc lamp. These two carbon arc lamps are used in early photoaging test equipment. The former was originally used Used in textile lightfastness testing, the latter was originally used for lightfastness testing of coatings. The illuminant of an enclosed carbon arc lamp is a set of carbon rods through which an electric current emits an arc. However, the spectral energy distribution of arc light emitted by carbon rods is quite different from that of natural light. There is neither short-wave ultraviolet radiation of natural light nor high-intensity energy of sunlight between 400nm and 800nm. The matching of the spectral energy distribution of sunlight-type carbon arc lamps and sunlight has been improved, but there is still a big difference in the spectral energy distribution between the two between 50nm and 350nm. Please refer to Figure 2 [2] for the specific spectral distribution.
Sunlight carbon arc lamps are rarely used in my country at present, but they are widely used light sources in Japan, and most of the JIS standards use sunlight carbon arc lamps. Many of our country's joint ventures with Japan still recommend the use of this light source. The spectral energy distribution of sunlight-type carbon arc lamps is also closer to that of sunlight, but the ultraviolet rays are concentrated and strengthened at 370nm to 390nm, and the simulation is not as good as that of xenon lamps, and the acceleration rate is between xenon lamps and ultraviolet lamps.
Carbon arc lamps require frequent replacement of carbon rods, and generally cannot accurately control the illuminance. Currently, commonly used test standards include ASTM G152-06, Cycle1, 2, 4, 5 (non-metallic materials), ASTM D822-01 (2006) (paint ), ASTM D3361-01 (2006) (no filter, coating), ASTM D1499-2005 (plastic), JISD0205-1987, NES M0135, etc.
At present, the Test Chambers that can be found in CHINA are mainly the SUGA brand imported from Japan, and there are also domestic ones, but the carbon rods must be imported from Japan. The use of carbon arc lamps is troublesome. Not only do you need to replace the carbon rods regularly, because the carbon rods are directly burned, the ashes generated after the carbon rods are burned are likely to cause pollution, and you also need to clean the filter regularly, clean the Test Chamber regularly, test consumables and labor costs are relatively large.
3. Xenon lamp aging test
At present, the xenon arc lamp is a better light source. By replacing the filter, it can better simulate outdoor natural sunlight and sunlight through window glass[2] . Xenon arc lamps were first used in the plastics industry. Because their test results can better simulate the actual weather resistance of products, many international standards, such as AATCC, ASTM, ISO and government organizations, use xenon arc lamps. The textile industry, a traditional user of carbon arc lamps, has now also changed the norm to adopt xenon arc lamps. Xenon lamps can simulate different types of sunlight through different filter combinations. Common filter types include: daylight filter, window glass filter, and ultraviolet filter. The irradiance intensity of light is usually
Four ways, see Table 1 for details. Different control methods can be converted, and usually the equipment manufacturer will provide a conversion formula.
At present, the Ci series of water-cooled xenon arc lamps of ATLAS and the Q-sun series of xenon lamp Test Chambers of Q-Lab are commonly used in CHINA. The internal structures of these Test Chambers are different, but the test principle is the same. Different filters get different types of spectra, and rain is simulated by spraying. Please refer to Table 2 for the current frequently used standards.
4. Metal halide light aging test
Metal halide lamps are also a good light source. The light source is usually a metal halide lamp, usually for component testing. Its wavelength range is 280nm-3000nm, and the irradiance intensity is 800-1200w/m 2 . The spectral energy distribution can be referred to in the figure 3 [2]. It can control temperature and humidity, and can obtain a relatively high temperature of the Test Chamber. It can reach a maximum of 80°C during the light period and 90°C during the dark period. Common test standards include DIN 75220, GB/T 2423.24, IEC60068-2-5, ISO 9022-9, ISO 12097-2, MIL-STD-810G (Method 505.5), PV 1211 and other standards.
5. Aging test requirements
5.1 Selection of light source
The first step to carry out the aging test is to choose a suitable light source. Different light sources may cause great differences in the results of the aging test. The following points are provided for your reference:
(1) Choose a suitable light source according to the test standard. For example, most standards in Japan will use carbon arc light source, while most European and American standards will choose xenon arc light source;
(2) Select according to the actual use of the sample: for materials used outdoors, in order to simulate the actual outdoor situation, xenon arc light source + outdoor sunlight filter is generally used; for indoor products or car interiors, xenon arc is generally selected Light source + window glass filter; military products generally choose metal halide light source;
(3) Select the light source according to the purpose of the experiment: for example, in order to simulate the outdoor performance of materials, choose xenon lamps and metal halide lamps. If you want to quickly screen materials and examine the UV resistance of materials, you can choose ultraviolet light sources first.
At present, xenon lamps and metal halide lamps have the advantages of wide wavelength range, the ability to simulate different lighting conditions through various filter combinations, spraying, and stable irradiance, and are increasingly becoming the preferred light sources for aging tests. Fluorescent ultraviolet lamps and carbon arc lamps are gradually phased out due to poor simulation performance, and many manufacturers are unwilling to continue to use them.
5.2 Appearance inspection and evaluation before and after the test
The inspection of the samples before and after the light aging test usually includes the appearance defects such as color, luster, chalking, cracking, etc. of the product, as well as the physical properties of the material such as tensile strength, bending strength, impact strength, etc. The general time for appearance inspection Shorter, usually below 1000h, and the detection of physical properties generally requires more than 2000h. Attention should be paid to visual inspection, as far as possible on the same point of the material.
5.3 Relevance and comparability of tests
Due to the poor stability of the light source, the reproducibility of the laboratory aging test results is still relatively poor; in addition, due to the difference in the spectral energy distribution of the light source, the results of the aging test between different light sources are not comparable; even the same light source The comparability of different equipment models is relatively poor.
