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50-year limit test
The Significance of Durability Research of Silicone Structural Sealant
First, what is the durability of sealant?
The durability of the sealant is an indicator to examine the adhesive sealability and the bulk performance of the sealant during its use. In the use environment, the sealant is subjected to cyclical stress while undergoing various environmental factors, so its durability is particularly important.
Second, what factors affect the durability of sealant?
Durability is the property of the sealant to resist aging. The aging of the sealant is an extremely complicated process that combines various internal and external factors.
Intrinsic factors: sealant chemical composition and aggregate structure;
External factors: physical factors, including heat, light, high-energy radiation and mechanical stress;
Chemical factors, including the effects of oxygen, ozone, water, acids, alkalis, etc.;
Biological factors, such as the role of microorganisms and insects.
Third, how to evaluate the durability of sealant?
In order to verify the durability of the sealant, that is, its actual outdoor service life, it is necessary to carry out aging tests on the sealant. Common aging test methods include laboratory accelerated exposure test (artificial weathering test) and natural weather exposure test (natural aging).
At present, relevant domestic and foreign standards, for the durability of the sealant, most of the detection methods adopted are artificially accelerated weathering tests. The main reason is that the natural climate exposure test has a long detection period and high test costs. After examining the aging of the natural environment, it is believed that the main factors that cause the aging of the sealant are light, heat and water, and of course, the erosion of ozone. In order to shorten the time for obtaining results, people use laboratory simulations and enhanced methods to accelerate the speed of sealant damage and expect to obtain test results similar to atmospheric exposure in a relatively short period of time.
Although artificial accelerated weathering test can reflect the durability of sealant to a certain extent, the actual condition of sealant aging in natural environment is much more complicated than that in laboratory test. For silicone adhesive Ketone glue is provided by the Industry Encyclopedia. The relationship between artificial weather accelerated weathering test and actual service life has not been established yet. Therefore, it is difficult to use the artificial accelerated weather aging test as the basis for judging the actual service life.
The natural weather exposure test (also known as outdoor weathering test) is similar to the actual use environment. Exposure of the sample to natural weather conditions exposes it to the combined effects of sunlight, temperature, oxygen, and other climatic factors and determines its performance. Change to evaluate the durability of the sealant that is the actual life. For the problem of the durability of the sealant, a more reliable conclusion can be obtained, which is the basis for the study of the durability of the sealant, and therefore has been paid attention and adopted by people. The best method for the aging performance of the sealant is to identify it by natural aging; the data obtained from many artificial aging tests must also be compared and verified by atmospheric aging tests.
Due to the ever-changing natural climate and aging performance of sealants, natural ageing tests are often conducted by selecting weathering sites in specific areas under typical natural climatic conditions.
Fourth, the durability of silicone structural sealant research
With regard to durability testing methods for structural sealants, there is currently no accelerated test method that can simulate 25-year aging under natural environmental conditions. The US standard ASTM C1184 proposes a 5,000-hour UV aging test. The Chinese GB/T16776 water-ultraviolet test is a simplified modification based on the US standard. The EU standard ETAG002 and the industry standard JG/T475 are for UV, temperature, water, and load. , contact materials and other aspects of the aging test.
Baiyun Chemical's products have passed the test of structural adhesive standards of the United States in 2007. This test was conducted by the DL laboratory in the United States. In 2013, it passed the test of various items of the EU standard ETAG002. Currently, the industry standard JG/T475 has been completed. Purpose test.
Baiyun Chemical Co., Ltd. has started the aging research of silicone structural adhesives under natural environmental conditions since 1997. Since the curtain wall natural exposure test has been conducted for 20 years, reliable detection data have been obtained using the “rebonding method”. The data shows that Baiyun Chemical has Durability of the product is ideal.
In addition, in order to investigate the impact of environmental factors in China's typical climatic regions on the durability of silicone structural adhesives, Baiyun Chemical has conducted structural adhesive natural exposure tests at exposure sites in Xinjiang and Guangzhou. The test cycle will last for up to 50 years, and prototypes have been released. In the past 5 years, initial natural aging test results have been obtained.
In recent years, there are research institutes that analyze the stress and strain of the SSG unit system. After simplified verification, combined with the climate conditions of the selected area, an accelerated experimental program is designed. Samples made of silicone rubber are selected and simulated. Samples subject to load, weight, displacement and exposure to the environment, such as temperature, UV, water, cleaning agents, etc., artificial accelerated aging test, test conditions for each 24-hour test cycle simulation using the equivalent of the actual use of the preset one year Typical conditions experienced by the medium SSG curtain wall system unit. The reliability of this accelerated test method needs further test validation and continued research.
1. The durability of the structural adhesive is very important for the application
2. Some of the existing products have been for 20 years or more, ensuring that there should be no problem for 25 years.
3. The demand for structural adhesives for construction has been more than 25 years. Durability research is still underway and we expect to make greater breakthroughs.