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Dongguan Minz Rubber & Plastics Co., Ltd.

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Knowledge of aging of silicone products

Release time:

2019-05-24 12:30

Source:

Aging of Silicone Productsthe relevant knowledge
 
What is silica gel aging: silica gel aging: due to the use of time and high temperature or in a complex environment will also cause some of its parameters to change, such as increased hardness, decreased strength, shorter elongation, etc.; Features can be distinguished from color, such as yellowing than normal.
 
The general shape is divided into extruded silica gel and molded silica gel. Inorganic silica gel is a kind of highly active adsorption material, which is usually made by the reaction of sodium silicate and sulfuric acid, and a series of post-treatment processes such as aging and acid bubble. Organic silica gel is an organic silicon compound, which refers to a compound containing Si-C bonds and at least one organic group is directly connected to the silicon atom. It is customary to use those organic groups and silicon atoms through oxygen, sulfur, nitrogen, etc. The compound is also used as an organic silicon compound.
 
1, long-term work does not cause permanent deformation. For a long time under high pressure, the deformation is more obvious for products with hard materials, whether it is silicone buttons or silicone miscellaneous parts.
 
2. The influence of stretching rate. Generally, the tensile rate of silicone rubber can reach up to 300 (relatively soft material), but excessive stretching in the use process will directly lead to deformation and loss of tensile degree permanent deformation, so in the use process can not be over-stretched, regardless of industrial products, daily necessities or silicone miscellaneous parts are the same.
 
3. Influence of temperature occasions. When silicone products work under humid and high temperature conditions, the stretching will gradually deform, but with the adaptation of temperature or temperature drop, it will also lead to slight deformation of silicone products. So whether it is in the industrial application of silicone accessories, sealing products, or try not to let silicone products long-term stretch.
Aging of silica gel is one of the main reasons for the damage of silica gel performance. Due to the different formulation and use conditions of the product, the aging process is different, so it is necessary to measure and evaluate the aging test to evaluate the degree of aging of silica gel and its effect on performance. Aging test is under external conditions, after a certain period of time, the test method before and after the performance of silica gel changes (usually performance degradation or deterioration).
 
There are two types of commonly used silica gel aging test methods: natural aging test methods, which are divided into aging test, atmospheric accelerated aging test, natural storage aging test, natural medium (including buried, etc.) and biological aging test.
 
Artificial accelerated aging test method. For thermal aging, ozone aging, light aging, artificial weather aging, light ozone aging, biological aging, high-energy radiation and electrical aging, and chemical medium aging. The ozone aging resistance test of silica gel is divided into two cases: one is static tension, the other is dynamic tension; the results of these two tests can evaluate the ozone aging resistance of silica gel. Conventional aging test instruments are thermal aging test chambers and ozone aging resistance test chambers:
 
Thermal aging test chamber is divided into two kinds of forced ventilation and natural ventilation. The inner container of the studio is divided into ordinary container and stainless steel container. The temperature of the test is also different due to the different types of glue. For natural silica gel, the thermal aging test temperature is usually 50~100 ℃, synthetic silica gel is usually 50~150 ℃, some special silica gel test temperature is higher, such as nitrile silica gel with 70~150 ℃, silicone fluorine glue generally with 200~300 ℃.
In short, the temperature of the test should be determined according to the specific situation, and the appropriate testing instrument should be selected. Ozone aging resistance test chamber is divided according to test requirements (static tensile, dynamic tensile), ozone concentration, working chamber volume, etc.
 
Analysis of aging test methods for silica gel and silica gel products; silica gel or silica gel products in the storage and use process and manufacturing process, due to physical, chemical, biological effects, resulting in its use performance gradually reduced, or even lose the use of value, this phenomenon is called aging. Therefore, it is of great significance to determine the aging performance of silica gel to estimate the service life of products and to study the aging and protection efficiency of silica gel.
 
1. Hot air aging test. Hot air aging test is one of the most common thermal oxidation tests. It is to measure the changes of physical and mechanical properties of silica gel samples under the action of hot air at normal pressure and specified temperature for a certain period of time.
 
2, silica gel ozone aging test, because the chemical activity of ozone is much higher than that of oxygen, so the aging of silica gel products is stronger, so that the molecular chain is broken, and the surface is cracked under the action of stress, resulting in the loss of use value of silica gel.
 
Ozone aging test is to determine the change of physical and mechanical properties or observe the earliest time of ozone cracking under the action of static or dynamic tensile stress, after a certain temperature and specified concentration of ozone. The static tensile strain test specimen is exposed to air containing a constant ozone concentration and a constant temperature test chamber, and the specimen is inspected for cracking at a predetermined time.
 
There are three methods for evaluating ozone cracking at selected ozone concentrations and test temperatures:
A. at the specified time and under the specified strain, check whether there is cracking, and if necessary, determine the degree of cracking.
 
B. At a specified tensile strain, determine the time to the earliest crack.
 
C. Determine the critical strain for a specified time. The so-called critical strain refers to the silica gel exposed to a certain concentration of ozone in the air at a given temperature, after a specified time, the maximum tensile strain does not appear ozone cracking.

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