Rubber application field is very wide. As a basic material products, they have good performance stability, excellent cost performance, post-processing is relatively simple, suitable for production into some special tool products or large accessories, but how to ensure the use of rubber effect? What tests do we need to do about rubber? LIB INDUSTRY can provide you with professional customized services.In the process of processing, storage or use of raw rubber or rubber products, it will be affected by heat, oxygen, light and other dry factors and gradually undergo physical and chemical changes, so that its performance is reduced, and it loses its use, this phenomenon is called the aging of rubber.
Aging Phenomenon of Rubber
The rubber aging process is often accompanied by some significant phenomena, such as the appearance of long-term storage of natural rubber soft, sticky, spots; Rubber products have deformation, brittleness, hardening, cracking, mold, loss of light and color change. In terms of physical properties, rubber has changes in swelling, rheological properties, etc. In terms of mechanical properties, tensile strength, elongation at break, impact strength, bending strength, compression ratio, elasticity and other indicators will decrease.
Reasons for Rubber Aging
The aging phenomenon of rubber is caused by its long-term heating, oxygen, light, mechanical force, radiation, chemical medium, ozone in the air and other external factors, so that its macromolecular chain chemical changes, destroying the original chemical structure of rubber, resulting in deterioration of rubber properties. The external factors that cause the aging of rubber mainly include physical, chemical and biological factors.
Physical factors include heat, light, electricity, stress, etc.;
Chemical factors include oxygen, ozone, acid, alkali, salt and metal ions;
Biological factors include microorganisms (mold, bacteria), insects (termites, etc.).
These external factors often do not act alone in the process of rubber aging, but affect each other to accelerate the rubber aging process. For example, tire sidewalls will be affected by heat, light, alternating stress and strain, oxygen, ozone and other forms of factors during use.
Different products under different conditions of use, the degree of action of various factors is different, and their aging conditions are also different. Even for the same product, the aging situation varies depending on the season and region of use. Therefore, the aging of rubber is a comprehensive chemical reaction caused by a variety of factors. Among these factors, the most common and important chemical factors are oxygen and ozone; Physical factors are thermal, light, and mechanical stress. Generally, the aging of rubber products is the result of one or several of them, the most common thermal oxygen aging, followed by ozone aging, fatigue aging and photooxygen aging.
Aging Test Needed for Rubber
Environmental reliability test can verify the reliability of products in the product development stage, trial production stage and mass production sampling stage, which is conducive to saving R&D and production costs and improving product quality.
Rubber finished products:
high temperature test,
damp heat test,
salt spray test,
gas corrosion test.
ozone aging test,
ultraviolet aging test,
xenon lamp aging test,
Aging Test Methods
1. Climate aging test
The so-called climate aging test is a research method that exposes the rubber material test sample to atmospheric environmental conditions, so as to obtain the aging rule of the material sample under atmospheric environment exposure, analyze the performance of the rubber material, and predict its service life.
The artificial climate aging test refers to the aging test method in which people simulate the real atmospheric environmental conditions indoors or strengthen a certain environmental factor to obtain the aging behavior of materials in a short period of time, which is also called artificially simulated aging or artificial acceleration. Artificial weathering is usually carried out in an Environmental Test Chamber. Commonly used artificial weathering chambers mainly include xenon weathering chambers, uv weathering chambers. These kinds of climate aging test chambers simulate or strengthen the natural environmental factors from the main climatic factors such as light, temperature, humidity, rain or condensation to achieve material aging. In addition, the aging test of materials should be carried out according to certain test standards.
2.UV aging test
Since the light energy possessed by ultraviolet light is equivalent to the bond energy of rubber chemical bonds, it can cause the breakage of rubber compound chains, which is the main factor leading to the aging and degradation of rubber materials. The ultraviolet aging test refers to the test method that exposes the rubber material aging test sample under the ultraviolet light field, so as to obtain the aging behavior and rule of the rubber material. Usually the ultraviolet aging test will stipulate that the ultraviolet region and the irradiation intensity, such as 40W/m2, are within the wavelength range of 300nm-400nm. The light sources used in the UV aging test usually include xenon lamps, fluorescent lamps, tritium lamps and deuterium lamps. Among them, the xenon lamp can simulate the solar spectrum very well, and the fluorescent lamp can simulate the ultraviolet spectrum in sunlight very well.
3. Ozone aging test
Ozone is an extremely rare gas in the atmosphere, but it is extremely destructive to rubber materials. Ozone can irreversibly react with unsaturated bonds and reducing groups in the chemical structure of rubber materials, resulting degradation, thereby losing their use value. Especially for rubber materials containing double bonds, it shows extremely strong destructive power. Ozone has a strong activity, it can decompose the more active atomic oxygen, and chemically react with the double bond in the rubber molecule, causing the rubber to age, crack and become brittle. The ozone aging test of rubber materials is usually carried out in an ozone aging test chamber. The ozone is provided by an ozone generator, and its concentration can be adjusted by mixing with air through a mixer. The concentration of ozone is generally determined according to the environmental conditions in which the material is actually used. In addition, the temperature, humidity and other factors in the ozone aging chamber can also be adjusted, so as to achieve the purpose of the test.
4. Hot air aging test
Heat is one of the main factors leading to the aging of rubber materials. Heat can accelerate the movement of rubber chains, resulting in the breakage of rubber chains, the generation of active free radicals, and the occurrence of free radical chain reactions, resulting in degradation or crossover of rubbers. The hot air aging test is one of the main test methods to evaluate rubber materials and study the aging resistance of rubber materials, and it is usually carried out in a constant temperature test chamber. The temperature in the chamber can be set according to the test requirements. The rubber material is exposed to the dryness and is regularly sampled and tested to obtain the aging behavior and law of the rubber material, so as to modify the rubber material in a targeted manner and improve its performance.
5. Temperature alternating aging test
Temperature is another important factor leading to the aging of rubber materials. For rubber adhesives, high temperature can accelerate the movement rate of rubber adhesive chains, and low temperature can cause internal stress in rubber adhesives. Alternation leads to chain breakage of the rubber adhesive and aging degradation. For rubber, high temperature can accelerate the thermal movement of molecular chains and cause rubber to cross-link, while low temperature can cause rubber molecular chains to freeze, making them brittle, reducing elasticity and aging. The high and low temperature alternating aging test is an aging test method for evaluating the temperature resistance of rubber materials. It is usually carried out in a Thermal Shock test chamber, from a certain temperature T1 (usually room temperature) to a certain temperature at a constant heating rate. T2, maintain the temperature of T2 for a certain period of time, then cool down to a certain temperature T3 at a constant cooling rate, maintain the temperature of T3 for a certain period of time, and then raise the temperature to T1, which is a temperature cycle. The length of the cycle can be determined according to the specific test requirements.
6. Damp heat aging test
Damp heat aging test is an effective method to evaluate the aging resistance of rubber materials in high humidity and high temperature environment. In a high-humidity environment, moisture can penetrate into the rubber material, causing swelling of the rubber material, hydrolysis of some hydrophilic groups, and aging degradation of the rubber material. In addition, the penetration of moisture into the rubber material can also lead to the dissolution and migration of additives in the rubber material, such as plasticizers, compounding agents and other substances, and affect the mechanical properties of the rubber material. Under the action of high heat, the heat can promote the penetration of water. Heat promotes the movement of rubber chains, reduces the intermolecular force, promotes the penetration of water, and accelerates the degradation of rubber materials. Different rubber materials have different formulations, so their damp heat aging mechanisms are also different. When performing damp heat aging tests, different aging standards should be selected according to different rubber materials. The damp heat aging test is usually carried out in the temperature and humidity test chamber, and the temperature and humidity can be set according to the test requirements.
Protection Methods for Rubber Aging
With the aging process of rubber, the properties of rubber gradually decline, and its use value is gradually lost. Therefore, research on aging and protection methods has extremely important practical and economic significance. Since the aging of rubber is a complex and comprehensive chemical reaction process, it is impossible to absolutely prevent the occurrence of rubber aging. Therefore, it is only necessary to carefully study the various causes of rubber aging, and to prescribe the right medicine according to these reasons, and take appropriate measures to delay the aging speed of rubber, so as to achieve the purpose of prolonging the service life of rubber. Since the factors leading to the aging of rubber products are different, corresponding anti-aging measures should be taken according to different aging mechanisms, mainly including physical protection and chemical protection. The physical protection method refers to avoiding the interaction between rubber and various aging factors as far as possible, such as rubber-plastic blending, surface coating or treatment, adding light shielding agent, adding paraffin, etc. The chemical protection method refers to actively adding substances to prevent or delay the rubber aging reaction, such as adding amine or phenol chemical antioxidants.Anti-aging is mainly based on reducing the unsaturated double bonds on the rubber chain of vulcanized rubber, for example, using some branched chain modification, using special chemical reactions to saturate the unsaturated bonds, so that the level of molecular structure can be improved. Aging ability, delay aging and prolong its service life.The second is to add anti-aging agents in the processing of rubber and plastics. For example, add ultraviolet stabilizers, anti-fungal agents, heat stabilizers, etc. to the formula of vulcanized rubber, and add antioxidants to prevent aging caused by ozone or oxygen.
Again, it is also possible to increase the physical protection of the coating and protective film, such as dipping anti-aging agent solution, painting, metal plating, etc.
LIB Environmental Aging Test Chambers
1.Professional technical team provides the best service for customers.
2.Rich industry experience and advanced equipment to conduct qualitative and quantitative analysis of each component of rubber.
3.Sound service network covering MAJOR COUNTRIES all over the world, providing customers with convenient and effective services.