UV Accelerated Weathering Tester is used to test wires, cables, insulators or coated rubber test pieces to compare the tensile strength and elongation of the test pieces before and after aging.
UV Accelerated Weathering Tester has researched and analyzed the experimental results, and the HTV samples have experienced different degrees of aging under the irradiation of 248nm ultraviolet laser, which is the combined effect of physical aging and chemical aging. Next, the Standard Group will answer you in detail.
Another important aging is caused by 248nm ultraviolet laser irradiation, namely chemical aging, which is an irreversible chemical reaction and is the result of changes in the molecular structure of materials. The chemical aging of rubber is carried out according to the mechanism of free radical reaction. According to the factors that cause free radical oxidation, it is mainly divided into two types: thermal oxidation aging and photooxidative aging.
Since the photon energy of the 248nm laser is higher than all the chemical bonds of HTV, the laser irradiation or irradiation in an oxygen atmosphere breaks some chemical bonds on the surface of the sample and destroys some groups, thereby forming ·H, ·CH3, etc., between free radicals react to each other.
Ultraviolet rays in solar radiation are the main cause of photo-oxidative aging of rubber. The energy of ultraviolet rays is equivalent to the chemical bonds in rubber, so ultraviolet radiation can cut many chemical bonds to form free radicals, and new forms of bonding substances are formed between free radicals and free radicals, and oxygen, which are generated in the presence of oxygen. Photooxidative aging.
The macroscopic description of sample aging can be attributed to physical aging. Physical aging refers to the transition of the condensed state structure of glassy polymer materials from non-equilibrium state to equilibrium state through the micro-Brownian motion of small-region chain segments, thereby making the physical and mechanical properties of the material. phenomenon of change. As a result, the free volume of the material decreases, the density increases, the modulus, tensile strength and hardness increase, the elongation at break and impact strength decrease, and the material changes from plasticity to brittleness, resulting in material failure at low stress levels. After calculation, the cumulative energy density of 1000 times of pulse irradiation in the experiment is 19.44J/cm2, which is equivalent to the continuous irradiation amount of outdoor sunlight for one day. After irradiation, the elasticity of the sample becomes smaller, the hardness becomes larger, and physical aging occurs. .
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