Thermal radiation and hot oxygen aging
the natural outdoor under the condition of visible light and infrared radiation mainly comes from the sun. Polymer absorption of visible light and infrared ray, and the transformation of heat energy. In addition, the polymer absorb ultraviolet part can also be converted into heat energy. Raise the temperature of the absorption of heat, prompting absorption parts. Atmospheric environment temperature is not high, usually because of the low plastic thermal diffusivity, when exposed to high temperature climate conditions, the surface temperature of the plastic products may be considerably more than the surrounding air temperature.
the rain, moist air, especially the water film condensation formation, can penetrate into products, the products inside the system some of the water soluble material, plasticizer and components being dissolved by water containing hydrophilic group, extraction or absorption, which changes the internal composition of the material, reduces the physical properties of products, accelerate the aging of materials. Experiments show that the polymer in the process of oxidation of light, the water actually played a catalytic role.
products surface temperature except by solar radiation intensity and environment temperature of other influence factors include products material characteristics, products color, heat storage conditions, air convection condition, etc. As temperatures rise, heat of high activity, can make the polymer molecular thermal motion acceleration. Single factor, but just the outside air temperature on the influence of polymer aging also is not very big. Thermal radiation damage from aggression and so on the material, mainly because of oxygen in the atmosphere at the same time there is a light, factors such as joint participation in joint action.
heat promote polymer oxidation reaction, heat and oxygen on the joint action of polymer, we call it a hot oxygen aging. Hot oxygen aging is another important factor promote polymer material aging. In fact, light oxygen aging and hot oxygen aging tend to occur at the same time, thus inhibiting two aging process of light stabilizers and antioxidants are often and use. All kinds of polymer materials is different on the thermal stability of oxygen, partly due to their different chemical structure.
protective plastic from ultraviolet enroach on, how to reduce the level of harmful radiation, is the outdoor use injection molding processing products must solve the problem. Currently widely used a kind of method, is uv protective agent is added to polymer. The selected additives must be easier than polymer to absorb ultraviolet light and energy conversion, or additives can immediately interact with formation of the active free radicals, and lose their activity.
cleanliness and oxygen permeability and other physical factors also has very big effect. However, in terms of many polymer products, when used in outdoor environment, only through effective stable processing, has practical application value. Water widely exists in various environments, in the atmospheric environment, water on the effect of polymer products for precipitation, rain water, moist air, condensation, and other forms. Precipitation dust on the surface of the products can be washed off, make it more fully accept sunlight exposure, so as to accelerate light aging.
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