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Rubber products, aging and ozone protection

ozone in rubber products in the atmosphere is an important factor in aging. Ozone is more lively than oxygen, thus its invasion of rubber, especially unsaturated rubber is much more serious than oxygen.

atmospheric ozone (O3) is composed of oxygen molecules absorb UV light in the Sun, hydrogen oxygen atoms combine with oxygen to form again. 20 ~ 30km high from the Earth's surface about 5X10-there is a concentration of ozone in the air '' with the vertical air flow and ozone were brought to the Earth's surface, ozone concentration from high altitude to the ground gradually. In addition, the UV-set in place and discharging place and adjacent to the motor, especially spark produces ozone. Ozone concentration in the atmosphere is usually 0 ~ 5X10-8. Area '' of ozone concentration; season, ozone concentrations are also different. Although near ground level ozone concentration is very low, but the damage to the rubber is not to be ignored.

not saturated rubber very easy occurred ozone of and ozone of Hou of appearance features, and hot oxygen aging different, a is rubber products of ozone of only in ozone by contact of surface layer for, whole ozone of process is inside of process; II is rubber and ozone reaction generated a layer silver hard film (about lOnm thick), in static conditions Xia this film can block ozone and rubber deep contact, But in dynamic strain conditions Xia or in static stretch State Xia Dang rubber of elongation or stretch stress over it of critical elongation or critical stress Shi, this layer film will produced cracked, makes ozone to and new of rubber surface contact, continues to occurred ozone of reaction and makes crack growth, addition crack appeared Hou due to base Department has stress concentrated, so more easy deepened crack then formed RIP. Cracks in the direction perpendicular to the stress direction, generally under small strain (such as 5%) only a small crack appears Wen, crack clearly visible, when rubber multi-directional force is difficult to spot a crack.

rubber reaction mechanism of ozone

ozone and unsaturated rubber reaction mechanism, may refer to the following instructions.

when ozone contact with rubber products, ozone first double bond and lively addition reactions, ozonolysis, and molecular ozonolysis is very unstable and decomposition Carbonyl Compounds II soon, and zwitterionic ③. In most cases the gender ion with Carbonyl Compounds back into isozonide ©, Amphion also formed two peroxide © or high peroxide © and when there is a reactive solvent such as methanol, zwitterion will react with methoxy hydroperoxides ⑦.

ozone and unsaturated rubber has a low activation energy, reaction is extreme, double bond of the reaction until the rubber consumption has been, at this point in the surface layer of rubber film of silver loses its elasticity, as long as no external forces the film cracked, the rubber will not continue to ozone. If the rubber stretch or to have ozone to produce dynamic, generated ozone cracking of thin film, exposing new rubber surface will react with ozone, which makes the crack continues to grow.

because it contains no double bond saturated rubber, though it can slowly react with the ozone reactions, not easy to crack.

a number of ozone cracking of unsaturated and growth studies. These researchers according to the experimental data put forward the mechanism of crack formation and growth, respectively. For example, some people think that crack is due to stress fracture due to ozonolysis decomposition chain, tend to separate more than once preferred outcome. Crack growth and ozone concentrations and rubber chain of sports-related, when the ozone concentration is constant, molecular chain movements greater, faster crack growth. Others believe that ozone cracking and growth and the rubber of the ozonolysis of the formation of a thin layer of ozone and associated with a different original rubber layer on the surface. For example, Murray think ozone rubber is the process of physical processes and chemical process concurrent process. When the rubber in contact with ozone, the surface of the double bond quickly reacts with ozone, most generate ozonolysis, making soft rubber chains rapidly changing as many ozonolysis-rigid chain. When there is a stress on the rubber, stress the rubber chain tension, make more double bonds in contact with ozone, contains more ozonolysis of the rubber chain ring, become more brittle. Brittle surface in stress or easily cracks under dynamic stress.