The structure of general recreational athletic shoe, outdoor shoe can divide into uppers, in sole and shoe outsole, outsole of the shoe can use rubber raw material to produce, because it is comfortable tall, the most important is antiskid wear-resisting.
These rubber outsole has the advantage of high elastic, wear-resisting, but wear for a long time, by oxygen, ozone, light, heat, moisture, mechanical stress and other aspects of the impact of easy aging, such as ozone cracking, then fracture.
So, why does ozone crack on the rubber outsole cause rupture?And how to prevent it?Let's take a look.
Why does ozone crack happen?Natural rubber (NR), butyl rubber (IIR), styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR).
These rubbers contain unsaturated double bond components.For example, the basic chemical composition of natural rubber is cis-polyisoprene;Isoprene rubber, full name is cis-1, 4-polyisoprene rubber, a high shunt-type synthetic rubber made from isoprene;Styrene butadiene rubber is prepared by copolymerization of butadiene and styrene.Butadiene rubber, full name cis-1, 4-polybutadiene rubber, is made by butadiene polymerization.
The unsaturated double bond is easy to react with ozone and oxygen under the action of light, which results in ozone cracking and photooxidation cracking, of which ozone cracking is the main cause, which greatly reduces the service life of shoes.
Oxygen can react with the free radical chain of rubber molecules, resulting in excessive crosslinking or breaking of the molecular chain.Ozone is more chemically active than oxygen, so it is much more destructive to rubber than oxygen.
The destruction mechanism of ozone and oxygen is basically the same, the difference is that the effect on rubber is unstable, it can be based on the deformation of rubber and corresponding changes, for example, when ozone ACTS on unsaturated rubber, will produce the same direction of stress crack, called "ozone crack";When ozone is applied to the deformed rubber, only the oxide film is generated on the surface without cracking.
The characteristic of ozone cracking is that the crack is perpendicular to the direction of stretching deformation of the rubber (see figure), and the rubber cracking speeds up with the increase of deformation, reaching the critical deformation value, the maximum speed.
Photooxidation cracking is different from ozone cracking in that it can occur without deformation and the cracks show random network.Generally, ozone cracking is more serious and deeper than photooxidation cracking.
So, how to know the rubber material ozone aging properties?Here introduce to you our Ozone aging testing chamber, to simulate and to strengthen the ozone in the atmosphere conditions, studied the effect of ozone on rubber, rubber resistance to ozone aging fast identification and evaluation of performance and the antiozonant shielding efficiency of the method, and then take effective measures, the anti aging in order to improve the service life of rubber products.
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