Is 15 year old Air and EVA/PU foam on borrowed time?

The Nike air max 95 x Atmos Animal from 2006 is 15 years old in 2021.

The picture below show how most pairs currently look, sat on brittle air bags and crumbling EVA foam. There are many factors that can accelerate this ageing process, I'm going to try and cover a few of them.

Humidity - The climate that the shoes are kept in is very important. The humidity can cause the elastomers to break down in the rubber/foam much faster than if they were kept in a more neutral environment.

Damp - A wet environment can cause mould spores to form on shoes and break down the materials. A small split or crack in the EVA can allow moisture to get into the foam. This over time causes the foam to become soft and brittle.

Temperature variation and UV - Having shoes sat in a location where they experience hot and cold temperature extremes. This process is effectively annealing the plastic and EVA foams. (Annealing is used to reduce stress in metals and plastics by heating and cooling them), however repeated exposure to this will reduce hardness and the spongy feel to the materials and causes them to perish and crumble. This is essentially the elastomers and polymers within the rubbers and foam evaporating and breaking down. Leaving pairs in the sun causes the elastomers to evaporate much faster and rubbers/foams loose their mailable and flexible property's often going hard and brittle. which leads to hairline cracks.

Wear - A common factor we find is shoes that have been worn gently over the years hold up much better than those DS and expected to preform after 15 years. This I think is down to two reasons; The first being that wear actually activates the materials used which activates them. The second slightly more disgusting, is the sweat and salts from your feet. After a few hours wear part of the sweat imbeds itself within the shoe. helping to preserve the materials.

With many skilled people it is possible to revive these ageing pairs with a sole swaps from a donor pair. This does encounter its own problems with sole moulds and manufacturing changing over the years. There can be slight modifications needed to get the soles to marry up.

As a rule of thumb anything coming up to 10-15 years old with an air bag and EVA/PU foam you are wearing at your own risk. There is no exact time figure based on the variables above but this is a good benchmark.

With new advances in technology and pushes in sustainability I believe that we will hopefully see shoes last much longer. There are already rubber soled shoes that are well into the 20+ age range. Older Jordan's/Puma suede/Adidas gazelles etc that hold up much better over time.

This is a work in progress and I will be adding to this article.