Why Do Shoes Disintegrate and Crumble?

When it comes to footwear, nobody wants their shoes to be disintegrating. When this happens, the shoe’s design is compromised and loses its effectiveness to provide your feet with what they need.

Three types of soles start disintegrating in the following ways:

  • Polyurethane sole – Due to Hydrolysis
  • Rubber sole – When chemicals start drying out, it makes the sole brittle and results in cracking
  • EVA sole – Due to repeated loading while walking or running

Shoes disintegrate when they are made from specific materials, which makes them porous and soft if they are left unworn and you keep them in storage or closet for a longer time. It results in holes, cracks, and eventually crumbling. It’s due to the chemicals in the rubber, which make the shoes more pliable. This happens when you keep shoes in storage or a closet for a longer time. The moisture and heat react with the chemical in rubber, which starts to deteriorate. It can cause holes which can lead to cracks in shoe soles. This chemical deterioration also occurs when excessive water is used on the rubber soles because it strips away the plasticizers that keep them protected. The soles made from plastic PU are more likely to disintegrate due to the oxidation of the polymer chains.

Why Do PU Soles Disintegrate?

Polyurethane soles are flexible, anti-slip, lightweight, and compression-resistant, due to which they are used in boots, dress shoes, and safety shoes. Due to such reasons, manufacturers still use PU material in their shoes.

The reason for the disintegration of polyurethane soles is due to the internal structure of the material. PU material consists of long polymer chains that are altered when subjected to moisture, heat, and sunlight. This process is agitated when shoes with PU soles are stored in damped places or subjected to wet surfaces for an extended period. The moisture decomposes those long polymer chains, which weakens their strength, and material starts peeling off.

To stop the polyurethane soles of your shoes from disintegrating into crumbles, keep the shoes in a cool and dry place with good airflow. The airflow will prevent accumulating moisture in the soles. Never store them with either high moisture or too high temperature, don’t leave them under the sun for a long time. This is the most effective method to make polyurethane soles last longer. Storing polyurethane soles in a dust-free environment will also make them stay in the same condition as new ones for a longer time. Also, keep your feet dry whenever you wear shoes and clean the shoe’s soles after every one or two weeks.

Why Do EVA Soles Disintegrate?

EVA soles generally do not crumble. EVA foam is more compressible and less abrasion-resistant as compared to PU foam. The reason for the disintegration of EVA foam soles is not the same as for PU soles. Ethyl Vinyl Acetate is a very soft foam material. Unlike PU, EVA is not subjected to hydrolysis. It has no internal structure like polyurethane that crumbles in high humidity conditions when kept longer in the closet. If the soles of your shoes with EVA soles are wearing fast, the chances are that you’re wearing them on rough surfaces that peel off the foam.

Since EVA is highly compressible, it loses its support and compactness over time due to constant loads and rubbing. Due to these reasons, the chances are that EVA foam material is subjected to wear and tear.

Do Leather Shoes Get Spoil if Not Worn for a Long Time?

No, leather shoes do not have a “shelf life.” In other words, they aren’t going to spoil if you don’t wear them. The leather will dry out and become stiff. Even if it was previously subjected to water damage, the moisture should be dried over time, and the shoes should return to a normal state of being able to have shape and flexibility.

Wearing the shoes regularly is obviously the best way to maintain their suppleness, but that isn’t always possible. Dry brushing the leather with a soft bristle brush on occasion helps to keep it supple. Vacuuming them (with a brush attachment) is also helpful, as it keeps dust mites and other allergens away. Wiping them down with a damp cloth is also beneficial, but make sure they are completely dry before putting them away again. The more you put them away wet, the more quickly they will dry out and become stiff.

After one to two weeks, apply leather conditioner onto your shoes and let them sit for about at least five minutes. Wrinkles and folds will quickly be gone. Then you can polish them off with a dry bristle brush to ensure all excess conditioner is removed from the surface of your shoes.

How Long Do Shoes Last in Storage?

Shoes can last more than 5 to 10 years if you keep them in a controlled environment. PU material usually starts disintegrating in a closet after 5 to 6 years. If the sole is entirely crumbled, as in the case of PU material, you might need to resole your shoes. The rubber soles, glued with the upper, have a shelf life of around 8 to 10 years.

If the shoes are made of rubber, and you left them unworn in a closet for a longer time, the glue starts drying out and stops playing its role to keep the sole bound with the shoes upper. If that’s the case with you, you can use shoe goo to bind the separated areas on your shoes if there are only minor separations.

To prevent the glue from vaporizing from rubber sole shoes, vacuum sealing is the best possible way. Here’s what a person comments on the forum about it:

The glue of any pair of 10-year old shoes is going to be vaporized if not correctly stored. Whenever you plan to collect shoes that won’t be worn all that often, I believe vacuum sealing is the best strategy. Due to vacuum sealing, I have vintage Air Tech Challenges in near perfect condition from the early 90s. I also have a pair of grass-court Vapor 9s that I’ve sealed as well. (Gemini)

You can check out this product to vacuum seal your shoes.

For leather dress shoes, use shoe trees or strips when storing them. This will prevent wrinkles in the leather. Also, remember that you should never let your shoes sit in direct sunlight for too long as this can cause the sides of the shoe’s sole to become dry and brittle, which can be very damaging if left untreated.