In the quest to keep footwear in perfect condition, many professionals store them carefully in the closet, believing this will preserve their quality. However, Safetline warns of a little-known problem that can affect footwear stored for a long time: the dreaded hydrolysis.
This chemical phenomenon causes polyurethane (PU) outsoles of safety footwear to literally crumble, even without constant use. It is frustrating to take your footwear out of the closet and find the sole crumbling, but here you will understand why this happens and how to avoid this unpleasant surprise.
What is hydrolysis in footwear?
Hydrolysis is, in simple terms, the breakdown of a material's chemical bonds through the action of water. In other words, water molecules (even in the form of vapor present in the air) react with components of the material, weakening its structure.
In the context of footwear, the target is polyurethane (PU), a polymer widely used in outsoles and midsoles to ensure lightness, flexibility, and shock absorption. Although resistant, polyurethane is not immune to hydrolysis. Over time, environmental moisture attacks the internal bonds of the PU, which begins to lose its structure and cohesion.
The result is an outsole that cracks, crumbles, or even detaches in small pieces, similar to ricotta falling apart. In other words, the sole chemically "rots." This explains why footwear can degrade even when stored: degradation occurs slowly, with no visible signs at first, but accelerates under certain conditions.
Why does safety footwear suffer from hydrolysis?
Modern safety footwear generally features dual-density PU outsoles (polyurethane layers of different densities) for their excellent comfort and durability properties. However, this material has a weak point: the reaction with moisture over the years. Even when stored in apparently dry environments, traces of air moisture can penetrate the outsole and initiate the degradation process. Some factors contribute to hydrolysis happening sooner or later:
- Prolonged storage time: the longer the footwear remains unused, the higher the chance of hydrolysis occurring. Sitting idle, the PU slowly absorbs moisture and weakens its internal bonds. Many notice the problem precisely when trying to use footwear stored for years.
- Hot and humid environment: high temperatures and high relative humidity accelerate the chemical reaction. In humid tropical climates (like much of Brazil), a PU sole can last less than half the time it would in a dry climate. Storing footwear in poorly ventilated places, such as closed closets, only worsens the situation by creating a humid microclimate.
- Lack of use and flexing: strange as it may seem, idle footwear can deteriorate faster than footwear that is used regularly. The movement and flexing of the sole help maintain the properties of the PU, preventing polymer particles from separating too soon. Without any mechanical stress, the material remains "dormant" and vulnerable to the continuous action of moisture.
- Dirt and trapped moisture: storing footwear dirty or wet is a recipe for accelerating hydrolysis. Mud, dirt, or sweat present on the footwear retain water in contact with the outsole, intensifying decomposition. In addition, fungi can proliferate in damp materials and contribute to deterioration.
- PU composition and quality: The resistance of a polyurethane outsole to the hydrolysis process is directly linked to the quality of the polymer used, the proper selection of chemical additives, and the precision of the formulation applied. When produced with high-performance raw materials and proper stabilizers, polyurethane exhibits excellent durability and maintains its mechanical properties.
Signs and consequences of hydrolysis
The consequences of hydrolysis in footwear become evident when the problem is already advanced. You may notice cracks, fissures, or crumbs coming off the sole. In extreme cases, bending the sole can cause it to snap into pieces. This compromises not only the aesthetic of the footwear, but above all its functionality and safety.
A split or crumbling outsole loses its ability to protect against punctures, slips, and impacts, putting the user at risk. Therefore, it is essential to inspect safety footwear stored for long periods before using it at work, ensuring you are not caught off guard on the job with falling-apart footwear.
How to prevent hydrolysis and extend footwear lifespan
Hydrolysis may be inevitable over many years, but it is possible to significantly delay the problem with a few simple care steps. Safetline recommends the following practices to prevent your footwear from deteriorating prematurely:
1. Wear your footwear periodically
Do not leave PPE sitting idle for long periods. Whenever possible, wear your safety footwear even if just for a few minutes or rotate between pairs so that none remains completely unused. Movement helps keep the polyurethane active and stable. Remember: unused footwear deteriorates faster; maintaining a usage rotation can add years to its service life.
2. Store in a dry, ventilated place
After the workday, store footwear in a cool, well-ventilated environment away from humidity. Avoid closed closets, hot environments, or proximity to heat sources. Places with temperatures below ~30 °C and humidity below 70% are ideal to prevent hydrolysis; although achieving these conditions is not always possible, it is worth choosing the driest place in the company or home to store PPE.
3. Keep footwear clean and dry
Clean your footwear regularly, removing dirt from the outsole and insole. Before storing, make sure it is completely dry (inside and out). Remember: clean, dry footwear preserves much better than dirty or soaked footwear, ensuring greater resistance and service life.
4. Use silica gel or desiccants
A valuable tip is to place silica gel sachets with stored footwear, either inside the box or hanging in the closet. Silica gel absorbs moisture from the surrounding air, keeping the environment dry and slowing down hydrolysis. There are even specific products for this, such as rechargeable sachets and humidity indicators—a simple solution that makes a difference. Just remember to replace or regenerate the silica according to instructions, as it loses effectiveness once saturated.
5. Avoid excessive heat and direct sunlight
Never leave your safety footwear exposed to the sun for long periods or near intense heat sources (such as ovens, boilers, or car trunks in the sun). Heat accelerates chemical reactions and worsens hydrolysis. Prefer to dry footwear naturally in the shade.
6. Footwear maintenance
Well-cared-for footwear as a whole tends to last longer and maintain its original properties for a greater length of time. To ensure that safety features are not compromised, it is essential to always follow manufacturer recommendations regarding cleaning and maintenance products. This way, you ensure not only greater durability, but also appropriate performance during work tasks.
By following these tips, you will significantly increase the service life of your safety footwear. It is important to establish a maintenance routine: just as we service machinery and equipment, PPE also deserves regular attention. Small preventive actions prevent accidents tomorrow and preserve your investment in quality footwear.
Safetline Commitment: quality that makes a difference
Safetline has been synonymous with quality and technology for over 50 years, manufacturing the most complete line of safety footwear in Brazil. All this experience is reflected in our dedication to offering durable and reliable products.
While some in the market may use lower-quality materials to cut costs (and end up producing outsoles that last less), Safetline does not compromise on excellence. Every Safetline footwear is made with selected raw materials and undergoes rigorous testing to guarantee maximum protection for the worker's feet.
Understanding hydrolysis is crucial to taking good care of your safety footwear. By following storage and use guidelines, you can avoid the frustrating scenario of seeing your brand-new footwear crumble without warning. If your footwear is already showing signs of degradation, it might be time to invest in a new pair.
Safetline is proud to offer highly durable safety footwear, ready to face heavy routines without letting you down. Contact us or discover our Safetline product line, protect your feet hassle-free, and count on us to walk side by side for your safety.
Personal Protective Equipment (PPE) essential to protect worker feet in various environments, such as industries, farming, and electrical services.
Also check out the complete guide to safety footwear as PPE to learn more about types, standards, and how to choose the ideal model.