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Why do safety shoe soles disintegrate (Crumbling soles)?

Have you encountered the sole coming apart from your safety shoes or boot in clumps after being stored or when you pull them out of storage to wear them? Our first thought is to blame the manufacturer, when we witness the “crumbling soles” of our safety shoes, particularly if the safety shoes or boots have only been worn a few times.

Is this a manufacturing defect?

This is a question we get from a lot of our customers.

No. Polyurethane soled safety shoes and boots are susceptible to hydrolysis-natural ageing process. Hydrolysis is the chemical breakdown of the PU polymer and the resulting physical breakdown or disintegration of the PU sole accelerated by the high humidity in tropical climates. As a consequence, PU loses flexibility over time and gradually becomes brittle, and starts cracking and crumbling.

Why use Polyurethane (PU) in safety shoes or boots?

Polyurethane (PU) soled footwear is often used in safety shoes as it offers several positive properties which are ideal for shoes.  A PU soled shoe is light, flexible, and comfortable. The PU sole has good wear resistance, tear resistance, oil resistance, acid, and alkali resistance. The most important anti-slip property is also excellent.

How do you avoid this?

Ageing of safety shoes is an entirely normal process that all PU-soled shoes go through. To maximize the lifespan of your PU boots, we recommend the following tips.

  • Store safety shoes or boots in a dry and well-ventilated space.
  • Clean the mud and grime off safety shoes or boots, dry naturally, if they have been worn before being stored.
  • Rotate stock (If applicable) frequently on a first in, first out basis. The basic PU sole used in most safety shoes on the market lasts for 1.5 years in tropical conditions and 2 years in normal conditions
  • Properly aerate the safety shoes or boots after use.

With proper care and storage of safety shoes or boots, hydrolysis should not be a common problem.

 Can they be returned?

For all KPR safety shoes and boots, the date of manufacture can be found on the tongue labels, outsoles, and shoe boxes and we base on this to determine the date of production of the model.

We can only accept warranty claims on a product that has been purchased within 6 months.  Because often, safety shoes or boots that experience hydrolysis has been purchased years ago, even though they were only worn a few times, they do not qualify for warranty claims.

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