When you have to buy safety shoes or boots, for your choice you should, among other things, take into account the materials an article is made of. What type of rubber or polymeric material is the most befitted for my application? What’s the difference between the different existing types of rubber and polymeric materials for safety footwear?
It’s known that the regulations about safety footwear help to prevent work-related accidents and injuries, but knowing the most important technical specifications and the optional features of this type of safety equipment can be of great help, too.
In this article I will explain to you what to do if you need safety shoes but you don’t have a clear idea of what type of rubber and/or polymeric materials they should be made of.
I bet that, when you’re done reading this article, you’ll be surprised by how easy it to choose the right product for your needs.
Rubber and polymeric materials for safety footwear
There is a precise number of rubber and polymer types on the market. Let’s see them one by one:
1. (N) Nitrile rubber is a copolymer made of a mix of synthetic rubber and butadiene. It’s used in the production of safety footwear because of its resistance to oils and hydrocarbon. Nitrile rubber has a better resistance to oils, acids, and puncture compared to natural rubber. It is a compact material, so its downside is weight.
2. (PU) Polyurethane is a synthetic material. It’s flexible and light, resistant to heat up to 266°F, oils, low-concentration acids and bases, and solvents. In low-density form (more porous) it is used in the soles of single-density PU and for the mid-soles of double-density PU soles (PU/PU). In high-density form it is used for the lower surface of double-density soles (the higher density provides better resistance to abrasion).
3. (R) What’s normally just called rubber more precisely consists of vulcanized rubber. Rubber is produced starting from latex extracted from rubber trees. As non-vulcanized rubber is fragile when cold and smells bad when hot, it’s vulcanized, which makes it a tougher material. Vulcanized rubber is resistant to temperatures up to 392°F, oils, low-concentration acids and bases and solvents. Vulcanization is a chemical process that turns rubber or similar polymers to more resistant materials. Heat and pressure cause the cross-linking and the expansion of the rubber. The sole is then shaped into a mold.
4. (PU/PU) Double-density PU is a synthetic material used in soles. In double-density soles the mid-sole is made of low-density polyurethane which provides comfort, whereas the outer layer is made of denser PU, to provide durability. Soles of this material can withstand high temperatures up to 392°F, oils, solvents and low-concentration acids and bases.
5. (PVC) Polyvinyl chloride is a polymer that has a good resistance to water infiltration and absorption, vegetable oil, fats, animal by-products, manure, disinfectants and several chemical substances. It can withstand temperatures up to 194°F, hydrocarbons, low-concentration acids and bases and solvents. It’s often used in the production of safety boots.
Futher types of rubber and polymeric materials for safety footwear
1. (RPU) This is a blend of rubber and polyurethane that provides lightness and sturdiness to the sole. It is used by some manufacturers and is considered tougher compared to PU/PU.
2. (TPU) Thermoplastic Polyurethane is softer and flexible compared to other polyurethane based materials and is used in hiking and safety shoes. TPU has a great resistance to wear and abrasion, as well as an outstanding slip resistance. As for RPU, some manufacturers of safety shoes use it and it is considered tougher compared to PU/PU.
Safety shoes: types of rubber soles
• Single-density rubber: (generally in glued soles). What’s normally just called rubber more precisely consists of vulcanized rubber. Rubber is produced starting from latex extracted from rubber trees. As non-vulcanized rubber is fragile when cold and smells bad when hot, it’s vulcanized, which makes it a tougher material. Additives such as nitrile give the compound some additional features, like resistance to the contact with hot surfaces. Single-density rubber soles are extraordinarily strong: they can withstand temperatures ranging from -22 to +572°F, they are resistant to puncture, hydrocarbons, microbes and to the contact with several chemical substances. However, rubber is heavier than PU and is less flexible at low temperatures. The abrasion resistance of rubber ranges from 4 to 5 in. Another important feature of this material is the resistance to hydrolysis, which makes it more durable than the other materials. Rubber soles are also known for the outstanding slip resistance.
RECOMMENDED USE: both in- and outdoors, when there’s the risk of contact with hydrocarbons, chemicals, acids. It’s a dense and heavy materials, so it is not the best choice is lightness is a priority.
Safety shoes: EVA and PU soles
• PU/RUBBER (generally injection-molded soles). Keeping the properties of pure rubber on the outer surface of the sole, PU is used for the mid-sole, so to make the footwear lighter. PU is the weak spot in extreme conditions, where rubber has better performances.
RECOMMENDED USE: both in- and outdoors, when there’s the risk of contact with hydrocarbons, chemicals and acids. It’s a dense and heavy material, which is why it is mixed with PU.
• EVA/RUBBER: (generally glued soles). EVA (Ethylenevinylacetate) is an insulating foam that doesn’t absorb water. EVA is elastic, as well as tear- and slip-resistant. In shoes, EVA is used as a cushion in the mid-sole. It’s popular in sport shoes because it is one of the lightest plastic materials used for mid-soles. Nowadays EVA is also used for glued soles in safety footwear, as material for the mid-soles, placed between the upper and the outsole (which is normally of rubber).
RECOMMENDED USE: both in- and outdoors, when there’s the risk of contact with hydrocarbons, chemicals and acids. It’s a dense and heavy material, which is why it is mixed with EVA.
Safety shoes: recommendations
Those are my recommendations for you if you’re looking for the best type of rubber or polymeric material for your safety footwear
Once you have chosen the safety footwear with the right material for your needs, you’ll be more protected at your workplace.
I guarantee that if you use safety footwear with the right type of soles you’ll live a better working experience!
What do you think of the different types of safety footwear?
Do you have any points to add?
Leave us a comment below!