Safety footwear or work boots as they are commonly known in Australia and New Zealand protect the wearers against a plethora of hazards. So how does safety footwear actually provide protection? What components and features must safety footwear have to provide effective protection against mechanical, thermal and electrical hazards?
The basic construction of shoes, sports shoes and safety footwear is very similar. If we take a cross-section of safety footwear, it is possible to see the various elements which make up the shoe and their respective functions.
In addition to the familiar and visible shoe components, this view reveals the inner workings of a shoe, offering a glimpse into the particular characteristics of safety footwear. In the following sections, we discuss the individual components which make up a safety shoe. We will first deal with the shoe upper (1-8), before moving onto the sole (9 and 10).
Shoe upper (blue)
- Toe cap ①
Depending on the type of footwear, various toe caps are available which meet different minimum requirements. A protective toe cap on safety footwear must withstand test energy of 200 J under a drop test, which is approximately equal to a 10kg weight being dropped from 2m, and a 15 kN (~1.5 tonne) compression test. Steel, aluminium and composite toe caps are currently all used in safety footwear, with the same minimum requirements for all materials. Composite toe caps have the benefits of being up to 40% lighter than steel, electrically non-conductive and insulating making them cooler in the heat and warmer in the cold. Composite toecaps also have the advantage of being metal free, meaning they do not set off metal detectors making them particularly convenient in security areas such as airports and are often referred to as airport friendly.
- Upper material ②
In addition to an assortment of leather types (full grain, nubuck and split leather), textiles and synthetic materials are also often used. The different characteristics of the upper material determine the use of the respective materials for various applications. These include, but are not limited to heat resistance, fire resistance, breathability, water permeability, weight, price, allergy risk and cleanability. Leather has excellent heat resistance and fire resistance while synthetic materials can be more breathable and lighter.
- Lining material ③
The shoe lining is in direct contact with the socks or foot inside the shoe. The lining material therefore fulfils important tasks such as guaranteeing breathability, water vapour transfer, climate control and quick drying capacity, as well as high levels of abrasion resistance. In addition, it should feel comfortable for the wearer. Various materials are also used for this purpose: leather, textiles, thermo-regulating textile materials and waterproof membranes.
- Heel cap ④
In order to offer a stable fit on the heel, the rear of the shoe features what is known as a heel cap. This can be made from card, bonded leather, thermoplastic or thermoplastic rubber and can be internal or external. Shaping the outsole is also possible, which would then replace the heel cap inside the shoe. The uvex x-flow range uses an external thermoplastic heel cap to reduce irritation on the heel and improve durability of the anatomical shape.
- Padding ⑤
The collar and tongue area are softly cushioned. This helps evenly distribute the pressure generated from the lacing system across the instep and to improve wearer comfort at the shaft. It is important to use soft, yielding and breathable materials, particularly in the area surrounding the Achilles tendon, so as to avoid irritation.
- Lacing ⑥
The shoe cross-section shows the lacing system. Shoelaces are an extremely effective way of customising the fit of footwear and adjusting the volume to put on and take off the footwear. On some styles we also use elastic shoelaces to allow a quick and easy fastening. The elastic laces also offer flexibility over the course of the day as they expand if the feet swell.
- Removable insoles ⑦
A removable insole or footbed is fitted above the insole board. Depending on the design of the removable insole, this provides additional shock absorption at the heel or front of the foot, as well as a partial support for the arch of the foot. The removable insole is breathable minimising the heat and moisture build up in the footwear. It has a pleasant, non-irritating surface structure and dries quickly. A wide-range of materials can also be used, including foams and non-woven materials.
- Insole ⑧
The insole forms a connection between the upper and the midsole. As far as materials are concerned, pulp fibres, foam, leather or non-woven materials can be used. The insole’s principal function is connecting the upper to the sole of the footwear, while additionally removing moisture. The insole materials used by uvex is also pH neutral, skin-friendly and excels through consistent antistatic or electrically insulating properties.
Sole (red)
- Outsole ⑨
Outsoles are typically made from thermoplastic polyurethane (TPU) and rubber (nitrile rubber). These materials can be differentiated according to their characteristics. In order to choose safety footwear that offers the best protection for a particular area of application, these characteristics should be considered. Rubber outsoles have better heat and chemical resistance properties compared to thermoplastic polyurethane (TPU). TPU outsoles typically resist temperatures of 130-150°C, while nitrile rubber outsoles can resist 300°C. All styles in the uvex x-flow range have a nitrile rubber outsole that is heat resistant outsole to 300°C.
- Midsole⑩
The midsole is designed to provide both cushioning and stability. Midsoles can be made from a range of materials but in safety footwear are typically made from polyurethane. Ideally midsole cushioning should have good shock absorption capacity while also having good energy return capacity while maintaining good stability. uvex i-PUREnrj midsole has been compounded to maximise the energy absorption and energy return while maintaining good stability. This important to minimise fatigue in the workplace by maximising walking efficiency.
Although this is not the case in our pictured cross-section, some models include penetration-resistant insoles and scuffcaps over the toe cap:
- Penetration-resistant insoles
Penetration-resistant insoles come in steel or textile variants. Here, too, the same demands are placed on both product types: penetration-resistant metal and textile inserts must be able to resist penetration from a test nail with a diameter of 4.5 mm under a specific force of 1,100N or approximately 110kg. Steel inserts are placed between the insole and the outsole. A penetration-resistant textile insert usually replaces the existing insole. This is just one of the differences between the two materials.
Given that steel inserts are manufactured in standard sizes and are not specially adapted to individual models of shoes, some areas around the edges of the insole may remain unprotected. Conversely, a textile insert replaces the insole. This means the entire foot is protected. It is also more lightweight, more flexible and prevents cold and heat transfer between the ground and the inside of the shoe.
- Scuffcaps
The scuffcap: although not in our profile, it plays an extremely important role in safety footwear for other application areas. Various types of leather, carbon-reinforced leather, polyurethane (PU) foam or thermoplastic polyurethane (TPU) can be used for scuffcaps. The fundamental role of the scuffcap is to protect the outer material on the toe cap from mechanical stress and improve durability. It thereby reduces wear and tear of the material and extends the service life of the shoe. While foam PU and TPU are more abrasion-resistant, carbon-reinforced leather has a greater degree of heat resistance.
Explore the range of uvex safety footwear. To learn more about safety footwear talk to uvex footwear specialist now.