Posted on February 03 2020
Steel vs. Alloy vs. Composite Safety Toes:
Understanding the Test Requirements and
Making an Informed Choice about What’s Best for You
Table of Contents
How Do I Know My Safety Boots are Safe?
Standardized Testing and Performance Criteria
Which Toe Cap Material is Best?
Conclusion
Robert N. Petersen
Senior Product Manager
Tingley Rubber Corporation
How Do I Know My Safety Boots are Safe?
As technologies advance in materials and processing methods, opportunities are created for improving the goods and services we use, including the performance of safety footwear. For example, steel toe caps have been used in footwear since at least the 1930s to provide toe protection against impact and compression injuries. Consumer desires for lighter weight boots and advances in aluminum alloys paved the way for utilization of alloy toe caps. More recently, innovations in polymer technologies opened a whole new frontier and over the past few years footwear manufacturers have started incorporating composite toe caps into their boots and shoes. Developments in carbon fiber technologies promise greater possibilities for enhanced protection in the future.
With many different options for toe cap construction, it’s understandable that users of protective footwear would have questions about whether the footwear they are wearing meets a safety requirement. The good news is that the American Society for Testing and Materials (ASTM) and the US Occupational Health and Safety Administration (OSHA) have taken all the guesswork out of this by setting clear requirements for safety footwear.
OSHA requires the use of personal protective equipment (PPE) to reduce employee exposure to hazards in the workplace. In fact, the US law outlined in section 29 CFR 1910.136(b)(1)(iii)) of the Code of Federal Regulations, and which OSHA follows as the PPE requirement, states that protective footwear must comply with the ASTM F2413, Standard Specification for Performance Requirements for Protective Footwear. To know whether the footwear you are wearing meets this standard, make sure the footwear bears the ASTM F2413 compliance label as shown in Figure 1.
Figure 1: ASTM F2413 Compliance Label
Standardized Testing and Performance Criteria
As their name implies, the ASTM is involved in standardization so that people can make apples-to-apples comparisons and the most informed decisions about products and processes. There are two main types of standards published by the ASTM:
- Standard Test Methods
- Standard Performance Requirements
The two main safety criteria in the US for safety footwear are Toe Impact Resistance and Toe Compression Resistance. While ASTM F2413 outlines the Standard Performance Requirements for safety footwear, ASTM F2412 outlines the Standard Test Methods for conducting the testing on said footwear. The two standards are interrelated. All toe cap protection works on the “defended space” concept where the toe cap provides a protective barrier area around the toes. The test method provides instructions on how to prepare the footwear sample for testing, what materials and/or equipment to use, how much force should be used, and where it should be applied, etc. The obtained test result is then compared to the performance requirement to determine a pass/fail result on that particular test.
Impact Test: In grossly simplified terms, a clay cylinder of specific height is placed upright on the footbed of the boot and within the space defined by the toe cap. An “impactor” of specific weight and design is dropped onto the toe cap with a specific force. The resulting height of the clay cylinder is then measured. This is the ASTM F2412 test process to obtain an impact test result.
Compression Test: Again, in grossly simplified terms, a clay cylinder of specific height is placed upright on the footbed of the boot and within the space defined by the toe cap. A specified compressive force is then applied to the toe cap over a specified period of time. The resulting height of the clay cylinder is then measured. This is the ASTM F2412 test process to obtain compression test result.
Determining a Pass/Fail Performance: The test values are now compared against the ASTM F2413 performance requirements to determine the pass/fail criteria for both tests. The performance requirement for both tests states that the post-test height of the clay cylinder must be at least 0.5 inches tall. In other words, the remaining height on the clay cylinder following the impact or the compression test represents the “space” occupied by your toes. If the height of the cylinder is 0.5 inches or more, then the footwear passes and can be labeled with the I/75 and C/75 designations. The footwear must pass both impact and compression tests to bear the ASTM compliance label.
Which Toe Cap Material is Best?
Choosing the toe cap type that is best for your specific needs is a matter of understanding the pros and cons of each and considering the type of work environment in which the safety footwear will be worn. The major determining factor will be your job, for which are the one best suited to evaluate the factors that are most important. Such factors may include the temperatures of your work environment, the amount of time spent standing vs. walking, and the type of heavy equipment in use around you. Answering these questions can help you make the right decision for your workplace.
The following section provides an overview of the benefits and drawbacks of each toe cap type.
Pros & Cons of Steel Toe Caps: Steel toe caps have been in use since around the 1930s and are still very popular in the safety footwear market today. Despite advances in composite technologies, pound for pound, steel is still stronger than composite materials. Therefore, a smaller quantity of steel can be used to achieve the required strength to pass the standards and it may look less bulky in a boot. Steel also has the added benefit of being less costly to manufacture resulting in safety footwear that is often less expensive than other toe cap designs. The drawbacks of steel toes are that they will readily transfer cold from the outside environment to the toes, and they will set off metal detectors.
Pros & Cons of Alloy Toe Caps: These toe caps are typically an alloy of aluminum and are generally lighter weight compared to steel, which will mean lighter weight safety footwear. A major drawback is that aluminum alloys tend to be more expensive compared than steel. Lastly, cold transmission is just as bad as steel so if you’re working outdoors in winter you may want to consider a composite toe cap.
Pros & Cons of Composite Toe Caps: The benefits of composite toe caps are being realized by consumers and they are rapidly being integrated into safety footwear. Composite materials in use at the time of this writing include, but are not limited to, Kevlar®, polycarbonate, fiberglass, and carbon fiber. Steel and aluminum alloy toe caps are much more thermally conductive compared to composites. This means that composite toe caps will help to keep feet and toes warmer especially when working outdoor in extreme cold or in refrigerated food processing plants. Some composites are also lighter than steel providing anti-fatigue benefits to the wearer. Lastly, composites will not set off metal detectors, nor will they conduct electrical current.
Figure 2: Toe Cap Construction and Comparison of Benefits
Conclusion
Tingley Rubber Corporation offers a wide range of materials, colors, tread patterns and toe cap types in our protective footwear so that users can select the best combination of features for their work environments.
Remember, no matter what the toe cap material, all safety toe footwear sold in the US must meet the standardized impact and compression performance requirements to be rated as ASTM F2413 compliant. Again, this certification label will be clearly marked somewhere on the boot itself. Make sure you can see it to know you’re in safety footwear that meets the toe impact and compression standards.
Please contact your local Tingley sales representative for more information on the types of safety footwear offered by Tingley and for help making the best decision for your specific needs.