Impact abrasion resistance of leather in motorcyclists’ PPE
Exploring the requirements covering these important products and the methods used to test their compliance.
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Riders of motorcycles are highly vulnerable to injury in an accident, so it is important for them to wear a helmet, gloves, protective clothing and footwear that are designed to prevent or reduce the severity of any resulting injuries.
Aside from motorcycle helmets (which are covered by separate regulations) and products for leisure use that only protect against non-extreme weather conditions, all protective wear for motorcyclists intended for the European market should be assessed against the requirements of the ‘Personal Protective Equipment (PPE) Regulation (EU) 2016/425’ and, for the UK market, against the ‘Personal Protective Equipment (PPE) Regulation (EU) 2016/425 (as retained in UK law and amended’)’.
While many items of motorcycle PPE are manufactured from synthetic and textile materials, leather is still an important material, and it is commonly used in footwear, gloving and clothing applications. Leather can be a hard-wearing and flexible material that makes it ideal for these types of applications, and can produce a highly desirable product for the end user.
Europe and the UK have currently taken the lead in the setting of safety standards for motorcyclists’ protective equipment, and there is a technical committee working group within CEN (the European standards body) that is devoted to this specialised work. The CEN/TC162/WG9 committee was formed around 20 years ago and since then has developed several safety standards for motorcycle rider protection.
As the products themselves differ, so do the standards in the tests and the performance requirements associated with each assessment. For example, both the footwear and the glove standards contain methods which allow the measurement of the impact resistance of the products. The footwear test includes impact resistance tests on the ankle and shin regions of a boot, while the glove standard contains impact resistance tests on the back of the hand, where additional protective material may be attached to protect the hand against accidental impacts during riding or handling a motorbike. There are a number of differences between the methods which include the profile and dimensions of the impact striker which is dropped onto the test specimen, the energy delivered by the striker as it impacts with the specimen and the requirements for the test which are usually expressed as the amount of peak force that has been measured on the underside of the test specimen which has been transmitted through the protector.
|EN motorcycle PPE performance standards|
|EN 13594:2015||‘Protective gloves for motorcycle riders. Requirements and test methods’|
|EN 13595-1:2002||‘Protective clothing for professional motorcycle riders – Jackets, trousers and one piece or divided suits. General requirements’|
|EN 13634:2017||‘Protective footwear for motorcycle riders. Requirements and test methods’|
|EN 17092:2020||‘Protective garments for motorcycle riders’
Part 2: Class AAA garments – Requirements
Part 3: Class AA garments – Requirements
Part 4: Class A garments – Requirements
Part 5: Class B garments – Requirements
Part 6: Class C garments – Requirements
All the standards contain an abrasion resistance test, and these tests will be considered in more detail later in this article.
Impact abrasion testing
The particular hazards for motorcyclists who are involved in road traffic accidents are falling from the motorcycle and suffering impacts with the road surface, their motorcycle, other road users or other obstacles. When impacting and sliding across the surface of the road, there is a significant risk of suffering abrasion. This type of damage is often called ‘road rash’, and can cause significant life-changing injuries if the rider is not adequately protected.
There are currently two different methods for measuring the abrasion resistance of a material intended for use in motorcycle PPE: ‘Cambridge’ and ‘Darmstadt’. The Cambridge method (figure 1) is more established, and is included in the footwear (EN 13634), gloves (EN 13594) and protective clothing (EN 13595) series of standards which are intended for riders using the products while undertaking aspects of their job. The test incorporates a ‘rolling road’ covered with an abrasive material, and starts with the specimen being impacted against the moving abradant. The impact phase of the test is important, as it can cause significant damage to the material being evaluated. The overall damage at the end of the test was considered by the European technical committee CEN/TC162/WG9 developing the test methods to be highly representative of that seen in motorcyclists’ suits from real-life crashes.
Specifically, the test involves a test specimen being dropped from a height of 50 mm with a force of 49 N onto a 60-grit abrasive belt moving at a speed of eight metres per second – approximately 18 mph. The test ends when the material under evaluation is holed, which is indicated by a copper wire placed underneath the specimen being broken. The result reported is the time (in seconds) to cause holing and both the average and lowest single abrasion time of four test pieces is reported. To ensure consistent results, the abrasive power of the belt is assessed using two layers of a standard reference denim cotton fabric and a calibration result is used to correct the specimen’s abrasion time.
The ’Darmstadt’ method (figure 2) is newer, and is included within the EN 17092 series of standards. This test simulates the stress that is placed on the protective garments worn by an average rider (with a body mass of 75 kg and a height of 1.75 m), when sliding from variable initial speeds to standstill on a concrete road surface. In one run, three specimens of the material(s) are mounted in holders in warp, weft and at 45 degrees (or for non-fabric specimens such as leather, mounted at angles of 120 degrees, 240 degrees and 360 degrees to the direction of travel).
The Darmstadt machine is capable of running at various speeds: 147 rpm, 265 rpm, 442 rpm and 707 rpm, with the fastest speed being more aggressive and used for the higher risk zones in the parts of the standard for products with a higher degree of protection for the user. The materials being assessed are attached to rotating arms positioned above a concrete tile and, once the desired speed has been reached, the test specimens impact on the surface and come to a natural stop. If the specimens have not holed through all the layers, a further two test runs are carried out. The requirements of the standard are that none of the nine specimens should show any holes with an opening of 5 mm or more in any direction on the layer that would sit the closest to the body.
The two methods generate results in different formats and units, and so it is not possible to compare them.
The Cambridge test requires a circular test specimen of 160 mm diameter, with an actual test area of approximately 75 mm diameter in the centre of this. The Darmstadt test pieces are slightly smaller, with a diameter of 125 mm and a test area of around 48 mm diameter in the centre. With such large test material requirements, it is usually very difficult to take the specimens from the finished products, so the standards permit the test to be carried out on sheet material.
Most products will contain multiple layers of materials which may vary in thickness and type in different areas. It is important that all constructions of materials are tested to ensure that the weakest types are evaluated.
Impact abrasion performance requirements
The results from the Cambridge abrasion machine are expressed in ‘number of seconds’ until all layers of material have shown breakthrough. Therefore, the performance required is expressed as a maximum number of seconds permitted. The EN 13594 glove standard, the EN 13634 footwear standard and the EN 13595 professional clothing standard contain a range of requirements for different zones and areas of product, and for two different levels of protection. For each of these standards, ‘Level 1’ relates to products which provide protection but with low weight and ergonomic penalties (the ease of undertaking a task while wearing the product), while ‘Level 2’ relates to products where these penalties may be greater. The requirements vary from a minimum abrasion time of 1.0 seconds for the highest risk areas of Level 1 garments to a minimum abrasion time of 12 seconds for the lower-risk areas of Level 2 footwear.
The results generated in the Darmstadt test are in accordance with a pass or fail criteria applied to an analysis of the test specimen following an assessment at a set speed of machine measured in revolutions per minute. The most severe test is at the highest speed of 707 rpm and the least severe test is at 147 rpm (the slowest speed). The standard is split into six parts, with parts two to six relating to different products classes – ‘AAA’, ‘AA’, ‘A’, ‘B’ and ‘C’. Class A products possess the lowest degree of protection, while Class AAA items offer the highest level. Classes B and C are special classes for garments that do not possess impact protectors and under/over garments respectively.
As the Cambridge tests are numerical in nature, it is easy to compare and differentiate results from various materials and products. The running of the test does not need the manufacturer to predict the categories and performance levels required, nor to know at which level the combination is planned to be used. This type of result supports development work and enables an identification of where a product may be upgraded to a higher specification level. A common method of ‘quality benchmarking’ is to use the numerical result given to compare against previous material constructions – those yet to be introduced or currently in development – even if the end goal is to achieve EN 17092 certification.
As the Darmstadt tests are carried out at a set speed, the manufacturer needs to predict the category and zone for which the combination of layers is intended to be used. This does not easily support the upgrading of the product to a higher specification without additional testing.
A brief introduction to ‘zoning’
When abrasion resistance is being assessed, there are several key zones that are present on a garment that must be taken into consideration, with each individual zone carrying its own specific requirements. For both EN 13595 and EN 17092, ‘Zone 1’ areas would include ‘high risk’ impact zones – for example, on the shoulders, elbows, knees, and hip areas. ‘Zone 2’ areas are deemed to be ‘moderate risk’ impact areas, and ‘Zone 3’ is deemed to be ‘low risk’. EN 13595 includes ‘Zone 4’ areas, which can be considered as ‘very low risk’ sectors and may be used for ventilation purposes.
While the standards contain numerous tests used to assess all the protective properties of motorcyclists’ PPE, impact abrasion resistance is one of the most important features that a product must possess. Abrasion injuries caused by a rider falling from a moving motorcycle can be life-changing or even life-threatening. The use of suitable PPE can greatly reduce these risks and, with a range of performance levels across the relevant standards, the rider is able to select the most appropriate equipment for his or her situation.
How can we help?
Please contact SATRA’s PPE team (email@example.com) for assistance with the evaluation of motorcyclists’ leather personal protective equipment.
This article was originally published on page 20 of the April 2021 issue of SATRA Bulletin.