Performance Testing for Gloves
Published: 01st Jul 2013
With our hands used in just about every activity we do, the risk of injury is high and the market for protective gloves large. Supplying protective gloves is not without its challenges, however. SATRA’s Mike Cooper looks at the regulations and testing requirements with a focus on testing gloves for protection against the cold.
Hands are frequently exposed to risks of injury. In many cases, removing the hazard is difficult and it can be more practical to provide some form of hand protection. This has led to the billion dollar global industry of manufacturing and supplying protective gloves and mitts.
Many different types of gloves are available to protect hands and forearms from cuts, abrasions, burns, puncture wounds, vibration, skin contact with hazardous chemicals and some electrical shocks. Another danger to hands comes from exposure to the cold. SATRA has recently invested in new technology to test the thermal protection of gloves and this article will focus in part on cold testing, as well as an overview of European standards and testing for other types of protective gloves.
Challenges and opportunities
Glove manufacturers are continuously looking for new combinations of materials to achieve the greatest protection possible, while still allowing the wearer enough dexterity to perform the intended activity. While significant advances have been made in combining multiple protective features in a single product, it is unlikely that a glove will ever be produced that protects against everything.
Most industrialised nations have introduced regulations relating to occupational health and safety and many have established standards covering personal protective equipment (PPE), including protective gloves. In Europe, items worn or held to provide protection fall within the scope of the Personal Protective Equipment (PPE) Directive 89/686/EEC.
This not only includes requirements for the physical protection of the wearer but also restrictions on the use of many substances on health and environmental grounds. The European Union (EU) provides some of the greatest challenges to those in the protective gloves’ market, but also excellent opportunities for those who can get it right.
It could be argued that one of the keys to success in the global market is an appreciation that many countries outside the EU look upon conformity to EN standards and the PPE Directive as proof that the glove has been tested to the highest specifications. Indeed, the legislative framework within the EU gives confidence that the products have been designed and manufactured to a safe and consistent standard.
Cold comfort: improved thermal testing
People may encounter a number of problems when working in a cold environment without proper hand protection. When our hands get cold, we can experience a loss of sensation and impaired movement. We find it more difficult to handle small objects and suffer a decreased grip, which can result in accidents from dropping objects or from applying too much pressure to compensate for the lack of grip. In extreme cases, exposure to cold environments without the right protection can lead to frostbite.
Heat loss from hands can occur via one of several mechanisms. The main ones are ‘conduction’ – heat transfer when the glove is in contact with a cold object or something they are holding, and ‘convection’ – heat loss into the surrounding atmosphere, which is highly dependent on movement of the surrounding air.
To assess the performance of a glove’s protection for the hands against cold hazards, there is a European standard referenced EN 511: 2006 which includes a range of tests. They include a test for contact cold and for convective cold.
The convective cold test is a complex procedure requiring specialist equipment. The apparatus required for this test includes a computer controlled heated hand placed in an environmental chamber. In the chamber, the temperature is set to at least 20º C below that of the heated hand, and there is a defined air-flow rate.
The principle of the assessment is to determine the electrical power required to maintain a constant temperature gradient between the surface of the heated hand and the atmosphere within the environmental chamber. The more electrical power required, the lower the thermal insulation value of the glove.
SATRA has recently invested in the technology to test the thermal insulation of gloves in this way, and our moulded hand includes an embedded heater and sensing cables that have been manually wound around the palm and fingers without crossing over. Figure 1 shows the heated hand inside the environmental chamber.
The other test for protection against cold is the contact cold test. This involves the glove materials being placed between metal plates which are set at different temperatures. The measured temperature drop across the test specimen is used to calculate its thermal resistance.
The physical characteristics of the glove also need to be assessed, such as its resistance to abrasion and tearing. These assessments are based on the EN 388 and EN 420 standards discussed later. There are also flexibility tests for coated materials and for gloves intended to be used in environments below -30° C.
Current CEN glove standards
The number of CEN standards covering protective gloves is well into double figures. See Box 1. Two of these are of particular importance because they are called up in so many of the other standards. The two in question are EN 420: 2003+A1: 2009, Protective gloves – general requirements and test methods and EN 388: 2003, Protective gloves against mechanical risks.
EN 420: 2003+A1: 2009
This standard is designed to ensure that the gloves themselves do not cause harm to the wearer and are comfortable to wear. Tests and requirements include the pH value and Chrome VI content of leather, plus water vapour transmission and absorption of materials. Also, procedures to examine the sizing of the glove and its effect on finger dexterity are covered, plus general requirements for the information to be supplied with and marked on the glove.
Sizing and dexterity
Gloves are fitted on a hand of the size that they are intended to fit and comments are made regarding comfort and fit. The wearer will then try to pick up five pins from 5mm to 11mm in diameter to give an indication of dexterity. The smaller the diameter of the pin that is picked up, the greater the dexterity result.
The length of the glove is measured using a graduated rule with a rounded end that fits into the tip of the middle finger. The glove is suspended from the rounded tip of the rule and the length measurement is recorded. EN 420 includes a list of minimum lengths for each glove size. Gloves which fail the minimum length can be classed as gloves for ‘special purpose’, but in such situations the manufacturer must indicate they are manufactured for a special purpose by a statement in the user instructions.
The pH value of both the leathers and textiles of a glove need to be determined. This pH value needs to be greater than 3.5 and less than 9.5. The test samples are taken from the palm of the glove. If other parts of the glove contain a different material, these materials will be tested separately.
Chromium VI is a restricted substance as well as being a known allergen. Each type of leather on a glove is tested separately and must comply with the requirement of less than 3 mg/kg of chromium VI.
Glove marking and labelling
Gloves should be marked with the relevant pictogram for the standard, name, trade mark of the manufacturer, style reference or code, and numerical size. The standard requires this information to be legible and indelible for the foreseeable life of the product.
Due to the material characteristics, some products such as thin latex disposable gloves cannot be marked as they may be damaged during the marking process. EN 420 allows the marking to be placed on the next immediate packaging.
EN 420 also sets out the general requirements for user information in all gloves. This is in addition to requirements in the specific performance standards and includes the various pictograms to be used on the marking and packaging.
EN 388: 2003
This European standard is widely used in assessing gloves for general industrial applications. It is also referred to in many of the specialist glove standards for activities such as welding and handling of chemicals.
It includes four main physical tests to assess the resistance of the glove’s palm area to mild abrasion, cutting, tearing and puncture. The performance of the glove is graded in accordance with four or five performance levels. The end user is then able to select a glove with a performance level profile that suits a particular work activity.
For example, a glove could be performance level 4 for abrasion but level 1 for tearing – in European standards the higher the number, the greater the protection. Although it is fairly easy to see how abrasion, cut and puncture resistance would protect the wearer in actual use, tear resistance seems more geared towards showing the strength and durability of the product.
When it comes to working near moving machinery, however, and the danger of entrapment is present, health and safety professionals need to consider tear resistance. In this instance, it may be safer to have a glove made of weaker tensile strength materials to allow the wearer to free their hand if necessary. For this reason, EN 420: 2003+A1: 2009 does require a warning in the user information for high tear resistance.
Samples are cut from the palm of a glove and rubbed against a 100 grit abrasive paper using a Martindale type abrasion machine (Figure 2). The number of cycles for the samples to hole is measured. Four performance levels are defined in EN 388 ranging from Level 1, where holing occurs between 100 and 500 cycles, to Level 4, where the material survives at least 8,000 cycles without holing occurring.
Blade cut resistance
Samples are taken from the palm of a glove and the number of cycles for a circular rotating blade to cut through the full thickness of the test sample is recorded. The test involves the blade moving back and forth over the sample, rotating in the opposite way to the direction of travel, under a (5 N) cutting force.
Blade sharpness is assessed by using the machine to cut through a standard reference fabric. The cut resistance of the glove is based on a relative index that compares the number of cycles to cut through when compared with the standard fabric. To account for the loss in sharpness over several cutting strokes, the standard canvas is cut before and after the test sample, the average number of the two calibration cycles is used as a divider to calculate the performance index.
Five performance levels are defined in EN 388 ranging from Level 1, a cut index of at least 1.2 but less than 2.5, to Level 5 a cut index of at least 20.0.
The EN 388 method, commonly referred to as the ‘Coup test’, is satisfactory for gloves with lower levels of cut resistance. Improvements in the resistance of glove materials, however, for instance through the addition of glass and steel, have highlighted the deficiency of this test at higher cut levels due to the rapid blunting of the test blade. Another test – EN ISO 13997: 1999 – has become widely used for assessing the cut resistance of higher performing gloves.
The EN ISO test uses the principle of a straight blade drawn across the sample material at a constant speed and constant force. The distance travelled to cause cut through at various forces is recorded and the results are calculated to predict the force required to cut through at 20mm of blade travel.
This method is now being seriously considered in the current revision of the EN 388: 2003 as being mandatory for use on these special materials which prematurely blunt the circular Coup test blade.
To test tear resistance, rectangular samples are taken from the palm of a glove. These are commonlyknown as ‘trouser tear’ specimens and are slit and torn apart using a standard tensile test machine (Figure 3 on page 61). Four performance levels are defined in EN 388 ranging from Level 1, a tear resistance of at least 10 N, but less than 25 N to Level 4, a tear resistance of at least 75 N.
Samples are taken from the palm of a glove and the force required to penetrate the sample with a defined stylus using a tensile test machine is measured. Four performance levels are defined in EN 388 ranging from Level 1 where the puncture force is at least 20 N but less than 60 N, to Level 4 where the puncture force is at least 150 N.
Chemically protective gloves
The European standard EN 374: 2003 consists of the following parts under the general title ‘Protective gloves against chemicals and microorganisms’: • Part 1: Terminology and performance requirements • Part 2: Determination of resistance to penetration • Part 3: Determination of resistance to permeation by chemicals
Part 1 details the performance criteria and also includes marking and user information requirements. It also sets out requirements for the reporting of the results of any claimed mechanical protection to EN 388: 2003.
Part 2 specifies the test methods used to determine the penetration resistance of gloves. The gloves are subjected to air leak and water leak tests to determine if any defects such as holes are present which would allow chemicals or microorganisms to penetrate through to the user’s hand.
Part 3 specifies the determination of the resistance of protective glove materials to permeation by potentially hazardous, non-gaseous chemicals under conditions of continuous contact. Permeation is the process by which a chemical moves through a protective glove material on a molecular level. Gloves are classified according to the time it takes the chemical to break through the glove material.
In order to be certified as chemically protective, the gloves must achieve a minimum of level 2 (breakthrough time of greater than 30 minutes) against at least three chemicals listed in EN 374-1.
An additional Part 4 is currently under consideration to enable the determination of degradation.
EN 407: 2004 –thermal risks
This is a general standard designed to be used for any glove which is to be produced and sold as providing protection against high-temperature thermal hazards. The standard includes six thermal tests: burning behaviour, contact heat, convective heat and radiant heat, as well as against small and large splashes of molten metal, plus reference to EN 388 and EN 420 for mechanical and general performance requirements. The test(s) selected are based on the intended use of the glove.
Gloves used specifically for welding applications are covered under the EN 12477 standard which sets minimum levels of EN 407: 2004 and EN 388: 2003 plus specific length requirements.
While hand injuries still form a high percentage of accidents both at work and at home, many of them are easily preventable by wearing appropriate protective gloves.
Increasingly, legislation and obligations on employers and manufacturers to provide improved safety equipment and adequate protection against hazards is leading to advances in material technology and better protective products. This is resulting in better designed and more comfortable gloves which, in turn, should lead to a reduction in injury statistics.
Published: 01st Jul 2013 in Health and Safety International