Great recent progress in technology hasn’t solved the problem of safety and protection of man in his working environment.
It is not always possible to eliminate or to reduce the dangerous and harmful factors in the workplace, and sometimes the only solution to protect a worker from hazards is to apply individual protective equipment. Some of the most commonly used examples of PPE are protective clothing.
The type of protective clothing depends on the type of harmful or dangerous factors present at the workstation. Therefore, the classification of clothing taking into account its protective properties is of utmost importance. We can distinguish clothing protecting against mechanical, thermal, chemical, biological agents, high visibility clothing, clothing protecting against electric shock, electromagnetic radiation or drowning.
Protective properties of the clothing are determined by the use of appropriate materials that constitute a barrier against dangerous factors, or sufficiently reduce their effects so that they are no longer a danger for the user. Depending on the harmful factors that the worker is exposed to, the clothing can be made of textiles, such as impregnated fabrics, nonwovens and knitwear coated on one or both sides with plastic, fabrics and knitwear made of high-efficiency fibres, systems of materials as well as leather, plastic and even metal rings.
When selecting the clothing for protection against hazards, it is important to know the basic parameters of the protective properties of the material, and to select the appropriate class of these parameters adequately to the level of risk. Unfortunately, some clothing frequently in use causes overheating to users due to materials that it is made from and its tight fit.
The dynamic development of science that creates new materials and composites generates real possibilities for constructing new types of clothing and modeling its protective features, bearing in mind its ergonomic aspects.
In this article the solutions and directions of development in protective clothing are presented, which aim at improving its useful properties and functionality. Particular attention is drawn to the possibility of applying active materials in protective clothing, which would react in beneficial ways for the user in terms of both external stimuli and in terms of the user’s functions. Attention is also drawn to the use of electronic systems in the clothing, thanks to which it can fulfill extra functions as far as information and communication is concerned.
Solutions worked out in the Central Institute for Labour Protection – National Research Institute (CIOP-PIB) are also presented here.
Solutions improving comfort
The necessity to protect a worker from chemical factors and atmospheric precipitation requires the application of tight protective clothing made from materials coated with synthetic polymers. Such clothing makes it impossible to release heat and sweat from the body, and working in it creates a heavy heat load for the user, which is proportionate to the effort expended 1, 2.
The result is a lack of comfort caused by the inability to release large amounts of sweat. This collects on skin and on the internal layer of tight clothing, creating a highly humid microclimate under the clothing, and causing an oppressive, suffocating feeling for the user.
A solution to this problem may be the application of steam permeable materials in protective clothing. Recently, there have been modern water vapour permeable materials produced on the market, which may be used in protective clothing. They are a barrier for hazardous factors and at the same time they let water steam out and make it possible for the excess of heat to be released, thanks to which the microclimate under the clothing is characterised by lower levels of humidity and temperature than is the case with traditional coated materials.
Of particular interest are laminates of flat textile materials and water vapour permeable films, microporous layers and materials produced from microfibres.
Water vapour permeable materials, however, cannot be applied in tight clothing protecting against aggressive chemicals. The discomfort of working in tight protective conditions can be lowered through using specialist underwear made from two-layer polyester-viscose knitted fabrics that may positively influence the sweat transportation3. The layer that is close to the body and made of polyester transports sweat to the layer made from viscose, remaining dry at the same time. This supports a beneficial microclimate close to the body and eliminates its contact with wetness.
The discomfort connected with intensively produced sweat may be limited greatly through applying fillers that absorb sweat, which are made from non-woven, highly sorptive fibres Oasis 102. They may be designed to collect sweat from the layer that fits tightly to the body, but also from external surface of the tight protective clothing, and to absorb water vapour under the clothing.
Protective clothing reacting to external stimuli
The characteristic feature of the products from this group is the fact that they receive stimuli directly from the environment or the human body and then react to them with significant physical, chemical and biological changes, reversible in many cases. New technologies are based on incorporating certain active materials into the fibers or modifying the surface of fabrics so as to provide them with certain features. Active materials are stimulated by: tension, electromagnetic field, temperature, humidity, UV or IR radiation, or chemical substances. Materials respond to these stimuli with the changes in geometric measurements, state of matter, dispersion of tension, or coefficient of light reflection.
The task of those dealing with the construction of protective clothing is to select appropriate active materials for predicted applications, so as to use it in a specified order.
Clothing with changeable heat insulation
Shape memory materials (SMM) are materials that, under the influence of certain stimuli, return from their shape once used to their original one, e.g. the one that has been ‘remembered’. The effect of shape memory is observed mostly in shape memory alloys and polymers.
Shape memory alloys (SMA) are a unique class of metal alloys that can change their shape when heated over a certain temperature. They could be used in clothing protecting against high temperature, flame, heat radiation and clothing protecting against cold.
In tests, NiTi spring wire was applied between the layers of the clothing in such a way that it remained flat at the room temperature, but expanded gradually and took on a cone shape at the temperature of 45-55C5. Such a solution could be used in protective clothing for firefighters and during tests on a thermal dummy it was stated that after applying the stream of high heat radiation, expansion of springs caused growth of heat insulation in the clothing system, preventing any burns.
SMA wire made of alloy that activates itself at a temperature lower than 5C, was placed between two layers of non-woven in clothing protecting against cold5. The effect of activity in materials was obtained on materials that at lower temperatures increase their volume, which enables constructing clothing of low thickness, more ergonomic and adjusting its insulation to outdoor environments.
Polyurethanes with shape memory of glaze temperature greater than 55C may be used in protective clothing, used, for example, in chemical, metallurgy or food industries. They were found useful also in intelligent waterproof membranes and water vapour permeable membranes that are currently used by the clothing industry to laminate fabrics and knitted materials, and as waterproof layers in clothing protecting against bad weather.
Together with the temperature increase, after exceeding the activation temperature, pores expansion in the membrane takes place and increases the permeability of water vapour. This is very beneficial from the thermoregulation point of view, as greater amounts of sweat may evaporate and be taken outside.
Shape memory materials used in PPE make for a light and ergonomic design that will be activated and become a barrier only when the danger level threatens the user. Scientists are working on protections that will make a cushion or a protective umbrella over a worker at the moment of an accident or a catastrophe.
Clothing with phase change (PCM)
Materials able to change their phase in a certain range of temperatures called the temperature of phase change, are known as phase change materials (PCM). During the change phase (e.g. from liquid to stable and the other way round) they absorb, store and release large quantities of energy in form of latent heat.
In the form of capsules, PCM may be incorporated into a textile in various ways. Currently, fibres including microcapsules of PCM are produced. They are totally surrounded by a polymer and permanently closed in the fibre.
The most famous is a polyacrylonitryle fibre known as Outlast, and has a heat capacity from 4.2-8.4 J/g 6. The latest viscose fibres with PCM microcapsules are characterised by heat capacity of 60 J/g 7. The cross-section of PCM fibres is presented in Fig. 1.
PCM can be introduced into textiles through imbuing, printing, coating or spraying.
Due to the fact that using protective clothing is connected with discomfort and causes heat stress for the user, there were attempts to use PCM in structures of protective clothing in order to cool the user’s body. Research in this field was carried out at Textile Testing and Innovation in the USA 9.
They were concerned with improving the comfort of clothing protecting against chemicals, where PCM was added to polymer coating, followed by laminating it with non-woven.
Research into new types of clothing was carried out on volunteers during a physical activity, at the same time carrying out studies on protective clothing with no PCM added. The skin temperature and the humidity of the microclimate of the underwear stayed at a lower level during tests of clothing with PCM microcapsules than without them, thanks to which a higher physiological comfort was obtained, and the time of using protective clothing was safely prolonged.
Research in PCM also concerns underwear designed to be worn under protective clothing 10. Selected PCM microcapsules were permanently bonded with polymer film that was later placed between two layers of material. Underwear produced from this material is light, covers the whole body and is designed for multiple use and easy maintenance. Studies on waistcoats with PCM where the positive effect in shaping a beneficial microclimate under clothing for surgeons were carried out at SINTEF (Health Research, Materials and Chemistry) in Norway11.
Research on the application of phase change materials for thermoregulation of the microclimate under the tight protective clothing are carried out at the Central Institute for Labour Protection – National Research Institute (CIOP-PIB). Two types of clothing were prepared with PCM to be used under protective clothing: waistcoats and underwear with viscose fibres including PCM microcapsules, and waistcoats with PCM macrocapsules placed in special channels of appropriately prepared knitted material. Tests on those materials showed that the use of clothing could be safely prolonged if waistcoats with PCM were worn under tight protective clothing, used for protection against chemicals, since the skin temperature and inside temperature for the user was lowered.12.
Active heating clothing
In many workplaces, PPE can intensify the peaks and troughs of temperature, so there has been a need to develop technologies that can regulate and even this out. Appropriate protection and comfort can be obtained only through an active shield, which changes its insulation together with the climate changes of the outdoor environment, and the level of heat emitted by the user. In order to do so, heating textiles are used, which are made from electroconductive fibres. Clothing equipped with integrated heating systems ensures precise temperature regulation.
Recently a model of protective clothing was designed for working in cold environments. It actively reacts to temperature changes and changes its heat insulation to provide the user with a state close to warmth comfort 13. Active elements installed in clothing are six heating inserts made of steel yarn fibres. Steering of the heating inserts is done by the measuring-steering system that collects data from microsensors of temperature, placed in two points in the microclimate under and on the clothing. The microcontroller makes decisions according to a certain algorithm and causes the turning on or off of the heating inserts. Heating inserts and the measuring-steering system make an independent system that can be installed in the clothing. Active heating clothing has been assessed positively during tests on users in a cooling room at the temperature of -24C.
In Fig.2 there is a heating insert and steering system in active heating clothing, protecting against cold.
Where heating elements are used in clothing designed for extreme sports and in protective clothing, e.g. for divers, in gloves used in extreme climate conditions, electroconductive and non-flammable materials are applied.
Integration of electronic microsystems
The integration of electronic microsystems with textiles enables us to create products that can be used in protecting health and in medicine, safety and rescuing, industry logistics and sport. Clothing is designed for sports people that has electronics monitoring installed, which can register the heart rate, the number of breaths taken and skin temperature. There is also clothing made with a GPS system installed, and with an electronic compass and altimeter.
Electronics find many practical uses in protective clothing, particularly that used in extreme conditions. Clothing has been prepared with electronic microsystems which enable the monitoring of the physiological parameters of the user and the corresponding level of danger. This has been designed for rescuing teams such as firefighting units 14. The task of such clothing is to control the physiological state of a firefighter, including the environment’s conditions and the level of effort spent while working (energy loss and the resulting physical stress).
The new clothing monitors: temperature of the skin, temperature between skin and clothing, outside temperature, heart rate frequency, firefighter’s mobility (move/non move). The information about monitoring parameters is collected and sent using a wireless system to the centre of monitoring located in the fire truck. The center, equipped with a computer system, quickly analyses the situation and helps a firefighter to make a decision on the possible necessity to evacuate from a risky area.
The new clothing means that the physiological condition of a firefighter (energy expenditure, work load) can be controlled in the most effective way during emergency actions.
The new generation firefighters’ clothing is certainly an important advancement and improvement to modern fire fighting techniques and it meets the requirements of PN-EN 469:2008 harmonised standard. Fig. 3 illustrates the firefighter’s monitoring system during an operation.
Increasing the safety of workers who perform in extreme conditions can be achieved by embedding sensors into protective clothing, which make it possible to monitor the hazard in a particular place where a man works. This is of particular importance in dangerous conditions, or in places that are difficult to reach where a worker is required to be very mobile. Then it is vital to monitor both the danger and the physical state of a worker. Research has been carried out on the type of a sensor which would make it possible to monitor the level of clothing worn and indicating a moment, often invisible, when the protective clothing stops protecting the worker.
A significant issue connected with placing electronic microsystems in clothing is energy powering. Mostly, it is lithium batteries that are currently used, but work is being carried out on alternative energy sources.
A material made of conductive polymers has been prepared which has the ability to transform visible light into electric energy. Another way could be to use energy generated from walking: to produce electricity, there could be piezoelectric devices placed in the soles of the shoes.
There has also been a suggestion of building a miniature silicon thermogenerator that would use the differences in temperatures of the surroundings to generate electric energy that would power the electronic elements present in clothing.
As presented above, properties of new materials show the wide possibilities of their application in protective clothing to protect a man who operates in conditions that are particularly hazardous and onerous. The development of protective clothing aims to ensure people have comfortable working and life conditions, better health and quality of life. Modern textiles and materials can fulfil their functions thanks to the advanced technologies, and their success is ensured by interdisciplinary tests and the application of the achievements and inventions from various fields of science, all used while creating new generation of protective clothing. Author Details:
Grazyna Bartkowiak, PhD
Head of Laboratory of Protective Clothing at the Central Institute for Labour Protection – National Research Institute Representative of the Central Institute for Labour Protection – National Research Institute in European Co-ordination of Notified Bodies – VG 5 Member of the board of the European Society of Protective Clothing Member of the Editorial Board of International Journal of Occupational Safety and Ergonomics (JOSE)
Development of the new methods and test standards for testing protective clothing and formulating requirements for protective clothing Development of the new materials and designs of protective clothing Research on comfort properties of protective clothing and influence of textiles packets on forming microclimate under protective clothing
Central Institute for Labour Protection – National Research Institute Centralny Instytut Ochrony Pracy Panstwowy Intytut Badawczy Czerniakowska 16 00-701 Warsaw www.ciop.pl
The CIOP-PIB is a legally and organisationally independent state research institution. CIOP-PIB’s main activities include, among other things: research and development in the field of Occupational Safety and Health (OSH); determination of exposure limits; standardisation; testing and certification (machinery, manufacturing devices, personal and collective protective equipment); education and training; promotion and dissemination of OSH. www.osedirectory.com/health-and-safety.php
Published: 10th Nov 2010 in Health and Safety International