Several kinds of polyurethanes are of commercial significance and can be conveniently classified as follows – flexible foams, rigid foams, elastomers, fibres and moulding compositions, surface coatings and adhesives. Today polyurethane foams are used in a wide variety of applications due to their versatility, lightweight, durability, ease of processing and cost efficiency. One area that takes advantage of the intrinsic properties of polyurethane foams is the sport and leisure market.
The first commercial use of viscoelastic/memory foam was when it was developed during the mid 1960’s as a result of NASA’s AMES research technology where it was used as a cushioning material to reduce the G forces experienced by astronauts during take-off and landing. Nowadays due to the foams ability to dampen vibrations as well as shock it is used in racing car cockpits as a noise and vibration harshness (NVH) foam and as the padded foam in racing driver’s helmets. Other types of foam that can be used in motor racing applications are reticulated polyurethane foam’s, the open cell structure of reticulated foam makes it particularly suitable for air filter applications and facilitates optimum engine performance in combination with maximum airflow/minimum pressure drop. The open cell nature of the foams allows them to be post treated with latices containing flame retardant additives to protect them against large ignition sources. Specially formulated reticulated foam is also used for fuel explosion suppression within fuel tanks of racing cars.
Motorcycle helmets and cycling helmets designed to protect the rider’s head during impact consist of two main components, a hard outer protective shell and an inner energy absorbing layer. The hard shell spreads the initial impact whilst the energy absorbing layer, which is often polyurethane foam, cushions and absorbs energy so that less impact energy is transferred to the rider’s skull and hence the brain. In contact sports such as American football, lacrosse, hockey and cricket hard protective helmets made from thermoplastic polymers such as polycarbonate are often lined with shock absorbing foams such as polyurethane or synthetic rubber foams. The cushioning and energy absorption properties of flexible polyurethane foam can be readily modified by adjusting the formulation used to manufacture the foam, making it suitable as a personal protection material for various types of sports headgear and for other body parts.
Polyurethane foam is widely used as a cushioning material for various types of gymnastic mats, martial arts mats, judo mats, wrestling mats and agility mats for use in schools, sports halls, leisure centres and climbing centres etc. The main type of foam used is combustion modified rebond foam( a re-cycled foam) made from scrap foam generated from block foam production and conversion operations, which has been chipped and bonded together with a polyurethane binder. Mats for high jumping and pole vaulting are filled with good quality low density polyurethane foam for impact protection. BS 12503-1:2001 (Parts 1-7) is the European Standard for classifying all types of sports mats by their use and their safety requirements such as shock absorption.
Bouldering is a form of rock climbing which takes place on boulders or small rock formations where no ropes are used to aid the climber. Boulder mats made from combinations of polyurethane foam are used for protection against falling. The mats are generally made of either two or three layers of polyurethane foam to provide different levels of support and impact cushioning. Higher density combustion modified rebond foam is used for the top layer (130-160kg/m3) with lower density combustion modified polyurethane foam being used for the lower layers.
Polyurethane foam logs are used in dismount pits in gymnastics centres and in large trampoline parks which have started to become popular in the UK. Different qualities of polyurethane foam can be used depending on how often the pits are used. Where the usage of the pits is high such as trampoline parks, higher density foams having better tear and abrasion resistance increases the longevity of the foam before it needs replacing.
Low to medium density high load bearing polyurethane packaging foams which are designed to provide mechanical damping of unexpected impacts are used as the foam core in rugby post protectors, and also in tackle and rucking shields. For tackle bag’s which allows the player to practice tackling high resilient foam is utilised.
Today, sports shoes are generally required to have as low a weight as possible, should be comfortable and have a resilient sole with good abrasion resistance. Polyurethane integral foams are able to meet these requirements. Nowadays running shoes normally consist of a thin running surface of solid or microcellular polyurethane with a centre/mid sole of softer foam of approximately 400kg/m3. For the insole viscoelastic/memory foam or high load bearing polyurethane foam’s are utilised to provide cushioning, the foams can also contain antibacterial additives to prevent problems with foot infections.
The characteristics of flexible polyurethane foams are predominantly determined by the starting materials and the formulations used in their manufacture, along with additives which can modify the polymer chemistry and other properties such as flammability, antibacterial, antistatic and acoustic properties etc. It is not surprising therefore that polyurethane foam is found in a variety of sport applications from personal protective equipment through to athletic footwear and as a sound absorbing material in sports halls.
We are delighted to announce that we will be exhibiting at the Foam Expo 2017 exhibition, in Novi, Michigan, USA, between 28th February and 2nd March 2017.
Foam Expo is North America’s first free-to-attend exhibition and conference for the technical foam industry. The exhibition will unite manufacturers and buyers of technical foam materials, products and services and will serve the entire foam manufacturing industry, including those working with raw materials, chemicals, manufacturing and processing equipment and all associated services.
Our stand #816 is located right in the middle of the exhibition hall, and we will be showcasing samples and some of the products we make, such as polishing pads.
We are looking forward to demonstrating our company’s capabilities to other members of the global technical foam industry. The exhibition gives us the chance to establish new relationships with other innovative foam manufacturers and foam converters.
Since Technical Foam Services was established in 1989, we have forged a reputation as being the UK’s primary converter of technical foams for a wide variety of applications, based on the polyurethane and polyethylene foams which tend to be manufactured in Europe. Foam Expo 2017 will assist us identify and start working with new foam manufacturers from around the world.
Managing Director of Technical Foam Services, Duncan Geddes, said: “We are really looking forward to the chance to meet fellow experts in the global world of technical foams. We believe we have a lot to offer foam manufacturers who currently don’t sell their materials or products into the UK and Europe, so our company can help them achieve this.
“Being wholly independent, with an established factory, wide range of machines, large warehousing capacity, we can be the perfect UK partner for your new grades of foam. Please come and introduce yourself at the exhibition, we’d like to meet you.”
Further information on the exhibition is available at http://www.foam-expo.com/
Asking how acoustic foam works is usually an invitation for a barrage of jargon, science and misinformation, with a minimum entry requirement of a PhD in physics and an unhealthy interest in manufacturing processes. Luckily for you, we’re going to cut through all the noise and tell you exactly what you need to
know about acoustic foam.
Let’s start with the basics
Acoustic foam can be used either to block out sounds from the outside world or to absorb sounds within a room to reduce reverberations. Both have their place, so it’s important to know what you’re trying to achieve before you invest in technical foam.
These days, some form of soundproofing is the norm for most industrial and domestic buildings. Whether you’re in a restaurant, school, open-plan office, gymnasium, church or hospital, they will probably either be designed to control the acoustics architecturally, or they will have acoustic foam installed to reduce background noise and block outside sounds.
Did you know that, according to Julian Treasure, author of Sound Business, open-plan offices can make employees 66% less productive? This is due to distractions and our need to quite literally hear ourselves think. Whether you want to improve sound quality for music production, manage acoustics in large open-plan buildings, insulate against noise from heavy industry, or simply reduce noise from traffic, acoustic foam is probably the answer.
Foams that absorb sound
If you want to absorb sound within a room then you need to soften the hard surfaces. If you’ve ever wondered why ‘cold’ buildings like churches and gymnasiums echo when you clap your hands, it’s because the sound is bouncing off of the walls and ceiling and is then being amplified by the shape of the room.
A common approach to soaking up sound within large rooms is to install soundproofing panels that are cut to size and fitted to the biggest surface areas such as floors and ceilings, as well as connecting areas such as pathways and corridors. This approach is effective at dampening ‘airbourne sounds’, but (you guessed it) there’s more than one type of noise.
Foams that block out sound
Ok, so noise is noise, but the different noises travel in different ways. If your problem is sound coming through the walls and ceilings from adjoining parts of the building, then you will need to soundproof the room. This requires materials with the opposite characteristics from the soft and lightweight foam that you’re likely to see in places like recording studios.
If you want to block out noise then you will almost certainly need to install soundproofing foam inside the wall construction. These are typically dense, heavy panels that are designed to ‘decouple’ the wall between rooms to stop sounds travelling via materials.
A room within a room
This leads us on nicely to the dream world of purpose-built environments that are designed for optimum sound.
In theory, the ‘room within a room’ method creates a completely soundproof area by both absorbing sound inside the room and blocking sound from the outside world. If this sounds crazy and slightly futuristic, then you’ll be surprised by how relatively common this is for businesses that need a highly controlled environment.
To illustrate how time-consuming this kind of venture can be, consider the recent case of the retail store that took two years to complete (yes, you read that correctly). Audio giant Sonos went to painstaking lengths to create the coolest store on the planet for audio geeks when they unveiled their flagship store in the heart of Soho in New York.
Designed by Partners & Spade, the 4,200 sq ft space was kitted out with seven listening rooms, each custom-built and insulated with four layers of acoustic sheet rock for walls and a 2,000 lb steel and bevelled glass door. The result? Audiophile heaven.
So, what else should you know about acoustic foam?
As the UK market leader, we’re always looking for new ways to improve our product range. We currently engineer specific types of foam of varying shapes, textures and thicknesses for almost every situation – from soundproofing foam through to Basotect panels, Class-O fire retardant foams, audio foams, speaker fronts and even microphone windshield foams.
But there are always interesting developments coming out. For example, scientists at the Swiss Federal Institute of Technology in Zurich are currently using theories from quantum mechanics to produce a new material that insulates vibrations rather than allowing them to pass through the foam.
Dubbed ‘super quiet sound proofing’, this new type of material (if successful) could dramatically reduce the amount of material needed to soundproof a room. The most exciting characteristic about this type of foam is that it could allow noise to pass in only one direction – handy for homeowners looking to get their own back
on noisy neighbours!
Practical next steps …
So, this article might not have resulted in PhD-level knowledge of physics, nor will it (we hope) have triggered an unhealthy interest in manufacturing processes, but it should clue you up enough to feel more confident when planning a project that requires acoustic foam.
Our parting advice is to identify the type of sound you want to reduce and assess the architecture of the room where you need to install sound control measures. Trust us when we tell you that this is the fun part – you’re better off leaving the more technical aspects of acoustic foam to professionals and getting on with enjoying some peace and quiet!
So, you’re looking to soundproof a room? You’ve come to the right place. If you’re reading this then the chances are you need advice on how to block out unwanted sound, whether it’s soundproofing an industrial building or setting up a professional recording studio.
Most people associate soundproofing with recording studios, but the truth is technical foams are actually more widely used than you might think. In reality, technical foams are used in all kinds of domestic and industrial environments to cover and isolate everything from walls, ceilings, duct pipes, HVAC systems, generators and compressor rooms.
For now, we’ll focus mainly on how to soundproof a recording studio and cover some of the main misconceptions people have about soundproofing and the questions we are most often asked when it comes to acoustic foam. So, let’s start by covering the basics …
1. What’s the difference between soundproofing and acoustic treatment?
Basically, one blocks out noise and the other improves the sound quality in the room. For studios, your first priority should be to soundproof the room by blocking out traffic and other background noise that will ruin your chances of recording a platinum-selling album.
This is more difficult that it might seem. You’re going to need professional soundproofing materials such as acoustic foam to cover the walls, ceiling and other areas that will transmit sound. There’s no single acoustic foam that will do it all (just like there’s no ‘perfect’ guitar), so we’ll look at the environment and recommend a
solution that will work for your situation.
If you’re looking for a rule of thumb? Go for a specialist foam that is as thick and dense as possible before getting into the nitty-gritty of choosing composite forms and surface types.
2. How effective are technical soundproofing foams?
They are highly effective, but only for their intended purpose. Just like when choosing a good producer, you’ve got to know what to look for. Differences such as airflow, cell size and density can significantly change the sound absorbing properties of the foam and its effectiveness at blocking out various types of sound frequencies.
The other main consideration is the surface shape. Pyramid, wedge and waffle structures are all popular shapes for their ability to disrupt sound waves and help absorb noise (that’s right, they do more than just look cool). This in turn reduces reverberation and echo in the room by stopping sounds from bouncing off the walls and other hard surfaces.
3. What about DIY soundproofing options? Do they work?
From egg cartons to old mattresses, cardboard sheets and even carpets and plywood – we’ve heard it all
(no pun intended). Cash-strapped musicians have tried so many DIY options over the years, but very few of them make any noticeable difference to sound reduction and in some cases they can even make the problem worse.
Egg cartons can actually amplify some sounds and materials like old mattresses soon become a breeding ground for dust, mould, mildew, or even worse. In any case, unless you’re making a ‘statement’ by recording your next indie album in a bathtub surrounded by stacks of cardboard boxes then you’re probably not considering the DIY option, right?
But just in case you need another reason, resorting to DIY soundproofing can actually be a fire hazard. Whether you’re filling the wall cavities with sawdust or nailing foam rubber to the walls, you’ll probably be in breach of building regulations. That’s why our polyurethane and melamine foams meet FMVSS302 or UL94 HF1 and Class 0 fire-retardant grades.
4. Will soundproofing foam block out traffic noise?
Unless you have the luxury of recording in a country home, it’s fair to assume that your studio will be in a city – and that means traffic noise. The simple answer is that acoustic foam can make a big difference to reducing noise from the street outside. There are two types of noise you need to reduce: airbourne noise and impact noise.
Airbourne noise is sound that is transmitted between rooms via flanking elements such as floor voids, corridors, windows and doors. This can be a challenge with older buildings where adjoining rooms have different uses. The way around this is to seal any gaps where air can enter the room (the usual suspects are windows and doors) and to install soundproofing foam that is cut to fit perfectly.
Impact noise, on the other hand, is sound transmitted between rooms via materials. An obvious example of this is the sound of footsteps on the floor above. To reduce impact noise you need to either stop the sound getting into the ceiling by adding a floating floor or installing an acoustic foam ceiling to reduce the noise. Another effective solution, especially with wooden floorboards, is to lay carpets or rugs to prevent the impact in the first place.
5. Is it possible to soundproof any type of room?
The ideal situation (especially when recording music) is to have a purpose-built room, but the reality is that even professional recording studios are often located within existing buildings that were originally built for other purposes. In fact, the rise in popularity of converting basements, lofts and garages for home studio use means that we now engineer, cut and install acoustic foam all kinds of buildings and environments.
For instance, the most popular rooms for home recording studios are usually lofts and basements, but garages and even stand-alone workshops can be soundproofed. Believe it or not, you can even soundproof your garden shed, as long as you have a big enough budget and don’t mind losing five inches of room space
to install proper walls and an acoustic door!
Hopefully this answers some of the basic questions and explains why there is no ‘one size fits all’ approach to soundproofing a room. If you’re preparing to soundproof a music studio (or indeed any type of industrial or domestic room) then the best thing to do is get in touch to discuss your requirements in more detail –chances are we will be able to help you.
We can also advise you on other specialist foams such as acoustic Basotect foam for walls, fire retardant Class 0 foams, audio foams such as microphone windshields, speaker foam covers, foam audio speaker fronts, ear defender mufflers and other bespoke solutions.
Remember, whatever your requirements, we’ll be able to recommend a range of technical foams to soundproof your recording studio and significantly improve both the noise isolation and the sound quality within the room. Then you’ll be ready to rock ‘n’ roll.
How foam helps our sporting heroes break records not bones
One YouTube trip through the superb footage of Ayrton Senna racing a Formula One car and you will see just how free and exposed the Brazilian is in his cockpit.
Think back to the high jump at school, and the thought of landing in a partially-filled sandpit. Or taking to the crease with only a bat and your coordination to prevent those shins being smashed by a spinning speed-ball of leather.
And then there’s “old faithful” – a striker goes down in a flurry of arms and rolls and agonising facial expressions. He clutches his ankle. It’s broken for sure! The team physio rushes onto the pitch, dunks his “magic sponge” into a bucket of ice cold water and dabs the ankle. A moment later, the striker is able to stand – with support mind you and one or two winces – another moment later, he takes a tentative step. It feels ok! It’s not broken after all. The game starts again. Ten minutes later, the striker scores. It’s part of the beautiful game and its power lies not in prevention but in miraculous recovery.
The latest technology on the other hand is all about prevention, not post-injury witchcraft. Take it from a man who ‘s life depended on it…
“I know a thing or two about protective clothing and equipment and although my ski helmet and goggles kept me safe in 1988, technology, materials and design…have all moved on enormously in the 28 years since,” said Great Britain’s Olympic ski jumper Eddie ‘The Eagle’ Edwards – someone who regularly took off at a height of 90 metres from the side of an ice-covered mountain.
It’s taken for granted now but the sporting landscape has changed dramatically in the past 20 years. You will have felt or witnessed the advantages of those changes, whether you realised it or not; whether you saved yourself from injury, embarrassment or something far worse. Here’s our list of how the latest foams are saving and enabling our sporting wannabes and heroes to practice, perform and produce medals!
Polyurethane foams are produced by forming a polyurethane based polymer concurrently with a gas evolution process. Provided these two processes are balanced, bubbles of gas are trapped in the polymer matrix and a cellular product results with the cells having a polyhedral type structure. Thus when considering the formation of a polymeric foam several factors such as bubble nucleation, bubble growth and bubble stability are of prime importance.
The first step in the preparation of a foam is the formation of a gas bubble in a liquid system. The reaction between di-isocyanate and water creates carbon dioxide gas and gives off exothermic heat. When the gas finally reaches a point of super saturation it is given off from the liquid in the form of bubbles. Bubble size may vary widely and is dependent to an extent on the nucleation of the system. Nucleation can be defined as the entrapment of gas in a semi fluid system to obtain bubbles ie, when the bubbles begin to grow nucleation is initiated.
In the case of flexible polyurethane foam manufacture surfactants are added to the foam formulation to act as stabilisers. Surfactants can be described as substances which provide resilience and stability to thin films and reduce the surface tension of liquids thus allowing easier bubble formation. Surfactants perform several functions:-
- a) Regulate nucleation to give a desired cell size.
- b) Control cell opening to obtain stable foam without shrinkage.
- c) Reduce surface tension
- d) Stabilise the rising foam and avoid coalescence.
- e) Aid emulsification.
Stabilisation of the cell walls is one of the most important factors in foam formation, the surfactant prevents the coalescence of rapidly growing cells until the cells have sufficient strength through polymerisation to become self-supporting. A wide variety of surfactants are available that can be used to regulate cell/pore size in the manufacture of polyester and polyether polyurethane foams to give foams with a wide range of cell sizes for various applications e.g. packaging, acoustic insulation, automotive, textile laminates, filtration, ceramic filters, sponges, seals, paint rollers, polishing foams and foams for medical applications.
As well as the various types of surfactants that can be used to regulate the cell size of polyurethane foam, mechanical factors are also important. These include foam head pressure, mixer speed and design, and extra gas loading of the reaction mixture in the mixing head either through gas loading of the bulk raw materials or injection of gas directly into the mixing head. To determine the cell count of a foam the number of cells/pores per linear inch or centimetre is measured. The old technique of eyeglass counting is still used by a number of foam manufacturers, however for some highly technical applications that require a foam with a particular cell size or structure, image analysis techniques may be utilised.
By the selection of suitable polyols/resins and isocyanates, suitable surfactants/stabilisers and production machine settings cell sizes from about 8ppi (pores per inch) up to approximately 100ppi can be achieved.
What is UL94v-0?
UL94v-0 is a fire standard set by UL – an American worldwide safety consulting and certification company headquartered in Northbrook, Illinois. UL94v-0 is used to determine the flammability of a specified material.
Why we test and measure to UL94v-0?
UL94v-0 is tested and measured to allow engineers to understand the flammability characteristics of a material, in this case silicone sponge.
If the material passes and is verified by UL themselves, a material can then be used in specific applications where fire safety is of a critical nature.
How UL94v-0 should be tested?
Five specimens firstly need to be prepared measuring 13mm (W) x 125mm (L). Maximum thickness should be 13mm
- The test specimen needs to be clamped into a vertical position.
- The Bunsen burner needs to have a flame height of 20mm.
- The flame then needs to be applied to the bottom edge of the specimen, so that the top of the burner is 10mm lower than the specimen.
- The flame is then applied for 10 seconds, moving the burner to allow for any movement of the specimen ensuring the flame keeps directly underneath the material.
- After 10 seconds the flame is removed and the time is measured and recorded as to how long the specimen continues to burn for.
- When the flame goes out the burner is reapplied to the specimen for a further 10 seconds.
- Again the burner is removed after 10 seconds and time is recorded for how long the specimen continuous to burn for.
Requirements for a UL94v-0 Pass?
- The specimens should not have an after flame time for more than 10 seconds after either application of the test flame.
- The total after flame time should not exceed 50 seconds for set of 5 specimens.
- The specimens should not burn with flame or glowing up to the clamp.
- The specimens should not drip flaming particles that ignite the cotton indicator.
- The specimens should not have glowing combustion that persists for more than 30 seconds after the second removal of the test flame.
Where do UL94v-0 products get used?
Generally, UL standards are used as a safety rating in a wide range of applications, from telephone receivers and computer screens to domestic ovens and hot water boilers. Whenever people are concerned about the hazards as a result of their product burning, then UL94 is becoming the most commonly referenced standard where there is no pre-existing industry norm.
Applications are too many to mention suffice to say that to enter into the American market, all household and domestic products such washing machines, televisions, vacuum cleaners as well as automotive and electrical/electronic wiring and components need to comply with UL at some point.
Industries where public safety is of the highest importance such as Rail, Automotive and Aerospace, UL94v-0 is seen as an essential safety standard. In the event of a fire would help to resist the flames, in turn reducing the risk of failure.
Polyurethane foams which are based on aromatic isocyanates will all exhibit various shades of yellowing when exposed to light i.e. to ultra violet radiation. Yellowing is a surface effect and has no significant effect on the physical properties of the foam. The degree of yellowing depends on the intensity of the radiation. Ultra violet radiation breaks down bonds in the polymer via a free radical reaction, free radicals are atoms that contain an unpaired electron. These reactions can be complex resulting in various coloured species being formed.
In flexible polyurethane foam manufacture the isocyanate most commonly used is Toluene di-isocyanate (TDI), whereas for high resilient, semi-flexible and microcellular foams various types of Diphenylmethane di-isocyanate (MDI) are used. Both TDI and MDI are classified as aromatic isocyanates as they are both based on benzene ring shaped molecules. Polyether polyurethane foams tend to yellow faster than polyester foams.
Light protecting agents/stabilisers can be added to the foam formulation at the manufacturing stage to aid in the delay of the yellowing process. These additives can be split into two groups:-
- Ultraviolet Absorbers (UVA) – these function by absorbing harmful ultra violet radiation and dissipating it as thermal energy.
- Hindered Amine Light Absorbers (HALS) – these do not absorb ultra violet radiation but act as radical scavengers to inhibit degradation of the polymer. Due to the fact that HALS are regenerated rather than consumed during the stabilisation process they tend to be more capable of providing better longer term light stability than UVA’s.
For polyurethane foam applications that require excellent ultra violet stability, non yellowing foam can be produced with the use of aliphatic isocyanates. Aliphatic isocyanates are isocyanates where the NCO (isocyanate group) is not directly attached to an aromatic/benzene ring and produce ultra violet stable, colourless polyurethane foam.
Aliphatic isocyanates are generally considered as speciality materials since they are used in significantly lower quantities than aromatic isocyanates which account for the bulk of isocyanates used for the production of polyurethane foam and other polyurethane products. These isocyanates are considerably more expensive than the aromatic isocyanates normally used and therefore the manufacturing costs to produce light stable foam are higher than for standard polyurethane foam manufacture.
Learn more about our reticulated foam solutions which covers a wide range of product applications.
Technical Foam Services are pleased to announce that our website now has a live chat feature. We feel that this will allow us to communicate on a personal basis to our visitors, and enable them to receive instant feedback.
The live chat will be accessible during office working hours Monday – Thursday 8am – 4.30pm and Friday 8am – 1.30pm. Any visitors outside of these working hours can still use the chat feature offline and will receive feedback the following working day.
The live chat feature on the website looks like this:
Click the online chat button on our website to speak to one of our advisors now.
Flexible polyurethane (PU) foam because of its relatively low cost and attractive property profile is used in a variety of applications such as automotive seating, transportation, upholstery and bedding, packaging and medical applications. However, due to its low density and open cellular structure PU foam has a large surface area and high air permeability and is therefore highly flammable upon the application of a sufficiently high ignition source and oxygen.
It is necessary to minimise the rate and level of mass loss during combustion, particularly for the most demanding applications such as mass transport, therefore flame retardants (FR’s) are added to improve the flammability properties of the foam. The choice of FR additive is largely dependent upon the intended application of the foam and the specific flammability requirements that the foam has to comply with. The type of FR used and the level of addition will influence the ease of ignitability, ability to create a char, burning rate and smoke evolution.
One of the most successful char promoting agents used to impart good flame resistance in PU foams and other polymer materials is expandable graphite which is manufactured by the oxidation of graphite using sulphuric acid and other oxidising agents. The layered platelet structure of graphite flake allows it to absorb the acid readily to create an intercalated graphite which, when exposed to high ignition sources, expands due to vaporisation of the intercalant and creates an intumescent char layer. Various grades of expandable/intercalated graphite are available. Differences in the method of intercalation used, purity of the original graphite flake, particle size and particle thickness all have an influence on the overall expansion achieved and the temperature at which expansion begins.
One of the main characteristics of graphite polyurethane foam is that there is no melting and dripping of the foam when exposed to a high heat source which helps in preventing flame spread. Creation of a char layer dramatically reduces the heat release rate, mass loss, smoke generation and toxic gas emission. Flexible graphite polyurethane foams can be manufactured on conventional slab stock foam making machinery or as moulded foam. Due to its very good fire retardant properties graphite foams can be modified to meet a number of high hazard applications as follows:
Aircraft Seating: Graphite foam is approved by a number of airlines worldwide for aircraft seating and meets the following requirements:
1) ATS 1000.01/ABD 0031, Airbus specification for smoke and toxicity.
2) FAR25.853 amendment 25-72 Part 1, Appendix F – Vertical burn test.
3) FAR25.853 amendment 25-72 Part 2, Appendix F – Kerosene burn test.
4) EASA – European Aviation Safety Agency regulations for seating materials.
Railway Seating: Meets the requirements of EN45545 a proposed new European Standard for rolling stock fire safety testing although this standard has not yet been fully adopted. At the moment there is a period of co-existence with currently accepted national standards such as:-
BS 6853 – 1999 (UK standard).
NF16 – 101 (French standard).
DIN 5510 (German standard ).
None domestic seating: BS 7176 : 2011 specifies the requirements for resistance to ignition of upholstered furniture for non domestic seating by testing composites. In essence the standard sets requirements for the ignitability of upholstered seating for different end use applications. Four hazard categories from low hazard to very high hazard are identified. Graphite foams can be formulated to comply with all categories including very high risk areas such as prisons and psychiatric units.
Acoustic/sound absorption applications eg. Conventional graphite polyurethane foams are used in anechoic chambers. Semi-rigid FR graphite foam is used as acoustic foam in building and construction applications.