A Green and Renewable Intumescent Flame Retardant System for Ethylene-Vinyl Acetate

This paper was published in Ind. Eng. Chem. Res. journal: 

Chitosan/Phytic Acid Polyelectrolyte Complex: A Green and Renewable Intumescent Flame Retardant System for Ethylene-Vinyl Acetate Copolymer


We describe the preparation and characterization of a green and renewable polyelectrolyte complex (PEC) containing phosphorus, nitrogen and carbon elements, based on the ionic complexation between chitosan and phytic acid. Introduction of this PEC to ethylene-vinyl acetate copolymer (EVA) leads to an improvement of the flame retardancy. As for the EVA/PEC composites with 20.0 wt % of PEC (EVA/20PEC), the char residue at 600 oC is 12 wt % higher than that of the pristine EVA under nitrogen atmosphere. Compared to the pristine EVA, the peak heat release rate and total heat release of EVA/20PEC show 249 W g-1 and 5.6 kJ g-1 decreases, respectively. The char residue of EVA/20PEC is full and compact, demonstrating excellent intumescent effect. Introduction of this PEC also contributes to a slight increase of the Young’s modulus while maintains the excellent ductility. This work provides a new approach for the development of environmentally friendly intumescent flame retardant system.

Hyperbranched poly(phosphoester)s as flame retardants for technical and high performance polymers

First published online 08 Sep 2014 in Polymer Chemistry.


A structurally novel hyperbranched halogen-free poly(phosphoester) (hbPPE) is proposed as a flame retardant in poly(ester)s and epoxy resins. hb polymeric flame retardants combine several advantages that make them an extraordinary approach for future flame retardants. hbPPE was synthesized by olefin metathesis polymerization according to a straightforward two-step protocol. The impact of hbPPE on pyrolysis, flammability (reaction-to-small-flame), and fire behavior under forced flaming conditions (cone calorimeter) was investigated for a model substance representing poly(ester)s, i.e. ethyl 4-hydroxybenzoate, and an epoxy resin of bisphenol A diglycidyl ether cured with isophorone diamine. The flame retardancy performance and mechanisms are discussed and compared to a commercial bispenhol A bis(diphenyl phosphate) (BDP). Both hbPPE and BDP combined gas-phase and condensed-phase activity; hbPPE is the more efficient flame retardant, and is proposed to be efficient in a greater variety of polymeric matrices. The hydrolysis of hbPPE is suggested to produce phosphorous acids, which, when available at the right temperatures, enhance the charring of the polymer in the condensed phase. The better fire protection behavior of the hbPPE is due not only to its higher phosphorus content, but also to the higher efficiency of the phosphorus it contains.

Making plant fibres flame-retardant might make them fly!

There is renewed interest in natural materials, as recyclability and environmental safety become more important in manufacturing and consumables.

It looks like a sleek car dashboard, but under its smooth surface flax fibres criss-cross through a three-dimensional matrix to reinforce it, making it stronger and lighter than traditional materials.

The use of natural fibres in composite applications is gaining popularity in many areas, and particularly the automotive industry. Daimler-Benz in Germany has been using the components made from different natural-fibre composites since 1994. Flax and other natural fibres are used to make 50 Mercedes-Benz E-class components. Similarly, the seat shells and their panelling are made from the latest in natural-fibre composite technology. Toyota developed a biodegradable plastic made from starch extracted from sweet potatoes and other plants. This plastic was combined with natural fibres for use in interior parts.

But the high moisture absorption and flammability of these composites has restricted their use in cars and other industries such as aerospace. This is why at the Council for Scientific and Industrial Research’s Port Elizabeth campus, in collaboration with Nelson Mandela Metropolitan University, we are researching strategies to make biocomposites safer and so increase the ways in which they can be used.

Traditional composites — which are materials made of at least two other materials — use synthetic fibres, such as glass, carbon and aramid, to make them hard and strong. But there are serious drawbacks: they are not biodegradable, consume a lot of energy to manufacture, and result in airbone fibres that cause respiratory problems. Airborne fibres are caused when sufficient amount of glass fibres are released into the air during manufacture, handling and aircraft fires.

So people are turning to natural fibres to avoid these problems. Flax, hemp, jute, sisal and kenaf are some of the most important natural fibres used in these composite materials, called biocomposites. They are abundant, easy to process, renewable and inexpensive….

Flax, with its hip-height glossy bluish-green leaves and pale blue flowers, is a fiber crop that is grown in cooler regions of the world. Producers extract the very long fibers inside the wooden stem of the plant, and then spin and weave them into linen fabric. Fabrics are made in the same way: linen yarn is generally woven into sheets, with multiple threads interlaced both horizontally and vertically on a loom. Flax fibre is used to make interior panels in cars, and car manufacturer Mercedes has incorporated non-woven fabrics mats into the interior panels of several models, such as the Mercedes E-class. Flax was chosen as it is cheap and eco-friendly.

Kenaf, which can grow taller than a man, is another important source of fibre for composites, and has many other industrial applications. The fibres in kenaf are found in its bark and wood, and can be spun and woven to a fine, crisp, linen-like fabric and used as reinforcement for composites.

Toyota has developed kenaf fibres for the interiors of its cars. Researchers at Universiti Malaysia Sabah, a university in Malaysia, are using kenaf fibres instead of glass fibres in front and back bumpers.

Hemp often gets a bad rap because of its association with marijuana. In reality it has countless uses and does not have psychoactive properties. The confusion between the two arises from the fact that they both come from the same plant species. Hemp contains less than 1% THC (delta-9-tetrahydrocannabinol), the active ingredient in the marijuana plant, which contains 5% to 20%. It can grow up to 15m in four months, making it a useful crop for textiles.

The valued primary fibres that encase the hollow, woody core of the hemp stalk can be spun and woven into a fine, crisp, linen-like fabric and used as reinforcement for composites.

At present the single largest use for hemp fibre is in cars, with various manufacturers — including Audi, BMW, Ford and Volvo — using natural fibres to create more eco-friendly and lightweight cars.

Why isn’t everyone using them? Well, because biocomposites have drawbacks of their own.

Natural fibres absorb moisture in humid climates and when they are immersed in water. The hemp fibre swells when composites are exposed to moisture.

As the fibre swells, tiny cracks develop between the fibre and the matrix, and water molecules infiltrate the gaps between the fibres and matrix, pulling them apart and reducing the material’s strength.

And water isn’t the only concern: fire is also a problem.

Firefighters and emergency crews involved in clean-up and restoration operations after crashes have expressed concerns about the long-term effects of their exposure to the fibres that are released from burning composites.

They also require special equipment to extinguish and handle the incinerated fibre composites.

Fibre-reinforced composites pose a serious health hazard in fire. When composites catch alight, they release a complex mixture of gases, organic vapours (such as carbon dioxide) and particulate matter (including tiny inhalable bits of fibre). These combustion products can cause acute and delayed health problems and, in the worst cases, can be fatal.

It is possible to overcome these challenges, though. Researchers around the world have found ways to apply surface treatments and flame retardants to these biocomposites to reduce their moisture sensitivity and flammability.

In the automotive industry, manufacturers can modify the fibre surface by treating it with chemicals to improve the adhesion between natural fibres and polymer matrices. This also decreases their ability to absorb moisture, making them stronger.

However, using flame retardants on biocomposites could expand their applications. Researchers can inhibit fire — or even suppress it entirely — by padding flax fabric with a flame retardant before weaving it into the fabric. Or they can mix a fire-inhibiting substance in with the plastic while it is still in its molten state (before it is moulded into a final product, such as the backs of aeroplane seats).

Tri-Dung Ngo, a researcher from the National Research Council of Canada, found that composites made from untreated flax fabric were flammable while others containing treated flax fibre fabric did not burn at all.

There is increasing interest in using natural fibres in the aerospace industry, where they are exposed to wide variations of temperature and humidity.

This can affect the strength of the structures, which is why our work at the CSIR in collaboration with Nelson Mandela Metropolitan University is critical.

The study of the long-term effects of temperature and humidity on the properties of natural fibres and composites, as well as on the fire retardants used to stop them from catching alight, means that these products — which are cheaper and more environmentally friendly than traditional composites — could find more applications, even in the demanding aerospace industry.

Source: Mail & Guardian

Sustainable Flame Retardant Technical Textile from Recycled Polyester (SUPERTEX)

The textile industry represents and important source of income and employment in Europe:

in 2005 the EU textile and clothing industry counted 155,000 enterprises employing more than 2.2 million people. Most of the production steps involved in the textile chain are not sustainable processes since they are chemicals consuming processes – such as finishing processes – and they are responsible for the production of large amount of waste, either wastewater and landfill waste. SUPERTEX project is aimed at demonstrating that a secondary raw material such as recycled Polyester (RPET) can be exploited within the Textile Industry for the fabrication of environmentally sustainable, high added value Technical Textile products.

Main objectives are: demonstration of the transferability of the production processes for PET multifilament yarns (MY) to RPET and recycled PET-polyolefin blends from post-industrial and post-consumer waste; addition of new functionalities (fire resistance) to the RPET-based MY; first application of RPET-based MY in the fabrication of textile structures for Mobiltech and Hometech markets.


A wide usage of a waste materials, such as PET for the production of multifilament yarns, mainly applied in the Technical Textile sector.


  • Demonstration of the transferability of the production processes for PET multifilament yarns (MY) to RPET and recycled PET-polyolefin blends from post-industrial and post-consumer waste. A marketable price in the range 2.0 – 3.0 €/kg is expected
  • A production technology for a range of textile materials based on RPET MY with different fineness, mechanical and functional properties, and performance comparable or better than conventional products from virgin polymer
  • Production of Flame Retardant (FR) textile by using safer products then the conventional products (alternative to antimony and halogenated compounds will be used)
  • A significant impact of the RPET MY textile is expected both upstream (RPET feedstock global market) and downstream (Technical Textile market) through replacement of virgin PET and other polymers….Read more

Source: http://ec.europa.eu

Recycling of waste poly(ethylene terephthalate) into flame-retardant rigid polyurethane foams

This  paper wes published in Journal of Applied Polymer Science , 3 MAY 2014.


Waste poly(ethylene terephthalate) (PET) textiles were effectively chemical recycling into flame-retardant rigid polyurethane foams (PUFs). The PET textile wastes were glycolytically depolymerized to bis(2-hydroxyethyl) terephthalate (BHET) by excess ethylene glycol as depolymerizing agent and zinc acetate dihydrate as catalyst. The PUFs were produced from BHET and polymeric methane diphenyl diisocyanate. The structures of BHET and PUFs were identified by FTIR spectra. The limiting oxygen index (LOI) of the PUFs (≥23.27%) was higher than that of common PUFs (16–18%), because the aromatic substituent in the depolymerized products improved the flame retardance. To improve the LOI of the PUFs, dimethyl methylphosphonate doped PUFs (DMMP-PUFs) were produced. The LOI of DMMP-PUFs was approached to 27.69% with the increasing of the doped DMMP. The influences of the flame retardant on the foams density, porosity, and compression properties were studied. Furthermore, the influences of foaming agent, catalyst, and flame retardant on the flame retardation were also investigated.

Compatibilizing effect of β-cyclodextrin in RDP/phosphorus-containing polyacrylate composite emulsion and its synergism on the flame retardancy of the latex film

This article was published in Progress in Organic Coatings,


Resorcinol bis (diphenyl phosphate)/β-cyclodextrin/phosphorus-containing polyacrylate (RDP/β-CD/P-PA)  composite emulsion was prepared by using β-CD as a compatibilizer. The flame retardancy of the composite latex film was investigated by microscale combustion calorimetry (MCC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Mechanical properties of the composite latex films were also studied and a possible compatibilizing mechanism was proposed. The results showed that the mechanical properties and flame retardancy of the RDP/β-CD/P-PA composite latex film were enhanced compared to the RDP/P-PA latex film. When the β-CD content increased from 0 to 10 wt%, the pendulum hardness of the RDP/β-CD/P-PA composite latex film increased from 0.18 to 0.54, and the peak heat release rate decreased from 382.1 to 311.9 W/g. TGA and MCC results demonstrated that both the char residual and the quality of the char formation were improved by the introduction of β-CD.


Infrared camera – a promising tool in fire testing and fire research

This article was published in Brandposten n°49.


Infrared cameras detect energy in the form of infrared radiation from hot bodies and create a thermal image of the temperature differences. The technology is currently used for many different applications and has in recent years increasingly been used in fire prevention measures. Among other things, infrared cameras contribute to improving fire safety in tunnels, including the Mont Blanc tunnel and the Bjørvika tunnel in Oslo, in that they can detect a fire much earlier than ordinary surveillance cameras.

SINTEF NBL has an infrared camera of type FLIR GF-309. The camera measures temperatures from -40 °C til 1500 °C, it “sees” through smoke and flames and provides useful supplemental information in fire tests and to fire research. The infrared camera provides visualization of temperature distribution on the surface of a specimen, and thermal video sequences show the temperature distribution changes with time. The sensitive optics of FLIR GF-309 can detect temperature differences of less than 25mK.

Applications for the infrared camera in fire testing and fire research

Finding the “hot spots”

Our infrared camera can be used to visualize and detect so called “hot spots”, i.e. areas of a  specimen that reaches substantially higher temperatures than the rest of the specimen, during exposure to a fire. Figure 1 is a good illustration of this. Here, the fire resistance of a non load-bearing wall with steel beams and to layers of ordinary plaster on each side is tested in a vertical furnace. The infrared image clearly shows areas where the surface of the wall has elevated temperatures.

The temperature of the “hot spots” can be extracted by analyzing the infrared pictures, either directly during the test or afterwards. This way it is possible to ensure that the hottest areas actually are the ones that are analysed, as opposed to using thermocouples, where the measuring points are predefined before the test. Detecting the local temperature growth is useful for anyone who

develops products and structures that are meant to resist fire. Areas that are particularly exposed to heat can be detected and thus improved in further product development. This is useful information for most product types, for example for passive fire protection, pipes, panels, fire doors, walls,  windows, and especially for products with potential weaknesses such as joints and connections… Read more:  click here (page 24)


Flammability and Thermal Stability of Cross-linked Polyethylene

Article- Publication Date: January 28, 2014-  Industrial & Engineering Chemistry Research

Effect of Functionalized Graphene Oxide with Hyper-branched Flame Retardant on Flammability and Thermal Stability of Cross-linked Polyethylene


In this work, GO was functionalized by a hyper-branched flame retardant, which was synthesized by the reaction of N-aminoethyl piperazine and di(acryloyloxyethyl)methylphosphonate. Subsequently, the resultant functionalized GO (FGO) was incorporated into the cross linked polyethylene (XLPE) to enhance the flame retardancy of the matrix. TEM images indicated that FGO exhibited uniform dispersion in XLPE matrix and strong adhesion with the matrix by cross-linking, which improved barrier effect due to reduced heat release and the free radical transfer between the matrix and graphene nano-sheets. The incorporation of FGO into XLPE matrix endowed polymer composites with flame retardancy and thermal stability. In addition, the homogeneous dispersion of functionalized GO with hyper-branched flame retardant in the polymer matrix improved the anti-oxidation and mechanical properties of XLPE-FGO nanocomposites compared to the XLPE-GO samples, demonstrated through the oxidative induction temperature and time test, oven aging test and mechanical test. Read more: here

Layered Security: Carbon Nanotubes Promise Improved Flame-Resistant Coating

NIST Tech Beat:

Using an approach akin to assembling a club sandwich at the nanoscale, National Institute of Standards and Technology (NIST) researchers have succeeded in crafting a uniform, multi-walled carbon-nanotube-based coating that greatly reduces the flammability of foam commonly used in upholstered furniture and other soft furnishings.

The flammability of the nanotube-coated polyurethane foam was reduced 35 percent compared with untreated foam. As important, the coating prevented melting and pooling of the foam, which generates additional flames that are a major contributor to the spread of fires.

Nationwide, fires in which upholstered furniture is the first item ignited account for about 6,700 home fires annually and result in 480 civilian deaths, or almost 20 percent of home fire deaths between 2006 and 2010, according to the National Fire Protection Association.

The innovative NIST technique squeezes nanotubes between two everyday polymers and stacks four of these trilayers on top of each other. The result is a plastic-like coating that is thinner than one-hundredth the diameter of human hair and has flame-inhibiting nanotubes distributed evenly throughout.


The brainchild of NIST materials scientists Yeon Seok Kim and Rick Davis, the fabrication method is described in the January 2014 issue of Thin Solid Films.*

Kim and Davis write that the technique can be used with a variety of types of nanoparticles to improve the quality of surface coatings for diverse applications.

The pair experimented with a variety of layer-by-layer coating methods before arriving at their triple-decker approach. All had failed to meet their three key objectives: entire coverage of the foam’s porous surface, uniform distribution of the nanotubes, and the practicality of the method. Inmost of these trials, the nanotubes—cylinders of carbon atoms resembling rolls of chicken wire—did not adhere strongly to the foam surface.

So, Kim and Davis opted to doctor the nanotubes themselves, borrowing a technique often used in cell culture to make DNA molecules stickier. The method attached nitrogen-containing molecules—called amine groups—to the nanotube exteriors.

This step proved critical: The doctored nanotubes were uniformly distributed and clung tenaciously to the polymer layers above and below. As a result, the coating fully exploits the nanotubes’ rapid heat-dissipating capability.

Gram for gram, the resulting coating confers much greater resistance to ignition and burning than achieved with the brominated flame retardants commonly used to treat soft furnishings today. As important, says Davis, a “protective char layer” forms when the nanotube-coated foam is exposed to extreme heat, creating a barrier that prevents the formation of melt pools.

“This kind of technology has the potential to reduce the fire threat associated with burning soft furniture in homes by about a third,” Davis says.

Y.S. Kim and R. Davis. Multi-walled carbon nanotube layer-by-layer coatings with a trilayer structure to reduce foam flammability. Thin Solid Films 550 (2014) 184-189.

Source:  http://www.nist.gov

Emergence of Natural halloysite clays as FR system…

In recent years, there are more and more  studies on the emergence of halloysite as an element of RF system:

Thermal stability and flame retardant effects of halloysite nanotubes on poly(propylene)

The suitability of halloysite nanotubes as a fire retardant for nylon 6

Nanocomposites of polypropylene/polyamide 6 blends based on three different nanoclays: thermal stability and flame retardancy

and here the last tentative: download pdf format


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