CHARON is a big step forward in fire protection. It is covered by UK Patent. GB1717130.7. This is a substance patent not an application patent.
It comes in two forms: liquids that can be used to react phenolic resins, create paints and films and low viscosity soak in treatments for timber and High viscosity liquids, available at 100% NVC or as aqueous solutions that are inherently intumescent Here. The principle behind CHARON is to take the functional components of a conventional intumescent formulation and react these into a polymeric molecule.
The CHARON flame retardants are a reaction product. What they are not is a mixture of separate compounds.
Thus the CHARON LFR’s are polymeric compounds that combine the functions (but not the structure) of the catalyst (ammonium polyphosphate), carbonific (pentaerythritol) and spumescent (melamine) that exist in conventional intumescent mixtures. After an extended development period, you may well have heard the principle expounded before.
CHARON Flame Retardants :
- Are more efficient than other flame retardants
- Produce less smoke than other flame retardants
- Are lighter than other flame retardants
- Contain no toxic components
- Are halogen free
- Have the widest range of applications
- Are biodegradable
- Are based on sustainable raw materials
How is CHARON different?
CHARON is inherently intumescent. This means that there is no longer the requirement to blend together the components of an intumescent system. This gives the advantage of allowing the use of an intumescent system in resins that traditionally have been protected by either halogens and gas phase synergists or other endothermic systems.
In a conventional intumescent mixture a number of intermediate reactions must occur before the separate components can react with each other. The major effect of using a system that is inherently intumescent is that these reactions have already taken place and therefore fire protection takes place at a lower temperature. If the protection starts at a lower temperature then polymers and substrates that would have otherwise decomposed to flammable fractions are more effectively protected.
The CHARON flame retardants activate with little or no smoke emission and if the polymers and substrates are prevented from decomposition to flammable fractions then the overall smoke yield is lower. CHARON flame retardants have a higher char yield than intumescent mixtures. If pyrolitic decomposition is reduced then the ability of the non-flammable char yield to protect underlying substrates from the flame or a heat front is greater.
In common with conventional intumescent mixtures the decomposition of CHARON flame retardants is endothermic throughout and the final char is the same mixture of finely divided amorphous carbon in condensed phosphoric acids.
The system is halogen free and therefore little additional effect can be expected from “gas phase” synergists.
Which CHARON do I want?
If you’re looking to create a flame retardant coating then you probably want to use CHARON PCP. It is a liquid provided at 80% solids that may be used to create water based two pack flame retardant intumescent clear varnishes and paints for protective coatings for structural steel, timber panels and doors as well as all thermoset and thermoplastic resins.
If you’re looking to protect composites like polyesters or epoxy prepregs then we generally recommend you use one of our two pack coatings:
- The coating requires no modification to the resin system or production process
- The inherent physical properties of the resin system are maintained
- The fact that the coating is on the surface means that the smoke production is lower than any flame retardant incorporated into the resin structure
- By using one of our topcoats the whole system can be suitable for external applications with no UV or moisture sensitivity.
If however you wish to incorporate your flame retardant into the resin matrix then you will be wanting to use CHARON LFR. CHARON LFR is an intumescent liquid that may be mixed into the base resins such as polyesters, epoxies, polyurethanes, and polysiloxanes to render them fire retardant or fire protective as composites, coatings, elastomers or foams.
The advantage of using CHARON in these resin systems is that the smoke production is so significantly reduced that it should allow the use of these materials in areas where previously they have been off limits, for example using polyester resins in underground trains.
If you are wanting to create latent curing phenolic resin systems then you will be wanting to use one of our CHARON Partial phosphate ester resin systems. These come in a range of viscosities and water contents, they can be fine tuned to your individual cure requirements
Can I use CHARON LFR in Thermoplastics?
Yes, But with some modifications if it is master batched. While CHARON products can be melt blended into most polymers (except PET) they are designed to activate at low temperatures. Hence, they cannot remain in the extruder barrel for too long. As soon as the blend is made the MFI increases significantly. Thus if the CHARON is injected into the molten polymer, the extrusion end of the barrel can be and must be at a lower temperature than the melt zone.
This means to produce a flame retarded version of the polymer it is necessary to start with the feed stock at a much lower MFI. For example a PP with MFI of 1 will become 12-13 if 30% CHARON is blended in.
How much CHARON LFR do I need?
This depends entirely on the target fire test rating being sought. As a rule of thumb to meet the severest conditions like EN 45545 HL3, Euroclass B, an OEL above 34% and an FPA class A(ASTM E84), you need about 30% on resin solids.
Can I use CHARON in latex emulsions?
Yes, but the CHARON may disrupt the emulsion. A good starting point is to seek a resin the pH below 6.0 . However, the CHARON LFR is a plasticiser and will lower both the MFFT and Tg. Hence, a fully flame retarded film will be soft. An emulsion with a very high MFFT and Tg is needed for hard films, This does not affect gunable sealants. These can easily be made with just two components, the CHARON LFR and the Acrylic resin
Can I use CHARON LFR in solvent based coatings?
Yes, while the CHARON LFRs are apparently polar they produce considerable shifts in the Hansen solubility parameters. The TEAS diagrams are shown in the CHARON LFR brochure. For example CHARON LFR 2L00 and 3L95 are insoluble in Styrene but will disperse and cure in unsaturated polyesters. Likewise the CHARON LFR’s are insoluble in Xylene and White Spirit but they will disperse in Short Chain Oil Alkyds.
An excellent flame retardant varnish can be made with CHARON LFR 2L95 dispersed into CAB in Dowanol PM.
Can I use CHARON LFR’s in PU and PIR?
CHARON LFR’s are compatible in all portions with the polyols used in PU and PIR. Excellent flame retardant foams, intumescent elastomers and large vehicle coatings have been formulated with CHARON LFR’s.
Can I use CHARON LFR in Thin Film Intumescents?
Yes and No. An excellent two pack product can be made on CHARON PCP, but this only suitable for factory application. However, CHARON 1H85 can be added to conventional APP water based intumescents to give an uplift in DFT efficiency.
Are there any significant problems?
In free radical curing systems the CHARON LFR’s may complex the accelerator, particularly cobalt oxyacids. Other accelerators appropriate to the system should be evaluated.
The pH of the CHARON LFR’s may appear low but this is a function of the zwitter ion used in the synthesis. CHARON LFR’s are non corrosive, non flammable, non toxic and free from REACH requirements.