Heat and Thermal Barrier Coatings and intumescent; paints and coatingsIndestructible Paint is often asked about “high temperature” coatings and have therefore summarised some of the major paints we are involved with.
First of all, what is “high” temperature. This may sound stupid, but the temperature is not the only major constraint, but whether it is simply a “peak” or constant running temperature. Many paint products will take an occasional excursion to 300ºc (570ºF) - or even 400ºC (750ºF), but if they are left for more than a few minutes will degrade significantly.
A few points to consider.
Flame retardant (retardant) paints often refer to the 65/65 test. This is a reference to the smoke emission compared to spread of flame often used in aircraft interiors. Example products include IP9189.
Intumescent paint. Our IP9189 to BSX37. A one time paint that expands into a heat protective foam crust when exposed to high heat (say 1100°C) gives off cyanide, so not normally used where people can be exposed, except in military, eg in the ammunition hold of fighting ships, to protect ammunition shell cases, etc.
Most intumescent paints are thick film mastics used in the building trade for protection of girders and other masonry type products. These are often an inch or more thick, and solid almost like a concrete layer.
There are also a few thin film intumescent paints which we are most interested in. These can vary from 250 microns (10 thou) to more than 1000 microns.
IPC’s involvement with thin film intumescent paints started in the 1970’s and 1980’s when we made PL161 for Rolls Royce.
PL161 was a stoving intumescent designed for working up to 150°C.
As gas turbine engines became more efficient, their operating temperatures went up, and we were requested to “invent“ a new product which resulted in IP9189.
This has been the state of the art product since it’s approval by Rolls Royce to MSRR 1055 in September 1997. This product is also approved and used by such customers as Eurocopter EC 135 where it is used to protect fibreglass composite doors, and it’s latest use is in the revolutionary amphibious AQUADA super car seen recently being driven by Richard Branson, where it protects the engine bay.
The standard aerospace test seems to be an FAA test where the definition of fire resistance is 5 minutes, and fire proof as 15 minutes. This is using a 110,000 BTU burner.
Definition of passing or failing can be varied, for example if a fuel pump keeps pumping for the required 5 minutes, this can be deemed a pass. Other requirements may be to keep the immediately underlying surface to stay below a certain temperature – 150°C for a bomb; 250°c for carbon fibre etc.
IP9189 Intumescent Paint (OMAT No.7/28B) has been subjected to tests within MSRR 1055, and also BSX 37.
Since then it has also been subjected to vibration testing; resistance to flammability after conditioning of 3000 hours at 150°C ; soaking in lube oil; testing at – 40°C; and on testing on the BRR 710 flight control box ; 40 pounds design weight was saved by re designing the box with no sharp corners and perforated; the “holey “ box with flight controls inside passed the 1100°C flame test!
However; we realize that the more we know; the more we realise there is to learn.
Our latest development - currently coded IP1265 was invented a couple of years ago using latest available technology, and tested for safety for a combat aircraft which needed a 15 minute “window” of fire resistance.
We developed a test which incorporated a 20mm thick piece of high strength steel the inside of which was liable to explode in the application when the inside temperature reached 150°C. Without our coatings; exposed to a bunsen burner at about 1000°C, the “inside” reached 150°C after about 4 minutes ; with about 800 microns IP9189, it reached 150°C after 13 minutes; with the new IP1265; it reached it in 22 minutes!
IP 1265 also has very little intumescent action; and is a low VOC product.
Here are a few details of thermal barrier paints.
These are paints containing heat resisting resins and insulating particles. We also define it as being a repeatable action, unlike intumescent paints which protect, normally against flame, only one time.
Effectiveness depends upon the insulativity of the particles and binder, the substrate; the temperature required, and even the heat source and type (flame; radiant heat etc.) which protection is desired from.
Insulativity will probably also be a function of the thickness of the coating.
Our current range is being expanded as we find new materials and requirements.
A thermal barrier can be used in conjunction with an intumescent; for example exploratory work with Westland showed a reduction of 100°C at the substrate by using 50019 under our IP9189, instead of IP9189 on it’s own.
50019 is one of the original materials developed that have been used as thermal barriers.
Example 1 (anecdotal ) from India where it was painted on the outside of furnaces, and the external temperature reduced from 130°C to 110°C, a by product was that furnace efficiency increased and electricity cost reduced.
Example 2 Formula 1 team McLaren painted it on spiders where without coatings; the outer part reached 127°C, and internally 40°C; but coated with 50019 + 37024, the comparable figures were 112°C and 35°C
Example 3 Westland helicopters 50019 painted under IP9189 saw a reduction of 100°C at the substrate
Example 4 PL 95-R1 is a Rolls Royce originated baking product for use up to 500°C;
Example 5 Pratt Canada painted oil tubes running too close to a hot engine part; the radiant heat reaching the tube was at 300°C; which was damaging the oil; a layer of PL95 reduced heat at the tube by 30%
Please contact our technical office for more information.
