Chemical Compatibility Series: Spray Polyurethane Foam Insulation and Paint


This is the third in a series of articles dealing with a topic that concerns all of us from time to time: chemical compatibility. With the rapid growth of the use of BlazeMaster fire sprinkler systems in residential and light hazard occupancies over the last 30 years, the incidence of compatibility issues has been kept low thanks to educational resources available from BlazeMaster manufacturers and Lubrizol.  The System Compatible Program® assists installers in choosing compatible ancillary products for use with BlazeMaster systems.  Manufacturers’ installation manuals and available on-site training provide guidance on everything from proper storage and handling of uninstalled pipe and fittings through the final system test.  In addition, Lubrizol has published a web page of general guidance on compatibility with a variety of commonly encountered construction products and a number of more in-depth articles on compatibility topics.  In this article we’re going to address two construction products that are often used in direct contact with BlazeMaster® fire sprinkler systems: spray polyurethane foam insulation and paint.

Part 1: Spray Polyurethane Foam Insulation

Spray polyurethane foam (SPUF) insulation has been installed in direct contact with BlazeMaster fire sprinkler systems for over 20 years, and its use has grown rapidly, particularly over the last 5 years.  Very seldom do problems arise from the use of these products together; and they can be avoided  by the use of best practices on the part of both the piping and the insulation installers.

SPUF insulation is typically applied with equipment that mixes the two liquid chemical components of the product in a spray nozzle through which the mixture is then applied to the structure.  Upon application, the two components quickly react with each other and foam up, creating a solidified foam structure with good insulating properties.  There are two potential ways that this process can have a detrimental effect on CPVC fire sprinkler systems installed in the same space: heat and compatibility.  Although heat is not strictly a chemical compatibility issue as the focus of these articles is meant to be, it deserves to be addressed here so that all types of potential problems can be avoided.

When the two components of the insulation react together, the reaction generates a large amount of heat.  Because the product has good insulating properties, that heat is not easily dissipated.  In fact, the temperatures inside the foam as it is curing are usually above both the boiling point of water and the softening point of CPVC.  SPUF insulation manufacturers usually provide instructions regarding maximum allowable application layer thicknesses and wait times between layer applications in order to avoid excessive heat buildup.  It is important that these instructions be followed carefully by the insulation installer in order to avoid excessive heat conditions which can damage installed piping.  Extra care should be taken in awkward building cavities, where keeping the application thickness below the allowable maximum may be difficult.

There are also several things the piping installer can do to minimize the potential for damage to the piping by the heat generated by SPUF insulation.  Since the temperatures experienced can be above both the boiling point of water and the softening point of CPVC, it is best if the sprinkler system is empty and not pressurized when the insulation is installed.  If the pipe is filled with water and/or pressurized, and then heated above its softening point, the pipe may experience ballooning under these conditions.  This causes the walls to become stretched and thin, eventually leading to rupture.  If the pipe is heated above its softening point without being filled and/or pressurized, it won’t balloon and will simply harden back up when the temperature falls.

In addition, the piping system designer should consider the possibility that compensation for thermal expansion may be necessary due to the heat generated by the SPUF as it cures.  If long runs of pipe will be buried in SPUF, expansion loops or offsets may be necessary to account for the expansion of the pipe due to the heat.  If expansion is not properly accounted for in the design, excessive stress can be concentrated in areas (typically elbow or tee fittings) where expansion is restrained.  Installation manuals available from the piping manufacturers give advice on proper design and placement of thermal expansion compensation.

As to its compatibility with CPVC, spray polyurethane foam insulation is a unique case, because it depends very much on the proper installation of the foam.  CPVC is not compatible with either of the liquid components that combine to make SPUF, but the cured foam has little or no effect on the CPVC.  Two things happen during the installation and curing process that cause the final product to have little or no effect on the piping.  First, the chemicals react rapidly, turning the largest part of the liquid components into a solid polymer that has no effect on CPVC.  Second, the material is rapidly blown into a foam, lifting the other additive ingredients of the SPUF up and away from the piping.  The foam creates a difficult path for the additives to get to the pipe surface, with many gas bubbles blocking the way.  This effectively inhibits other additive ingredients in the foam from migrating to the pipe’s surface.  All this depends on the components being properly mixed and applied so that they foam up and cure properly.

In 2009, Lubrizol assisted the Spray Polyurethane Foam Alliance (SPFA) to determine if chemical compatibility issues exist with FlowGuard Gold®, BlazeMaster® and Corzan® CPVC pipe and fittings. A variety of types and grades of foams were properly applied to CPVC assemblies and tested under conditions of elevated temperature and pressure.  SPFA findings conclude that those spray polyurethane foams tested did not pose a chemical compatibility problem. In addition, Lubrizol is unaware of a CPVC failure that was the result of chemical incompatibility with properly mixed and applied spray polyurethane foams. When two-component foams are improperly mixed and there is an excess of either component present on the piping or when the material fails to foam, compatibility problems may arise from the unreacted excess or additives of either component being left in contact with the pipe or fittings.

Part 2: Paint

Paint is frequently applied to BlazeMaster piping systems either intentionally for aesthetic purposes, or unintentionally from overspray when nearby surfaces are painted.  Lubrizol is aware of only one system failure ever caused by painting of the pipe and fittings, and that was with a two part epoxy paint.  That type of paint is therefore not recommended for painting BlazeMaster piping systems.  Lubrizol is not aware of any failure issues that have ever arisen due to other types of paints being applied in normal coats to CPVC, including water-based latex paints, alkyd paints, enamels, spray paints, or paints with added mold inhibiting ingredients.

When BlazeMaster piping is to be painted for aesthetic purposes, the following pointers should be followed:

  • Lubrizol recommends the use of water-based latex paint, which is the most commonly available type of interior paint.
  • Do not allow the paint to puddle on or around the pipe. Paint should be applied in such a way that it dries in the amount of time indicated by the paint manufacturer.  Extended exposure to puddles of paint which cannot dry normally may be detrimental to the pipe or fitting material.
  • It is not recommended to paint the pipe or fittings prior to installation. Paint on the pipe ends or inside fitting sockets will interfere with solvent cementing, potentially causing leaky joints or blowouts.  Wait until after the piping is installed and the cement is cured before painting the piping system.
  • Do not allow sprinkler heads to become coated with paint, as that may impede their function in a fire situation.
  • Do not allow paint to get inside the piping system through openings such as drops or adapters. Paint inside the piping system may peel off and impede flow through the sprinkler head in a fire situation.
  • Check with local authorities before painting the piping system, as some may require that the printing on the pipe be left visible for inspecting

For more information on other compatibility topics and Lubrizol’s FBC system compatibility program please visit

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