Spray Foam Insulation Chemicals: What Panel Manufacturers Need to Know

On a cold room project the job is not finished when the panels are in place. Joints, pipe and cable penetrations, the points where steel members meet the panels and irregular surfaces the panels cannot cover still need insulation. Most of these gaps are closed on site with spray foam. Spray foam chemistry rests on the same foundation as the polyurethane systems used on panel lines, but the application conditions and quality criteria are different. In this guide we look at what spray foam insulation chemicals are made of, how open cell, semi-rigid and closed cell systems differ, which machine settings matter, which quality checks to run on site and which safety obligations apply, all from a panel manufacturer's point of view.

What Are Spray Foam Insulation Chemicals?

Spray polyurethane foam is a reactive system made of two components that mix at the moment of application. Component A is the polyol blend: alongside the polyols it carries the catalysts that steer the reaction, silicone surfactants that control cell structure, the blowing agent and, where needed, flame retardants. Component B is an isocyanate based on polymeric MDI, typically with an NCO content between 30.5 and 32.5 percent.

Both components are heated in a high-pressure proportioner, travel through separate hoses to the gun and only meet in the mixing chamber at the gun tip. The reaction starts as soon as the mix reaches the surface; within seconds the foam expands, bonds to the substrate and hardens. On a panel line the mix foams under controlled conditions between moulds or belts. With spray foam the reaction happens in the open, at the real surface temperature and humidity. That is why spray systems need their own formulation expertise and their own application discipline.

Open Cell, Semi-Rigid and Closed Cell: Three Different Systems

Spray foam systems fall into three main groups by cell structure. The choice depends on whether the project's priority is thermal insulation, acoustic insulation, or mechanical strength and moisture resistance.

Open Cell Spray Foam

The cells are open to each other, giving a soft and flexible structure with a very low applied density. Our open cell spray foam system PLUSOL-R-101-18, for example, is applied at about 9.5-10.5 kg/m³ and expands to roughly 140 times its liquid volume. Its thermal conductivity is 0.035 W/m·K, and consumption for a 10 cm layer is around 1 kg/m². It performs strongly in sound insulation and is the usual choice on timber and plasterboard. It is not recommended for metal or concrete surfaces.

Semi-Rigid Spray Foam

Semi-rigid systems strike a balance between open and closed cell. A system such as PLUSOL-R-101-20 is applied at 22-24 kg/m³, delivers thermal and acoustic insulation together at 0.035 W/m·K and keeps its form on the substrate. Consumption for a 10 cm layer is 2.2-2.4 kg/m².

Both open cell and semi-rigid systems are rated F under EN 13501-1. After application they must be covered with a lining such as plasterboard.

Closed Cell Spray Foam

Most of the cells are closed, so the foam is rigid, dense and resistant to moisture. It is the strongest option for thermal insulation. Our fire resistant spray polyurethane system PLUSOL-R-102-62 has a closed cell content above 92 percent, a thermal conductivity of 0.022 W/m·K and a compressive strength above 150 kPa at 10 percent deformation. At an applied density of 34-36 kg/m³, 100 mm gives a thermal resistance of about 4.55 m²·K/W. The system achieved a Class A result in the ASTM E84 tunnel test with a flame spread index of 10; you can read the details in our ASTM E84 article.

Why It Matters to Panel Manufacturers

For manufacturers of sandwich panels and cold room panels, spray foam completes the product. A panel's thermal performance can easily be lost through the joints and penetrations left during installation. In cold chain facilities these gaps also lead to condensation and ice build-up. The spray system that closes them on site needs to deliver thermal performance that matches the panel core.

The chemistry speaks a common language too. Cream and tack-free times, free-rise density, closed cell content and thermal conductivity, the values a panel line tracks every shift, also decide spray foam quality. We cover PUR and PIR core chemistry in PIR Insulation Board: A Technical Guide and what to look for when sourcing raw materials in our polyol supplier guide.

Choosing the Blowing Agent

The blowing agent is what makes the foam expand. In water-blown systems, carbon dioxide released by the reaction of water with isocyanate expands the foam; our open cell and semi-rigid systems work this way and contain no CFC, HCFC or HFC. In closed cell systems, physical blowing agents trapped inside the cells contribute to low thermal conductivity. As F-gas regulations phase down HFCs with a high global warming potential, the blowing agent now has to be judged on regulation as well as performance.

Reaction Profile and Machine Settings

With spray foam the reaction is measured in seconds. Open cell systems cream in 3-5 seconds and are tack-free in 6-8 seconds; for semi-rigid systems these values rise to 5-11 and 11-15 seconds. At that speed even small deviations in machine settings show up directly in foam quality.

• Mixing ratio: 100/100 by volume for these systems. A ratio drift leaves the foam soft, brittle or tacky,
• Component and hose temperature: kept at 40-45 °C. Cold material mixes poorly and the cell structure suffers,
• Component pressure: 90-110 bar. Low pressure weakens mixing, and the two components must be at balanced pressure,
• Ambient and substrate temperature: 10-40 °C or 20-45 °C depending on the system; the surface must be dry and clean,
• Preparing component A: for open cell and semi-rigid systems, component A is mixed for at least 15 minutes before application and kept mixing throughout.

Quality Control on Site

Spray foam quality can be confirmed after application with a few simple checks. Core density is measured on a cut sample and compared with the technical data. The cell structure is inspected by eye; coarse or irregular cells, separation between layers and colour differences point to a ratio or temperature problem. Thickness is checked at several points, because thin areas become thermal bridges. Adhesion can be tested roughly by trying to pull the foam off the substrate by hand.

In the laboratory, thermal conductivity is measured to EN 12667, compressive strength to EN 826 and closed cell content to ISO 4590. The fire classification required by the project should be documented with a test report such as EN 13501-1 or ASTM E84.

Storage and Safety

Store the components at 15-25 °C in their dry, tightly closed original containers, protected from moisture and direct sunlight. The isocyanate component reacts with moisture, and an open container develops a skin and sediment. Shelf life depends on the system; for our open cell and semi-rigid systems it is 6 months for component A and 12 months for component B.

In the European Union, under the REACH Annex XVII restriction, industrial and professional use of products containing more than 0.1 percent free monomeric diisocyanate by weight has required training since 24 August 2023. Current training requirements should be checked on the official Safe Use of Diisocyanates portal. Spray application calls for suitable respiratory protection, chemical-resistant gloves, full face protection and coveralls; enclosed spaces must be ventilated and unprotected people kept out of the work area. Always read the Safety Data Sheet before application.

Common Mistakes

• Spraying too thick in a single pass: reaction heat builds up inside the foam, the cell structure breaks down and the foam can shrink,
• Spraying onto a cold or damp surface: adhesion weakens, and the foam delaminates or blisters,
• Starting before the machine is up to temperature: the first square metres come out with a poor ratio and mix and remain weak spots,
• Leaving class F foam exposed: open cell and semi-rigid foam must be covered with a lining such as plasterboard,
• Choosing the wrong system for the job: using open cell foam on metal or concrete, or relying on closed cell alone where acoustic insulation is expected, will not give the expected result.

Conclusion

Spray foam insulation chemicals are a complementary solution that closes the gaps a panel manufacturer leaves on site and protects the overall thermal performance of the project. The right system follows the priority: open cell for acoustic insulation and economy, semi-rigid for a balance of heat and sound, closed cell for the highest thermal insulation, strength and documented fire performance. On site, the mixing ratio, component temperature and pressure, and substrate conditions decide the result.

You can explore all our spray systems on our polyurethane spray foam, closed cell foam and spray polyurethane raw materials pages. Contact our technical team to choose the right system for your project and request a sample.