40W Rigid Spray Polyurethane Foam | Rayston Water-Blown Insulation
Contents
- What is 40W spray polyurethane foam and when should you specify it?
- Water blowing agent and make-up of 40W spray polyurethane foam
- Applied foam properties: density, closed cells, λ, μ, water absorption and fire
- 40W spray foam aged thermal performance table (thickness / λ / R)
- Mix ratios and site application conditions
- Component properties and laboratory reactivity
- Safety, storage, equipment cleaning and empty containers
- 40W spray polyurethane foam vs other Rayston grades: which one to choose?
- 40W spray polyurethane foam: FAQ
- Engineering summary
- Related links
Rayston Spray Foam 40W by Krypton Chemical: a water-blown rigid spray polyurethane foam with 38–42 kg/m³ applied density, λ = 0.031 W/m·K and μ ≥ 70, free of HFCs and HCFCs, for spray-applied thermal insulation — figures from the technical datasheet.
- Product: Rayston Spray Foam 40W
- Grade: 40W · water-blown
- Application: spray-applied thermal insulation
40W spray polyurethane foam (Rayston Spray Foam 40W) is a two-component rigid SPF system from Krypton Chemical, S.L., sprayed directly onto vertical walls and ceilings from the inside where the surface is not subject to permanent loads. The blowing agent is water, and the system is free of HFCs, HCFCs and VOCs according to the datasheet. Key figures: applied density 38–42 kg/m³, declared thermal conductivity λ = 0.031 W/m·K, closed-cell content < 80% and water vapour diffusion resistance factor μ ≥ 70, according to the official technical datasheet (last revised 02/06/2026).
This article covers a single grade of the Rayston Spray Foam range (the water-blown W line). For a full comparison of all seven grades, see the general guide: spray polyurethane foam. Its closest neighbours are the lighter 30W spray foam and the denser 50W spray foam, which has a declared compressive strength.
01
What is 40W spray polyurethane foam and when should you specify it?
40W spray foam (Rayston Spray Foam 40W) is a rigid polyurethane foam made from a two-component system (polyol + isocyanate). Sprayed directly onto the substrate, it forms a continuous, seamless, fully adhered insulation layer that limits thermal bridging at corners and junctions.
Use declared in the datasheet:
- Spray-applied thermal insulation on surfaces not subject to permanent loads, such as vertical walls and ceilings from the inside.
- On façades: repels water while still allowing the construction to breathe to some degree.
With an applied density of 38–42 kg/m³, 40W sits in the middle of the water-blown line, between 30W (28–35 kg/m³) and 50W (48–56 kg/m³), with the same declared λ as 30W (0.031) and a higher μ (≥ 70 vs ≥ 60).
According to the datasheet, the product contains no fibres and no biohazardous materials, nor any substances classed as hazardous construction and demolition waste. It is for industrial and professional use only and not suitable for DIY. The cured foam is 100% recyclable by environmentally friendly mechanical means, with no gas capture needed for recycling or disposal.
Manufacturer: kryptonchemical.com.
Internal links: Knowledge base · Products · Documents.
02
Water blowing agent and make-up of 40W spray polyurethane foam
40W spray foam uses water as its blowing agent, which places it in Rayston’s water-blown line (30W / 40W / 50W), as opposed to the HFO family (HFO 35 / HFO 40 / HFO 50) and the 8W open-cell grade.
The datasheet states that the system is free of ozone-depleting substances and fluorinated greenhouse gases: it contains no HFCs, HCFCs or VOCs. It also states that thermal conductivity λ remains stable from application throughout the life of the product.
Designation code according to the datasheet:
PU EN 14315-1-CCC2-CT4 (20)-GT18(20)-TFT11(20)-FRB30(20)-W0,2-MU70
Reference standard for use as thermal insulation in buildings (ThIB): EN 14315-1:2013, together with guidance document NB-CPR/SG19-17/167r2 dated 24/01/18. The CE marking block confirms that reaction to fire and compressive strength do not deteriorate over time, and that the declared thermal resistance accounts for ageing.
03
Applied foam properties: density, closed cells, λ, μ, water absorption and fire
Applied density
38–42 kg/m³
UNE-EN 1602
Closed-cell content
< 80%
— (row notes “does not allow water through”)
Reaction to fire
Euroclass E (all thicknesses)
UNE-EN 13823:2002
| Property | Value | Standard / TDS reference |
|---|---|---|
| Applied density | 38–42 kg/m³ | UNE-EN 1602 |
| Free-rise density (lab) | 35 g/L | EN 14315-1:2013 |
| Closed-cell content | < 80% | — (row notes “does not allow water through”) |
| Declared thermal conductivity λ | 0.031 W/m·K | UNE-EN 12667 |
| Reaction to fire | Euroclass E (all thicknesses) | UNE-EN 13823:2002 |
| Short-term water absorption | ≤ 0.2 kg/m² | EN 14315-1:2013 |
| Water vapour diffusion resistance factor μ | ≥ 70 | EN 14315-1:2013 |
Brief engineering notes:
- An applied density of 38–42 kg/m³ places 40W midway between 30W (28–35) and 50W (48–56) in the W line.
- Closed-cell content is declared as < 80%, and the designation code carries CCC2.
- μ ≥ 70 is higher than 30W (μ ≥ 60), i.e. greater resistance to water vapour transmission on the declared figures.
- No numerical compressive strength is given in the 40W sheet; if compressive strength is a design requirement, look at 50W or HFO 50.
- Reaction to fire is Euroclass E for all thicknesses and, according to the CE marking block, does not deteriorate over time.
04
40W spray foam aged thermal performance table (thickness / λ / R)
Base the thermal calculation on the target-thickness row of the aged performance table, not on the general λ value alone. For 40W spray foam, λ = 0.031 stays constant from 30 to 200 mm, and thermal resistance R increases with thickness.
R (m²·K/W)
Aged λ (W/m·K) 0.031 · thickness 30–200 mm
30 mm
1.00
35 mm
1.15
40 mm
1.30
45 mm
1.45
50 mm
1.60
55 mm
1.70
60 mm
1.95
65 mm
2.10
70 mm
2.25
75 mm
2.40
80 mm
2.60
85 mm
2.75
90 mm
2.90
95 mm
3.05
100 mm
3.25
105 mm
3.40
110 mm
3.55
115 mm
3.70
120 mm
3.85
125 mm
4.05
130 mm
4.20
135 mm
4.35
140 mm
4.50
145 mm
4.70
150 mm
4.85
155 mm
5.00
160 mm
5.15
165 mm
5.30
170 mm
5.50
175 mm
5.65
180 mm
5.80
185 mm
5.95
190 mm
6.15
195 mm
6.30
200 mm
6.45
Worked example: at 50 mm, R = 1.60 m²·K/W; at 100 mm, R = 3.25; and at 200 mm, R = 6.45 — with λ = 0.031 in every row. The 40W table is numerically identical to the 30W table; the two grades differ in density, μ and reactivity.
| Thickness (mm) | Aged λ (W/m·K) | R (m²·K/W) |
|---|---|---|
| 30 | 0.031 | 1.00 |
| 35 | 0.031 | 1.15 |
| 40 | 0.031 | 1.30 |
| 45 | 0.031 | 1.45 |
| 50 | 0.031 | 1.60 |
| 55 | 0.031 | 1.70 |
| 60 | 0.031 | 1.95 |
| 65 | 0.031 | 2.10 |
| 70 | 0.031 | 2.25 |
| 75 | 0.031 | 2.40 |
| 80 | 0.031 | 2.60 |
| 85 | 0.031 | 2.75 |
| 90 | 0.031 | 2.90 |
| 95 | 0.031 | 3.05 |
| 100 | 0.031 | 3.25 |
| 105 | 0.031 | 3.40 |
| 110 | 0.031 | 3.55 |
| 115 | 0.031 | 3.70 |
| 120 | 0.031 | 3.85 |
| 125 | 0.031 | 4.05 |
| 130 | 0.031 | 4.20 |
| 135 | 0.031 | 4.35 |
| 140 | 0.031 | 4.50 |
| 145 | 0.031 | 4.70 |
| 150 | 0.031 | 4.85 |
| 155 | 0.031 | 5.00 |
| 160 | 0.031 | 5.15 |
| 165 | 0.031 | 5.30 |
| 170 | 0.031 | 5.50 |
| 175 | 0.031 | 5.65 |
| 180 | 0.031 | 5.80 |
| 185 | 0.031 | 5.95 |
| 190 | 0.031 | 6.15 |
| 195 | 0.031 | 6.30 |
| 200 | 0.031 | 6.45 |
05
Mix ratios and site application conditions
Mix ratio by volume (polyol : isocyanate)
100:100
Mix ratio by weight
100:108
Component temperature
30–60 °C
Working pressure
60–120 bar
Ambient temperature
0 to 40 °C
Relative air humidity
< 90%
Wind speed
< 30 km/h
Substrate temperature
5–40 °C
Substrate moisture
No surface condensation
| Condition | Value in the 40W datasheet |
|---|---|
| Mix ratio by volume (polyol : isocyanate) | 100:100 |
| Mix ratio by weight | 100:108 |
| Component temperature | 30–60 °C |
| Working pressure | 60–120 bar |
| Ambient temperature | 0 to 40 °C |
| Relative air humidity | < 90% |
| Wind speed | < 30 km/h |
| Substrate temperature | 5–40 °C |
| Substrate moisture | No surface condensation |
Apply the system with dedicated spray equipment at the mix ratios above. The manufacturer’s recommendations do not relieve the applicator of reviewing the application method and running on-site trials whenever there is doubt about the system’s suitability for the project conditions.
06
Component properties and laboratory reactivity
The following values are given at 20 °C in the datasheet section on supplementary component information and reactivity:
Hydroxyl value
Polyol: 180–220 mg KOH
DIN-53240-2
Viscosity
Polyol: 320–450 mPa·s
Isocyanate: 180–250 mPa·s
INT-IT-17
NCO content
Isocyanate: 30–32%
UNE-92120-1
| Property | Polyol | Isocyanate | Standard |
|---|---|---|---|
| Hydroxyl value | 180–220 mg KOH | — | DIN-53240-2 |
| Viscosity | 320–450 mPa·s | 180–250 mPa·s | INT-IT-17 |
| NCO content | — | 30–32% | UNE-92120-1 |
| Cream time | 4 ± 1 s | EN 14315-1:2013 | |
| Thread (string) time | 11 ± 1 s | EN 14315-1:2013 | |
| Drying (tack-free) time | 18 ± 1 s | EN 14315-1:2013 | |
| Free-rise density | 35 g/L | EN 14315-1:2013 |
These are reference laboratory times; working times on site depend on component temperature, working pressure and ambient conditions within the declared ranges. The 40W sheet does not give the polyol water content.
07
Safety, storage, equipment cleaning and empty containers
Occupational safety
Component B of 40W spray foam contains isocyanates, so always follow the safety data sheet (MSDS): good ventilation and/or respiratory protection (combined organic vapour and particulate filters) together with protective clothing. Use the product only for the applications described in the datasheet; it is intended for industrial and professional use and is not suitable for DIY.
Storage
Store both components between 10 and 25 °C, always protected from moisture ingress. Under suitable storage conditions and in the original packaging, the maximum shelf life is 6 months from the date of manufacture.
Equipment cleaning
After application, clean the machine carefully to avoid contaminating the next system used on the same rig. Solvents are not recommended for cleaning machine parts; a plasticiser-based cleaning fluid such as Rayston Fluid is preferred. Remove component B completely from all parts exposed to air and replace it with cleaning fluid.
Empty containers and environment
Handle empty containers with the same precautions as full ones and hand them over as hazardous waste to a licensed waste manager. A and B can be mixed 1/1 to obtain an inert material, provided the quantity does not exceed 5 litres, to avoid a dangerous build-up of heat. Never mix residues with any other product without knowing the possible reactions.
08
40W spray polyurethane foam vs other Rayston grades: which one to choose?
Choosing a grade is a design decision governed by the application, density, λ, μ and any declared compressive requirements — not by the trade name alone. Within what the 40W datasheet figures support:
1
Water-blown, 38–42 kg/m³ applied density, declared λ 0.031, μ ≥ 70 within the W line → 40W is the direct candidate.
2
Lower density with the same λ (0.031) and μ ≥ 60 → compare 30W (28–35 kg/m³).
3
A numerically declared compressive strength with λ = 0.030 → see 50W (48–56 kg/m³).
4
5
Declared sound insulation with lightweight open cells → 8W, not 40W.
This section does not replace the building’s thermal calculation or the technical datasheet of the selected grade. For a side-by-side comparison of all seven grades, see the spray polyurethane foam guide.
09
40W spray polyurethane foam: FAQ
What is 40W spray foam, in short?
A two-component rigid polyurethane foam system (Rayston Spray Foam 40W) from Krypton Chemical, water-blown, with an applied density of 38–42 kg/m³, for spray-applied thermal insulation on surfaces not subject to permanent loads.
What is the declared thermal conductivity of 40W spray foam?
λ = 0.031 W/m·K to UNE-EN 12667. In the ageing table, λ stays at 0.031 for all thicknesses from 30 to 200 mm; use the R value in the target-thickness row.
Is 40W spray foam closed-cell?
Closed-cell content is declared as < 80% (the datasheet notes “does not allow water through”), and the designation code carries CCC2. The HFO grades, by contrast, declare > 90%.
What is the difference between 40W and 30W spray foam?
λ and the R table are identical (0.031), but 40W is denser (38–42 vs 28–35 kg/m³) and has a higher μ (≥ 70 vs ≥ 60); polyol viscosity, thread time and drying time also differ between the two sheets.
What is the correct mix ratio?
100:100 by volume and 100:108 by weight (polyol : isocyanate), with a component temperature of 30–60 °C and a working pressure of 60–120 bar.
Is it suitable for permanent loads?
No, according to the datasheet wording: the declared application is on surfaces not subject to permanent loads (typically vertical walls and interior ceilings). Any use outside this scope requires an independent engineering decision.
What is the reaction-to-fire classification?
Euroclass E for all thicknesses, tested to UNE-EN 13823:2002; according to the CE marking block, reaction-to-fire performance does not deteriorate over time.
What is the shelf life and how should the components be stored?
Up to 6 months from the date of manufacture in the original packaging, with both components stored between 10 and 25 °C and fully protected from moisture.
10
Engineering summary
40W spray polyurethane foam (Rayston Spray Foam 40W) is a rigid, water-blown grade in the middle of Krypton Chemical’s W line: applied density 38–42 kg/m³, declared closed cells < 80%, declared λ of 0.031, constant in the ageing table from 30 to 200 mm, μ ≥ 70, short-term water absorption ≤ 0.2 kg/m² and reaction to fire Euroclass E. Its declared use is spray-applied thermal insulation on surfaces not subject to permanent loads, and the system is free of HFCs and HCFCs. Settle the final choice against the datasheet figures and the project thickness, and refer to the general guide to compare it with the other grades.
11
Related links
General guide
Grade articles
40W
Rayston Spray Foam 40W
| Grade | Trade name | Article |
|---|---|---|
| 8W | Rayston Spray Foam 8W | 8W spray foam |
| 30W | Rayston Spray Foam 30W | 30W spray foam |
| 40W | Rayston Spray Foam 40W | This article |
| 50W | Rayston Spray Foam 50W | 50W spray foam |
| HFO 35 | Rayston Spray Foam HFO 35 | HFO 35 spray foam |
| HFO 40 | Rayston Spray Foam HFO 40 | HFO 40 spray foam |
| HFO 50 | Rayston Spray Foam HFO 50 | HFO 50 spray foam |
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