PEX · grade
PEX FOAM
Properties of the FOAM condition, compared with the other PEX grades.
Chemically or radiation cross-linked closed-cell PE foam for pipe insulation, gaskets and impact padding — pick by density (30–200 kg/m³).
What is PEX FOAM?
PEX FOAM is PEX in the FOAM grade — chemically or radiation cross-linked closed-cell PE foam for pipe insulation, gaskets and impact padding — pick by density (30–200 kg/m³). PEX FOAM has a yield strength of 19 MPa (2.76 ksi) and a tensile strength of 0.5 MPa (0.0725 ksi) — weaker than 86% of polymer grades. Elongation at break is 120% and the elastic modulus is 0.68 GPa (0.0986 Msi). PEX FOAM has a density of 0.06 g/cm³ (0.0022 lb/in³), lighter than 87% of polymer grades. Its glass-transition temperature is -120°C (-184 °F). PEX-A is the default condition FabDigit quotes; FOAM is available on request or by drawing note.
Advantages
- Low moisture uptake — 0.01%, better than 97% of polymer grades
- Forms and bends easily — 90/100, better than 92% of polymer grades
- Low embodied carbon — 2.3 kg CO₂/kg, better than 92% of polymer grades
- Good corrosion resistance — 92/100, better than 91% of polymer grades
- Lightweight — 0.06 g/cm³ (0.0022 lb/in³), better than 87% of polymer grades
Limitations
- Poor heat conductor — 0.04 W/m·K (0.0214 BTU/hr·ft·°F), worse than 91% of polymer grades
- Hard to polish — 25/100, worse than 90% of polymer grades
- High mold shrinkage — 2.2%, worse than 88% of polymer grades
- Low strength — 19 MPa (2.76 ksi), worse than 86% of polymer grades
- Difficult to weld — 10/100, worse than 84% of polymer grades
PEX FOAM properties
Typical room-temperature values for PEX FOAM — 7 properties are specific to this condition; the rest are grade-level values shared by every PEX grade. Each bar shows where the value sits among the polymer grades in FabDigit's library — further right is higher.
Physical5
PEX FOAM has a density of 0.06 g/cm³ (0.0022 lb/in³), lighter than 87% of polymer grades. Its glass-transition temperature is -120°C (-184 °F).
Mechanical10
PEX FOAM has a yield strength of 19 MPa (2.76 ksi) and a tensile strength of 0.5 MPa (0.0725 ksi) — weaker than 86% of polymer grades. Elongation at break is 120% and the elastic modulus is 0.68 GPa (0.0986 Msi).
Thermal11
PEX FOAM is rated for continuous service to 90°C (194 °F). It conducts heat at 0.04 W/m·K (0.0214 BTU/hr·ft·°F), worse than 91% of polymer grades. Thermal expansion is 170 µm/m·K (94.4 µin/in·°F).
Electrical7
PEX FOAM is an electrical insulator with a dielectric strength of 25 kV/mm (635 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (92/100), better than 91% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of PEX FOAM takes about 82 MJ of energy and emits 2.3 kg of CO₂ — less than 83% of polymer grades. Typical recycled content is 0%.
Manufacturability8
PEX FOAM's machinability is fair (45/100, worse than 77% of polymer grades); weldability not recommended (10/100); formability excellent (90/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other PEX grades and fills
PEX is also supplied in 10 other conditions. The full side-by-side table is on the PEX overview.
- PEX-ADefaultHighest and most uniform cross-link density with thermal shape memory — choose for expansion (cold-expansion) fittings, tight bends and kink repair by heating.22 MPa tensile
- XLPE-CABLEUltra-clean peroxide-curable PE compound for 0.6/1 kV to 500 kV cable insulation — 90 °C continuous, 250 °C short-circuit rating.20 MPa tensile
- FOAMChemically or radiation cross-linked closed-cell PE foam for pipe insulation, gaskets and impact padding — pick by density (30–200 kg/m³).0.5 MPa tensile
Working with PEX FOAM
Is PEX easy to machine?
Cuts cleanly with a tubing cutter or sharp knife; milling/turning is possible but gummy — use sharp positive-rake tools, high speed, low feed and air cooling.
Can PEX be welded?
Cannot be heat-fused or solvent-cemented once cross-linked; join with cold-expansion (PEX-a), copper-crimp, stainless-clamp or push-fit fittings, or use electrofusion only on the uncrosslinked skin of specialty products.
Can PEX be formed, bent or molded?
Extruded and cross-linked in-line (Engel/Sioplas) or post-irradiated; PEX-a can be reformed and shrunk back with a heat gun (shape memory), other types bend cold to ~6–8× OD with support bends.
What surface finishes work on PEX?
No paint or plating adheres without corona/flame treatment; surfaces are matte and colour is provided by masterbatch (red/blue/white/black) rather than coating.
PEX chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| peroxide crosslinker (DCP)PEX-a and XLPE cable grades only | 0.5 – 2.5 | 1.5 |
| vinyl silane + catalystPEX-b (Sioplas/Monosil) route | 1 – 2.5 | 1.8 |
| antioxidant / thermal stabilizerhindered phenol + phosphite; chlorine resistance package for potable water | 0.1 – 0.6 | 0.3 |
| UV stabilizer / carbon blackUV-stabilized variants only | 0 – 2.5 | 0 |
| gel content (degree of crosslinking)ASTM D2765 / ISO 15875-2: PEX-a ≥70%, PEX-b ≥65%, PEX-c ≥60% | 60 – 89 | 72 |
| ethylene (PE base resin)HDPE/MDPE base, density 0.94–0.95 before crosslinking | ≥ 95 (balance) | — |
PEX FOAM — frequently asked
What is PEX FOAM used for?
PEX FOAM is typically used for radiant floor heating tubing, potable water plumbing, hydronic piping and insulated cable jacketing. In short: cross-linked, not fusible; hot-water rated polyethylene; PEX-a shape memory.
What is the yield strength of PEX FOAM?
PEX FOAM has a typical yield strength of 19 MPa (2.76 ksi) and a tensile strength of 0.5 MPa (0.0725 ksi) — weaker than 86% of polymer grades. Strength varies by condition: see the 11 listed tempers.
Is PEX FOAM easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 77% of polymer grades). Cuts cleanly with a tubing cutter or sharp knife; milling/turning is possible but gummy — use sharp positive-rake tools, high speed, low feed and air cooling.
Can PEX FOAM be welded?
Not readily — weldability is rated not recommended (10/100). Cannot be heat-fused or solvent-cemented once cross-linked; join with cold-expansion (PEX-a), copper-crimp, stainless-clamp or push-fit fittings, or use electrofusion only on the uncrosslinked skin of specialty products.
What surface finishes work on PEX FOAM?
No paint or plating adheres without corona/flame treatment; surfaces are matte and colour is provided by masterbatch (red/blue/white/black) rather than coating.
Can PEX FOAM be formed, bent or molded?
Extruded and cross-linked in-line (Engel/Sioplas) or post-irradiated; PEX-a can be reformed and shrunk back with a heat gun (shape memory), other types bend cold to ~6–8× OD with support bends.
What is the maximum service temperature of PEX FOAM?
PEX FOAM is rated for continuous use to about 90°C (194 °F), and briefly to 110°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM F876 — Crosslinked Polyethylene (PEX) Tubing — ASTM International (2023)
- ISO 15875-1/-2 — Plastics piping systems for hot and cold water installations, Crosslinked polyethylene (PE-X) — ISO (2018)
- ASTM D2765 — Degree of Crosslinking (Gel Content) in Crosslinked Ethylene Plastics — ASTM International (2016)
- ASTM F2023 — Oxidative Resistance of PEX Tubing to Hot Chlorinated Water — ASTM International (2020)
- IEC 60502-1/-2 — Power cables with extruded XLPE insulation — IEC (2021)
- Crosslinkable PE pipe and cable compound datasheets (Borealis/Borouge, Uponor, Rehau, Wanhua) — various producers (2024)
- Engineered Materials Handbook Vol. 2: Engineering Plastics — ASM International (1988)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.