Polymer
PEX
Properties, grades, machining, finishes and uses — values shown for the PEX-A condition.
Polyethylene chemically or radiation cross-linked into a thermoset-like network, giving improved thermal stability, creep resistance and chemical resistance versus uncross-linked PE; standard for hot/cold water piping.
Reference datasheet — PEX is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
What is PEX?
Polyethylene chemically or radiation cross-linked into a thermoset-like network, giving improved thermal stability, creep resistance and chemical resistance versus uncross-linked PE; standard for hot/cold water piping. PEX has a density of 0.94 g/cm³ (0.034 lb/in³), lighter than 76% of polymer grades. Its glass-transition temperature is -120°C (-184 °F). PEX has a yield strength of 19 MPa (2.76 ksi) and a tensile strength of 22 MPa (3.19 ksi) — weaker than 86% of polymer grades. Elongation at break is 500% and the elastic modulus is 0.68 GPa (0.0986 Msi).
What is PEX used for?
- Radiant floor heating tubing
- Potable water plumbing
- Hydronic piping
- Insulated cable jacketing
Advantages
- Low moisture uptake — 0.01%, better than 97% of polymer grades
- Conducts heat well — 0.4 W/m·K (0.231 BTU/hr·ft·°F), better than 93% 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
Limitations
- 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
- Difficult to machine — 45/100, worse than 77% of polymer grades
PEX properties
Typical room-temperature values for PEX-PEX-A (highest and most uniform cross-link density with thermal shape memory — choose for expansion (cold-expansion) fittings, tight bends and kink repair by heating), compiled from standards, handbooks and producer data. Each bar shows where the value sits among the polymer grades in FabDigit's library — further right is higher. Other conditions have their own pages: see tempers.
Physical5
PEX has a density of 0.94 g/cm³ (0.034 lb/in³), lighter than 76% of polymer grades. Its glass-transition temperature is -120°C (-184 °F).
Mechanical10
PEX has a yield strength of 19 MPa (2.76 ksi) and a tensile strength of 22 MPa (3.19 ksi) — weaker than 86% of polymer grades. Elongation at break is 500% and the elastic modulus is 0.68 GPa (0.0986 Msi).
Thermal11
PEX is rated for continuous service to 95°C (203 °F). It conducts heat at 0.4 W/m·K (0.231 BTU/hr·ft·°F), better than 93% of polymer grades. Thermal expansion is 170 µm/m·K (94.4 µin/in·°F).
Electrical7
PEX 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 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's machinability is fair (45/100, worse than 77% of polymer grades); weldability not recommended (10/100); formability excellent (90/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
PEX grades and fills
PEX is supplied in 11 conditions, each with its own property set. Open one for its full datasheet. PEX-A is what FabDigit quotes unless the drawing says otherwise.
- 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
9 further conditions are listed below with a summary only.
| Condition | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
PEX-ADefault peroxide (Engel) cross-linked | Highest and most uniform cross-link density with thermal shape memory — choose for expansion (cold-expansion) fittings, tight bends and kink repair by heating. | — | 22 | 500 | 60 Shore D | — |
silane (moisture) cross-linked | Lowest-cost, highest-volume route (Sioplas/Monosil); slightly stiffer and stronger than PEX-a, best chlorine resistance ratings — choose for standard crimp/clamp potable water and radiant tubing. | — | 25 | 420 | 63 Shore D | — |
electron-beam (radiation) cross-linked | Clean, additive-free cross-linking done after extrusion; stiffest of the three and free of peroxide/silane residues — choose where extractables must be minimal. | — | 26 | 380 | 64 Shore D | — |
azo (Daoplas) cross-linked | Legacy azo-compound route, rarely produced today; recognised by ISO 15875 but generally superseded by PEX-a/b/c. | — | 24 | 400 | 62 Shore D | — |
Oxygen-barrier PEX (EVOH coated / co-extruded) | PEX with an EVOH oxygen-diffusion barrier per DIN 4726 — mandatory for closed hydronic/radiant loops with ferrous boilers, pumps or manifolds. | — | 24 | — | — | — |
aluminium-cored multilayer composite pipe | PEX/aluminium/PEX laminate: fully oxygen-tight, holds bent shape and cuts thermal expansion by ~7× — choose for exposed runs and where a rigid, formable pipe is wanted. | — | — | — | — | 0.45 W/m·K |
XLPE cable-insulation grade (peroxide-cured, LV/MV/HV) | Ultra-clean peroxide-curable PE compound for 0.6/1 kV to 500 kV cable insulation — 90 °C continuous, 250 °C short-circuit rating. | — | 20 | 500 | — | — |
UV-stabilized / carbon-black PEX | Carbon-black or HALS stabilized compound for outdoor, snow-melt and buried-service tubing exposed to sunlight during long construction periods. | — | 24 | — | — | — |
Flame-retardant XLPE (halogen-free, LSZH) | ATH/MDH-filled cross-linked polyolefin for LSZH cable jackets and building wire where flame spread and smoke toxicity are regulated. | — | 12 | 180 | — | 0.45 W/m·K |
Cross-linked PE foam (IXPE/XPE, closed cell) | Chemically or radiation cross-linked closed-cell PE foam for pipe insulation, gaskets and impact padding — pick by density (30–200 kg/m³). | — | 0.5 | 120 | — | 0.04 W/m·K |
NSF/ANSI 61 & 14 certified potable-water grade | Fully certified tubing with chlorine-resistance class per ASTM F2023 — required for potable plumbing in North America and GB/T 18992 markets in China. | — | 24 | — | — | — |
Working with PEX
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.
Strength versus weight in the polymer family
Yield strength against density for every polymer grade FabDigit runs. PEX is highlighted; hover a dot for its name, or open the interactive family chart.
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) | — |
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.
Equivalent designations
Standards and trade names that resolve to PEX in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- F876
- EN / DIN / Werkstoff-Nr.
- 16892ISO 15875
- ISO
- 15875
- GB (China)
- GB/T 18992
- Also called
- PEXPE
How much does PEX cost?
PEX is a standard-cost polymer ($$), cheaper than about 72% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
PEX — frequently asked
What is PEX used for?
PEX is typically used for radiant floor heating tubing, potable water plumbing, hydronic piping and insulated cable jacketing. In short: cross-linked, not fusible; hot-water rated polyethylene; PEX-a shape memory.
What is the yield strength of PEX?
PEX has a typical yield strength of 19 MPa (2.76 ksi) and a tensile strength of 22 MPa (3.19 ksi) — weaker than 86% of polymer grades. Strength varies by condition: see the 11 listed tempers.
Is PEX easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 77% of polymer grades). Cuts cleanly with a tubing cutter or sharp knife; milling/turning is possible but gummy — use sharp positive-rake tools, high speed, low feed and air cooling.
Can PEX be welded?
Not readily — weldability is rated not recommended (10/100). Cannot be heat-fused or solvent-cemented once cross-linked; join with cold-expansion (PEX-a), copper-crimp, stainless-clamp or push-fit fittings, or use electrofusion only on the uncrosslinked skin of specialty products.
What surface finishes work on PEX?
No paint or plating adheres without corona/flame treatment; surfaces are matte and colour is provided by masterbatch (red/blue/white/black) rather than coating.
Can PEX be formed, bent or molded?
Extruded and cross-linked in-line (Engel/Sioplas) or post-irradiated; PEX-a can be reformed and shrunk back with a heat gun (shape memory), other types bend cold to ~6–8× OD with support bends.
What is the maximum service temperature of PEX?
PEX is rated for continuous use to about 95°C (203 °F), and briefly to 110°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does PEX cost?
PEX is a standard-cost polymer ($$), cheaper than about 72% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.