Noryl vs ABS: Dimensional Stability, Heat, and Electrical Properties

Noryl (the SABIC trade name for modified polyphenylene oxide, or PPO/PPE blends) and ABS (acrylonitrile butadiene styrene) are both opaque, medium-stiffness thermoplastics widely used for enclosures, housings, and structural parts. ABS is the more familiar and lower-cost material — easy to machine, easy to glue and paint, and adequate for a wide range of applications to about 180°F (82°C). Noryl commands a price premium but earns it with superior dimensional stability across humidity, a higher continuous use temperature of 220°F (104°C), and better electrical insulation properties. The choice between them is driven by the combination of operating temperature, humidity exposure, and whether electrical performance is in the design specification.

TL;DR

• Noryl (PPO) is rated for continuous service to 220°F (104°C); ABS is rated to 180°F (82°C).
• Noryl absorbs virtually no moisture (0.06%); ABS absorbs 0.2–0.4%, leading to greater dimensional change in humidity swings.
• Noryl has lower dielectric constant and dissipation factor — better electrical insulation performance at high frequency.
• ABS is easier to bond with solvent cements and accepts paint without priming in most cases; Noryl requires surface preparation before painting.
• ABS is typically 20–40% less expensive than Noryl in equivalent stock forms.
• Noryl is the right call for electrical enclosures, instrument housings, and parts that must hold dimension across humidity.
• ABS is the right call when cost leads, temperature is moderate, appearance finish is needed, and gluing or painting is part of assembly.

Side-by-Side Specifications

When to Choose Noryl (Modified PPO)

Electrical Enclosures and Instrument Housings

Noryl's combination of low dielectric constant (2.65–2.75) and very low dissipation factor (0.0006–0.002 at 1 MHz) makes it a precision electrical insulator with stable properties across frequency and temperature. In high-frequency circuit housings, radar components, antenna structures, and precision instrument cases, the electrical property advantage over ABS is measurable and meaningful. Where ABS grades lose dielectric properties above 100°F, Noryl maintains them to 220°F.

Parts That Must Hold Dimension Across Humidity Swings

Noryl's 24-hour water absorption of 0.06% is among the lowest of any engineering thermoplastic. Over a wide relative-humidity swing — from a dry winter interior to a humid summer environment or a condensing outdoor application — a Noryl part changes dimensions by a fraction of what an equivalent ABS part does. For precision enclosures where gasketed lids must seal consistently, for instrument housings where component fits depend on plastic dimensional stability, and for any outdoor part that cycles through dew and dry, Noryl's moisture indifference is a real engineering advantage.

Higher-Temperature Applications Up to 220°F

The 40°F gap between Noryl's HDT (220°F) and ABS's (~185°F) matters in applications near heat sources: motor housings, enclosures mounted adjacent to heat-generating electronics, parts that see solar gain on a dark-colored outdoor installation, or assemblies that are autoclaved or heat-sterilized. ABS will distort under these conditions; Noryl will not.

Flame-Retardant Designs Without Halogenated Additives

Several Noryl grades achieve UL94 V-0 or V-1 through the inherent flame-resistance mechanism of the PPO chemistry rather than through added halogenated or brominated compounds. For products sold in markets with stringent RoHS or REACH requirements, or where halogen-free flame retardancy is specified, Noryl grades offer a compliant path that standard FR-ABS does not provide cleanly.

When to Choose ABS

Cost-Sensitive Enclosure and Housing Applications

ABS is one of the highest-volume engineering thermoplastics in the world, and its stocking and pricing reflect that volume. When the operating conditions fall within ABS's capability — temperature to 180°F, indoor or protected outdoor use, non-precision electrical insulation — there is no technical justification for the Noryl premium. ABS rod, sheet, and tube are broadly available with short lead times, and the price advantage compounds when large quantities are involved.

Parts That Will Be Painted or Finished

ABS has exceptional affinity for paints, lacquers, and most decorative finishes without surface preparation or priming. Consumer electronics, appliance housings, and automotive interior parts specify ABS partly because of this finish compatibility. Noryl requires surface preparation (solvent wiping, light sand, or primer) before paint adhesion is adequate — an additional process step that adds time and cost in a painted-parts operation.

Assemblies Joined with Solvent Cement

ABS bonds exceptionally well with MEK, methyl chloride, and acetone-based solvent cements, producing joints that approach base-material strength with simple application techniques. This makes ABS the natural choice for glued assemblies — display cases, housings assembled from machined blanks, and fabricated boxes where bonded joints are the primary connection method. Noryl's resistance to solvents (a property advantage in chemical environments) works against it here — solvent cements have less effect on Noryl, and joint strength from solvent bonding is lower.

High-Impact Applications at Moderate Temperature

Standard ABS has notched Izod impact strength of 5–10 ft·lb/in, roughly twice the lower end of Noryl's range. Where impact resistance is the primary mechanical requirement — protective housings subject to drops, tool cases, safety enclosures on portable equipment — ABS's toughness advantage may make it the better choice even where Noryl's electrical or temperature properties would otherwise be beneficial.

Specs Head-to-Head

Dimensional Stability and Moisture

This is Noryl's most decisive advantage over ABS. The numbers tell the story: Noryl absorbs 0.06% moisture at equilibrium in 24-hour immersion; ABS absorbs 0.20–0.40%. Over the full relative-humidity range from dry to saturated air, the linear dimensional change in ABS (expressed as the moisture expansion coefficient) can be 3–5× greater than in Noryl. For a 12″ part, the difference between 0.06% and 0.4% moisture absorption translates to roughly 0.004–0.040″ of dimensional change — the difference between a gasketed cover that seals reliably and one that requires adjustment.

Thermal Performance

Noryl's 40°F heat deflection advantage over ABS at 264 psi load is maintained across grades and translates to real-world performance. Enclosures mounted on heat-generating electronics regularly see surface temperatures above 180°F during worst-case load; ABS enclosures can distort at these temperatures, creating fit and sealing problems. Noryl does not. For UL-recognized electrical components, the higher RTI (Relative Temperature Index) of Noryl grades simplifies listing at elevated continuous-use temperatures.

Electrical Insulation

Noryl's dielectric constant of 2.65–2.75 and dissipation factor below 0.002 at 1 MHz place it among the best-performing structural engineering thermoplastics for high-frequency electrical insulation. ABS's dielectric constant of 3.0–3.5 and dissipation factor of 0.006–0.020 are adequate for low-frequency applications but begin to matter in RF and microwave designs. For antenna radomes, circuit housings, and high-frequency connectors, Noryl's lower loss tangent is a measurable advantage.

Machinability

Both materials machine well with carbide tooling. ABS is softer and produces longer chips; flood coolant or air blast is useful for clearing chips in deep pockets. Noryl is slightly stiffer and produces shorter, more manageable chips. Both achieve good surface finishes with sharp tooling at appropriate speeds. Noryl's greater stiffness makes it marginally easier to hold tolerance in thin-wall machined parts because it deflects less under cutting forces.

Cost and Availability

ABS sheet, rod, and tube are broadly stocked commodity items. Expect $1.50–3.00/lb for natural (ivory) ABS sheet depending on thickness and quantity. Black and custom-color ABS sheet is widely available from sign and display distributors.

Noryl sheet and rod carry a premium of 20–40% over ABS, reflecting both the material's higher resin cost and lower production volume. Noryl is most commonly available as natural (beige/tan) or black sheet; rod is available to approximately 4″ diameter from specialty suppliers. Lead times for larger cross-sections or non-standard thicknesses can be 2–4 weeks.

Common Alternatives

• Polycarbonate — higher impact than both, optically clear in sheet form, rated to ~240°F; more expensive than ABS, similar cost to Noryl. See the Noryl vs polycarbonate comparison.
• HDPE — lower cost than ABS, chemically resistant, but lower stiffness and harder to paint/bond. For outdoor structural applications where appearance is not critical.
• Acetal (Delrin) — for machined precision parts requiring better bearing/wear properties than either ABS or Noryl; more expensive, opaque.
• Glass-filled Noryl — for applications needing lower CTE and higher modulus than standard Noryl; trades some toughness for stiffness and dimensional stability.

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