PPA: Properties, Uses & Cost Guide
Tensile data verified against MatWeb.com database & manufacturer datasheets · Last updated July 2026
Published: 2026-05-31
Polyphthalamide (PPA) is a semi-aromatic high-temperature nylon that bridges the gap between standard aliphatic nylons (PA66, PA6 — HDT ~65-85°C) and ultra-high-performance thermoplastics (PEEK, PEI — cost 5-10× PPA). The aromatic diacid...
Polyphthalamide (PPA) is a semi-aromatic high-temperature nylon that bridges the gap between standard aliphatic nylons (PA66, PA6 — HDT ~65-85°C) and ultra-high-performance thermoplastics (PEEK, PEI — cost 5-10× PPA). The aromatic diacid component (typically terephthalic acid and/or isophthalic acid comprising >55% of the diacid content — this is what makes it a 'polyphthalamide') raises the glass transition temperature to 125-135°C (vs 50-65°C for PA66) and the melting point to 310-325°C (vs 255-265°C for PA66). With 30-50% glass fiber, PPA achieves an HDT of 270-285°C at 1.82 MPa — approaching PEEK territory at one-third to one-fifth the material cost.
PPA's dominant application is automotive under-hood components: thermostat housings, coolant pump impellers, charge-air cooler end caps, and EGR valve components exposed to 130-180°C coolant/glycol and hot engine air. PPA resists long-term glycol/water aging significantly better than PA66 (which hydrolyzes and embrittles above 130°C in coolant). It also provides excellent resistance to road salt (CaCl₂, NaCl solutions — which cause stress-corrosion cracking in PA66), automotive fluids (oil, transmission fluid, power steering fluid), and biodiesel exposure.
Processing Warning: PPA requires mold temperatures of 120-170°C (oil-heated molds — water-heated max 95°C is too cold). Inadequate mold temperature produces an amorphous skin layer that post-crystallizes in service, causing dimensional change, warpage, and loss of mechanical properties. PPA absorbs moisture MORE SLOWLY than PA66 (aromatic backbone reduces water affinity) — but still requires drying to <0.05% moisture (80°C for 4-8 hours, desiccant dryer) before processing. Wet PPA hydrolyzes at melt temperature, same failure mode as all nylons.
Recommended Applications
PPA is commonly specified for:
⚠ Not Recommended For
PPA is not recommended for:
- Moisture-critical dimensional applications without post-molding conditioning (nylon absorbs up to 8% moisture, changing dimensions 0.5-2%)
- Strong acid or oxidizing environments (mineral acids attack nylon; use PVDF or PTFE)
- Electrical insulation in humid environments (moisture absorption degrades dielectric properties)
Selection & Application Guide
Nylon (PA6/PA66) is the workhorse engineering plastic — offering the best balance of mechanical strength, toughness, wear resistance, and cost for general industrial applications. Choose PA66 over PA6 when higher temperature resistance and stiffness are needed; choose PA6 when impact resistance and flexibility matter more. Both absorb moisture significantly (2-3%), which affects dimensions and properties — consider this in your design.
Real-World Applications
Glass-filled PA66 (30% GF) provides the temperature resistance (HDT 255°C at 0.45 MPa), stiffness, and under-hood chemical resistance for engine covers and air intake manifolds at 4-8× lower cost than PEEK.
Cast nylon (PA6) provides quiet operation, inherent lubricity, and wear resistance for gears, sprockets, and bearing surfaces in conveyor and packaging equipment.
PA66 with flame retardant additives meets UL94 V-0 for electrical connectors and terminal blocks at much lower cost than high-temperature alternatives.
PA6/PA66's combination of strength, flexibility, and weatherability makes it the universal material for cable ties, zip ties, and plastic fasteners in construction and electrical installations.
Processing & Cost Considerations
Manufacturing Tips
- Nylon is hygroscopic and must be thoroughly dried before processing (80-100°C for 4-6 hours for PA6, 80°C for 3-4 hours for PA66). Moisture above 0.2% causes splay marks and reduced molecular weight due to hydrolysis. Use dehumidifying dryers for consistent results.
- Nylon's moisture absorption affects dimensions — parts can grow 0.5-1.0% in length after conditioning to 50% RH. Design molds to account for post-molding dimensional changes, or specify condition the parts before critical assembly operations.
- Glass-filled nylons (30% GF) require hardened mold surfaces (P20 or H13 steel) and hardened screw tips due to abrasive wear. Expect 2-3× faster mold wear compared to unfilled nylon processing.
Nylon is among the most affordable engineering plastics at $3-8/kg for unfilled grades and $6-15/kg for glass-filled grades. This 10-30× cost advantage over PEEK makes nylon the default choice for the vast majority of mechanical applications below 120°C. When higher temperature resistance is needed, consider PA46 (Stanyl, $15-25/kg) or PPA ($12-25/kg) before jumping to PEEK.
Technical Properties
| Density | 1.35-1.52 g/cm³ (depending on glass loading) |
|---|---|
| Tensile Strength | 200-240 MPa (30-50% GF) |
| Melting Point | 310-325 °C |
| Shrinkage Rate | 0.3% (50% GF) |
| Flexural Modulus | 12-17 GPa (30-50% GF) |
| Hdt | 280 °C at 1.82 MPa (50% GF) |
| Continuous Service Temp | 180 °C |
Engineering Tool: Shrinkage & Cost Estimator
Calculate part weight, mold cavity dimensions accounting for shrinkage, and material cost — all locally in your browser.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Solvay Amodel | |
| BASF Ultramid Advanced | |
| DuPont Zytel HTN | |
| EMS Grivory HT |
Frequently Asked Questions
What is the difference between PA6 and PA66?
PA66 has a higher melting point (260°C vs 220°C for PA6), higher stiffness, and better chemical resistance. PA6 has better impact resistance, better surface finish, and faster molding cycle times. For most structural applications above 80°C, PA66 is preferred. PA6 is chosen for its toughness and lower cost in less demanding applications.
How does moisture affect nylon properties?
Moisture acts as a plasticizer in nylon — conditioned (50% RH) PA66 has 50% lower tensile strength than dry-as-molded but 2-3× higher impact strength. This means dry nylon is strong but brittle; conditioned nylon is tougher but weaker. Always specify whether mechanical properties are dry or conditioned for your application.
Can nylon be used for food contact?
Yes. Specific PA6 and PA66 grades comply with FDA 21 CFR 177.1500 for food contact. Natural (unpigmented) grades are most commonly certified. Glass-filled and flame-retardant grades may not be compliant — verify with the manufacturer. Nylon is widely used in food processing machinery components.
Is nylon resistant to UV exposure?
Unprotected nylon degrades under UV exposure, losing tensile strength and becoming discolored. For outdoor applications, specify UV-stabilized grades with carbon black or hindered amine light stabilizers (HALS). Carbon black provides the best UV protection but limits color options. HALS allow lighter colors with moderate UV resistance.
What is the difference between extruded and cast nylon?
Extruded nylon (PA6 or PA66) is produced by melt extrusion and has consistent properties. Cast nylon (PA6G, also called MC nylon) is produced by anionic polymerization in a mold, yielding higher molecular weight and better mechanical properties — approximately 20% higher tensile strength and 30% better impact resistance. Cast nylon is used for large-diameter rods, tubes, and custom shapes.
Related Diagnostics & Materials
PEEK Polyetheretherketone: High-Performance Polymer...
Polyetheretherketone (PEEK) is a colorless organic thermoplastic polymer in the polyaryletherketone (PAEK) family,...
Ultem PEI (Polyetherimide): High-Temperature Amorphous...
Polyetherimide (PEI), best known by Sabic's trade name Ultem, is an amorphous high-performance thermoplastic...
PTFE Teflon: Ultimate Chemical Resistance & Low-Friction...
Polytetrafluoroethylene (PTFE), widely known by the trade name Teflon, is a fluoropolymer with the lowest...
PPS Ryton: Polyphenylene Sulfide High-Temp...
Polyphenylene sulfide (PPS), best known by Solvay's trade name Ryton, is a semicrystalline high-performance...
LCP Vectra: Liquid Crystal Polymer for Micro-Molding &...
Liquid Crystal Polymer (LCP), best known by Celanese's trade name Vectra, is a unique class of thermotropic...
Vespel Polyimide: Extreme-Temperature Polymer for...
Polyimide (PI), commercially known as DuPont Vespel, is the highest-temperature-rated polymer commercially...
PAI Torlon: Polyamide-Imide Extreme-Performance Polymer...
Polyamide-imide (PAI), commercially known as Solvay Torlon, occupies the performance space between PEEK and...
PES Veradel: Polyethersulfone Transparent High-Temp...
Polyethersulfone (PES), commercially known as Solvay Veradel or BASF Ultrason E, is an amorphous high-temperature...
References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
- ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org