Polyphthalamide (PPA) occupies the niche between conventional polyamides and fully aromatic polymers: it withstands service temperatures at which PA6 and PA66 already deform, and it absorbs almost no water. A structured reference for R&D engineers and process specialists — from the chemistry of the benzene ring to the point where switching to PPA becomes economically justified.
What is polyphthalamide
Polyphthalamide (PPA) is a semi-aromatic thermoplastic polyamide in which at least 55% of the carboxyl groups derive from aromatic dicarboxylic acids: terephthalic or isophthalic. Under the ISO 1043 classification it belongs to the PA group, but technically it is a distinct class between aliphatic polyamides (PA6, PA66, PA12) and fully aromatic aramids. PPA fills the intermediate niche: strength and heat resistance approaching those of high-performance polymers, combined with processability on standard thermoplastic equipment.
Chemistry and structure
Picture PA66 — a linear polymer built from regular blocks of hexamethylenediamine and adipic acid. Now replace the aliphatic adipic acid with aromatic terephthalic acid. A rigid six-membered benzene ring appears between the amino groups, and this has three consequences. First, the melting point rises from about 260 °C (PA66) to 310–320 °C — the aromatic rings increase the thermal stability of the polymer backbone. Second, equilibrium water absorption drops severalfold — the hydrophobic rings displace water from the amorphous regions. Third, modulus and strength typically increase by 20–30% compared with a PA66 of the same formulation.
Pure PA6T would be unprocessable: it melts above its thermal decomposition temperature. Industrial PPA grades are therefore copolymers (6T/66, 6T/6I, 10T/10I), in which part of the terephthalate is replaced with isophthalate or an aliphatic acid to bring the melting point down to a workable 290–330 °C. The principle is the same as rebar in concrete: the aromatic rings are the rigid rods, while the aliphatic segments form the matrix that preserves shape and processability.
Properties
The values below are typical for semi-aromatic PPA compounds; specific figures depend on the filler type and content (glass or carbon fiber, 30–50%) and on the grade. Actual Material Wizard grades with datasheet values are covered in the section below and in their TDS.
| Parameter | Typical value (PPA, reinforced) | Method | Note |
|---|---|---|---|
| Density | 1.3–1.7 g/cm³ | ISO 1183 | depends on filler type/content |
| Melting temperature (Tm) | 290–320 °C | ISO 11357-3 | DSC, higher than PA66 |
| Glass transition temperature (Tg) | ~125–135 °C | DSC | affects dimensional stability |
| HDT at 1.8 MPa | 260–315 °C (glass-filled) | ISO 75-2 | for GF HSL grades |
| Elastic modulus | 12–24 GPa (GF/CF) | ISO 527 | depends on filler |
| Water absorption, 24 h | ~0.25–0.3% | ISO 62 | several times lower than PA66 |
| Water absorption, saturation | ~1.8% | ISO 62 (50% RH) | versus 6–9% for PA6 |
| Flammability | HB to V-0/5VA | UL 94 | V-0 in FR grades, halogen-free |
| Chemical resistance to fuels/glycols | high | ISO 1817 | typical for the class |
How it is produced
The base process is a two-stage melt polycondensation. First, terephthalic acid reacts with hexamethylenediamine in a pressurized autoclave to form a prepolymer (a salt-like fraction). The salt then desorbs water as the temperature is raised and builds up molecular weight. Isophthalate is introduced in the same way for 6T/6I copolymers, as are aliphatic diamines (for example, decamethylenediamine) for PA10T.
Commercial polyphthalamides reached the market in the early 1990s (Amoco Amodel); other producers later expanded the range — Solvay (Amodel), Envalior (ForTii), DuPont (Zytel HTN), BASF (Ultramid Advanced), Mitsui (Arlen). Ukraine has no domestic aromatic polyamide capacity, so processors work with imported resin or locally compounded grades.
Typical applications
- EV battery modules. Housings and components requiring continuous service at 150–180 °C, halogen-free UL94 V-0 flame retardancy and low water absorption. Leading automakers use polyphthalamides extensively in precisely these assemblies.
- Aerospace and critical connectors. Connector housings, brackets and bushings in hot zones near the engine and in air-conditioning systems. PPA enables metal replacement with weight savings.
- Oil and gas equipment. Parts operating in hydrogen sulfide (H₂S) environments at elevated temperatures, where filled PPA is considered as an alternative to metal inserts.
- SMT electronics. Connector and relay housings that pass solder reflow at ~260 °C, where standard PA66 already deforms.
- FFF/FDM 3D printing. PPA CF-based filaments — for parts where PA6/PA66 no longer holds the service temperature (tooling, heat-resistant jigs).
PPA versus its class neighbors
| Property | PA6 | PA66 | PA12 | PPA |
|---|---|---|---|---|
| Tm, °C | ~220 | ~260 | ~178 | 310–320 |
| HDT 1.8 MPa (base), °C | ~70 | ~80 | ~50 | ~125 |
| HDT (+30% filler), °C | ~220 | ~240 | ~145 | ~290 |
| Water absorption (saturation), % | ~9 | ~2.5 | ~1.3 | ~0.3 |
| Modulus +30% CF, GPa | ~22 | ~25 | ~15 | ~27 |
| Relative raw-material cost (approximate) | 1× | ~1.3× | ~2.5× | severalfold higher |
PPA is not a "better polyamide" — it is a different polyamide. In most jobs PA66 GF30 or PA66 CF30 will be cheaper and easier to process. Polyphthalamide starts to pay off when the continuous service temperature exceeds 180 °C; when dimensional stability in humid environments is critical; when the part contacts aggressive chemicals (fuels, glycols, H₂S); or when weight is critical and a CF composite replaces metal.
Industry designations
Under ISO 1043: PA6T/66 is a co-PPA of terephthalate and adipate; PA10T is based on decamethylenediamine. A filler index is often appended: a designation such as "PA6T/66 + CF33" means a polyphthalamide with 33% carbon fiber. Commercial designations may carry modification suffixes: HG (hydrolysis resistance), V0 (halogen-free UL94 V-0), HSL and others — their meaning should be checked against the documentation of the specific manufacturer.
UL94 V-0 flame retardancy in polyphthalamides is achieved with non-halogenated flame retardants (phosphinates, phosphorus–melamine systems). This is critical for the EV segment, where a number of automakers restrict halogenated flame retardants in their internal standards.
Limitations to keep in mind
- High processing temperature. Barrel temperatures are typically 320–340 °C — tens of degrees above PA66. The narrow processing window demands tight control of the temperature profile and melt residence time.
- Pellet moisture sensitivity. Drying before molding is mandatory; residual moisture at high temperatures accelerates hydrolysis and reduces molecular weight.
- Abrasiveness of CF/GF reinforcement. Carbon and glass fiber wear the screw, check ring and hot runner — a wear-resistant configuration should be specified.
- Hot mold. For good surface quality and crystallinity the mold is typically heated to 130–150 °C.
- Cost. The resin is severalfold more expensive than aliphatic polyamides, so the switch must be justified by temperature, chemical-resistance or dimensional-stability requirements.
- Anisotropy. In filled grades, shrinkage along and across the flow direction differs — this affects warpage and requires attention to gate design.
What to verify before launching PPA in serial production
- Pellet moisture before molding and compliance of the drying regime with TDS recommendations.
- Barrel temperature profile and melt residence time — to avoid thermal degradation within the narrow window.
- Mold temperature and its effect on crystallinity, surface finish and dimensional stability.
- Wear of the screw, check ring and hot runner under abrasive CF/GF reinforcement.
- Warpage and geometric stability due to shrinkage anisotropy; gate correction where needed.
- Part behavior after thermal cycling and in humid aging cycles (for critical connectors).
- Raw-material batch consistency and reproducibility of properties from delivery to delivery.
Polyphthalamide in the Material Wizard range
Material Wizard offers several types of polyphthalamide-based materials — from high-temperature glass-filled grades to a rigid electrically conductive compound. Exact properties are given in the TDS of each grade; below are guide values based on datasheet data.
High-temperature glass-filled grades — the Examid® PPA GF HSL line (heat-stabilized long-life): PPA GF33 / GF40 / GF50 HSL. Per TDS — HDT approximately 270–315 °C (rising with glass fiber content 33→50%), tensile modulus typically 11–23 GPa, heat stabilization for long-term service at elevated temperatures. This is the default choice where a part operates continuously at 200 °C and above.
Where flame retardancy is required (EV components, electrical engineering) — FR grades: Examid® PPA GF45 V0 (UL94 V-0, HDT 290+ °C) and Examid® PPA GF30 5VA (top 5VA rating), as well as PPA GF33 V0 IR (V-0, IR-reflective).
For high-stiffness, electrically conductive structural parts — Examid® PPA CF33 X — a carbon-nylon compound: a blend of PA66 and semi-aromatic PPA with 33% carbon fiber. Per TDS: tensile modulus 24 GPa, flexural strength 350 MPa, HDT 180 °C (1.8 MPa), Tm 245 °C, water absorption 0.25%, CTI 750 V, GWFI 750 °C, density 1.29 g/cm³, UL94 HB. Aimed at rigid housings, frames and load-bearing elements with dimensional stability and electrical conductivity, rather than at the maximum temperature class.
Examid® PPA CF33 X PA66/PPA + 33% carbon fiber · modulus 24 GPa · flexural 350 MPa · HDT 180 °C · CTI 750 V · electrically conductive Request supply terms →Buy with delivery across Ukraine: the grades are available in standard packaging; the minimum order quantity is agreed individually. For serial production — drying at 80–100 °C for 2–4 h (dew point ≤ −40 °C, moisture ≤ 0.10%), barrel profile typically 300–325 °C, wear-resistant configuration of machine components for the abrasive fiber.
If PPA is overkill but the maximum stiffness of carbon-nylon is needed, a rational option is Examid® PA66 CF40 — 40% carbon fiber. Per TDS: tensile modulus 30–38 GPa, HDT ~245–255 °C; a more economical alternative where the full temperature class of polyphthalamide is not required.
Examid® PA66 CF40 Carbon-nylon with maximum CF content · modulus 30–38 GPa · HDT ~245–255 °C · aluminum replacement Request supply terms →More grades and properties — in the Material Wizard polyphthalamide product hub. For polyamide basics, see "What is polyamide 6" and "PA66 vs PA6".
5 expert questions about PPA
1. Do you really need PPA, or will a heat-stabilized PA66 GF suffice?
If the continuous service temperature stays below ~180 °C and there are no strict water-absorption requirements, heat-stabilized PA66 GF often solves the task at lower cost. PPA is justified precisely at the edge of the temperature class and where dimensional stability in humid environments is critical.
2. What HDT margin should be kept relative to the service temperature?
HDT is a reference point under a standard load, not a service limit. For mechanically loaded parts it is prudent to keep a margin between the service temperature and the HDT, and creep must always be verified under real operating conditions.
3. Will the existing injection molding equipment cope?
Usually yes, but with caveats: barrel temperatures of 320–340 °C, mold heating to 130–150 °C and a wear-resistant configuration of machine components for the abrasive fiber. If the shop already runs PPS or PEEK, PPA is technologically simpler.
4. How to correctly replace an imported PPA grade with a local one?
Through a protocol: request a sample, run trial molding on an optimized temperature profile, validate geometric tolerances and key mechanical properties on your part. A "by name" substitution without trials is a source of hidden rejects.
5. What are the typical mistakes at the start of a production run?
Insufficient pellet drying (hydrolysis and loss of strength), a mold that is too cold (matte surface, under-crystallization), ignoring shrinkage anisotropy (warpage) and the lack of a wear-resistant configuration for CF/GF reinforcement.
FAQ
How does PPA differ from PA66?
PPA contains aromatic benzene rings in the main chain, which PA66 lacks. This raises the melting point from about 260 to 310 °C, cuts water absorption severalfold and typically increases the modulus by 20–30%. The trade-off is a higher resin price and more demanding processing (higher molding temperatures, sensitivity to pellet drying).
Can an imported PPA be replaced with an MW grade?
It depends on the task. For high-temperature applications MW offers glass-filled Examid® PPA GF33/40/50 HSL (HDT ~270–315 °C) and flame-retardant PPA GF45 V0 (UL94 V-0) / GF30 5VA. For rigid electrically conductive parts — Examid® PPA CF33 X (a PA66/PPA blend with 33% carbon fiber, modulus 24 GPa, CTI 750 V). Before switching — the standard procedure: request a sample, run trial molding, validate tolerances and key properties on your part. Ask our specialist — we will suggest a grade and a validation protocol.
Does molding PPA require special equipment?
Standard thermoplastic injection molding equipment copes, but with caveats. Barrel temperatures of 320–340 °C are higher than for PA66, so the screw material must be wear-resistant. The mold is heated to 130–150 °C, otherwise the part surface will come out matte.
Why is the water absorption of PPA so low?
The benzene rings in the aromatic blocks of polyphthalamide are hydrophobic. Water molecules, which in ordinary PA66 "settle" between the amide groups, do not find enough unoccupied hydrogen bonds in PPA for adsorption. This makes the material dimensionally stable in humid environments — critical for optical and precision connectors.
Is PPA worth using for ordinary automotive parts?
Usually not. For engine-compartment parts operating at 130–180 °C, heat-stabilized PA66 GF30 is more economical. PPA starts to pay off when the temperature continuously exceeds 200 °C or when minimal dimensional shift in humid air is required.