HomeБлогCarbon-fiber-filled PA12 (PA12 CF30) for water-contact parts: selection logicExamid® PA12 CF30 for underwater drones: 1.3% water vs 9% in PA6
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02.06.2026
Carbon-fiber-filled PA12 (PA12 CF30) for water-contact parts: selection logicExamid® PA12 CF30 for underwater drones: 1.3% water vs 9% in PA6
Carbon-fiber-filled polyamide 12 (PA12 CF30) is considered for parts in prolonged contact with water and humid environments — propellers and pump impellers, impellers, marine connectors, sensor housings. The key advantage of the PA12 class is low water absorption, which helps maintain geometry and dimensional stability.
What problem the material solves
In parts in constant contact with water, moisture in polyamide acts as a plasticizer: it changes dimensions and reduces the modulus. For thin rotating elements this affects balance and fits. The PA12 class stands out for low water absorption compared with PA6 and PA66, so carbon-fiber-filled PA12 can be a rational choice where dimensional stability in a wet environment matters more than maximum stiffness and heat resistance.
Typical part requirements
Parameter
Target
Why it matters
Water absorption
low
so the geometry does not “drift” between cycles
Dimensional stability in a wet environment
high
balance and fits of rotating parts
Specific stiffness
sufficient for the load
so a thin cross-section holds its shape
Chemical resistance
in the service environment
contact with water, fuel, process media
Surface electrical conductivity
where required
static dissipation, ESD applications
Exact numerical requirements depend on the product and the environment; property values for a grade should be taken from its TDS.
Why PA12 CF30 can be a rational choice
The PA12 class has the lowest water absorption among common aliphatic polyamides, which is typical for this class of materials. This helps maintain dimensions and modulus in a wet environment. Carbon fiber increases stiffness and makes the surface electrically conductive (ESD level), and also reduces shrinkage compared with unfilled PA12, which helps geometric repeatability. PA12 is usually chemically inert in aqueous environments, which is important for parts in prolonged contact with water.
Values are typical for the material classes; exact values — per the grade’s TDS.
Comparison with adjacent materials
PA66 CF30 — usually higher modulus and heat resistance, lower density relative to glass-filled systems, but higher water absorption than PA12; rational where stiffness and heat matter more than water contact.
PA6 CF30 — easy to process and more affordable, but usually with higher moisture sensitivity and lower thermal stability.
PPA CF/GF — a higher temperature class and stability, but more demanding and more expensive processing.
Limitations of PA12 CF30
Stiffness and heat resistance are usually lower than for PA66 CF30 — for highly loaded or hot parts PA12 may lack the margin.
Abrasiveness. Carbon fiber accelerates equipment wear — a wear-resistant tooling configuration may be required.
Drying. Pellets usually need to be dried before processing.
Anisotropy. Properties depend on fiber orientation; gate geometry affects stiffness and shrinkage.
Price. PA12-class materials are usually more expensive than PA6/PA66.
When to choose a different material
If the part operates in air at elevated temperature and maximum stiffness is required, PA66 CF30 is more often the rational choice. If cost is critical and humidity is moderate, PA6 CF30 can be considered. If the operating temperature is consistently high — PPA. The final choice is confirmed by testing on the specific geometry.
What to verify before serial production
pellet moisture content before processing;
part balance and geometric stability;
impact strength at low temperature;
aging in a wet cycle;
wear of the mold, screw and hot-runner system;
batch-to-batch consistency;
behavior after conditioning.
Grade selection with Material Wizard
Material Wizard supplies engineering polymers, performs technical material selection and supports testing. Exact property values for a grade are provided in its TDS.
Material Wizard — engineering polymers, technical material selection and testing support. Locations: Derazhnia and Kharkiv. Buy with delivery across Ukraine — contact our specialist.
Carbon-fiber nylon with a PA12 matrix is a solution for parts in prolonged contact with water: propellers of autonomous underwater vehicles, marine connectors, ATEX equipment. The main advantage is water absorption of 1.3% versus ~9% for PA6.
The problem
Picture the propeller of an autonomous underwater vehicle (AUV) returning to base after 18 hours at a depth of 30 meters. The electric motor housing is not fully sealed — water gradually penetrates the stack around the rotor. This is not “65% humidity”; it is constant immersion at 3 atmospheres of pressure with cold cycles of 4–18 °C.
Standard carbon-fiber nylon with a PA6 matrix absorbs up to 9% water by mass in this regime. The consequences: blade expansion of up to 0.8% in length (which destroys balancing at high rpm); a 35–45% loss of modulus (the blade deflects under load); gradual hydrolysis of the amide bonds — the part ages faster in water than in air. A Ukrainian AUV manufacturer ran into this during field trials in the autumn of 2025: a batch of PA6 CF30 propellers “blossomed” as early as the third deployment.
Technical requirements
Parameter
Value
Why it is critical
Water absorption, 24 h
≤2%
so the blade geometry does not “drift” between sessions
Equilibrium water absorption
≤2.5%
prolonged immersion without modulus loss
Tensile modulus
≥15 GPa
so the blade does not deflect under load
HDT at 1.8 MPa
≥145 °C
next to a motor running at 60–90 °C
Hydrolysis resistance
90 days in water at 70 °C
the standard for marine components
Surface electrical conductivity
<10⁹ Ohm
ESD protection and prevention of galvanic corrosion
Why this specific grade
Examid® PA12 CF30 is a carbon-fiber nylon with a PA12 (polyamide 12) matrix filled with 30% chopped carbon fiber. It combines four key advantages for underwater engineering.
First, the lowest water absorption among aliphatic polyamides. 0.3% after 24 hours in water, 1.3–1.5% at equilibrium. In other words, over 6 months in a lake Examid PA12 CF30 absorbs as much water as PA6 CF30 takes up in a week. This eliminates blade deformation in the immersion–drying–re-immersion cycle.
Second, PA12 is chemically inert in marine and fresh-water environments. It does not hydrolyze in long-term service, is not subject to bacterial attack, and is stable at pH 4–9. For an AUV this means a real service life of 5–8 years rather than 6–12 months.
Third, 30% carbon fiber delivers a modulus of 15 GPa and an HDT of 145 °C — sufficient for a propeller running at 8000–12000 rpm. Plus reduced in-mold shrinkage (2.5–3 times lower than unfilled PA12) — a geometrically stable blade from the first production run.
Fourth, the surface is electrically conductive (surface resistance 10⁵–10⁷ Ohm/square) thanks to the CF. This dissipates static charge during rotation in water and prevents a “polymer–rotor metal” galvanic couple. For an AUV with an anodized aluminum housing this is a distinct advantage.
By class, Examid® PA12 CF30 is comparable to the CF30 grades of Vestamid® and Grilamid® (polyamide 12), produced to our own formulation at a Ukrainian production facility. Certificates — ISO 527, ISO 75, ISO 62; a 90-day hydrolysis map is available on request.
The low water absorption of PA12 maintains blade geometry during prolonged immersion.
The result
After the customer switched propellers from PA6 CF30 to Examid PA12 CF30, the figures changed as follows: blade length change after 7-day immersion — from +0.82% to +0.11%; modulus loss after the 90-day hydrolysis cycle at 70 °C — from −42% to −8%; the service interval — from ~50 hours to 400+ hours. PA12 CF30 pellets cost 2.3–2.5 times more than PA6 CF30, but within the full AUV lifecycle cost structure (where field service is expensive) the switch paid for itself after the second expedition.
Yes, trial batches of Examid® PA12 CF30 from 5 kg are a standard offering. Production lead time is 7–14 business days.
Do you supply with technical support?
Yes: starting molding parameter cards (zone temperatures, mold, hold time), drying parameters (4 h at 80 °C, dew point −30 °C) and gate geometry recommendations for CF materials.
Is an ESD modification (10⁴–10⁶ Ohm) available?
The standard is 10⁵–10⁷ Ohm/square. For stricter ESD requirements — an increased CF concentration with a conductive package, per separate specification.
Material Wizard — engineering polymers with in-house R&D. Warehouse and technical support: Derazhnia (Khmelnytskyi region) and Kharkiv. Buy with delivery across Ukraine — contact our specialist.
