Evonik VESTAMID LC-GF30 BK is a black-pigmented polyamide 12 compound reinforced with 30% by mass short glass fiber. The ISO 1043-1 designation is PA12-GF30. The base polymer is polylaurolactam, which has a lower amide-group density than polyamide 6 or polyamide 66. This structural difference controls moisture absorption, chemical resistance, and low-temperature impact behaviour. The product is supplied in cylindrical pellets and is intended for injection moulding of dimensionally stable technical components. Published data for this exact LC configuration are limited; therefore the typical values cited in this document are drawn from the nearest published VESTAMID L-GF30 BK datasheets and general industrial PA12-GF30 ranges. They are not specification limits and must be verified against the lot-specific certificate of analysis.

Melt processing parameters and pre-drying requirements

Pre-drying is mandatory to a residual moisture content below 0.10% by mass. A closed-loop desiccant dryer with a dew point below -30°C is operated at 80°C for 4–6 h. If a vacuum dryer is used, 80–90°C for 2–4 h is typical. Moisture content is verified by Karl Fischer titration or a calibrated moisture analyzer, not by observation of surface condensation. At a shop-floor temperature of 23°C and relative humidity of 50%, dried pellets can regain sufficient surface moisture to affect surface finish within 20–30 min; hoppers should therefore be closed or blanketed with dry air.

Melt temperature at the nozzle is held between 250°C and 290°C. The preferred set point is 260–280°C. Cylinder zone temperatures are profiled from 240°C in the feed zone through 250–270°C in the compression zone to 270–280°C in the metering zone. Higher melt temperatures above 290°C increase oxidative degradation of the polyamide 12 matrix and can reduce impact strength. Lower temperatures below 250°C increase glass-fiber attrition and can create unmelted particles in thin sections.

Mold temperature is controlled between 60°C and 110°C, with 80–90°C preferred for parts where post-mould shrinkage must be minimized. Mold-temperature variation across the cavity should be kept within ±5°C, because adjacent walls cooled at different rates can differ in mould shrinkage by more than 0.1 percentage point. Holding pressure is set at 50–70% of injection pressure, and holding time is determined by gate freeze; for a 2.0 mm wall, gate freeze often requires 8–12 s with an 80–90°C mould.

A general-purpose screw with a compression ratio of 1.8–2.5 and an L/D ratio of 18–22 is adequate. For glass-filled grades, a bimetallic barrel, hardened screw flights, and check-ring clearance below 0.05 mm are used to control abrasive wear. Back pressure is limited to 50–150 bar. Screw surface speed is limited to 0.5–1.0 m/s to reduce fiber breakage.

During production-scale injection moulding, shot-to-shot cushion variation greater than 2.0 mm can produce visible glass-fiber orientation differences in weld regions and increase notched Charpy scatter by more than 20%. Hot-runner systems with internally heated or externally heated full-flow manifolds are preferred. Dead spots and sharp edges in manifold channels must be eliminated because glass-filled PA12 will form solidified glass-rich deposits that can break away and block gates.

What distinguishes a 30% glass-filled polyamide 12 from PA6 and PA66 compounds?

Polyamide 12 contains fewer amide linkages per unit mass than PA6 or PA66. In water immersion at 23°C, PA12-GF30 reaches saturation at approximately 1.5–2.0% by mass, while PA6-GF30 and PA66-GF30 reach approximately 9.5–10.0% and 8.0–9.0% respectively under the same ISO 62 conditions. This difference is the main reason PA12-GF30 retains a larger proportion of dry-as-moulded tensile modulus and dimensional stability in humid service. However, the heat deflection temperature under 1.8 MPa for PA12-GF30 is typically 165–175°C, which is lower than the 240–260°C range for PA66-GF30. Components exposed to continuous static loads above 150°C in air should not be designed with PA12-GF30 without creep rupture data.

Compared with PA6-GF30, PA12-GF30 generally has lower density and better low-temperature impact. At -30°C, notched Charpy values for PA12-GF30 are typically 9–12 kJ/m², whereas PA66-GF30 frequently falls to 6–8 kJ/m². In fuel-contact applications, PA12-GF30 has superior resistance to zinc chloride road salts and aliphatic diesel fuel. PA66-GF30 may be selected for hot-oil environments above 130°C, where its higher crystallinity provides better creep resistance.

Because fiber orientation governs shrinkage and local modulus, direct substitution of PA12-GF30 into a tool designed for PA66-GF30 may require changes in gate size and location. Fibers oriented parallel to flow raise tensile modulus along that axis but reduce strength across weld lines. Weld-line tensile strength in glass-filled grades is commonly 30–50% lower than the bulk value. Published data for this specific LC configuration is limited; comparative selection should be based on the actual lot-specific datasheet and not solely on generic PA12-GF30 tables.

Dimensional stability, mould shrinkage, and humidity-conditioned property retention

Under ISO 294-4, plaque shrinkage for PA12-GF30 is typically 0.2–0.5% parallel to flow and 0.5–0.9% perpendicular to flow, depending on wall thickness, gate type, melt temperature, and mold temperature. The anisotropy is controlled more by glass-fiber orientation than by polymer crystallinity. Post-mould shrinkage in service at 80°C is generally below 0.1% after 24 h when the part is conditioned. Humid storage at 23°C and 85% RH typically increases dimensions by 0.3–0.6% because water uptake lowers the glass transition and plasticizes the polyamide matrix. Dimensional checks before and after conditioning should be separated by at least 48 h because moisture absorption is diffusion-controlled and thickness-dependent.

Conditioning in boiling water or potassium acetate solutions accelerates moisture uptake but may extract low-molecular-weight polyamide fractions and artificially change surface energy. ISO 1110 is used for accelerated conditioning of polyamides when comparative data are required.

When injection moulding replaces metal in fuel and cooling-system brackets

In automotive fuel and cooling system components, PA12-GF30 is used where metal replacement reduces mass and assembly steps. Quick-connect couplings, fuel rail brackets, coolant thermostat housings, pneumatic valve bodies, sensor housings, and cable conduits are common. Chemical resistance is tested according to ISO 1817 by immersion in reference fuels and coolants at 60°C for 500–1000 h. Typical acceptance criteria include retention of at least 70% of tensile strength and no visible surface cracking. For diesel and biodiesel contact, short-term exposure to B10 diesel is commonly validated. Exposure to methanol-based fuels or high-percentage biodiesel at elevated temperature may require case-specific testing because PA12 can soften and stress-crack in polar fuels. The glass reinforcement reduces creep under constant clamp load but introduces anisotropy. Brackets with long load paths along a weld line should be redesigned with a higher safety factor than unreinforced PA12 or with the gate relocated.

Coolant contact at 100°C for 1000 h in ethylene glycol/water 50:50 is a common validation condition. PA12-GF30 generally retains sufficient tensile strength but may show surface blistering if the glycol degrades and forms acidic by-products. Coolant buffering at pH 7.5–9.0 is recommended. Parts with threaded brass inserts should not be exposed to hot aqueous glycol above 120°C without long-term creep testing because differential thermal expansion between brass and PA12-GF30 can relax insert retention.

The compound resists aliphatic hydrocarbons, mineral oils, greases, diesel fuel, and aqueous zinc chloride solutions at ambient temperature. It is not resistant to concentrated sulfuric acid, formic acid, phenol, cresol, or hydrofluoric acid. Hydrofluoric acid also attacks the glass fiber. Chlorinated solvents and strong oxidizing acids can cause surface etching or environmental stress cracking. For compressed air systems, PA12-GF30 is compatible with oil-mist lubricated air but may hydrolyze after long exposure to pure steam at 121°C. The maximum continuous service temperature in steam should be limited to 90–100°C unless steam resistance is explicitly validated.

Verification of regulatory status and lot-level documentation

The supplier documentation should include a safety data sheet, REACH statement, and lot-specific certificate of analysis with melt volume-flow rate, residual moisture, and spectroscopic identification. This black glass-filled grade is not typically positioned for food-contact or potable-water approvals; separate approval letters are required where those end-uses are specified.

For potable-water or food-contact applications, separate approval letters are required.