Evonik VESTAMID® LC-GF30 NC is a natural-colour, glass-fibre-reinforced polyamide 12 injection-moulding compound. The material is identified in ISO 1043 notation as PA12-GF30, with the GF30 marking indicating a nominal glass-fibre content of 30% by mass and NC indicating the uncoloured formulation. The grade is typically selected where lower equilibrium moisture uptake, lower density, and better low-temperature toughness are required than can be obtained from PA6 or PA66 glass-fibre compounds. Representative dry-as-moulded values include a density of 1.23 g/cm³ to ISO 1183-1:2019, a tensile modulus of 6,200 MPa, a tensile stress at break of 95 MPa, and a tensile elongation at break of 4–6% tested to ISO 527-1/-2:2019. These values are not specification limits; they are typical datasheet values for natural PA12-GF30 compounds of this class and should be confirmed against the current manufacturer datasheet for the LC-GF30 NC grade.

Property Baseline for Dry-As-Moulded Test Coupons

The following values are reported for dry-as-moulded test specimens prepared according to the relevant ISO specimen dimensions and conditioning protocols. They are included to establish the baseline for engineering calculations rather than as a replacement for lot-specific test data.

Drying is the first processing boundary. VESTAMID LC-GF30 NC is a hygroscopic compound; surface moisture at the granulate bed is not representative of core moisture. A desiccant dryer with a closed-loop dew point below -30°C and a granulate inlet temperature of 80°C is recommended until residual moisture is below 0.1% by mass. Typical drying time is 4–12 hours, but this is a throughput-, bed-depth-, and initial-moisture-dependent variable. At ambient conditions above 60% RH, the drying requirement is not optional: hopper dryers without a desiccant wheel can hold the granulate at an equilibrium moisture above 0.2% and fail the threshold. Moist granulate processed above 220°C undergoes hydrolytic chain scission; the practical indicators are splay, silver streaks, gas porosity, part surface roughness, and a measurable loss in tensile stress at break. The damage is irreversible in the melt and cannot be corrected by boosting holding pressure.

In the plasticating unit, screw geometry should provide moderate shear and minimised fibre attrition. A three-zone screw with an L/D of 18–25:1 and a compression ratio between 2.0:1 and 2.5:1 is generally suited for PA12-GF30. High-compression screws above 3.0:1 may increase melt temperature gradients and fibre breakage, causing tensile modulus and impact regression. Shallow feed-zone depths are preferred for uniform granulate bed transport; grooved feed sections can localise pressure but are not universally required. Back pressure should be set at 20–50 bar hydraulic, depending on screw diameter and shot capacity. Elevated back pressure above 60 bar improves homogenisation but increases shear heating and fibre length reduction. Fibre length after plastication is typically lower than the original glass strand length; the residual fibre length distribution determines the plateau of the dynamic modulus and notched impact response.

Melt temperature should remain in the 220–250°C band, with the upper boundary set by hydrolysis and thermal decomposition rather than by short-term viscosity. At melt temperatures above 260°C, residence times should be restricted to a few minutes; the maximum practical barrel residence time at 250°C is approximately 10 minutes, but the exact threshold depends on moisture, oxygen, and machine size. Mould wall temperature is normally 40–80°C. Below 40°C, thin-wall parts may exhibit high frozen-layer orientation, reduced crystallinity, and lower surface quality; above 80°C, cycle time increases without substantial mechanical benefit unless the part is exposed to post-mould annealing. The transition from flow-controlled to packing-controlled solidification occurs close to the gate freeze time; cushion and hold pressure must be set to maintain pressure through this transition. A cushion of 2–4 mm and a hold-pressure profile of 60–80% of peak injection pressure are typical starting values, but gate geometry and part thickness override generic settings.

How Do Fibre Orientation and Moisture Absorption Govern Dimensional Stability?

Fibre orientation is controlled by gate location, part thickness, melt velocity, and the frozen-layer formation during injection. In thin-walled sections the fibres align preferentially in the flow direction, producing higher longitudinal stiffness and lower shrinkage; transverse fibre orientation is less effective and typically exhibits higher shrinkage. For this grade, mould shrinkage determined on plaques per ISO 294-4 is commonly reported as 0.1–0.2% flow-direction and 0.3–0.4% transverse. The anisotropic shrinkage is not a defect but a design variable; weld lines, abrupt thickness changes, and multi-gate layouts generate orientation mismatches that can reduce the local tensile stress at break by more than 30% compared with the ISO tensile specimen value when a weld line is present. Tool designers compensate by moving gates to low-stress regions, adding flow leaders to reduce stagnation, or adjusting hold pressure to influence packing and fibre orientation relaxation.

Injection moulding of glass-reinforced materials creates a layered orientation distribution across the wall: a frozen skin, a highly oriented sub-skin, and a more random core. The skin/core ratio changes with part thickness. Thin sections below 1.5 mm are dominated by oriented layers, producing higher tensile modulus in the flow direction and more anisotropic shrinkage. Thick sections above 4 mm develop a larger core with lower orientation and more isotropic shrinkage. The consequence is that the same material can display different effective shrinkage on the same part if wall thickness changes abruptly from one zone to another. Differential shrinkage generates warpage at thickness transitions, ribs, and bosses. For PA12-GF30 the difference between flow and transverse shrinkage is commonly 0.1–0.3 percentage points; on a 200 mm feature this corresponds to 0.2–0.6 mm dimensional variation, which is unacceptable in precision housings without tool compensation.

Moisture absorption is the second dimension-stability factor. PA12 has a lower equilibrium water uptake than PA6 and PA66. Saturation to ISO 62:2008 is approximately 1.0–1.2% at 23°C in water, while conditioned exposure at 23°C and 50% RH typically produces 0.6–0.8% moisture content. Because the glass fibre does not absorb water, the absolute swelling is lower than unreinforced PA12. Dimensional change from dry to equilibrium at 50% RH is usually below 0.15% in the flow direction and 0.25% in the transverse direction. This is markedly lower than the 0.5–1.0% moisture-induced dimensional change that can occur with PA6-GF30 and PA66-GF30 systems in humid air. The water uptake also reduces the glass transition from the dry state toward subambient; for PA12 this shift is less operationally significant than the larger absorption-driven plasticization of shorter-chain polyamides.

Fibre orientation also affects weld lines. When two melt fronts converge, the fibres do not bridge the weld plane effectively; the weld line region has local fibre depletion and orientation perpendicular to the load path. The resulting weld-line tensile stress at break can be reduced by more than 30% and elongation at break by more than 50% compared with the base material values shown in ISO specimens. Gate location should move weld lines away from load-bearing geometry or, where unavoidable, the weld line should be crossed by post-mould features such as ribs or gussets that carry part of the load. Production-scale failure mode is usually brittle fracture along the weld line, not bulk material yielding. This failure mode is not visible on the datasheet but is usually the controlling factor in part qualification.

When the Selection Benchmark Moves to PA6 and PA66 Glass-Fibre Compounds

The primary differentiator is moisture absorption. In humid or wet service, PA6-GF30 and PA66-GF30 absorb enough water to shift glass transition, reduce stiffness, and increase dimensional movement. PA12-GF30 absorbs approximately one-fifth of the water of PA6-GF30 at saturation. This is not a marginal difference when the application includes a snap-fit or a bearing clearance: a PA66 component that expands by 0.8% in humid air can lose dimensional clearance that a PA12 component would retain. The lower density of PA12-GF30 also provides mass reduction of roughly 8–10% relative to PA66-GF30 for the same part volume. This is relevant in automotive or sporting goods where part mass is directly counted.

Mechanical trade-off: PA6 and PA66 glass-fibre grades are stiffer and stronger in the dry state, but that comes with processing and environmental penalties. Melting temperatures are higher: around 220°C for PA6 and 260°C for PA66 versus 176°C for PA12. Injection moulding of PA66-GF30 requires higher melt and mould temperatures, often with tool temperatures above 80°C to control crystallinity; PA12-GF30 can be moulded at 40–80°C, reducing energy input and cycle time. The lower melt temperature also reduces thermal stress in hot-runner systems and allows co-moulding with lower-temperature seals or inserts in some multi-component processes.

At subzero temperatures, PA12-GF30 shows a broader ductile response than moisture-conditioned PA66-GF30. The aliphatic C12 monomer sequence of PA12 results in lower amide group concentration per unit chain length; this lowers water affinity and shifts the ductile-to-brittle transition in impact to lower temperatures. The trade-off is lower dry heat resistance: PA12-GF30 is not a substitute for PPA-GF30 or PPS-GF30 in underhood parts that must withstand continuous exposure above 150°C or repeated hot oil exposure at 170°C. The material should be specified with a defined continuous-use temperature and fluid-exposure protocol; published data for this specific grade under all OEM fluid combinations is limited, and component-level testing is required.

In automotive fuel and vapour-management components, PA12-GF30 is used for quick connectors, line clips, sensor housings, and structural brackets where low fuel permeation and road-salt resistance are required. Fuel-permeation performance is not an intrinsic ISO datasheet property; it is measured on finished parts using permeation cells and reference fuels such as CE10 or aggressive alcohol-containing test fuels. The material's resistance to zinc chloride and other road de-icing salts is a key factor in underbody applications. PA12 is known for resistance to stress cracking in the presence of zinc chloride, but glass reinforcement introduces local stress concentrations at weld lines and gate areas; component-level validation to OEM cold-salt spray standards is necessary.

Pneumatic and hydraulic tube fittings, cable protection, and industrial housings use the material because of vibration tolerance, lower moisture uptake, and easier processing. In compressed-air systems, PA12-GF30 reduces water absorption compared with PA6-GF30 and therefore maintains better dimensional accuracy of thread forms and sealing lands. The material is not recommended for continuous exposure to hot strong acid, concentrated sulfuric acid, or high-pressure steam above 100°C without explicit testing, because the polyamide backbone can hydrolyze under acidic or prolonged aqueous conditions. For UV-exposed exterior components, the NC natural grade must be stabilised or painted; the unfilled natural formulation is not a UV-resistance package. Published data for this specific configuration under long-term UV weathering is limited, and outdoor qualification should use an appropriate carbon black or UV-stabilised grade. Regulatory status should be confirmed against current REACH candidate lists and RoHS 2011/65/EU annexes; the datasheet alone is not a compliance certificate.