EMS-Grivory Grilamid TRVX-50X9 nat is designated under ISO 1043-1 as PAMACM12-GF50. The designation denotes a polyamide synthesised from a cycloaliphatic diamine, MACM, and dodecanedioic acid, compounded with a nominal 50% glass fibre by weight. The “nat” suffix indicates natural colour. In the filled form the material is opaque despite the amorphous nature of the MACM12 matrix. Manufacturer literature lists density at 1.57 g/cm³ to ISO 1183, dry-as-molded tensile modulus of 16,000 MPa at 1 mm/min to ISO 527-1/-2, and dry tensile stress at break of approximately 170 MPa. Because the polymer is amorphous, no crystalline melting point is reported in ISO 11357 DSC analysis; the glass transition and Vicat softening point govern the upper thermal range. Published water absorption at 23°C and 50% RH is approximately 1.2% to ISO 62. These values are lot-average typicals, not specification limits.

Lot release usually includes melt volume-flow rate to ISO 1133-1:2022, moisture content to ISO 15512, and tensile modulus on dry-molded specimens. The melt volume-flow rate is used to control batch-to-batch processability. If incoming MVR shifts outside the agreed control window, screw recovery time and nozzle pressure can vary even with the same barrel temperature profile. Glass content is verified by ash content to ISO 3451-1; a 50% nominal glass loading yields an ash content close to 50% after correction for sizing and inorganic residues.

How Does the MACM12 Backbone Lower Moisture Uptake and Property Drift?

At 23°C and 50% RH, semicrystalline PA66-GF50 materials typically absorb 1.5%–1.8% moisture. Grilamid TRVX-50X9 nat absorbs approximately 1.2%. The difference occurs because the MACM12 repeat unit contains fewer amide groups per unit mass than PA6 or PA66, and the cycloaliphatic diamine reduces the free volume available for hydrogen-bonded water clusters. The mechanical consequence appears in tensile modulus retention. The dry 16,000 MPa value falls to about 15,000 MPa after conditioning to equilibrium at 50% RH, a decline of roughly 6%. PA66-GF50 grades commonly lose 10%–15% modulus over the same conditioning window. Dimensional response remains anisotropic because glass fibres constrain hygrothermal expansion differently in flow and transverse directions. Moisture uptake increases dimensions primarily in the transverse direction. Parts machined after molding should be stored at controlled humidity before final dimensional inspection. For round-robin validation, conditioning per ISO 1110 followed by 24 h at 23°C/50% RH is routinely used. Published data on creep at elevated humidity for this specific configuration are limited; designers should request long-term creep curves if static loads above 30 MPa are applied at 60°C.

Injection molding begins with desiccant drying at 80°C for 4–8 h. A dryer dew point of ≤ -30°C is typical; the target pellet moisture is ≤0.08%. Open hopper exposure to ambient air above 60% RH should not exceed 30 min unless a dry-air hopper is used. Barrel temperatures are set to a flat or slightly reverse profile: rear 250–270°C, centre 260–280°C, front 260–270°C, nozzle 250–280°C. Nozzle melt temperature below 250°C increases viscosity and may cause short shots in wall sections below 1.2 mm. Melt temperature above 300°C or residence times longer than 8 min at 270°C should be avoided. Since the matrix is amorphous, no crystallisation plateau exists; screw recovery can be rapid, but shear heating from the fibres becomes the primary control variable. Mold temperature is typically 60–100°C. Higher mold temperatures reduce frozen-in orientation and improve surface replication but do not change a crystallisation shrinkage value. For precision parts, mold temperature is held within a ±5°C range across cavities to limit differential solidification stresses.

Fiber attrition is controlled by back pressure, screw speed, and nozzle geometry. Back pressures above 5 MPa hydraulic and screw surface speeds above 0.3 m/s can reduce average fibre length from a gently plasticated 250–350 µm to below 150 µm. Short-term tensile modulus remains nearly unchanged, but Charpy notched impact energy may decline by 20%–30%. Screw L/D 20–22, compression ratio 2.0–2.5, and a shut-off nozzle with a flow-channel diameter of at least 3.5 mm for small shot weights limit additional fibre breakage. Injection pressure is typically held below 1,000 bar machine pressure; holding pressure is set at 50%–70% of injection pressure and held until gate freeze-off. For gates with land thickness of 1 mm or less, packing time of 2–3 s per millimetre of nominal wall is often sufficient. Vent depths are kept below 0.02 mm to avoid flash while allowing air evacuation. In multi-cavity tools with more than 8 cavities, cavity-to-cavity weight variation should be held below 0.5% to maintain consistent glass orientation and mechanical properties. Regrind ratios above 30% are not recommended for load-bearing parts unless the regrind is dried and fines are removed, because the recycled fraction shifts fibre-length distribution toward shorter fibres.

Warpage prediction for glass-reinforced amorphous polyamide requires fibre-orientation coupling. The flow-direction coefficient of linear thermal expansion is typically lower than the transverse value; published data for GF50 polyamides often show transverse CTE values in the range of 2–3 times the flow-direction value. Moisture-induced expansion shows a similar anisotropic ratio. Finite-element solvers that treat the material as isotropic will underpredict post-conditioning flatness error by 30%–50%. When tolerances are below 0.2 mm on a 100 mm length, process development should include a design-of-experiments that varies mold temperature and holding time, with warpage measured after ISO 1110 conditioning rather than immediately after ejection.

When a Multi-Gated Tool Places Weld Lines in Force-Bearing Sections

Weld-line strength is a critical processing boundary in any GF50 system. Double-gated plaque testing to ISO 527-2 on 50 wt% glass-reinforced polyamides routinely shows weld-line tensile strength 50%–60% lower than the no-weld reference. For PAMACM12-GF50 natural, mold-filling simulation can be used to shift knit lines away from stressed ribs or bosses; where this is not possible, the design stress at the weld should be lowered by at least the same factor. Mold temperatures of 80–100°C and injection speeds above 200 mm/s may improve weld-line mechanical response, but published data for this exact MACM12-GF50 formulation are limited. Asymmetric gating in flat articles with length-to-thickness ratios above 150:1 can produce persistent post-conditioning warpage because flow-direction and transverse-direction mechanical properties differ. Sequential valve gating is preferred over single-edge gating when flatness after moisture conditioning must remain below 0.3% of part length. Ribs and bosses near gate locations generate local fibre orientation and sink marks that packing pressure cannot fully remove; rib thickness should remain below 60% of the adjacent wall to limit sink depth and differential shrinkage. If bosses are load-bearing, a support gusset or metal insert is preferred over a thick unfilled boss volume because glass fibres do not selectively reinforce thick sections.

Within the EMS-Grivory TRVX family, the 50X9 designation denotes the 50% glass fibre level. Lower-filled variants such as TRVX-30X9 are specified where lower density or higher elongation is required. Manufacturer grade charts show dry tensile modulus increasing from roughly 9,000 MPa for a 30% glass-filled MACM12 grade to 16,000 MPa at 50% glass, while tensile strain at break falls from approximately 5% to 3%. Compared with an unfilled transparent Grilamid TR 90, the GF50 grade raises tensile modulus by a factor of about 5 but eliminates optical transparency and reduces unreinforced ductility. Against PA12-GF50, the MACM12 backbone generally offers higher glass transition temperature and lower moisture uptake, while PA12-GF50 can retain more ductility at sub-zero temperatures; low-temperature impact should be verified by ISO 179/1eA at the application temperature. Against PA66-GF50, the MACM12 grade is selected where moisture-induced dimensional movement and stiffness loss are the dominant risks, not necessarily where peak heat deflection temperature is required.

Applications with validation histories include structural brackets, sensor housings exposed to damp-heat cycling, and precision pump carriers. Qualification programmes often combine ISO 188 hot-air aging at 120°C or 150°C depending on underhood classification, IEC 60068-2-30 damp-heat cycles, and residual tensile testing to ISO 527-2. The lower moisture uptake relative to PA6-GF50 or PA66-GF50 is the reason the grade appears in components that must pass post-conditioning dimensional checks. The material is not intended for continuous exposure to acidic hydrolysis above 80°C or to hot water above 90°C without part-level assessment. Solvent and fuel resistance should be evaluated per ISO 175 using the actual fluid mixture, because oxygenates and aromatic constituents can shift the response of amorphous polyamides. Long-term UV exposure of the natural grade can degrade surface appearance and fracture resistance; outdoor parts require UV-stabilised black or coated variants unless hidden from direct sunlight. For applications requiring heat deflection above 240°C, a semicrystalline PPA GF50 or PPS GF50 is often substituted. Published data for long-term tensile strength retention at 150°C for this specific grade are limited; short-term heat deflection temperature is not a substitute for long-term aging data.

The following standards are commonly referenced in part qualification for PAMACM12-GF50: