EMS-Grivory Grilamid TRV-4X9 is a 40% glass-fibre-reinforced polyamide 12 (nylon 12) injection moulding grade supplied in dry-as-moulded condition. The grade is based on a PA12 homopolymer matrix with chopped E-glass fibre at a nominal filler mass fraction of 40%. The dry designation indicates residual moisture below 0.10% by weight, normally maintained by moisture-barrier packaging until processing. Density measured according to ISO 1183 is 1.31 g/cm³. Saturated water absorption measured at 23°C according to ISO 62 is approximately 1.1%. The material is specified where unreinforced PA12 lacks stiffness but where the higher moisture uptake and chloride stress-cracking tendency of PA66 create dimensional or chemical-resistance problems.

Representative dry values from the manufacturer technical datasheet for this grade are shown below. These data are generated on standard injection moulded test specimens and may not reproduce directly in parts containing weld lines, variable fibre orientation, or highly stressed thin sections.

Unreinforced PA12 typically exhibits a dry tensile modulus below 2,000 MPa. The 40% glass reinforcement in TRV-4X9 therefore increases stiffness by approximately a factor of five. Tensile stress at break in the dry state is about 150 MPa, but this value is sensitive to fibre orientation at the test cross-section. The 3% strain at break reflects a semi-brittle failure mode in which crack initiation occurs at fibre ends and propagates through the matrix with limited ductility. Notched Charpy impact energy falls from approximately 15 kJ/m² at 23°C to 9 kJ/m² at −30°C. The low-temperature decline is greater than unfilled PA12 but smaller than many glass-reinforced PA66 compounds. In moulded rib structures or across intentionally placed weld lines, load capacity may be 25–40% lower than ISO 527-1/-2 tensile-bar values, and a knock-down factor should be applied during part design.

How does dry-as-moulded conditioning differ from ISO 1110 accelerated conditioning for this product?

Conditioning to moisture equilibrium changes the tensile response substantially. Dry data are generated on specimens sealed immediately after moulding and tested before moisture uptake exceeds 0.10%. When the PA12 matrix absorbs moisture under accelerated conditioning to ISO 1110 or at 23°C/50% RH, the amide groups become plasticised: tensile modulus and tensile strength decrease, while elongation at break and notched impact energy increase. The change is smaller than in PA66 because the PA12 backbone contains fewer amide groups per unit chain length. For a part operating in continuous water contact or in condensation-prone enclosures, dry values will overestimate stiffness and underestimate impact ductility. Conditioned values at the target relative humidity should be obtained from the current EMS-CHEMIE datasheet; if conditioned data are not available, testing should be performed on production parts after moisture saturation.

The selection of this grade for chemical exposure should be based on ISO 175 immersion testing with the actual service fluid. PA12 is less susceptible to stress cracking from chloride salts such as zinc chloride and calcium chloride than PA66. This distinction is relevant for snap-fit connectors, cable ties, and fasteners exposed to road de-icing chemicals. The matrix also resists aliphatic hydrocarbons, hydraulic oils, greases, and many automotive coolants. Strong mineral acids, concentrated oxidising agents, chlorinated solvents, and certain fuel blends containing methanol or ethanol can attack the PA12 backbone or produce surface degradation. The glass-fibre reinforcement does not improve chemical resistance of the matrix and can provide exposed fibre ends that accelerate localised attack under aggressive conditions.

Injection moulding: melt temperature, screw configuration, and pre-drying boundaries

Pre-drying is required when packaging has been opened beyond the supplier dry-handling window. Desiccant drying at 80°C for 4–8 h is typically sufficient to reduce moisture below 0.10%; at ambient relative humidity above 60%, open storage should be limited to 30 min and dryer dew point should remain below −30°C. Residual moisture above 0.15% produces surface splay, gas streaks, and viscosity shifts that alter mould filling. Melt temperature measured at the nozzle is maintained between 250°C and 280°C. Barrel temperatures are distributed from feed throat to nozzle to achieve that melt temperature without exceeding 300°C for more than a few minutes, above which PA12 undergoes thermal degradation and yellowing. Mould temperature is set to 80–110°C to obtain adequate crystallinity and reduce post-mould warpage. On production-scale hydraulic injection moulding machines with clamp force in the 80–120 t range, process stability is generally achieved with shot size at 50–80% of barrel capacity, back pressure of 30–80 bar, and screw rotation of 100–200 rpm. A low-shear three-zone screw with non-return valve and L/D ratio of 20:1 or greater is preferred. Excessive screw speed or high back pressure increases fibre breakage, lowers notched impact strength, and raises coefficient of linear thermal expansion in the flow direction.

Observed production defects in moulded parts include gas streaks at the gate when residual moisture exceeds 0.15%, surface delamination near hot-runner drool, and warpage in flat parts ejected before adequate cooling. Mould temperature below 80°C creates a dull surface and low crystallinity, increasing post-mould dimensional movement. Mould temperature above 110°C extends cycle time without a corresponding strength increase. Holding pressure and packing time should be set using in-mould pressure measurement rather than screw position alone. For wall stock below 1.5 mm, flow length is limited by the filled melt; cold-runner starting values of 1.0–1.5 mm gate diameter and 6–8 mm runner diameter are typical. Hot-runner systems should avoid dead spots because PA12 can degrade into yellowish specks when residence time exceeds 10 min at the upper melt temperature.

Typical applications are located in automotive fluid management, chassis fastening, and fuel-system retention: quick connectors, brake-line clips, sensor housings, and electrical connector backshells. Mould shrinkage in the flow direction is commonly below 0.2%, while transverse shrinkage can reach 0.5–0.7%, depending on gate location and fibre alignment. Multi-gated parts develop weld lines where fibre orientation is disrupted. Across an ISO 527-1/-2 specimen geometry cut from prototype mouldings with deliberately placed weld lines, tensile strength may fall below 75 MPa, and the weld line becomes the preferred crack initiation site. Process simulation is used to position weld lines away from snap-fit retention features and pressure boundaries. Tooling force estimates are often derived from projected area and maximum cavity pressure of 400–600 bar, but tool trials remain necessary because thin walls and high glass content raise filling pressure.

When a PA66 GF40 part is replaced with Grilamid TRV-4X9 in chloride-salt and moisture-sensitive underhood locations

Substitution is not drop-in without thermal review. A PA66 GF40 part may have an HDT/A above 240°C under ISO 75-1/-2, whereas Grilamid TRV-4X9 is limited to approximately 165°C under the same 1.80 MPa load. The PA12 grade, however, has a saturated water uptake of about 1.1%, compared with 5–6% for PA66 GF40. Humid ageing therefore causes less dimensional growth and less tensile modulus depression in the PA12 compound. In chloride-salt environments, the PA12 matrix is less notch-sensitive and less prone to stress cracking in thin-wall snap fits with moulded-in stress. If the application sees continuous metal contact above 150°C or repeated peak exposure above 170°C, PA12 is not an acceptable substitute. For wet and salt-prone but thermally moderate underhood locations, the reduction in moisture sensitivity justifies the substitution. The final decision should be supported by ISO 16750-4 environmental testing on the production part rather than by material datasheet values alone.

Within the wider Grilamid family, TRV-4X9 differs from unreinforced and lower-glass grades in both melt viscosity and failure behaviour. The 40% glass content raises tensile modulus and HDT relative to a 30% glass-reinforced PA12, but decreases flow length and notched impact energy because the molten compound carries a higher filler volume fraction. Compared with a 50% glass-reinforced PA12 analogue, TRV-4X9 generally has lower warpage and better surface appearance in thick sections, but sacrifices some ultimate stiffness. The dry designation also distinguishes the material from preconditioned or moisture-controlled grades; the processor remains responsible for drying before moulding. Suffix codes for colour and heat stabilisation alter melt flow and long-term heat resistance, and the exact lot datasheet should be consulted before tooling decisions.

Thermal ageing boundaries and long-term heat resistance of the dry PA12 GF40 system

The glass transition of dry PA12 is near 50°C, the melting point is 175°C, and the HDT/A is 165°C. These values do not define a safe continuous service temperature. In hot-air ageing, PA12 is susceptible to oxidative chain scission and loss of notched impact long before gross weight loss occurs. For service above 100°C and expected lifetime beyond 10,000 h, ageing tests such as ISO 188 or IEC 60216 should be conducted on moulded test bars or parts. At 150°C, unstressed short-term exposure may be tolerated, but under sustained mechanical load the creep modulus falls rapidly and the part may distort before chemical degradation is visible. Glass reinforcement improves creep resistance compared with unfilled PA12 but does not remove the underlying PA12 thermal limit. Published data for this specific configuration is limited, and the current EMS-CHEMIE ageing curves should be requested for the final grade, colour, and conditioning state.

In electrical connector bodies and sensor housings, the compound is selected for dimensional stability and limited moisture uptake rather than for high-voltage insulation. The material is typically classified UL 94 HB at 0.8 mm; it is not self-extinguishing in the V-0 sense and should not be used where flame-retardant performance is mandatory. Comparative tracking index and glow-wire ignition temperature must be verified according to IEC 60112 and IEC 60695-2-11 on the final part, because glass fibres can reduce tracking resistance relative to unfilled PA12. Surface contamination, mould release, and thermal ageing can further shift electrical performance.