EMS-Grivory Grilamid XE 3997 nat is a natural-colour, short-glass-fibre-reinforced polyamide 12 injection-moulding compound. The material designation according to ISO 1043 can be expressed as PA12-GF30; the suffix “nat” indicates an unpigmented, natural base resin. In supplier literature, the term “Conditioned” refers to specimens brought to moisture equilibrium at 23 °C and 50 % RH under ISO 291 or by the accelerated procedure of ISO 1110, not to the moisture content of pellets at the point of supply. This distinction is necessary because the conditioned state changes the mechanical response in service: absorbed water acts as a plasticiser and lowers stiffness while improving ductility and room-temperature impact. The PA12 backbone provides lower equilibrium moisture uptake than PA6 or PA66, while the short-glass reinforcement increases modulus and reduces isotropic mould shrinkage relative to unfilled PA12. Components are specified in the conditioned state when they operate in humid air, enclosed housings, or under-hood environments and must retain dimensional stability, fuel and oil resistance, and low-temperature impact toughness. Because the grade is natural, colour concentrates can be added, but colourant effects on nucleation, crystallinity, and impact should be validated on production tooling before series release.

What Distinguishes Conditioned PA12-GF30 from Dry-Moulded Data?

For a PA12-GF30 compound, dry-as-moulded specimens are typically tested at a moisture content below 0.10 wt%. Conditioning at 23 °C/50 % RH raises the absorbed moisture to approximately 0.5–0.7 wt%; saturated water absorption is approximately 1.4 wt%. The plasticising effect reduces tensile modulus and tensile strength at break, while elongation at break and Charpy notched impact at 23 °C increase. Low-temperature impact may remain close to the dry value or decrease slightly because the moisture-related toughening mechanism is less effective below the β-transition of the PA12 matrix. Table 1 summarises representative values from current supplier technical literature. These are single-point data under ISO 10350-1 specimen preparation and are not design minimums.

Tensile modulus is measured at 1 mm/min; tensile strength and elongation are measured at 5 mm/min for ISO 527-1/-2. Charpy specimens are edgewise notched according to ISO 179-1/1eA. Heat deflection temperature is determined at 1.80 MPa with a 120 °C/h heating rate. The melting peak is taken from the second heating cycle of ISO 11357-3. For design calculations, the conditioned tensile modulus and conditioned secant modulus at the service strain are more relevant than dry values when ambient humidity is uncontrolled.

Because the “Conditioned” designation applies to test specimens, not to pellet moisture content, melt processing requires the same drying discipline as any unfilled or reinforced PA12. Pellet exposed to ambient humidity should be dried to <0.10 wt% residual moisture before melting. Desiccant-wheel dryers are preferred; the dew point should not exceed −40 °C. Typical drying conditions for cold or damp material are 80 °C for 4–6 h. Hot-air dryers are not recommended because they cannot reach the required dew point in humid production areas. On a production-scale three-zone reciprocating-screw injection moulding machine with an L/D ratio of 20:1 to 25:1 and a compression ratio of 2.5:1, the barrel profile is normally set from 230 °C in the feed zone to 250 °C in the compression zone and 260 °C in the metering zone. The melt temperature measured by an insertion pyrometer should be kept between 240 °C and 270 °C; the upper limit is 280 °C for short residence. Mould temperature should be maintained between 60 °C and 90 °C. Table 2 consolidates the processing envelope.

Residence time is a threshold risk. In actual moulding trials, residence times below 5 min can produce melt-temperature variation and poor glass-fibre dispersion, whereas residence beyond 12–15 min can generate brown streaks, a drop in notched impact, and surface splay. When stoppages exceed the maximum residence time, the barrel should be purged with fresh feed at the lower melt-temperature limit. Reground sprues and runners may be introduced at up to 30 wt% if they are clean, dry, and not thermally degraded. For components used in fuel contact, pressure-bearing fluid handling, or safety-relevant bracketry, use of 100 wt% virgin compound is typical unless a controlled regrind study is available. The conditioned data in Table 1 should not be used to justify processing with wet pellets; residual moisture above 0.10 wt% during melting produces hydrolysis and lowers molecular weight even if the part is later conditioned after moulding.

Chemical Resistance and Environmental Boundary Conditions

The PA12 matrix of Grilamid XE 3997 nat gives resistance to mineral oils, greases, aliphatic hydrocarbons, engine coolants, and zinc chloride solutions. Zinc chloride resistance is one reason PA12 is selected over PA6 or PA66 in automotive under-hood applications where road-salt and galvanic corrosion products generate zinc chloride. Glass-fibre reinforcement can reduce apparent chemical resistance at cut edges because fibre wicking creates a capillary path for fluid entry into the part. For sealed or welded housings this effect is mitigated. Stress-cracking resistance in chloride-containing environments should be evaluated with constant-strain fixtures according to ISO 22088 or the relevant OEM method, using moulded plates with the same fibre orientation and weld-line condition as the final part. Continuous exposure to hot water above 80 °C requires hydrolysis-resistance validation, since PA12 can undergo molecular-weight reduction in aqueous service over extended time. Published data for this specific formulation under long-term hot-water exposure are limited. The material should not be used with strong mineral acids, oxidising agents, or polar solvents that dissolve or swell PA12; methanol and ethanol can cause surface attack at elevated temperature. For natural-grade parts, outdoor UV exposure without a stabilised black or UV-stabilised colour package is not recommended for long-term aesthetic retention.

In the form supplied, EMS-Grivory typically declares conformity to Directive 2011/65/EU RoHS and Regulation (EC) No 1907/2006 REACH for this natural compound. Converter-created colour concentrates, processing aids, or post-moulding coatings require separate compliance confirmation.

In direct comparison with PA6-GF30, Grilamid XE 3997 nat absorbs roughly one-quarter of the equilibrium moisture at 23 °C/50 % RH, which produces less stiffness loss between dry and conditioned states and better dimensional stability in humid air. Compared with PA66-GF30, the PA12 grade has a lower density, improved zinc chloride stress-cracking resistance, and lower heat deflection temperature; PA66-GF30 remains stiffer and more heat-resistant in dry and conditioned states. Against unfilled PA12 grades such as Grilamid L 20, the 30 wt% short-glass reinforcement in XE 3997 nat raises the tensile modulus from the range of 1,000–1,500 MPa to more than 6,000 MPa dry and reduces linear mould shrinkage, but it also introduces anisotropic flow-direction properties and lower elongation at break. Against PA11-GF30, the PA12 grade offers broadly similar low moisture uptake and chemical resistance, with a slightly lower melting peak; field selection is usually determined by regulatory, supply-chain, or supplier-specific testing rather than by a single property. Compared with the black version of the same base compound, the natural grade may have different colourant package and therefore different UV ageing behaviour; carbon-black grades are preferred for outdoor parts unless secondary painting or UV-stabilised colour concentrates are used.

Rheological characterisation for this specific grade should be performed by capillary rheometry according to ISO 11443 if gate-pressure calculations are required. Published data for the complete shear-rate and temperature matrix are limited, so fill simulations should be calibrated with measured melt-pressure data from short-shot trials on the intended mould.

When the Moulded Part Must Survive Cold Impact and Automotive Fluids

Typical uses include under-hood clips, quick-connector housings, pneumatic valve bodies, filter housings, cable-conduit fittings, and enclosures exposed to mineral oil or fuel vapour. In these service conditions, the conditioned mechanical data are used for deflection and snap-fit calculations because the part is not dry. Snap-fit design should use the conditioned secant modulus at the expected strain, and the maximum snap-fit strain should remain below the conditioned yield strain; using dry tensile modulus can produce brittle snap-fit failure. For glass-fibre-reinforced PA12, the mechanical response is anisotropic. Tensile modulus and strength along flow are higher than across flow, and weld lines can reduce impact strength by more than 50 % compared with a simple ISO bar. Gate location and venting should be determined by short-shot studies on production tooling; a fill simulation alone is not sufficient. Moulded parts should be tested at −30 °C or −40 °C with the actual gate and weld-line configuration, because laboratory ISO bars overstate the toughness of complex moulded geometries. For continuous hot-air exposure above 120 °C, the natural PA12-GF30 grade may embrittle over time unless a heat-stabilised variant is validated. Fibre attrition during melt processing reduces the number-average fibre length and lowers tensile modulus and impact; screw speed, back pressure, and shot-to-barrel-volume ratio should be set to minimise this attrition. The processing window in Table 2 is therefore a boundary condition for preserving the property set reported in Table 1.

Incoming material should be monitored for moisture content and melt volume-flow rate according to ISO 1133-1:2022 at a specified condition; lot-to-lot variation in natural PA12-GF30 can affect filling behaviour. The supplier certificate of analysis should be retained for traceability. Post-moulding conditioning may be accelerated by warm-air or water immersion, but through-thickness moisture distribution differs from standard ISO 291 equilibrium; parts should be allowed to equilibrate before dimensional inspection.