EMS-Grivory Grilamid LVX-65H SST nat is a polyamide 12 injection-moulding compound reinforced with 50% glass fibre by weight and supplied as natural-coloured pellets in a dry-as-moulded condition. The grade is identified by the manufacturer as Grilamid LVX-65H SST nat and fits the generic ISO 16396-1 classification for a heat-stabilised, glass-fibre-reinforced polyamide 12, commonly expressed as PA12, GF50, H. The SST suffix is an EMS-Grivory stabilisation and property-modification designation, not a generic ISO or ASTM material code. The dry state means that pellet moisture is controlled at packaging, but it does not remove the need for pre-drying after bag opening or storage above 60% relative humidity.

The grade is positioned for load-bearing injection-moulded parts that must resist moisture-driven swelling, retain toughness at low temperature, and avoid the density penalty of 50% glass-filled PA66 or die-cast metal. Typical evaluation areas include pneumatic valve bodies, push-in fittings, cable cleats, fuel-line retainers, gear carriers, and sensor housings. Validation for pneumatic connectors is normally performed by pressure cycling and burst testing under ISO 14743 or equivalent customer specifications. For exact grade-specific values, the EMS-Grivory technical datasheet and lot certificate should be consulted; the comparative ranges below are class-typical for heat-stabilised 50% glass-fibre PA12 and do not replace certified product data.

What Limits the Continuous-Use Temperature of a 50% Glass-Filled PA12 Compound?

Thermal performance in dry-moulded glass-filled PA12 is governed less by the glass fibre and more by the polyamide 12 matrix. The melting peak of PA12 homopolymer is typically 175–180°C by differential scanning calorimetry according to ISO 11357-3, while the glass transition is near 40–50°C. Heat deflection temperature under 1.8 MPa loading is therefore a short-term rigidity indicator, not a continuous-use temperature. Glass reinforcement raises HDT/A into the 150–180°C range for many 50% glass-filled PA12 compounds, but oxidative embrittlement and creep under load become limiting above 100°C in hot air. Long-term load-bearing parts exposed above 80°C should be assessed by tensile creep testing under ISO 899-1 at the expected stress and service temperature.

For applications requiring sustained exposure above 150°C, a 50% glass-filled polyphthalamide or semi-aromatic polyamide may be required because its aromatic content raises creep resistance and thermal-oxidative stability. Compared with those higher-temperature polymers, Grilamid LVX-65H SST nat retains lower moisture absorption and better dimensional stability than many PA66 grades, but it does not match the dry strength of PPA. The natural grade is also not inherently UV-stabilised; outdoor exposure requires a black or UV-stabilised alternative or additional protective packaging.

Production-scale injection moulding of 50% glass fibre PA12 begins with moisture control. A desiccant dryer with inlet air dew point at or below −30°C is specified; drying at 80°C for 4–12 h reduces pellet moisture to 0.10% or less. Opened bags stored above 60% RH should be returned to drying before moulding. Residual moisture can be measured by Karl Fischer titration or ISO 15512 method. Excess moisture volatilises in the melt, producing splay, nozzle drool, reduced weld-line strength, and hydrolytic chain scission. The threshold is not a cliff-edge at room temperature, but wet pellets above 0.2% moisture increase the risk of visible defects and property loss.

Melt Rheology, Screw Geometry, and Barrel Temperature Profiling

Shear thinning in a 50% glass fibre PA12 melt is pronounced, but the grade remains more viscous than unfilled PA12 because of fibre-fibre and fibre-wall interactions. A general-purpose three-zone screw with L/D 20:1–25:1 and compression ratio 2.0–2.5 is commonly used, but glass abrasion requires a wear-protected screw and bimetallic barrel. Barrel temperatures from feed to nozzle are typically profiled from 220–240°C at the feed zone to 250–270°C in the metering zone, with nozzle temperature 250–270°C. Melt residence time above 270°C should be kept below 8 min to limit thermal degradation of the PA12 backbone. Mould temperature is normally maintained between 70°C and 110°C; higher mould temperature reduces skin orientation, improves weld-line strength, and lowers in-plane shrinkage but can extend cycle time.

Glass fibre attrition in the screw is the main rheological conflict. High backpressure and high screw speed reduce retained fibre length and can lower impact and modulus in the moulded part. Backpressure is generally set between 0.3 MPa and 0.8 MPa hydraulic, and peripheral screw speed is kept below 0.2 m/s. Fibre length distribution can be checked by ashing moulded plaques at 600°C according to ISO 3451-1 and optical microscopy. Weld-line strength retention in glass-filled polyamides is commonly 40–60% of the parent tensile strength; tensile testing of weld-line specimens should follow ISO 527-2. Gate and runner sizing must account for faster freeze-off of glass-filled melt. Direct gates, edge gates with diameters not below 1.0 mm, and hot-runner systems with externally heated manifolds are preferred over long cold-runner drops.

Exposure of a 50% glass fibre PA12 part to humid air at 23°C and 50% relative humidity produces a smaller dimensional change than the same part moulded in PA66 GF50. The lower equilibrium moisture absorption, typically 0.5–0.8% for the PA12 class versus 4.5–5.5% for PA66 class, reduces hygroscopic swelling in pneumatic housings and fluid-contact brackets. Moisture conditioning still affects PA12. Tensile modulus falls after conditioning, while notched impact rises. Parts measured immediately after demoulding may therefore differ from conditioned parts by more than the dry-to-conditioned shift seen in unfilled PA12 once fibre constraint is considered.

When Dimensional Stability in Humid Service Outweighs Short-Term Tensile Peak

When a design requires dimensional stability in humid service, a PA12 GF50 compound can be selected over a PA66 GF50 because the lower moisture uptake reduces expansion, warpage, and electrolyte corrosion paths in assembled metallic inserts. The trade-off is lower dry tensile strength: class-typical dry tensile stress at break for PA12 GF50 is 120–150 MPa, while PA66 GF50 reaches 190–230 MPa. In chemically aggressive service involving hot water, acid condensation, or road salt, PA12 often provides better stress-cracking resistance than PA66, but compatibility assessment under ISO 175 is required for each fluid.

In comparison with unfilled Grilamid L grades, the LVX-65H SST nat product shifts the property profile from ductile to stiff. Unfilled PA12 tensile modulus is typically 1,400–1,600 MPa, while the 50% glass fibre class reaches 11,000–14,000 MPa. Elongation at break drops from above 200% for unfilled PA12 to 1.5–3.0% in dry-moulded GF50 grades. The glass-filled material also displays anisotropic shrinkage. For 2 mm plaques, mould shrinkage parallel to flow is commonly 0.1–0.3%, while transverse shrinkage is 0.4–0.8% when measured to ISO 294-4. This anisotropy must be included in part design and simulation, especially for flat covers, flanges, and housings with internal ribbing.

In melt processing, the first variable to control for flatness is cavity filling pattern. Uneven glass orientation at weld lines, abrupt wall-thickness changes, and gate frost can create warpage that cannot be corrected by add-on tolerances. Mould filling simulation should use fibre-orientation data supplied by EMS-Grivory; generic PA12 GF50 data may not capture the SST modifier effect on viscosity and orientation. When tight post-mould dimensions are required, parts should be conditioned at 23°C and 50% RH for at least 24 h before dimensional inspection.

Substituting Grilamid LVX-65H SST nat for Die-Cast Zinc or Machined POM

Replacing zinc die-cast brackets with a glass-filled PA12 compound changes the failure mode from plastic yield or brittle overload of metal to creep, moisture swelling, and weld-line sensitivity. The density reduction is significant: zinc alloys are typically 6.6–7.2 g/cm³, while PA12 GF50 is 1.30–1.35 g/cm³, producing roughly 80% mass reduction at identical envelope. However, the elastic modulus of zinc, 85–96 GPa, is far above the 11–14 GPa tensile modulus of the polymer. Direct metal-to-plastic substitution without ribbing or wall-thickness adjustment therefore creates excessive deflection. The replacement design should be re-evaluated using structural finite element analysis with creep data under ISO 899-1 and moisture-conditioned modulus values.

Compared with machined POM-C or POM-H parts, the PA12 GF50 compound offers higher heat deflection temperature and lower moisture expansion in many humid conditions. However, unfilled or glass-filled acetal can provide lower dry sliding wear and lower coefficient of friction in bearing contact; the PA12 GF50 grade is not inherently a bearing grade. If rotational or sliding contact is required, a bearing additive or a different tribologically modified grade should be selected. For pneumatic fittings, PA12 GF50 also avoids the zinc chloride corrosion risk that can affect zinc castings in marine or salt-exposed environments.

Chemical exposure and regulatory status must be confirmed at grade level. Polyamide 12 is generally resistant to aliphatic hydrocarbons, oils, greases, fuels, and salt solutions, but it is attacked by strong mineral acids, phenols, formic acid, and high-pressure steam. Fluid-contact compatibility should be screened under ISO 175 or environmental stress-cracking tests such as ISO 22088-3. Published data for this specific configuration in aggressive automotive or industrial fluids are limited; the grade should not be approved for production without part-level immersion testing.

Regulatory Documentation and Food/Water Contact Status

RoHS compliance for electrical and electronic equipment should be confirmed from the EMS-Grivory declaration against Directive 2011/65/EU Annex II restricted substances. REACH Article 33 SVHC communication is product-specific and must be requested from the supplier; absence of an SVHC in raw material declarations does not exempt the upstream supply chain. For food-contact applications, polyamide 12 may be evaluated under FDA 21 CFR 177.1500 and corresponding EU regulations, but approval for this exact glass-filled, stabilised grade must be obtained from EMS-Grivory regulatory documentation. Potable water contact requires separate assessment under recognised programmes such as NSF/ANSI 61, WRAS, or KTW; product-specific approval is not automatic for natural GF50 PA12.

Because the natural grade contains no carbon black, ultraviolet exposure causes surface degradation and chalking over time. Black or UV-stabilised grades should be used for outdoor load-bearing parts. Flammability class for natural 50% glass-filled PA12 is generally HB under UL 94; parts requiring V-0 or V-1 classification must use a flame-retardant grade or evaluate the specific wall-thickness dependence on the supplier yellow card. Electrical properties such as comparative tracking index under IEC 60112 and volume resistivity under IEC 62631-3-1 should be taken from the product datasheet, because glass fibre type and stabiliser package influence surface and bulk electrical behaviour.