Evonik VESTAMID® LXM4 Nylon 12, 4% glass fiber reinforced, is a compound in the VESTAMID L polyamide 12 family. The polymer matrix is synthesised by hydrolytic polycondensation of laurolactam. The grade-specific modification is a nominal short glass fiber addition of 4% by mass, which is low enough to preserve the chemical resistance and low moisture uptake of PA12 while raising tensile modulus, creep resistance, and dimensional repeatability relative to an unfilled PA12 base. In supplier documentation the customary test designations include ISO 1183-1 for density, ISO 527-1/-2 for tensile properties, ISO 179-1/1eA for Charpy impact, ISO 1133-1 for melt volume-flow rate, ISO 11357-3 for melting temperature, ISO 75-1/-2 for heat deflection temperature, and ISO 294-4 for mould shrinkage. Published data for this exact configuration is limited; tooling and process capability studies should be validated against the current Evonik datasheet rather than against generic PA12 literature.

Low Glass Fiber Loading Effects on Shrinkage and Weld-Line Integrity

The 4% fiber fraction is below the concentration at which short glass fibers dominate the in-plane shrinkage field. In injection moulded plaques, the large flow-direction and cross-flow shrinkage divergence observed in 30% glass fiber PA12 grades is muted. Unfilled PA12 commonly exhibits mould shrinkage between 0.9% and 1.4% under ISO 294-4, while PA12-GF30 can fall below 0.4% in the flow direction. The low-glass compound occupies an intermediate band, with the practical consequence that flat covers and clamping rails are less prone to out-of-plane warpage than equivalent parts moulded from neat PA12. The low fiber loading also reduces the degree of anisotropic post-shrinkage after exposure to elevated temperature. Weld-line strength is a separate constraint. When two melt fronts meet in a double-gated tensile specimen, fiber orientation at the weld plane is predominantly parallel to the front, leaving little fiber bridging across the interface. The result is a weld-line tensile strength below the bulk value. For wall sections below 2 mm, production tooling should include overflow wells, sequential valve gating, or gate positions placed away from the principal stress vector. Mould-filling analysis should be used to identify the meeting angle of the flow fronts because low meeting angles below 45° produce a longer weld plane and a higher probability of low-temperature crack initiation.

Melt processing of this product is governed by moisture control and tool temperature. The material is less hygroscopic than PA6 or PA66, but absorbed moisture above 0.1% by ISO 15512 Karl Fischer titration is capable of hydrolytic chain scission and surface splay. Sealed bags are usually supplied dry. Once opened, exposure to relative humidity above 60% for more than 8 h justifies re-drying. Desiccant drying at 80 °C to 90 °C for 4 h to 6 h with a supply-air dew point below -30 °C is adequate for most injection moulding operations. The compound is processed on a single-screw injection moulding machine equipped with a general-purpose polyamide screw of L/D ≥ 20 and a shut-off nozzle. Barrel profiles between 220 °C and 250 °C are typical, with a tool temperature of 40 °C to 60 °C. Tool temperature below 30 °C is not recommended for thin sections because the quenched skin layer can delaminate under ejection stress when the low fiber content does not provide sufficient melt stiffness. In capillary rheometry per ISO 11443, the low fiber volume fraction has limited effect on shear viscosity at shear rates above 1,000 s⁻¹, but at shear rates below 10 s⁻¹ the dispersed fiber network can raise viscosity and reduce die swell. This means that thick-walled parts with long flow lengths may require slightly higher pack pressures than unfilled PA12 to compensate for low-shear melt stiffness.

What Distinguishes a 4% Glass Fiber Addition from Neat PA12 and PA12-GF30 in Service?

The product sits between unfilled PA12 and PA12-GF30 in stiffness, density, and ductility. Generic unfilled PA12 grades report tensile elongation at break above 200% by ISO 527-1/-2, whereas PA12-GF30 grades often fall below 5%. The 4% glass fiber loading reduces elongation relative to neat PA12 but leaves enough permanent deformation capacity for snap-fit and press-fit assemblies that would be marginal in a high-glass compound. Tensile modulus of unfilled PA12 is commonly near 1,500 MPa; a low-glass formulation can be expected to add a few hundred MPa, while PA12-GF30 is typically reported between 6,500 MPa and 8,000 MPa depending on fiber length distribution and orientation. Density follows the same hierarchy. Unfilled PA12 is near 1.01 g/cm³, PA12-GF30 is commonly near 1.23 g/cm³, and the low-glass grade remains marginally above the unfilled density. Heat deflection temperature under 1.8 MPa per ISO 75-1/-2 is expected to fall between the unfilled PA12 value, often below 60 °C, and the PA12-GF30 value, often above 90 °C. The low fiber content therefore does not constitute a structural upgrade in the same sense as 30% glass fiber reinforcement; it is a controlled stiffness modification.

Component classes suited to this material include electrical connector backshells, cable glands, pneumatic clips, automotive interior brackets, and fluid-line retention clips. In fluid-contact service, PA12 is established for aliphatic hydrocarbons, mineral oils, greases, and automotive fuels. The 4% glass fiber fraction introduces no significant barrier enhancement over neat PA12 and does not create the permeability advantage of high-fiber compounds. Published data for this specific configuration is limited; converters designing fuel-contact components should perform OEM-level fuel exposure rather than relying solely on coupon immersion. For dry electrical applications, the material is typically evaluated for comparative tracking index and glow-wire performance according to IEC 60112 and IEC 60695-2 where a fire rating is required for the assembled part. Electrical grade performance depends on pigments, regrind level, and conditioning; it should be re-tested on production-coloured resin.

Chemical Resistance Boundaries, Moisture Uptake, and Regulatory Documentation

PA12 has a lower amide-group density than PA6 or PA66, which limits moisture absorption and the associated dimensional change. Saturation water uptake for neat PA12 is commonly near 1.4% by ISO 62, while PA6 can exceed 9%. The 4% glass fiber fraction lowers the absolute dimension change per unit moisture uptake without changing the fundamental absorption kinetics. The material is therefore suitable for humid interior environments and outdoor enclosures where PA6 would accumulate excessive moisture. Limitations include concentrated mineral acids, phenols, benzyl alcohol, and saturated steam above 140 °C. Stress cracking should be validated with production lubricants and cleaning agents because low-fiber PA12 can show environmental stress cracking under aggressive surfactants at elevated temperature. The compliance matrix below summarises the standard designations and regulatory boundaries commonly associated with a VESTAMID PA12 compound.

When Dimensional Stability and Humid Environments Govern Material Selection

At 23 °C and 50% relative humidity, conditioned PA12 absorbs roughly 0.7% water. In constrained assemblies this moisture-driven expansion can exceed thermal expansion effects. The 4% glass fiber fraction reduces the effective linear coefficient of expansion in the flow direction but leaves the cross-flow coefficient closer to neat PA12. Designers should not assume isotropic expansion in thin ribs, bosses, or weld regions. Conditioned specimens used for mechanical testing should be equilibrated per ISO 1110; dry-as-moulded data overstate modulus and understate toughness. This is a common source of discrepancy when lot-to-lot process capability studies are compared across different plants.

For extrusion of tubing and small profiles, the low glass fiber loading reduces melt strength relative to PA12-GF30. The air gap between die and calibration sleeve should be minimised, and vacuum calibration tanks should be operated at water temperatures between 20 °C and 40 °C. Melt temperatures in the 240 °C to 260 °C range improve surface uniformity, but screw-speed variations above ±5% can produce wall-thickness instability in annular dies because the low fiber content provides less structural retention in the melt. Screens finer than 60 mesh are generally avoided upstream of thin-wall profile dies because the pressure increase can exceed the barrel pressure limit of small single-screw extruders with L/D 25 to 30.

Regrind use is limited to 20% by mass in non-appearance parts where glass fiber length distribution remains within the supplier's accepted range. Multiple re-melting cycles reduce fiber length and lower notched impact; when regrind content exceeds this threshold, shot-to-shot variability increases because the mixture contains a bimodal distribution of glass fiber lengths. For appearance parts with exposed surfaces, the low fiber fraction is less abrasive than PA12-GF30 but can still produce surface roughness after prolonged runs exceeding 20,000 shots if hot-runner tips are not maintained.