Evonik Lauramid A Nylon 12G is a semi-crystalline thermoplastic compound whose matrix is polyamide 12 and whose discontinuous filler phase is milled or chopped glass fibre. The designation follows the legacy Lauramid nomenclature: the 12 identifies the laurolactam-derived backbone, the G suffix indicates glass-fibre modification, and the A prefix identifies the base-resin viscosity class. The material is supplied as cylindrical pellets with a bulk density of 0.75–0.85 g/cm³ measured under ISO 60:2023. The unfilled matrix exhibits a melting endotherm at 176 °C when heated at 10 K/min in accordance with ISO 11357-3:2018; glass reinforcement does not substantially shift the crystal-phase melting range because the fibre is not a nucleating additive at this loading. Water-absorption behaviour separates this product from short-chain aliphatic polyamides. After saturation at 23 °C in water, a 2 mm unfilled plaque absorbs approximately 1.5% moisture by mass, while PA66 absorbs approximately 9.0%. At 23 °C and 50% RH, conditioned uptake for the PA12 matrix is 0.7–0.9%. The lower equilibrium moisture uptake reduces the shift in tensile modulus between dry-as-moulded and humid service, a property exploited in clearance-critical automotive connectors.

The product is normally specified on engineering drawings by the ISO 1874-1 designation PA12-GF30 or by the supplier lot code, with glass content of 30% by mass stated on the certificate of analysis. Published data for this exact grade under all listed standards is limited; the mechanical and thermal envelope below is class-typical for a 30 wt% glass-fibre-reinforced polyamide 12 and should be verified against the lot-specific certificate of analysis.

The tensile modulus of the 30 wt% glass-reinforced grade is about 3.5–4.0 times that of the unreinforced Lauramid A resin, while the notched Charpy impact at 23 °C falls from 30–40 kJ/m² for the unfilled resin to 10–14 kJ/m² for the reinforced compound. At -30 °C, the reinforced material typically retains 6–8 kJ/m², acceptable for clips and housings but requiring radiused transitions in load-bearing ribs. The heat deflection temperature under 1.8 MPa is 160–170 °C, an increase of about 55–65 °C over the unfilled matrix. This permits short-term exposure in engine-compartment areas where peak air temperature does not exceed 130 °C, but it does not equal the continuous thermal stability of semi-aromatic polyamides or PPS.

What limits melt-temperature selection and residence-time control?

At the moulding machine, the recommended melt temperature for glass-reinforced polyamide 12 is 230–250 °C. The lower limit is constrained by incomplete fibre wetting and the appearance of unmelted resin domains when filling sections below 1.0 mm; the upper limit is set by thermal-oxidative chain scission. On a 400-ton injection-moulding press with a 22:1 L/D general-purpose screw, residence times above 8 min at 250 °C have produced silver streaking and visible glass-fibre agglomeration on moulded surfaces. Pre-drying in a desiccant dryer at 80 °C for 4–6 h reduces moisture below 0.10 wt%, which is required to prevent hydrolysis-induced molecular weight loss. A dew point below -20 °C permits drying times as short as 3 h; if dried pellets remain in an uncontrolled hopper at 60% RH for more than 30 min, moisture regain can exceed 0.15 wt% and should be corrected by an additional 2 h drying step.

Rheological measurements in accordance with ISO 1133-1:2022 place the melt mass-flow rate of a 30 wt% glass-filled PA12 grade near 8–15 g/10 min at 235 °C under a 5 kg load. In-tool pressure transducers show that filling a 2 mm plaque requires approximately 350–450 bar hydraulic pressure with a 35 mm diameter screw and a mould temperature of 60–80 °C. Mould temperatures below 50 °C accelerate skin freezing and increase glass-fibre orientation at the frozen layer; this raises near-surface flexural modulus but reduces notched impact strength at weld lines. Melt-temperature variation of ±5 °C around 240 °C is usually acceptable for surface appearance, but weld-line strength falls measurably at the lower process boundary when injection speed is below 40 mm/s.

When glass-fibre orientation dominates shrinkage anisotropy

Glass-fibre orientation during filling creates a measurable difference between flow-direction and transverse-direction shrinkage. In injection-moulded plaques with a 2 mm wall thickness, flow-direction shrinkage measured by ISO 294-4:2018 is commonly 0.2–0.5%, while transverse shrinkage reaches 0.6–1.0%. If gate placement is confined to one end of a rectangular housing, differential shrinkage produces bowing along the long axis; observed warpage can exceed 1.2 mm over a 150 mm span when the mould temperature is below 60 °C. Preferential fibre alignment near the frozen layer increases flexural modulus parallel to flow by up to 15% relative to the transverse direction. Tooling layouts should therefore use multiple gates or sequential valve-gate actuation to reduce orientation imbalance.

At weld lines, fibre ends concentrate and act as stress risers. Tensile strength retention at a weld line is typically 40–55% of the parent material value when measured in accordance with ISO 527-2:2012. When welded regions are unavoidable, a mould temperature at the upper end of the 60–80 °C range and an injection speed above 60 mm/s improve strength retention to approximately 60%. Processing at low melt temperature increases melt viscosity and preferentially freezes high-orientation layers, which can be exploited for stiffness but at the cost of ductility. A mould temperature of 80 °C permits relaxation of flow-induced orientation and reduces warpage, but it extends cooling time by 10–20% compared with a 60 °C mould. For wall sections above 4 mm, a packing pressure of 500–700 bar hydraulic and holding time of 6–8 s per 2 mm nominal wall thickness are typically needed to avoid sink marks at bosses and ribs.

Unlike short-chain aliphatic polyamides, the polyamide 12 backbone provides a lower concentration of hydrogen-bonding amide groups, which directly reduces equilibrium moisture uptake and improves retention of stiffness in humid air at 50% RH. A conditioned PA66 component may absorb 2.0–2.5% moisture at 23 °C and 50% RH, while the PA12 equivalent absorbs 0.7–0.9%; the dimensional growth associated with the PA66 uptake is approximately three times higher. For precision clearance fits in fuel-system connectors and brake-cable guides, the PA12 grade is therefore preferred over short-chain aliphatic polyamides when relative-humidity cycling is part of the qualification sequence. Compared with glass-reinforced PBT, the polyamide 12 compound has a lower density, typically 1.24 g/cm³ versus 1.53 g/cm³ for 30 wt% glass-filled PBT, and it retains higher notched impact at -30 °C. Compared with glass-reinforced PA6, the PA12 grade shows lower moisture uptake and better retention of dielectric properties, but its tensile strength is slightly lower at equivalent glass loading; PA6-GF30 typically reaches 120–140 MPa tensile stress at break, while this PA12 class is 105–125 MPa. The material is not a direct substitute for high-temperature semi-aromatic polyamides such as PPA, because continuous-use temperatures above 150 °C can cause progressive thermo-oxidative embrittlement in glass-reinforced PA12.

Concentrated mineral acids, especially sulfuric acid and hydrochloric acid at elevated temperature, degrade PA12 through acid hydrolysis; boiling phenols dissolve the polymer. The compound is not recommended for continuous immersion in methanolic calcium chloride solutions because of environmental stress-cracking risk. Chlorinated hydrocarbons and zinc chloride solutions can reduce long-term ductility under sustained load. Representative uses include automotive quick-connect fittings, cable sheathing, electrical connector bodies, gear wheels, pump rotors, and industrial housings where PA66 or PBT exhibit excessive moisture uptake or stress cracking. For under-hood components tested under ISO 16750-4 thermal cycling, the material is usually specified with a maximum continuous service temperature below 130 °C.

Batch-to-batch rheological variance and regrind-induced molecular weight drift

Incoming material control should include viscosity number and moisture content, not solely melt mass-flow rate. The viscosity number of the base resin, measured in 96 wt% sulfuric acid per ISO 307:2019, is typically 150–180 mL/g for the unreinforced matrix. A reduction of more than 8–10 mL/g between batches indicates molecular weight loss and can lower weld-line strength even when tensile modulus remains unchanged. Regrind addition at 20–25% by mass is generally tolerated for non-safety parts, but repeated heat histories shift the viscosity number downward by 10–20% after three cycles on a 20:1 L/D extruder. For safety-critical components such as brake-fluid reservoirs, regrind content is usually limited to 0% unless the customer specification explicitly permits a controlled recycling stream under IATF 16949 process control.

Fibre-length degradation during compounding and moulding is a more important variable than base-polymer viscosity. Twin-screw compounding with a 32 mm diameter, 36:1 L/D extruder at 250 °C and 350 rpm reduces glass fibre length to a volume-median of 180–250 µm, while a 26:1 L/D single-screw extruder can produce median fibre lengths below 120 µm. The resulting tensile modulus can shift by 0.5–0.8 GPa between otherwise identical lots. For this reason, incoming inspection should include moulded tensile bars rather than pellets alone, and the certificate of analysis should state the moulding conditions used for specimen preparation.