Aurora Kunststoffe AUROmid PA12 TR90 natural 1102 PA12, Conditioned is an unfilled amorphous transparent polyamide 12 grade supplied as natural pellets in a moisture-conditioned state. The grade designation 1102 identifies the natural colour formulation; the conditioned designation indicates that the granulate has been brought toward equilibrium under controlled humidity, typically following the conditioning principles of ISO 1110 or ISO 291. As an amorphous PA12, the material does not exhibit a defined crystalline melting point. The glass transition temperature is approximately 155 °C as measured by differential scanning calorimetry under ISO 11357-2. Density is 1.00 g/cm³ under ISO 1183-1, and saturation water absorption is approximately 1.5 % under ISO 62. The low density and transparent amorphous morphology distinguish the grade from semi-crystalline PA12 and from glass-filled aliphatic polyamides in optical, fluid-handling, and lightweight snap-fit components.

What Property Changes Are Observed in the Conditioned State?

Conditioning introduces approximately 0.7 % absorbed moisture at 23 °C and 50 % relative humidity for polyamide 12 backbones, which is lower than the approximately 2.7 % typical of PA6. The absorbed water reduces tensile modulus and yield stress while increasing toughness. The following representative values apply to a natural transparent PA12 TR90 in conditioned equilibrium. Lot-specific certificates of analysis and the grade-specific technical datasheet should be used for production release.

The listed values are typical for conditioned transparent PA12 TR90 and not guaranteed specification limits. Dry-state values for tensile modulus and yield stress are higher, while conditioned values better represent the in-service state after moisture equilibration. The grade has a lower moisture regain than PA6 or PA66, which reduces post-moulding dimensional drift in humid environments.

On production injection moulding machines, pre-drying in a desiccant dryer with a −40 °C dew point is required for 4–6 h at 80 °C when hopper-open storage or humid air has produced residual moisture above 0.10 %. Residual moisture is determined by Karl Fischer titration or ISO 15512. Failure to dry can produce splay, silver streaks, and surface voids because steam evolves at barrel temperatures above 240 °C. Use a general-purpose three-zone screw with an L/D ratio of 20:1–25:1, compression ratio 2.0:1–2.5:1, and a non-return ring. High-shear compression screws designed for semi-crystalline PA66 are not required and may introduce uncontrolled melting. Barrel temperatures are typically set from 240 °C in the feed zone to 280 °C at the nozzle; melt temperature measured by air-shot pyrometer should not exceed 290 °C. Mold temperature should be held between 40 °C and 60 °C. If mold temperature exceeds 80 °C, cycle time lengthens because the part must vitrify below the glass transition and no crystallisation plateau assists solidification. Pinpoint gates below 0.8 mm can create high shear and gate blush. Full-round edge gates or tunnel gates of 1.0 mm minimum are preferred for transparent parts.

Rheological measurements under ISO 11443 at 270 °C with a capillary die of 1 mm diameter show shear-thinning behaviour across apparent shear rates from 100 s⁻¹ to 10,000 s⁻¹. The flow response is more shear-sensitive than low-viscosity PA66 grades. Gate shear rates above 100,000 s⁻¹ may cause surface haze, melt fracture, and local molecular orientation that remains frozen because no crystallisation anneals it. Mold-filling simulations should use Cross-WLF viscosity coefficients generated from capillary data rather than generic polyamide 12 coefficients for thin-wall parts below 1.5 mm nominal wall. On a hydraulic injection moulding line with 1200 kN clamp force, reducing injection velocity from 120 mm/s to 60 mm/s can reduce visible haze more effectively than raising melt temperature beyond 280 °C. Cavity pressure sensors in the nozzle, runner, and end-of-fill positions are recommended for switchover at 300–500 bar hydraulic pressure and a holding-pressure profile of approximately 50 % of peak cavity pressure for 4 s.

Control of Moisture Uptake and Post-Processing Dimensional Drift

At 23 °C and 50 % relative humidity, polyamide 12 reaches approximately 0.7 % moisture; at saturation in water it reaches approximately 1.5 %. Conditioning lowers the tensile modulus by about 15–20 % relative to the dry state and raises Charpy notched impact. Dimensional drift during subsequent storage is smaller than for PA6 or PA66 because the equilibrium moisture content of PA12 is lower. Post-moulding shrinkage after 24 h at room temperature is typically below 0.7 %. Anisotropic differential shrinkage in the flow and transverse directions is usually less than 0.2 % because solidification is amorphous. If secondary machining, solvent bonding, or hot-plate welding is planned, the part should be allowed to reach moisture equilibrium before final critical dimension inspection. For validated assemblies, dimensions should be recorded after conditioning for 48 h at 23 °C and 50 % RH, not immediately after demoulding.

Chemical compatibility is closer to semi-crystalline PA12 than to PMMA or polycarbonate in many hydrocarbon environments. The material withstands aliphatic oils, automotive greases, diesel, and many hydraulic fluids, but published data for this specific configuration is limited. Polar solvents, hot aqueous acids, strong bases, and alcohol-containing fluids may induce stress cracking, particularly in geometries with high hoop stress or moulded-in residual stress. Chlorinated solvents and ketones reduce the softening temperature and are not recommended for load-bearing parts. The absence of crystallinity can increase permeability to some organic vapours relative to semi-crystalline PA12. Barrier performance in fuel lines or vapour separators should therefore be confirmed by permeation testing under ISO 7229 or ISO 15105-1.

Why Can This Grade Replace Polycarbonate in Clear Fluid-Handling Components but Not in Autoclave Trays?

Compared with polycarbonate, AUROmid PA12 TR90 natural 1102 offers lower density and improved resistance to many hydrocarbons. However, the maximum continuous service temperature is limited by HDT/A of 90 °C and Vicat B50 of 120 °C. Steam sterilisation at 121 °C or dry heat above 120 °C may produce distortion, surface fogging, or hydrolysis over repeated cycles. The grade is therefore unsuitable for reusable autoclave trays, surgical instruments, or laboratory cages requiring repeated high-temperature sterilisation. Compared with PMMA, the polyamide is tougher and less brittle, but PMMA can offer higher visible-light transmission and higher surface hardness. Compared with standard semi-crystalline PA12, the transparent grade has higher heat deflection temperature but lower barrier properties and lower resistance to hot polar media because the amorphous phase permits faster penetrant diffusion.

Post-Mould Solidification Without a Crystalline Plateau

Unlike standard PA12, which develops spherulitic crystallinity during cooling and shows a melting endotherm near 175–178 °C, the TR90 backbone remains amorphous because the cycloaliphatic building blocks disrupt chain regularity. Differential scanning calorimetry at 10 K/min shows a glass transition near 155 °C and typically no measurable crystalline melting enthalpy above 1 J/g. Structural stabilisation therefore occurs by vitrification only. The part is normally ejected when surface temperature falls below approximately 80–90 °C. Premature ejection creates out-of-flatness because the frozen skin is thin and no crystalline phase provides stiffness. If gate seal is lost, the absence of crystallinity also reduces post-shrinkage compensation. Holding pressure must be maintained until the gate freezes; otherwise, sink marks can appear over thick bosses even in flat geometries.

Optical transmission through 2 mm polished plaques is approximately 85–90 % in the visible range when measured by ISO 13468-2. Haze is usually below 3 % under ISO 14782. The natural grade is not crystal-clear like PMMA because the PA12 backbone imparts a slight yellow index. If colour-critical optical parts require low yellowness index, the part should be measured after conditioning because moisture uptake shifts the refractive index and can reduce light transmission through surface condensation. Through-transmission laser welding is restricted because the transparent matrix and amorphous morphology reduce beam absorption. Carbon-black or laser-absorbing additives are required for through-transmission welding.

ISO 294-4 mould shrinkage for a 60 mm × 60 mm × 2 mm plaque is typically 0.5–0.7 % parallel and 0.6–0.8 % perpendicular. The differential is small relative to semi-crystalline polyamides. Regrind from sprues and runners may be added up to 20 % in non-optical applications if the material is dried and free of contamination. For optical parts, regrind use should be avoided because repeated thermal history raises yellowness index and reduces lot-to-lot consistency.

If Regulatory Compliance Becomes a Decisive Criterion in Final-Part Qualification

Process boundaries include avoiding melt residence times above 30 minutes at melt temperatures above 270 °C, because amide interchange and thermal yellowing may shift molecular weight distribution and optical colour. Avoid combination with acidic polymers, amine-based release agents, or metallic stearates that can catalyse hydrolysis at processing temperatures. Purging after semi-crystalline polyamides or glass-filled compounds with a low-viscosity purging grade is recommended before moulding transparent parts. Parts destined for high-humidity service should be designed with generous radii and uniform wall thickness, and weld lines should be moved away from tensile load paths. Published data for welded assemblies in this specific configuration remains limited.