EMS-Grivory Grilamid TR 90 UV is an amorphous, light-stabilized transparent polyamide moulding compound based on a PA 12/MACMI backbone. The designation “Nylon 12, Conditioned” refers to the moisture state obtained during accelerated conditioning according to ISO 1110, typically at 70 °C and 62 % relative humidity until equilibrium moisture intake. In this state, tensile modulus and yield stress decrease relative to dry-as-moulded values, while notched impact and elongation response increase. Density is 1.00 g/cm³ when determined by ISO 1183-1, which places the material in the low-density class of unfilled transparent polyamides. The material is supplied as cylindrical granules and is intended for injection moulding of transparent functional components.

The amorphous character is achieved by interrupting the crystallizable PA 12 sequence with cycloaliphatic diamine-derived co-monomers. This molecular design suppresses spherulitic crystallization during cooling and produces a single-phase transparent matrix. Water absorption at saturation in 23 °C water is approximately 3.0 %, and the conditioned moisture level relevant to ISO 1110 is lower because conditioning is performed at 70 °C and 62 % relative humidity. Equilibrium moisture under standard test atmosphere 23 °C/50 % RH is approximately 1.5 % by weight, which is lower than many short-chain aliphatic polyamides but higher than polycarbonate or PMMA.

The grade differs from semicrystalline polyamide 12 in morphology rather than polymer class alone. Because the backbone is formulated to suppress crystallinity, optical clarity is retained in wall thicknesses up to approximately 3 mm, depending on mould temperature and cooling rate. Published transmission data for this specific conditioned configuration are limited; however, unfilled amorphous polyamides of this family typically show total luminous transmittance above 90 % at 2 mm thickness when measured against ISO 13468-1. Residual haze in thick sections is controlled by avoiding excessive shear heating and by maintaining mould temperature above the recommended lower limit. The commercial designation “TR 90 UV” identifies the amorphous transparent polyamide family and the ultraviolet light stabilization package; the modifier “Nylon 12, Conditioned” is often used in database-driven material selection to distinguish it from dry-as-moulded data sets and from semicrystalline PA 12 grades. In electronic material databases, the conditioned data set is paired with the same density but altered mechanical and thermal properties according to ISO 1110. Users who export data into simulation tools should verify whether the imported modulus corresponds to the dry or conditioned state because the difference can exceed 10 % in tensile modulus.

How does accelerated moisture uptake shift the short-term mechanical profile?

Conditioning introduces 1.0–1.5 % moisture into the amorphous matrix, acting as a plasticizer. Tensile modulus determined at 1 mm/min per ISO 527-1/-2 decreases from approximately 1600 MPa dry to 1400 MPa conditioned. Yield stress shifts from approximately 60 MPa to 50 MPa. Tensile strain at yield moves from 6 % to 7 %, while nominal strain at break remains above 50 % in both states. Charpy notched impact according to ISO 179/1eA at 23 °C rises from approximately 10 kJ/m² dry to 15 kJ/m² conditioned; at −30 °C the notched impact remains in the range of 8–10 kJ/m². These are representative values for natural grades, and lot-to-batch variation should be verified against the shipping certificate.

These values are not specification limits and must not be used as design allowables without project-specific verification. The shift from dry to conditioned values is reversible on drying, which is relevant when dimensional checks are performed after moulding.

Injection moulding parameters and melt-phase considerations

The material is processed on reciprocating-screw injection moulding machines with a screw L/D ratio of 20:1 to 25:1 and a low-compression screw to minimize shear-induced degradation. Recommended melt temperature is 250–270 °C, measured at the nozzle, with barrel zones from feed to nozzle typically set at 230 °C, 240 °C, 250 °C, and 260 °C. Mould temperature is set between 40 °C and 80 °C. The lower portion of the mould-temperature range supports faster cycle times; the upper portion is preferred for polished lens surfaces and for thick sections exceeding 3 mm where flow marks and internal stress must be minimized.

Residual moisture at processing must be controlled below 0.10 % by weight. A desiccant dryer with a dew point of −30 °C or lower and a drying temperature of 80 °C for 4–6 h is required for material in open containers. Drying performance is monitored by sampling from the machine feed throat and measuring moisture by Karl Fischer coulometric titration according to ISO 15512. Typical residual moisture after 4 h at 80 °C in a desiccant dryer with dew point −40 °C is 0.05–0.08 %. In high-humidity environments above 60 % RH, hopper drying should be maintained with insulated feed lines to prevent re-absorption. Moisture levels above 0.10 % produce silver streaks, splay, and hydrolysis-induced molecular weight reduction in the melt. If the hopper residence time exceeds 12 h, the material may yellow slightly even under hopper nitrogen purge, and regrind content should be limited to 20 % by weight to avoid additive depletion.

Short-shot defects in thin-wall optical housings are observed when nozzle temperature falls below 240 °C; flow leaders should be sized at least 0.8 mm for wall sections below 2.0 mm to prevent premature gate freeze. Published processing guides for EMS Grilamid TR grades recommend holding pressure 60–80 MPa hydraulic, with a changeover position adjusted so that cushion remains 3–5 mm. Screw rotation should be kept below 100 m/min peripheral speed to limit frictional heat and preserve the UV stabilizer package. Injection velocity is set to fill 80–90 % of cavity volume within 0.5–1.0 s for thin-wall parts, followed by a controlled switchover to holding pressure. Excessive shear rates above 10 000 s⁻¹ should be avoided in gate regions because molecular orientation and birefringence can increase. Simulation with Cross-WLF viscosity parameters calibrated at 250 °C, 270 °C, and 290 °C is recommended for complex light-guide geometries.

Tool venting is critical because volatiles from the UV stabilizer package can produce burn marks at the end of fill. Vent depths of 0.02–0.03 mm are used for polyamide grades; vent land length should not exceed 2 mm. For polished lenses, vacuum venting with a system pressure below −0.08 MPa relative to atmospheric reduces gas entrapment and improves replication of micro-optical features. Hot-runner systems with open-pipe nozzles are acceptable if melt residence time is less than 10 min at 260 °C. In cold-runner tools, full-round runners with diameters of 4–6 mm are used for medium-shot components; tunnel gates require a minimum land length to restrict excessive shear. On multi-cavity spectacle frames, cavity-to-cavity fill imbalance can be corrected by runner balancing to less than 5 % difference in shear-rate history across cavities. If a cavity experiences gas burn at the parting line, vent depth should be reduced from 0.03 mm to 0.02 mm only after confirming that parting-line flash is not created at 60 MPa holding pressure.

Relative to semicrystalline PA 12 grades, Grilamid TR 90 UV exhibits isotropic shrinkage and lower shear sensitivity because solidification is not dominated by crystallization. Mould shrinkage is typically 0.4–0.6 % for unrestricted flow direction at 2 mm wall thickness, with post-mould shrinkage below 0.1 % after 24 h at 23 °C. The absence of a crystalline melting peak means the material undergoes a glass transition near 155 °C when measured by differential scanning calorimetry at 10 K/min. This places dry heat deflection temperature under 1.8 MPa load in the range of 90–110 °C, lower than some reinforced crystalline polyamides but consistent with transparent amorphous thermoplastics.

The UV-stabilized formulation is intended for applications in which PMMA may require secondary hardcoating or polycarbonate may suffer solvent stress cracking. Typical use cases include spectacle frames, protective visors, sensor covers, light pipes, and transparent housings for consumer electronics. The material retains amorphous optical clarity while providing a lower density than polycarbonate and better resistance to sebum and cosmetic agents than PMMA in laboratory immersion tests. Published data for long-term outdoor weathering of the conditioned UV grade are limited; accelerated weathering should be performed according to ISO 4892-2 using cycle 1 or cycle 2 conditions with black-standard temperature 65 °C and relative humidity 50 %.

Transparent grades of this family are sensitive to abrasive cleaning and to alkaline hydrolysis under prolonged immersion at pH above 10. Optical performance after conditioning is influenced by the moisture-induced reduction in refractive index and stress-optical coefficient. Refractive index at 589 nm is approximately 1.51; light pipe designs must account for increased dispersion relative to PMMA. The UV stabilizer package suppresses surface microcracking better than external UV lacquers, but it does not provide a hard scratch-resistant surface; Taber abrasion resistance is lower than glass and coated polycarbonate.

The UV package includes hindered amine light stabilizer and UV absorber components, which can contribute to a slightly higher yellowness index immediately after moulding compared with the unstabilized Grilamid TR 90. Yellowness index measured per ASTM E313 may be 1–2 units higher in the UV grade; after weathering, the stabilized grade shows lower delta yellowness index than the unstabilized control. The stabilizer does not eliminate the need for thermal discipline; residence time above 280 °C can deplete the UV absorber and create localized gel particles. Batch-to-batch variation in yellowness index of natural grades has been reported below ±0.5 units when measured on 2 mm plaques; this is acceptable for non-optical cosmetic components but may require lot qualification for lenses.

Compared with unstabilized Grilamid TR 90, the UV grade shows a small melt-viscosity difference at low shear rates because of the stabilizer package. Spiral flow data for the UV grade should be requested from the supplier because the stabilizer package can reduce flow length by 5–10 % compared with unstabilized TR 90. This must be considered when converting existing tools qualified with non-UV TR 90.

Published capillary rheometry data for the UV grade are limited; however, unfilled amorphous polyamides of this family typically show shear-thinning behaviour in the temperature window 250–270 °C, with apparent viscosity at 1000 s⁻¹ below 200 Pa·s. Rheological lot qualification is recommended for thin-wall designs below 1.5 mm.

Against PMMA, this polyamide offers higher elongation at break and better impact resistance, but lower surface hardness and higher moisture uptake. Against transparent polycarbonate, Grilamid TR 90 UV has lower density by approximately 20 %, higher flow length for equivalent wall thickness, but lower notched impact at room temperature. Solvent stress-crack resistance in isopropanol and synthetic sebum is generally superior to PMMA and polycarbonate; however, published test data for the UV-conditioned grade are limited, and chemical compatibility should be confirmed using ISO 22088-3 constant-strain immersion testing.

Joining and assembly operations require prediction of the conditioned moisture state. Laser transmission welding of Grilamid TR 90 UV to itself is feasible if the upper, transparent part is kept below 0.10 % moisture and the lower absorbing part contains a laser absorber. Adhesive bonding with cyanoacrylate or two-component polyurethane adhesives can be used, but polyurethane adhesion may improve on flame- or plasma-pretreated surfaces. Solvent bonding is not recommended because aggressive solvents can induce microcrazing in the amorphous matrix. Post-mould anti-scratch hardcoats can be applied by spray or dip coating; adhesion requires cleaning with isopropyl alcohol and drying at 60 °C for 30 min before coating. The conditioned state does not interfere with vacuum metallization after adequate pre-bake at 80 °C to remove surface moisture. Published bonding strength data for the conditioned UV grade are limited.

Published declarations for the EMS-GRIVORY Grilamid TR 90 UV grade list compliance with RoHS Directive 2011/65/EU as amended by delegated directive (EU) 2015/863 and REACH Regulation 1907/2006. The material does not contain intentionally added perfluorooctanoic acid. The grade is not intended for implantable medical devices or for continuous food-contact use unless specific regulatory approval is obtained for the finished article. In applications where the conditioned state is part of the service condition, dimensional and mechanical verification should be performed on specimens conditioned according to ISO 1110 because dry-as-moulded data may overestimate stiffness and underestimate impact. For cover lens tooling, the combination of 80 °C mould temperature and 60 MPa holding pressure has been used to reduce stress birefringence; published data for this specific configuration is limited.