EMS-Grivory Grilamid TR 90 LXS PAMACM12 is an amorphous transparent polyamide manufactured from bis(4-amino-3-methylcyclohexyl)methane (MACM) and dodecanedioic acid (C12). The chemical designation PAMACM12 identifies the repeat unit formed from the cycloaliphatic diamine and the 12-carbon dicarboxylic acid. The grade suffix LXS designates a light-stabilised formulation built on the standard Grilamid TR 90 base resin. In specification records, the material is listed as an amorphous polyamide for injection moulding of transparent optical and structural components. Typical application categories include eyewear frames and lenses, transparent sensor housings, light-guide components, and cosmetic packaging where chemical resistance and low part mass are specified. Representative values cited below are drawn from supplier technical literature and are tested according to the indicated standards; lot-specific certificates should be requested for production validation.

What Distinguishes PAMACM12 from Other Transparent Polyamides?

The primary structural difference in PAMACM12 is the combination of a cycloaliphatic diamine with a long-chain aliphatic dicarboxylic acid. The cycloaliphatic MACM unit suppresses crystallinity, while the C12 segment reduces amide-group density relative to shorter-chain polyamides. This changes water absorption, density, and dimensional stability. Compared with Grilamid TR 55, another amorphous transparent polyamide in the same product family, Grilamid TR 90 LXS has a supplier-reported density of 1.00 g/cm³ per ISO 1183-1, whereas TR 55 is listed at approximately 1.06 g/cm³. Water uptake at equilibrium is lower for the C12 backbone. The LXS suffix separates the grade from unmodified TR 90 because the stabiliser package is intended to reduce colour shift and transmittance loss under ultraviolet exposure. Compared with semicrystalline PA6 and PA66, PAMACM12 does not develop spherulitic crystallinity during normal injection moulding; transparency is therefore retained. However, the amorphous structure also means that true crystalline melting is absent, and upper service temperature is defined by the glass transition and heat deflection behaviour rather than by a melting point.

Representative dry-as-moulded physical data for Grilamid TR 90 LXS are listed below. The values are single-point supplier data and should not be treated as minimum or maximum specification limits.

In optical applications, transmittance and haze are not resin constants alone; they are influenced by tool polish, gate design, wall thickness, and melt-temperature history. Total luminous transmittance at 2 mm thickness is approximately 91 % when measured according to ISO 13468-1. The light-stabilised LXS formulation is intended to improve retention of transmission and reduce yellowing under xenon-arc exposure per ISO 4892-2, with the supplier reporting indicative exposure curves rather than a single universal lifetime. For edge-lit light guides, total transmittance alone is insufficient; luminous distribution, internal haze, and edge-surface polish need to be measured on production-configured injection tools. Published data for this specific optical configuration are limited and should be generated with the selected gate geometry and mold finish.

Secondary operations such as laser welding, hard coating, and solvent bonding require process-specific qualification. Laser welding of natural transparent PAMACM12 is possible in through-transmission geometry using a 940 nm diode laser and an absorbing mating part or additive, because the natural grade transmits a significant fraction of near-infrared radiation; the exact transmission window at the weld wavelength should be measured on moulded plaques. Hard coats applied to lenses and sensor windows must withstand the low surface energy of polyamide; adhesion is typically improved by plasma or corona treatment. Solvent bonding can induce local stress cracking; cycloaliphatic and ester-based solvents should be screened by ISO 22088-2 before production release.

For outdoor-exposed components, the LXS grade can be evaluated by ISO 4892-2 using method A artificial weathering with xenon-arc and daylight filter. The test parameters include irradiance at 0.51 W/m² at 340 nm, black-standard temperature of 65 °C, and chamber temperature of 38 °C; the supplier should be asked for matching data on the specific colour and thickness. If the part is used in an automotive interior, comparison with ISO 105-B06 or OEM-specific lightfastness protocols is required, because the UV dose and temperature differ from outdoor exposure.

Injection Molding and Drying Boundaries for Grilamid TR 90 LXS

Pre-drying is mandatory before melt processing. The material must be dried in a desiccant dryer to a residual moisture level of ≤0.10 % by weight. Supplier processing guidance specifies drying at 80 °C for 4–8 h with a drying-air dew point of −30 °C or lower. At ambient relative humidity above 60 %, dried material should be transferred to the press through a dry-air-conveyed closed hopper; open-air exposure should not exceed 10 min. Melt temperature is normally set between 250 °C and 280 °C, with nozzle set points not exceeding 290 °C to avoid yellowing. Mold temperature should be maintained between 60 °C and 100 °C; the upper portion of this range improves replication in highly polished optical cavities but raises cycle time. A 25 mm reciprocating screw with an L/D ratio of 20:1 and a compression ratio of 2:1–2.5:1 is suitable for production-scale molding. Holding pressure is typically 50–80 MPa, with back pressure kept at 0.5–1.5 MPa to homogenise the melt without excessive shear-heat generation. Residual moisture above 0.10 % at melt temperature causes splay, bubbles, and a reduction in Charpy notched impact strength due to hydrolysis of the amide backbone.

Hot-runner systems for transparent PAMACM12 should be open-channel with heated tips and no dead spots; valve-gate sequential control is preferred for lenses and sensor covers to minimise gate blush and flow lines. Mold shrinkage is approximately 0.7–0.9 % in the flow direction and 0.8–1.0 % transverse when measured according to ISO 294-4, but ribbed housings and non-uniform wall thickness will produce local deviation. Shot-to-shot variation on production presses is controlled by limiting melt residence time to less than 5 min at 280 °C, because prolonged residence shifts optical transmission and can produce visible yellowing or black specks from degraded material. Purging with transparent PMMA or a supplier-recommended purge compound should follow machine shutdown when the cylinder is dedicated to transparent parts. Melt-volume-flow-rate checks under ISO 1133-1 at 275 °C and 5 kg load can support incoming resin consistency; suppliers publish a nominal range for the specific flow variant.

In production-scale injection moulding of transparent housings, incoming resin consistency is commonly monitored by melt volume-flow rate under ISO 1133-1 at 275 °C and 5 kg load. The supplier’s certificate of analysis reports lot-specific data for density, moisture content, and, where requested, optical transmission on standard plaques. Processing records on a 25 mm reciprocating screw show that shot-to-shot variation in optically critical parts is reduced when screw recovery is maintained at 50–100 rpm and cushion is held above 2 mm. Variation in moulded colour can arise from dwell time, not resin lot differences; thermal imaging of the mold surface should be used to detect cooling-channel imbalance exceeding 5 °C across the cavity.

When Grilamid TR 90 LXS Replaces PMMA in Stress-Cracking-Sensitive Optical Housings

In transparent housings where PMMA exhibits low-impact fracture or stress cracking around metal inserts, Grilamid TR 90 LXS offers a notched Charpy impact strength of 12 kJ/m² at 23 °C per ISO 179-1/1eA and an unnotched Charpy value of no break per ISO 179-1/1eU. Its density of 1.00 g/cm³ per ISO 1183-1 is approximately 16 % lower than the 1.19 g/cm³ typical of PMMA. The tensile modulus of 1600 MPa is roughly half the 3300 MPa typical of PMMA; structural replacements therefore require thicker rib sections or metal reinforcement. Compared with polycarbonate, Grilamid TR 90 LXS has lower density and better resistance to some semi-polar cleaning agents, but the heat deflection temperature is lower. The table below provides representative standardised values for material substitution screening. Design validation must include load-bearing tests on production parts because standard test plaques do not capture weld-line effects, insert stress, or moulded-in orientation.

Application examples include ophthalmic frames and lenses, transparent housings for handheld devices, sensor covers, light-guide components, and cosmetic packaging. In eyewear frames, the combination of low density and no-break unnotched Charpy at 23 °C is a critical processing and service criterion. For sensor covers, the material is used where the cover must survive repeated cleaning agents without environmental stress cracking; transmittance at the required wavelength should be measured on the actual wall thickness using ISO 13468-1. For light-guide components, tool surface and gate placement dominate output uniformity; resin selection should include an assessment of warpage after conditioning at 23 °C and 50 % RH according to ISO 62.

Because the MACM12 backbone is amorphous, chemical resistance follows the polyamide pattern but the long C12 segment reduces moisture-induced property shifts. Immersion testing according to ISO 175 is used to evaluate compatibility with aliphatic hydrocarbons, oils, greases, and neutral aqueous solutions. Polar solvents such as alcohols and ketones can swell the material at elevated temperature; strong acids and strong bases attack the amide group and reduce molecular weight. Stress-cracking screening can be conducted under ISO 22088-2 using constant-strain fixtures; field reports describe replacement of polycarbonate in housings exposed to semi-polar cleaning agents, but concentration, strain, and temperature boundaries must be validated with the supplier’s chemical-resistance database. Food-contact status is not an intrinsic property of the resin alone; grade-, lot-, and condition-specific compliance declarations should be obtained under FDA 21 CFR 177.1500 and EU Regulation (EU) No 10/2011. Electrical and electronic applications may require documentation against Directive 2011/65/EU and Regulation (EC) No 1907/2006.

The TR 90 base chemistry is also offered in different flow and stabilisation variants. Higher-flow grades may have slightly lower impact strength; flame-retardant transparent polyamide grades may contain phosphorus-based additives and require different drying and mold temperature windows. The PAMACM12 designation should not be treated as interchangeable with PAMACM9 or PAMACM14, which use different dicarboxylic acid chain lengths and have different water absorption, density, and flexibility. When substituting between transparent polyamide grades, the full ISO data set must be compared because density alone does not predict shrinkage or processing behaviour.

Operational boundaries are defined by moisture, temperature, and chemical environment. Continuous exposure to hot water above 80 °C can hydrolyse the amide chain and reduce mechanical properties; steam sterilisation at 121 °C should not be specified without supplier validation. Alkaline media above pH 10 and acidic media below pH 3 can accelerate surface attack and depth-dependent degradation. The LXS light-stabilisation package does not provide an indefinite outdoor service life; direct-sunlight parts should be tested under ISO 4892-2 and, where possible, correlated with outdoor exposure according to ISO 4582. Painted or coated surfaces may require plasma or primer treatment because the low-surface-energy polyamide surface can reduce adhesion. If load-bearing dimensions are exposed to elevated temperature, the HDT A value under 1.80 MPa of 98 °C should be used as an upper reference, not as a continuous-use limit; creep modulus curves should be requested from the supplier for the specific service temperature.