EMS-GRIVORY Grilamid TR 55 LY Nylon 12, Dry is a transparent amorphous polyamide supplied as dry-as-packaged pellets for injection moulding and limited profile extrusion. The grade designation places it within the Grilamid TR transparent polyamide family, while the LY suffix is associated with lubricated or release-modified processing behaviour; the exact additive package should be confirmed from the supplier for a specific lot. A Nylon 12 backbone is retained to limit equilibrium moisture uptake compared with short-chain aliphatic polyamides, while cycloaliphatic repeating units suppress crystallinity and produce optical clarity. Representative dry-as-moulded data include a density of 1.06 g/cm³ measured according to ISO 1183-1 and a tensile modulus of approximately 2200 MPa under ISO 527-1/-2. The dry condition is a packaging moisture specification, not a permanent state: pellets are typically sealed with residual moisture below 0.10%, but exposure to ambient air above 60% relative humidity initiates measurable re-adsorption through the amide groups.

Unlike semicrystalline PA 12, Grilamid TR 55 LY does not display a sharp crystalline melting point. Its thermal response is governed by a glass-transition temperature near 125°C under ISO 11357-1/-2 and a deflection temperature under load of approximately 100°C using ISO 75-1/-2 method A at 1.8 MPa. This distinction matters in service: the 125°C glass transition is not a continuous load-bearing use temperature, because modulus decays through the transition. The amorphous morphology reduces dry-state shrinkage and improves optical clarity but gives a different stress-strain response than oriented semicrystalline forms. Components requiring dimensional stability after moulding should therefore be evaluated at the expected service temperature and moisture condition rather than using dry-room data alone.

What processing constraints follow from the amorphous morphology of TR 55 LY?

Amorphous transparent polyamide melts are pseudoplastic and generally require higher melt temperature than semicrystalline PA 12 of comparable viscosity. Injection moulding should use a general-purpose three-zone screw with an L/D ratio of at least 20:1 and a non-return valve suited to low to medium viscosity polyamide melts. A closed-loop desiccant dryer with dew point below -40°C is recommended when pellets have been exposed to ambient air. Drying at 80°C for 4–8 h is typical, with the target final moisture below 0.10%. Hopper residence should be short, and the hopper should be blanketed with dry air where plant humidity exceeds 60%. Barrel settings from rear to nozzle of approximately 220°C, 250°C to 270°C, and 270°C produce a melt temperature of 250–280°C. Mould temperatures between 40°C and 80°C are used; the upper end of this range generally lowers internal stress and improves weld-line optics. Melt temperatures above 280°C can produce yellowing, and residence time at melt temperature should be held below 10 min to limit thermal degradation. Hot-runner systems with externally heated manifolds and no dead spots are preferred for transparent polyamide grades. Production-scale trials on hydraulic machines show that excessive screw decompression before recovery draws air into the melt and increases splay in clear mouldings.

Gate design influences optical quality and stress distribution. For wall thicknesses between 1.5 mm and 3.0 mm, gates should be located away from visible surfaces and sized to generate shear heating without jetting. Published moulding guidance for transparent amorphous polyamides recommends a minimum gate land length of 0.5–1.0 mm and a vent depth not exceeding 0.02 mm to release air without flash. Weld lines in clear parts can be minimised by raising mould temperature to 60–80°C and maintaining a moderate injection speed. Thin-wall components with flow-length-to-wall-thickness ratios above 150:1 may require higher injection pressure and gas counterpressure; published data for this specific thin-wall configuration in TR 55 LY is limited, so spiral-flow or cavity-short-shot studies are required before tool acceptance.

Humidity cycling and dimensional stability in transparent fluid-contact parts

Absorbed moisture plasticises the polymer and reduces the glass-transition temperature. The equilibrium water uptake of Grilamid TR 55 LY at 23°C in water is approximately 3.5% under ISO 62. By comparison, unreinforced PA 6 can exceed 9% under the same condition, which makes the Nylon 12-based grade less dimensionally reactive in humid service. A 2 mm moulding exposed to water at 23°C may increase in mass by 3.5%; the resulting linear expansion is lower than that observed in PA 6, but it is not zero. Moulders should test finished parts according to ISO 62 and ISO 294-4 when directional expansion matters, because moulded-in stress and flow orientation change the dimensional response. The polymer is not a vapour barrier; oxygen and carbon dioxide permeation should be evaluated under ISO 15105 if barrier performance is part of the application specification.

Values are single-point comparators drawn from supplier documentation and published literature; they are not a product specification. Lot-to-lot variation, conditioning history, wall thickness, and conversion method influence actual results. Compared with PMMA, Grilamid TR 55 LY has lower modulus and surface hardness but higher notched impact and better resistance to many alkaline cleaning agents. PMMA typically has a tensile modulus above 3000 MPa, whereas the polyamide grade is approximately 2200 MPa. Compared with polycarbonate, the polyamide grade offers lower density and better resistance to hydrocarbon fluids but lower heat deflection temperature and lower notched impact. Compared with transparent PA 6, the Nylon 12-based product reduces moisture-triggered dimensional change but may be less stiff and higher in raw-material cost.

Chemical exposure behaviour differs from polycarbonate. Transparent polycarbonate is prone to environmental stress cracking in the presence of plasticising solvents, whereas the polyamide 12-based grade typically tolerates aliphatic hydrocarbons, oils, greases, and many weak alkaline media. It is attacked by strong acids, oxidising agents, and some phenolic solutions; concentrated formic acid and m-cresol are known solvents for polyamides. For parts under moulded-in stress, exposure to methanol or ethylene glycol at elevated temperature can cause environmental stress cracking. Development programmes should include ISO 22088-1 strain testing or ASTM D543 immersion testing on finished mouldings rather than relying on dry-resin data. Published data for TR 55 LY in fuel blends containing high aromatic concentration is limited; qualification under SAE J2027 is recommended for automotive fuel-contacting transparency applications.

When repeated steam sterilisation is required in medical or food-contact tooling

Steam autoclave cycles at 121°C expose amorphous polyamide to both temperature and moisture. Because the glass-transition temperature is near 125°C, a 121°C sterilisation cycle places the polymer close to its thermal transition. Temporary haze can appear as water is absorbed; transparency is usually recovered after drying unless oxidative surface damage has occurred. Repeated autoclave cycles may reduce tensile strength, so qualification plans should include ISO 527-1/-2 testing after 50 and 100 autoclave cycles rather than after a single cycle. For medical device components, final-article biocompatibility testing per ISO 10993-1 is required; resin-level statements are not sufficient for finished-device compliance. Food-contact status may be evaluated under FDA 21 CFR 177.1500, but the additive package, colourants, and processing aids require explicit supplier confirmation for the exact grade and end-use condition. High-pH detergents and dry-ice cleaning should be avoided because alkaline hydrolysis can occur at elevated temperature and reduce surface clarity.

Assembly and post-machining operations influence performance. Machined holes and cut edges create stress concentrations that in clear polyamide may show microcrazing when exposed to alcohol-based cleaning agents. Annealing at 80–100°C for 2 h in dry air can reduce moulded-in stress; however, annealing near or above the heat deflection temperature can distort parts, so supported or fixed annealing is required. Ultrasonic welding can be performed with a shear joint and low amplitude to avoid melt flash and transparency loss. Laser welding of transparent polyamide to a laser-absorbing counterpart has been demonstrated, but process limits for TR 55 LY should be established according to DVS 2216-1 or the supplier welding guidelines. Solvent bonding is generally not recommended; cyanoacrylate adhesives may stress-crack amorphous polyamide in the presence of residual moisture.

Typical applications include transparent filter bowls, sight glasses, flow meters, cosmetic packaging, pump housings, and clear technical housings where hydrocarbon resistance and low moisture absorption are required. For internal pressure-bearing components, creep rupture data must be generated under ASTM D2990 or ISO 899-1, because momentary tensile strength alone is insufficient. Components subjected to ultraviolet exposure require a UV-stabilised alternative grade or secondary topcoat; the standard dry grade is not a weatherable formulation. The principal operational boundaries for Grilamid TR 55 LY are maximum continuous use temperature, resistance to strong acids and oxidising media, sensitivity to moisture before processing, and relaxation behaviour under load at elevated temperature. Where service involves hot water above 80°C under stress, glycol/water mixtures above 90°C, or fuel blends with high aromatic content, prototype testing under end-use conditions is mandatory. Published data for this specific configuration under combined hot-water and glycol exposure is limited, so a direct substitution from polycarbonate or polysulfone should not be made without comparative testing.