When a specification references EMS-Grivory Grilamid TR 90 Nylon 12, Conditioned, the designation identifies an amorphous transparent polyamide 12 from EMS-Grivory that has been equilibrated under ISO 1110 conditions at 23°C and 50% relative humidity. The conditioned state is not a separate polymer, additive package, or surface treatment; it is a physical moisture-equilibrium condition in which the polymer absorbs approximately 0.5–0.7 wt% water. Absorbed water plasticises the amorphous matrix, reducing stiffness and glassy-state modulus while increasing ductility and impact absorption. Because the properties of polyamides shift with moisture content, conditioned data are preferred when components operate in humid air, contact perspiration, or are subjected to intermittent condensation. Grilamid TR 90 is distinguished from semicrystalline polyamide 12 by optical clarity: the absence of spherulitic crystallinity suppresses light scattering, yielding natural transparent grades with light transmission reported by the manufacturer above 90% at 2 mm wall thickness according to ISO 13468-2. Nominal density is 1.00 g/cm³ per ISO 1183-1, lower than polycarbonate and many transparent engineering thermoplastics. The grade is supplied in natural, UV-stabilised, and pigmented variants, and is processed by injection moulding and extrusion into spectacle frames, medical housings, automotive fluid reservoirs, industrial sight glasses, and transparent fluid-handling components.

How Does Moisture Equilibrium Affect Stiffness, Impact, and Electrical Behaviour?

The property shift between dry-as-moulded and conditioned Grilamid TR 90 is measurable and design-relevant. In the dry state, the amorphous polyamide 12 backbone exhibits a tensile modulus on the order of 1.6 GPa and yield stress near 60 MPa when tested to ISO 527-1/-2. After conditioning to 23°C and 50% RH, tensile modulus typically falls to approximately 1.2 GPa and yield stress to approximately 50 MPa. The reduction is smaller than that observed in PA 6 or PA 66, whose equilibrium moisture uptake at the same relative humidity is several times higher. The following table compares representative manufacturer-published values for natural-grade material; values for coloured or UV-stabilised variants can differ by formulation, wall thickness, and conditioning time.

Impact behaviour is particularly moisture-sensitive. The notched Charpy value at 23°C rises from the dry value to a conditioned value near 11 kJ/m² because absorbed water acts as a plasticiser and increases molecular mobility. Unnotched specimens typically do not break in either state, but conditioned material gives higher toughness for snap-fit insertion and impact-loaded optical housings. The electrical insulation behaviour moves in the opposite direction: absorbed water increases ionic mobility, so volume resistivity and surface resistivity measured after conditioning are lower than dry values by one to two orders of magnitude. Electrical design should therefore use conditioned values for devices exposed to sweat, wet wiping, or tropical storage, not dry-as-moulded electrics. Flexural and creep properties follow a corresponding reduction; published data for this specific configuration are limited, so long-term load-bearing parts in humid service require application-specific creep testing rather than linear extrapolation from dry short-term values.

Melt processing of Grilamid TR 90 is controlled by its amorphous morphology. No crystallisation plateau exists in the screw-recovery or cooling phases, so mould shrinkage is more isotropic than in semicrystalline PA 12, and warpage is reduced in thick-to-thin transitions. Pre-drying at 80°C in a dehumidified-air dryer with dew point below −30°C is required to a residual moisture level below 0.10 wt% before injection moulding or extrusion. Because transparent polyamide regains moisture rapidly, dried pellets should be conveyed in closed lines or blanketed with dry air. On production-scale profile extrusion lines using a 25 mm single-screw extruder with L/D 30, moisture regain after 2 h of open hopper exposure at relative humidity above 60% has been associated with bubble defects in the extrudate. For standard injection moulding, melt temperature is maintained between 240°C and 280°C, with mould temperature between 60°C and 90°C. The upper portion of the mould-temperature range improves surface gloss and reduces anisotropic stress in transparent parts. Because the material is amorphous, holding pressure and cooling time are set by part wall thickness rather than by crystallisation kinetics. Overheating above 300°C or excessively long residence time can produce yellowing and molecular-weight reduction; therefore, shot size should normally occupy 50–80% of barrel capacity and total residence should be kept below 10 min at melt temperature. For sheet and profile extrusion, a single-screw extruder with L/D 25–30 and a barrier or mixing screw is used, with melt temperature near 250°C and calibration or roll temperatures in the 60–90°C range.

Tooling and part-design decisions for transparent Grilamid TR 90 depend on the same amorphous-flow behaviour that reduces warpage. Mould surfaces are typically polished to SPI/SPE A-1 or A-2 finishes because surface roughness transfers directly to the optical part. Venting in the cavity and runner system is specified at 0.02–0.03 mm land depth to prevent burn marks and silver streaks without generating flash. Gate placement is biased toward thick sections; fan gates, side-edge gates, and cold runners with cold slug wells are preferred over small pinpoint gates that can produce jetting and flow lines in transparent parts. Hot-runner systems with stagnant zones or dead corners can cause yellowed resin to enter the melt stream, producing visible colour streaks. Regrind usage for optical parts is generally limited to 20–30%, and the fraction must be dry, dust-free, and free of black specks. In production-scale injection moulding on machines with clamp force between 600 kN and 1,200 kN, gate freeze must be confirmed before hold-pressure release because premature hold release in amorphous transparent parts creates sink marks and refractive-index changes around the gate. These defects are not always visible until the part is viewed under crossed polarisers or after moisture conditioning.

When Transparent Amorphous Polyamide 12 Replaces Polycarbonate in Chemical-Contact Optics

Grilamid TR 90 occupies a position between polycarbonate, PMMA, semicrystalline PA 12, and other transparent polyamides. Compared with polycarbonate, Grilamid TR 90 has a lower density, 1.00 g/cm³ versus 1.20 g/cm³, lower tensile modulus, and typically better resistance to environmental stress cracking in the presence of many oils, greases, and non-polar media, although polycarbonate remains superior in dry heat deflection under load and in scratch-related surface hardness when hard-coated. The polyamide 12 chemistry of Grilamid TR 90 provides lower equilibrium moisture uptake than PA 6 or PA 66; at 50% RH, PA 66 absorbs around 2.5 wt% water, whereas Grilamid TR 90 absorbs roughly 0.5–0.7 wt%. As a result, the conditioned tensile modulus of Grilamid TR 90 drops less from its dry value than that of PA 66.

Against PMMA, Grilamid TR 90 has higher impact toughness and better chemical stress-cracking resistance to ethanol, sunscreen, and perspiration, but PMMA offers higher light transmittance, higher surface hardness, and lower moisture-induced dimensional change in non-contact optical applications. Compared with semicrystalline PA 12, the amorphous TR 90 grade provides optical transparency and a higher glass transition temperature, but semicrystalline PA 12 retains a crystalline phase that can act as a barrier and may be preferred for certain fuel-contact applications requiring maximum aliphatic hydrocarbon resistance. Within the EMS-Grivory transparent polyamide range, grades differ primarily in melt viscosity and additive packages: UV-stabilised and blue-tinted variants are available where outdoor exposure or cosmetic neutrality is required. Selection between such grades is based on flow length, ultraviolet exposure, and food-contact or medical-grade documentation rather than on base polymer chemistry alone.

For outdoor optical parts, UV-stabilised variants are specified; natural-grade material without UV absorber is not recommended for prolonged direct weathering because photo-oxidation at the surface can produce yellowing and microcracking. Artificial weathering under ISO 4892-2 with xenon arc and moisture cycles is used for validation. Published data for this specific configuration are limited, so component-level UV testing is required for sunglass frames and exterior sensor lenses.

Thermal, Chemical, and Regulatory Boundary Conditions for Conditioned Grilamid TR 90

Continuous-use temperature in air for natural Grilamid TR 90 is constrained by thermo-oxidative stability rather than by melting. The material remains shape-stable at moderate load up to approximately 110–120°C as measured by ISO 75-1/-2 at 1.8 MPa under dry conditions; moist environments slightly lower this limit because water plasticises the matrix. Prolonged exposure above 130°C can induce yellowing and embrittlement unless oxygen is excluded. The polymer is resistant to many non-polar oils, greases, fuels, alcohols, and aqueous salt solutions, but it is incompatible with strong mineral acids, oxidising acids, and certain chlorinated solvents that can cause swelling or surface attack. Amine-based chemical environments and some phenols should be evaluated case by case because they can induce stress cracking.

Food-contact and medical applications require grade-specific compliance verification. Depending on the exact grade and colourant package, EMS-Grivory may provide documentation referencing FDA 21 CFR 177.1500 or EU Regulation (EC) No 10/2011; not all variants are listed for all food types, and migration testing under the intended temperature and simulant conditions remains the responsibility of the food-contact article manufacturer. For medical devices, selected grades are supplied with biocompatibility documentation according to ISO 10993-1 for specified contact durations and sterilisation cycles. Steam autoclave, ethylene oxide, and gamma irradiation are commonly used, but repeated steam exposure above 134°C can reduce molecular weight and shift optical properties; gamma radiation above standard doses can produce measurable colour shift. Electronic and industrial applications are subject to RoHS and REACH documentation supplied by the resin producer for the specific SKU.

In transparent fluid-handling parts, the conditioned state is particularly relevant because the component is often in equilibrium with humid air on the outer surface and an aqueous or hydrocarbon fluid on the inner surface. The resulting moisture profile can create a through-thickness gradient in modulus and refractive index; designers should avoid treating conditioned values as uniform through thick sections. For optical parts with wall thickness above 5 mm, moisture diffusion time to equilibrium can exceed several weeks at 23°C, so short-term testing may not reflect final service properties. Published data for this specific gradient condition are limited; therefore, functional validation under the intended temperature, humidity, and chemical exposure is required.