EMS-Grivory Grilamid TR 90 NZZ nat is an impact-modified, transparent polyamide 12 (PA 12) supplied as natural, unpigmented granules and designated for processing in the dry condition. The base polymer is an amorphous PA 12, which distinguishes it from semi-crystalline PA 12 grades by the absence of a true melting endotherm; thermal characterisation under ISO 11357-1/-2 identifies a glass transition rather than a melting point. In the impact-modified variant, a dispersed elastomeric phase is incorporated to shift dry-state failure from low-energy crack propagation toward shear yielding. The natural designation indicates that no visible-light-scattering pigments are included, although the base resin may contain process stabilisers. Because optical clarity in a two-phase blend requires the dispersed phase to be either below the scattering threshold or refractive-index matched to the matrix, the NZZ nat variant is controlled during compounding to preserve transparency while increasing energy absorption. Current EMS-Grivory material datasheets should be consulted for grade-specific melt volume-flow rate, mechanical values, and processing limits; the technical descriptions below are typical family data referenced to the stated test standards and are not purchase specifications.

What Distinguishes Grilamid TR 90 NZZ nat from Unmodified Transparent Polyamide 12?

Unmodified transparent PA 12 grades in the Grilamid TR 90 family typically exhibit dry notched Charpy impact strength values of 8–12 kJ/m² at 23 °C under ISO 179-1:2010. The impact-modified designation changes the ductile-brittle transition: at temperatures below 0 °C, a non-modified transparent PA 12 can fall below 4 kJ/m², whereas an impact-modified grade retains a larger fraction of its room-temperature impact energy. The trade-off is expressed as a reduction in tensile modulus and surface hardness. For transparent impact-modified grades, the modifier particle size must remain below approximately 200 nm for low haze; if compounding is performed on a twin-screw extruder without sufficient distributive mixing, coalescence of the elastomer phase produces a milkier appearance and non-uniform impact resistance across a moulded part. Viscosity also changes: the addition of an impact modifier generally raises complex viscosity in the low-shear region, so the melt volume-flow rate measured under ISO 1133-1:2022 on an impact-modified grade may be lower than that of an unmodified TR 90 grade at the same temperature and load. In thin-wall flow lengths, this viscosity increase can be offset by raising melt temperature within the recommended band, but the residence-time limit must not be exceeded.

Typical property envelope for Grilamid TR 90 grades in the dry, as-moulded state is shown below. Values are derived from manufacturer technical literature for transparent PA 12 and may vary by modifier content, colour, and conditioning history.

These values are not grade-specific purchase specifications. For the NZZ nat variant, the impact-modified shift is most visible in notched Charpy values and possibly in a small reduction in light transmittance compared with non-impact-modified transparent PA 12. Conditioning to equilibrium moisture increases energy absorption but lowers modulus; therefore, the dry moulded state is the most conservative condition for load-bearing design.

Optical performance is evaluated not only by total light transmittance but by haze, yellowness index, and clarity. Under ASTM D1003-21, a natural transparent PA 12 grade can show total transmission above 88 % through a 2 mm plaque, but haze is influenced by mould polish, surface texture, dust, and processing moisture. A mirror-polished tool with surface roughness below 0.1 µm Ra can reduce surface scattering; if the mould surface is not polished, measured haze increases without a change in bulk transmittance. The impact modifier presents a second scattering source. In an optimised dispersion, the elastomer phase is either fine enough or refractive-index matched such that bulk haze remains below 5 %. Compounding on a co-rotating twin-screw extruder with an L/D ratio of 40:1 or greater and controlled screw temperature profile is used to prevent thermal damage to the modifier and to break the elastomer phase to the target particle size; after pelletising, the granulate is dried and sealed to prevent moisture regain.

The Dry Moulded State Controls Impact Response and Mechanical Property Retention

After injection moulding, the component leaves the tool in a condition close to the dried granulate. Because PA 12 still absorbs atmospheric water, mechanical properties drift over days to weeks until equilibrium is reached. This drift is smaller than in PA 6 or PA 66, but it is not negligible: the tensile modulus of a dry transparent PA 12 may drop by 15–25 % when conditioned to 50 % RH, while elongation at break rises. For impact-modified grades, moisture-induced matrix softening can increase notched impact energy but reduce the load at which creep failure occurs. Designers calculating snap-fit deflections or press-fit retention must therefore use the conditioned modulus for long-term service. In accelerated testing, specimens defined by ISO 527-2:2012 type 1A are conditioned to either dry-as-moulded or standard atmosphere 23 °C/50 % RH before tensile testing; comparing only dry values across grades overstates stiffness under real service conditions. The impact-modified natural grade also exhibits a slight interaction between moisture uptake and optical clarity in thick sections: absorbed water does not normally create haze in amorphous PA 12, but surface condensation or microcracking at the elastomer-matrix interface after repeated thermal cycling can scatter light at low levels.

Chemical resistance of the PA 12 backbone is a central reason for specifying Grilamid TR 90 NZZ nat in transparent housings that contact aliphatic hydrocarbons, automotive fuels, oils, or many industrial cleaning agents. The material is not resistant to strong acids, oxidising agents, or certain polar solvents; prolonged contact with alcohols can produce environmental stress cracking when the part is under external load. Impact-modified grades may be more sensitive to stress-cracking fluids because the elastomer phase swells and reduces craze resistance at the interface. Where exposure limits must be verified, testing under ISO 22088-2 can provide ranking data for a specific fluid and strain level. Regulatory compliance must be established for the intended use: migration limits for food-contact applications are set out in European Commission Regulation (EU) No 10/2011, and any medical or drinking-water application must be assessed under the applicable framework. The natural grade does not contain intentionally added cadmium, lead, or chromium-based pigments; however, supply-chain declarations for REACH and RoHS should be confirmed against the current safety data sheet and product compliance certificate.

In melt rheology, transparent amorphous PA 12 behaves as a pseudoplastic fluid; apparent melt viscosity decreases with increasing shear rate. The melt volume-flow rate measured under ISO 1133-1:2022 at 275 °C/5 kg for transparent PA 12 grades is often in the range of 15–35 cm³/10 min for unmodified grades, while impact-modified variants may be lower because of higher molecular weight or modifier content. Mould-filling simulation requires temperature-dependent viscosity coefficients; using a standard PA 6 database for a transparent PA 12 produces incorrect pressure-drop predictions. Spiral flow tests on a 2 mm cavity at the recommended melt temperature can be used to compare flow behaviour across lots, but the value is not a material property because it depends on tool geometry and mould temperature.

When Dimensional Stability and Optical Clarity Must Coexist in a Single Component

Transparent sight glasses, fluid-level indicators, and optical sensor windows require flatness, low birefringence, and stable light transmission. In these applications, the low water absorption of PA 12 relative to PA 6 or PA 66 reduces the dimensional change caused by humidity cycling. Mould shrinkage for the TR 90 family is typically below 0.6 % under ISO 294-4, but anisotropic flow orientation can create differences between flow and transverse directions. The impact-modified grade can display slightly higher shrinkage than unmodified TR 90 because the elastomer phase has a higher coefficient of thermal expansion and lower modulus. When a part is gated asymmetrically, differential packing of the melt produces residual stress that can appear as visible birefringence under polarised light; for optical parts, gate location should be placed to create a uniform flow front and the holding pressure should be high enough to maintain a cushion above 2 mm during the entire packing phase. Mould temperature is a further controlling parameter: a tool held at 60–80 °C lowers residual stress but increases cycle time and may increase mould fouling from volatiles if the granulate is not adequately dried.

Compared with other transparent grades in the EMS-Grivory portfolio, Grilamid TR 90 NZZ nat occupies a specific position. Grilamid TR 55 is a transparent PA 12 grade with a different flow-length and impact-response balance; the NZZ nat variant is used where higher toughness is required but where the slight loss in stiffness can be tolerated. Grilamid TR 90 UV includes an ultraviolet stabiliser package for outdoor exposure; the natural NZZ nat grade should be considered only for indoor or shielded service unless an additive masterbatch is used. Against transparent polyamide 6/66 copolymers, the PA 12 backbone provides lower saturated water uptake, better retention of electrical insulation resistance in humid environments, and lower density. Against polycarbonate, the PA 12 grade has better chemical resistance to many cosmetic and cleaning agents but lower notched impact strength and lower modulus. These comparisons are qualitative and must be confirmed by application-specific testing.

Injection Moulding Process Window and Moisture Limits

The dried condition is critical: moisture levels above 0.10 wt% can hydrolyse the polyamide during melting and reduce impact strength, increase yellowness, and generate surface splay. Desiccant drying at 80 °C for 4–8 h to a dew point of -30 °C or lower is typical; drying time may be extended for regrind or if storage conditions exceed 60 % RH. Melt temperature should be held in the 250–280 °C range, measured at the nozzle. Mould temperature can be set between 40 °C and 80 °C; the lower end is sufficient for simple non-structural parts, but optical parts benefit from the upper end. Screw geometry is preferably a three-zone general-purpose screw with a compression ratio of 2.0–2.5:1 and low-shear mixing elements if colouring is added. Hot-runner channels should be sized to avoid dead spots, because transparent PA 12 can thermally degrade at stagnation points and produce black specks or yellow streaks. Processing experience on injection moulding machines with clamp forces above 1,000 kN indicates that impact-modified transparent PA 12 may require a longer screw recovery time than unmodified transparent PA 12 at the same back pressure; the exact difference depends on modifier content and screw design. If gas bubbles or surface streaks appear, the first corrective action is to verify the dew point and drying time rather than increase melt temperature, since overheating accelerates discoloration.

In transparent filter bowls for compressed-air lines, the combination of impact modification and low moisture uptake is used to reduce brittle failure under pressure pulses while maintaining visual inspection of the filter element. The material’s pressure-bearing capability should be calculated using the conditioned tensile modulus and with a safety factor appropriate for pressurised glass-like plastics; long-term hydrostatic testing at 23 °C and at the maximum service temperature is required because impact-modified grades may creep more than unmodified grades under continuous hoop stress. In medical or diagnostic device housings, the natural material can be coloured with approved masterbatch or used unpigmented for light-transmitting covers, but each colourant or additive must be assessed for migration, biocompatibility, and effect on impact performance. In applications where repeated steam sterilisation is required, published data for this specific configuration is limited; the high glass transition temperature of the PA 12 backbone may allow short cycles, but the elastomer phase and any colourants can undergo cumulative thermal oxidative degradation, so end-use qualification must include multiple sterilisation cycles.