INEOS Styrolution Terluran 990 is an amorphous acrylonitrile-butadiene-styrene injection-moulding grade supplied as natural pellet and selected precoloured compounds. The melt-volume rate of 24 cm³/10 min under ISO 1133-1:2022 places the material in the high-flow segment of the Terluran range, while the notched Charpy impact at 23 °C of 20 kJ/m² under ISO 179-1/1eA defines a medium-impact application window. Typical lot-average physical data are summarised in Table 1. These values are not specification minima or maxima and should be used with the supplier’s product certificate for lot-level compliance.

Material Identity, Rheological Signature, and Specification Limits

Table 1 contains representative physical, thermal, and rheological values for Terluran 990. Density and melt-volume rate provide incoming quality-control reference points, while tensile and flexural data support short-term load-bearing calculations. The thermal values are relevant because the material is amorphous and therefore does not exhibit a crystalline melting point.

Because the material is amorphous, the Vicat and heat deflection values are the controlling upper service-temperature indicators rather than a crystalline melting peak. Compared with Terluran GP-22, Terluran 990 is more fluid and therefore reduces injection pressure in thin-wall filling; compared with Terluran HI-10, the 990 grade has lower notched impact strength, particularly at -30 °C, and should not be substituted into impact-critical parts without end-use verification. The lower low-temperature toughness follows from the same morphology that yields the higher melt fluidity.

Pre-drying is mandatory when ambient relative humidity exceeds 60%. Desiccant-bed drying at 80 °C for 2 h to 4 h is required, targeting a machine-throat moisture content below 0.1%. For high-gloss surfaces, residual moisture below 0.05% is recommended. Drying temperatures above 85 °C can initiate pellet surface sticking in hopper beds. A desiccant dryer with a dew point of -20 °C or lower is specified for production-scale operation; tray dryers are acceptable only for small batch trials with periodic moisture verification.

What Processing Boundaries Govern Thin-Wall Injection Moulding?

The processing melt-temperature envelope for Terluran 990 is normally 230 °C to 260 °C. A mid-range setting of 240 °C to 250 °C is used in many moulding lines to balance cavity-pressure demand and colour stability. Below 220 °C, thin-wall sections may exhibit jetting, gate blush, and non-linear fill-pressure increases. Above 270 °C, thermal degradation of the polybutadiene phase produces visible yellowing and styrenic volatiles. Machine nozzles should be fitted with an open nozzle orifice of 3 mm to 6 mm; needle shut-off systems require adequate bore sizing to avoid excessive shear at the high flow rates this grade can sustain.

Screw geometry on injection units should use a length-to-diameter ratio of 20:1 to 24:1, a non-return valve, and a compression ratio near 2.0:1 to 2.5:1. For moulded-in stress control and surface gloss, the tool temperature should be set at 60 °C to 80 °C. Lower mould temperatures from 40 °C to 50 °C shorten cycle time but increase frozen-in orientation and reduce gloss; they are not advised for painted or dimensionally critical parts without post-processing.

During production-scale trials on hydraulic machines in the 800 kN to 2500 kN clamp force range, cavity-pressure transducers have shown pack pressures of 35 MPa to 60 MPa for 2.0 mm wall sections. Packing time should exceed gate-seal time; gate seal can be inferred from the point at which the cavity-pressure decay becomes linear. If the cavity-pressure trace loses pressure abruptly during hold, premature gate freeze is occurring and the gate geometry or tool temperature should be reviewed.

Start-up and shutdown purges with acrylic or general-purpose ABS are used to limit residence-time degradation. At melt temperatures above 250 °C, barrel residence time should be kept below 6 min. If an interruption exceeds this, the machine should be purged until discoloured material clears. Hot-runner manifold and tip temperatures should not be raised above 260 °C, because carbonized specks can form in dead spots and appear on Class-A surfaces.

For tooling calculations, a mould shrinkage of 0.4% to 0.7% should be used as a preliminary figure. Shrinkage is lower and more isotropic than that of semi-crystalline polyolefins, but frozen-in orientation near gates can produce anisotropic shrinkage of up to 0.2% difference between flow and cross-flow directions. Final tool dimensioning should incorporate in-flow and cross-flow shrinkage plaques, preferably with cavity-pressure-controlled processing.

When Substituting Terluran 990 for Higher-Viscosity ABS Grades in Existing Tools

Substituting Terluran 990 for a higher-viscosity grade such as Terluran HI-10 in existing tooling usually permits lower injection pressure and shorter hold-pressure duration, because the lower melt viscosity reduces gate and runner pressure drop. However, the change in viscosity also alters packing behaviour. With unchanged gate dimensions, gate freeze may occur earlier or later depending on wall thickness and tool temperature. For wall sections below 1.2 mm, shear heating at the gate can raise local melt temperature above the barrel set-point and mask insufficient melt preparation; shot-to-shot flow-length variation then becomes sensitive to screw recovery and backpressure consistency.

Where a part was originally qualified with a high-impact grade, Terluran 990 has lower notched Charpy impact at both 23 °C and -30 °C, with the greatest relative difference at low temperature. Substitution into brackets, power-tool housings, or safety-related fittings therefore requires drop-weight or instrumented impact testing at the end-use temperature and strain rate. For sub-zero impact conditions, published data for this specific configuration is limited, and part-specific validation is required.

Terluran 990 shares the chemical-resistance profile common to unstabilized ABS. Immersion or contact with ketones, esters, aromatic hydrocarbons, and chlorinated solvents softens the styrene-acrylonitrile matrix or induces environmental stress cracking. Detergent and cleaning-agent exposure should be screened according to ISO 175; if the part is under external load, environmental stress-cracking tests such as ISO 22088 can identify critical strain thresholds. The grade is not inherently stabilized for prolonged outdoor UV exposure, and black pigmentation or a UV-stabilized ABS variant should be evaluated for exterior service.

Regulatory documentation including RoHS 2011/65/EU conformity and REACH registration status is supply-chain specific and should be requested from INEOS Styrolution for the relevant production lot. The product contains no intentionally added halogenated flame retardants. If food-contact suitability is being evaluated, the resin family is referenced in FDA 21 CFR 177.1020, but article-specific migration testing is required because compliance depends on monomer residuals and the additive package.

Clean, dry sprues, runners, and rejected parts can be reintroduced at up to 20 wt% in many non-appearance applications if the regrind is free of dust and dried to the same moisture target as virgin material. Repeated heat histories lower impact strength and can shift colour, so 100% regrind use is not recommended for high-gloss or tight-dimensional applications. Additive packages containing free amines should be evaluated at processing temperature because amine migration can alter paint adhesion or produce surface deposits.

Typical application fields are housings for small kitchen appliances, floor-care equipment, office electronics, toys, bathroom accessories, and non-load-bearing interior trim. The grade is selected where high melt fluidity, high surface gloss, and moderate impact resistance are sufficient. For continuous service above 85 °C, a high-heat ABS or another polymer class is required. For impact-critical or safety-related components, a higher-impact Terluran grade should be retained unless end-use testing demonstrates acceptable performance with Terluran 990.