The INEOS Styrolution ABS grade TERLURAN 2842 is an unfilled acrylonitrile-butadiene-styrene injection-moulding material positioned for thin-wall components requiring high surface gloss, medium impact resistance and short cycle times. The grade is supplied in pellet form and is typically processed on standard three-zone reciprocating injection-moulding machines. Published datasheet values for specimens conditioned at 23 °C and 50 % RH under ISO 291 list a density of 1040 kg/m³ per ISO 1183-1:2019 and a melt volume-flow rate of 22 cm³/10 min at 220 °C under 10 kg load per ISO 1133-1:2022. That flow index places the product above many unfilled standard ABS grades that exhibit MVR values below 10 cm³/10 min, and below high-heat ABS or certain PC/ABS blends. Small domestic appliance housings, personal-care equipment shells, toys, office-equipment trims and electrical enclosures are typical application fields. The product is not a flame-retardant or fibre-reinforced grade; property limitations must be reviewed when heat distortion above 100 °C or flexural modulus above 3000 MPa is required.

What residual-moisture limit controls melt stability and surface reproducibility?

Moisture absorption in unpredried ABS granules follows a reversible diffusion process under ambient storage. In warehouse conditions above 60 % RH, surface moisture can exceed 0.1 wt% even in newly opened packaging; the recommended residual moisture for TERLURAN 2842 is below 0.05 wt%. Drying at 80 °C for 2–4 h in a desiccant dryer with air dew point no higher than −30 °C is required to prevent hydrolysis of the polybutadiene phase and splay on moulded surfaces. Splay appears as silver streaks radiating from the gate when trapped water vapour expands during injection decompression; it can be misdiagnosed as shear-induced melt fracture. On production lines, dew-point monitoring is more important than time-based drying alone, because equilibrium moisture content is set by air dew point and temperature rather than by hopper residence time alone. Hopper temperatures above 80 °C can cause granule bridging and agglomeration; below 70 °C, the drying time needed to reach 0.05 wt% may exceed normal shift intervals. Moisture-related volatile residues also contribute to mould deposit, gate-area dull patches and reduced weld-line strength. Published data for the specific effect of residual moisture on TERLURAN 2842 melt viscosity are limited, but the observed surface-defect threshold is reproducible across desiccant-dried and undried production lots.

Melt preparation on a reciprocating screw should use a barrel temperature profile of 230–260 °C from feed throat to nozzle, with the melt temperature checked by pyrometer rather than inferred from barrel set points. Screws with L/D ratio 18:1–22:1 and compression ratio 2:1–3:1 provide adequate homogenisation without excessive adiabatic temperature rise. Below 230 °C, the higher melt viscosity raises injection pressure, reduces packing efficiency and can freeze gates prematurely in wall sections thinner than 1.0 mm. Above 260 °C, residence times longer than 5 min cause thermo-oxidative degradation of the butadiene phase, visible as yellowing and measurable as a drop in notched impact. Mould wall temperature should be held between 40 °C and 80 °C; the upper part of the range favours high 60° gloss and reduces mould-in stress. Cavity pressure transducers are recommended when nominal wall thickness falls below 1.2 mm, allowing transfer from injection to holding pressure at a defined cavity-pressure threshold and reducing gate-crater defects. Injection speed should be high enough to avoid premature solidification at the flow front, but excessive speed can generate jetting and gate blush.

When high-gloss thin-wall mouldings replace lower-flow ABS or PC/ABS

Substitution with TERLURAN 2842 is most appropriate when the flow-path-to-wall-thickness ratio exceeds 150:1 and the part surface must remain high-gloss without secondary finishing. The melt volume-flow rate of 22 cm³/10 min lowers required injection pressure and allows reduced clamp force for a given projected area. For a projected area of 150 cm² and an average cavity pressure of 300 bar, the theoretical clamp force is 450 kN; a 600 kN machine therefore provides a reasonable margin. Compared with high-impact ABS grades displaying MVR below 10 cm³/10 min, TERLURAN 2842 trades sub-zero ductility for fluidity; the Charpy notched impact at −30 °C is typically below 10 kJ/m². Compared with PC/ABS blends, the product has lower heat resistance under 1.8 MPa load, with typical HDT/A near 94 °C, but it processes at standard ABS melt temperatures and avoids the higher melt-temperature and purging requirements of PC/ABS. In appearance-critical parts, low-flow ABS often produces dull end-of-fill zones and flow lines; TERLURAN 2842 shifts the visible defects to weld-line regions and gate blush, which are addressed by gate position, sequential valve-gate timing or local tool-temperature control.

Mechanical and thermal property profile under ISO 527, ISO 179 and ISO 306

Typical injection-moulded values for TERLURAN 2842 after conditioning at 23 °C and 50 % RH per ISO 291 include tensile modulus 2300 MPa and tensile stress at yield 45 MPa per ISO 527-1/-2:2012; tensile strain at yield 2.6 %; flexural modulus 2400 MPa and flexural strength 65 MPa per ISO 178:2019; Charpy notched impact 18 kJ/m² at 23 °C and 8 kJ/m² at −30 °C per ISO 179-1:2010; Vicat softening temperature VST/B/50 96 °C per ISO 306:2022; heat deflection temperature HDT/A under 1.8 MPa 94 °C per ISO 75-1/-2:2013; and linear mould shrinkage 0.4–0.7 % per ISO 294-4:2018. The values indicate a medium-impact ABS: the product is not suitable for load-bearing parts requiring sub-zero ductility comparable to high-impact ABS or PC/ABS. The modulus range is typical of unfilled ABS and is not sufficient for structural applications requiring flexural modulus above 6000 MPa. Published data for continuous cyclic fatigue, creep under sustained load and chemical ageing specific to this grade are limited; design verification under application-specific stress-cracking media and load levels is required.

Mould shrinkage is anisotropic; linear shrinkage parallel to flow is typically lower than transverse shrinkage by 0.1–0.2 percentage points. Post-mould shrinkage after 24 h at 80 °C can add approximately 0.1 %, so precision tool compensation should be based on ISO 294-4:2018 measurements from short-shot studies or cavity-specific process data. Water absorption at equilibrium at 23 °C and 50 % RH is about 0.2 %; saturation water absorption per ISO 62:2008 can approach 1.0 %, reducing modulus and increasing dimensions slightly. In components with tight dimensional tolerances across changing humidity, the effect of absorbed water should be evaluated on moulded parts rather than on dry-as-moulded test bars.

The ABS matrix is sensitive to aromatic hydrocarbons, chlorinated solvents, esters and ketones under stress. Environmental stress cracking may occur when moulded-in tensile stress exceeds a critical threshold in contact with these media, even when short-term visual swelling is absent. Parts should be tested under ISO 22088-3:2006 or ASTM D543 using the actual chemical contact scenario and the actual moulded-in stress state. Dilute acids and alkaline solutions are often compatible at room temperature within concentration- and stress-limited service, but published data for TERLURAN 2842 under all chemical classes are limited. In household and personal-care applications, contact with citrus-based cleaners or isopropanol should be evaluated on the final moulded part, because unstressed standard test bars do not reproduce the gate-area residual stresses of production parts.

If regrind content exceeds 30 wt%, melt viscosity and low-temperature impact shift measurably

Regrind from sprues, runners and rejected parts can be dry-blended with virgin TERLURAN 2842, but the addition level requires control because multiple heat histories degrade the polybutadiene phase. At regrind fractions above 30 wt%, injection moulders typically observe a reduction in melt viscosity and a decline in Charpy notched impact at −30 °C that exceeds normal virgin lot-to-lot variation. The change may be masked at 23 °C but becomes visible in low-temperature testing. Sieve analysis of regrind should exclude fines below 1 mm; fines melt early and generate black specks or yellow streaks. Gravimetric blenders with a precision of ±0.5 wt% are preferable to volumetric mixing when regrind exceeds 15 wt%. Melt volume-flow rate should be rechecked by ISO 1133-1:2022 after regrind addition; a change greater than 10 % relative to virgin pellets indicates a need to adjust barrel temperature or reduce regrind ratio. Batch-to-batch variance in impact also depends on the number of regrind passes; one closed-loop pass is less damaging than repeated post-industrial recycling.

Apparent shear-rate dependence measured by capillary rheometry at 230 °C for TERLURAN 2842 shows pseudoplastic behaviour typical of unfilled ABS. At shear rates between 100 s⁻¹ and 5000 s⁻¹, viscosity declines by approximately 60–80 %, which supports filling of thin-wall sections but reduces the shear sensitivity of die swell and can affect jetting control. The melt shows measurable viscosity instability after 5 min at 260 °C; therefore barrel capacity should not exceed 2–3 shot sizes in high-cycle production. When a hot-runner system is used, the manifold temperature should be held at 240–250 °C and hot-runner residence time should be verified by colour drift on natural material. Published data for hot-runner residence-time limits specific to this grade are limited.

High-gloss surfaces without secondary finishing depend on tool temperature, not only melt temperature.

Gloss formation is controlled by replication of the tool-surface polish onto the part skin. A mould temperature of 60–80 °C and sufficiently high injection speed are usually required to achieve a 60° gloss above 90 when measured per ASTM D523 or ISO 2813:2014. Tool surfaces with roughness of 0.05–0.2 µm Ra must be maintained; scratches, pitting or plate-out reduce local gloss. Mould deposits from residual moisture, overheated melt or additive migration accumulate near gate areas and create dull patches, requiring periodic cleaning with approved mould cleaners. Closed-loop mould-temperature control with an accuracy of ±2 °C across cavity halves is recommended. If the mould is below 40 °C, surface gloss may fall because the molten skin freezes before replicating the tool polish, although dimensional tolerances may remain within specification in thicker sections.