INEOS Styrolution ABS TERLURAN HI-12 is a high-impact injection-moulding acrylonitrile-butadiene-styrene grade positioned for thin-wall components that must absorb low- to medium-velocity impact without brittle fracture. The material consists of a styrene-acrylonitrile matrix modified with a dispersed polybutadiene rubber phase; the rubber particles typically contain occluded SAN sub-inclusions below 1 µm, which increase the energy required for craze nucleation and crack propagation. Published property data place the melt volume-flow rate at 220 °C with 10 kg load in the range 9–18 cm³/(10 min) when tested to ISO 1133-1:2022, and the notched Charpy impact strength at 23 °C in the range 20–32 kJ/m² when tested to ISO 179-1/1eA. Density is 1.04–1.06 g/cm³ under ISO 1183-1. These values are representative of natural grade; coloured lots, regrind content, and moisture condition can move the results within the tolerances stated on the certificate of analysis.

Because Terluran HI-12 is amorphous, mould shrinkage is lower than that of semi-crystalline alternatives and is typically 0.4–0.7%, depending on wall thickness, melt pressure, and flow direction. The coefficient of linear thermal expansion is approximately 80–110 × 10⁻⁶ K⁻¹ under ISO 11359-2. These values should be applied to boss, rib, and snap-fit dimensions rather than polyolefin shrinkage factors.

What separates Terluran HI-12 from Terluran GP-22 and Terluran HI-10?

Terluran HI-12 differs from Terluran GP-22 primarily in rubber phase volume and impact response. GP-22 has a lower rubber fraction, which raises tensile modulus and hardness but reduces notched impact energy. The practical result is that GP-22 is less capable in cored-out bosses, snap-fit hooks, and housings subjected to off-axis assembly loads. HI-12 sacrifices some rigidity for higher notched impact strength and more stable sub-zero behaviour. Within the Terluran product family, HI-12 is positioned with a higher melt volume-flow rate than HI-10 and a higher notched Charpy impact than GP-22. The higher melt flow of HI-12 compared with HI-10 allows filling of nominal wall sections down to 1.2–1.5 mm at moderate injection pressures, although pressure-drop predictions should be confirmed by filling simulation for each tool. Applications requiring UL 94 V-0 at thicknesses below 2.0 mm are outside the normal specification range of an unmodified high-impact ABS unless confirmed by a specific lot.

On production machines with worn non-return valves, shot-to-shot volume variation can produce sink marks and flash; the check ring should be replaced when cushion variation exceeds 2 mm. Changeover from PVC to Terluran HI-12 requires thorough purging with a polystyrene or acrylic purging compound; residual PVC can release hydrogen chloride at ABS processing temperatures and catalyse degradation of the polybutadiene phase. Coloured lots may shift melt viscosity because of pigment carriers, and the lot-specific MVR should be checked before barrel temperatures are adjusted.

Melt rheology and processing window

The single-point MVR value is not sufficient for designing a moulding process. Injection moulding simulation requires shear-viscosity data obtained by capillary rheometry over a shear-rate range of 100–1000 s⁻¹ and melt temperatures from 220–260 °C. A Cross-WLF or similar model fitted to these data is suitable for most filling software. The melt is pseudoplastic; when average cavity shear rates exceed 10 000 s⁻¹, viscous heating can raise local melt temperature and alter flow behaviour in thin sections. This is relevant for ribs with thickness below 0.8 mm.

On injection moulding machines, a single-flight, three-zone screw with an L/D ratio of 20:1 to 25:1 and a compression ratio of 2.0:1 to 2.5:1 is suitable. Screw rotation speed is generally maintained between 50–150 min⁻¹ for screws of 25–60 mm diameter; higher speeds can generate excess shear heating beyond the barrel setpoint. Back pressure is normally set between 5–15 bar to stabilise shot weight without over-shearing the melt. Barrel zones should follow a rising profile from hopper to nozzle within 220–260 °C, with nozzle temperature typically 230–250 °C. Mould surface temperature is controlled between 30–60 °C; the upper value improves weld-line strength, texture replication, and low-gloss appearance but increases cycle time. Cooling time increases with wall thickness, and a mould temperature increase from 30 °C to 60 °C can add 10–20% to cooling time in sections above 2.5 mm.

Specific injection pressure is typically 70–140 MPa at the screw tip for thin-wall parts, although runner and gate geometry may require more. Holding pressure is commonly set at 50–70% of filling pressure. Packing time should be terminated at gate freeze-off; for a 2 mm gate, this is often 2–6 s, but weight-stability or gate-seal testing must confirm the actual value. Insufficient packing produces sink marks and excess shrinkage; excessive packing time is uneconomic and may overpack the cavity near the gate.

Barrier screws and mixing sections can be used, but high-shear mixing elements should be evaluated because they may raise melt temperature above 260 °C. On machines with screw diameters above 60 mm, screw rotation should be reduced to maintain acceptable surface velocity. Jetting occurs when injection speed is too high through a small gate and the flow front does not adhere to the cavity wall; a tab gate or fan gate reduces this fault. Mould venting is required to avoid diesel effects and burn marks at the end of fill. Vent depth for ABS is commonly below 0.03 mm, because the low melt viscosity at the upper processing range can otherwise cause flash.

When residual pellet moisture exceeds 0.02% before melt processing

Terluran HI-12 is not as hygroscopic as polyamide, but surface moisture adsorbed during storage in humid conditions can disrupt the melt front. The practical processing limit is commonly set at 0.02% residual moisture by weight. Improper drying leads to volatilisation of water in the melt, producing splay marks, silver streaks, delamination at the flow front, and reduced notched impact strength due to microvoid formation. The required drying condition is 80 °C for 2–4 h in a desiccant dryer with a dew point below -20 °C. Residual moisture should be verified by a moisture analyser using ISO 15512 or an equivalent method. When ambient relative humidity exceeds 60%, open containers can regain enough moisture within 30–60 min to affect surface quality; closed transfer lines or machine hopper dryers are preferred.

Drying above 90 °C should be avoided for extended residence because pellet surface oxidation and yellowing can develop before melting. If a machine is stopped for more than 15 min with a full barrel, the material in the hot runner or screw front should be purged before moulding resumes. Degraded ABS is identified by yellow-to-brown discolouration, black specks, and reduced toughness; this is usually a local thermal history problem rather than a property of the supplied pellets. Regrind use is permitted only within the levels allowed by the part qualification, and dried regrind must be blended with virgin material at a constant ratio to limit batch-to-batch flow variation.

Mechanical property validation for Terluran HI-12 is normally performed on specimens conditioned at 23 °C and 50% relative humidity unless the part specification calls for dry-as-moulded testing. Tensile values are determined to ISO 527-2/1A/50; representative tensile modulus is 1900–2300 MPa and tensile yield stress is 35–45 MPa. Flexural modulus values are typically higher because of the stress distribution in the ISO 178 three-point bend configuration and should not be interchanged with tensile modulus. Notched impact values are obtained with either ISO 179-1/1eA or ASTM D256, but the two methods are not directly comparable because of differences in ligament area and test geometry.

The polybutadiene rubber phase in Terluran HI-12 produces a measurable drop in notched impact between 23 °C and -30 °C. The lower sub-zero values in the table below are not intended for design at the minimum temperature but indicate the ductile-to-brittle transition that must be validated for winter transport or assembly. Specimen thickness also affects impact energy: increasing Charpy specimen thickness from 3 mm to 4 mm can reduce notched impact energy because of plane-strain constraint. Actual part wall thickness must therefore be used when assessing brittle failure risk.

The table values are envelope ranges from public product information and are not a purchase specification. The certificate of analysis and supplier processing guidance remain the authoritative documents. Published fatigue data for this specific grade are limited. For cyclic snap-fit applications, strain limits based on tensile yield strain should be applied, and ABS is generally not recommended for living hinges subjected to several thousand flexural cycles; polypropylene or thermoplastic elastomer systems are more appropriate for that load case.

In injection-moulded appliance housings, power-tool casings, and consumer electronics housings, Terluran HI-12 is used where the component must survive defined drop tests without cracking. OEM acceptance tests in this product class commonly specify impact exposure such as 5 drops from 1.0 m onto concrete or steel for a 1.5 kg portable tool housing, but the exact requirement depends on part weight, wall thickness distribution, and boss design. The higher impact strength of HI-12 relative to GP-22 allows thinner wall sections and fewer reinforcing ribs under the same impact requirement. Weld lines remain the limiting feature: even with optimised gate location, a weld line in high-impact ABS may retain only 50–60% of the bulk notched impact strength, with a larger reduction at sub-zero temperatures.

Automotive interior trim applications such as lower instrument-panel covers, seat side trims, and door inner trims use the flow-impact balance of Terluran HI-12. These parts are typically textured with grain depths between 10–25 µm and require draft angles of at least 1° on textured walls to release without scuffing. Dimensional stability after humidity cycling is assessed before and after exposure to 40 °C and 90% relative humidity for 48–72 h; ABS parts may show slight dimensional growth, generally below 0.1%. For coated or foamed-in-place parts, adhesion is tested by cross-hatch to ISO 2409. Surface free energy after cleaning is recommended to be above 38 mN/m for solvent-based coatings and above 48 mN/m for UV-cured coatings; these are processing targets, not material specifications, and can be achieved by corona or plasma treatment if mould release agents are controlled.

Terluran HI-12 is not intended for unpainted exterior applications with continuous direct sunlight. Unstabilised high-impact ABS undergoes surface yellowing and gloss loss under UV-B irradiation because of the photo-oxidative sensitivity of the butadiene double bond. For exterior trim, ASA grades are preferred because the acrylate rubber phase lacks that unsaturation. If a part made from Terluran HI-12 is painted and used in an exterior location, the paint layer must provide the UV barrier, and adhesion loss after thermal ageing above 80 °C should be validated by the coating specification.

Regulatory documentation for Terluran HI-12 supplied in the European Economic Area includes supplier declarations of conformity with RoHS Directive 2011/65/EU and REACH Regulation (EC) No 1907/2006, with lot-specific documentation identifying substances of very high concern. For toys, food-contact articles, or medical devices, the grade is not universally pre-approved; end-product testing is required under the applicable regulation, such as EU Regulation 10/2011 for food-contact plastics or the relevant toy safety standard. Chemical resistance is a function of stress state, temperature, and test duration. The grade resists many dilute acids and alkalis but is attacked by ketones, chlorinated solvents, and certain esters. Environmental stress cracking can occur when a stressed part contacts aromatic hydrocarbons or low-molecular-weight esters; compatibility with cleaning fluids, PVC plasticisers, and adhesives should be tested on the actual moulded part under service load.

For hot-runner systems, valve-gated sequential injection is preferred for high-gloss black parts because it avoids visible weld lines and provides uniform packing. Hot-runner tips should have no dead spots and should be operated within the melt-temperature window of 220–260 °C; if a tip exceeds 280 °C, local degradation can occur even when barrel settings remain correct. Each hot-runner drop should be independently controlled to avoid temperature differences above 5 °C between gates, which produce gloss variation and unbalanced filling. Venting should be checked before high-velocity injection of thin-wall high-impact ABS; insufficient venting leads to diesel effects and burn marks at the end of fill.