LG Chem ABS AF-312C is an unfilled, high-flow acrylonitrile–butadiene–styrene copolymer intended for injection-moulded components in which thin walls, long flow paths, and multi-cavity tool layouts require elevated melt fluidity without moving to a lower-viscosity polymer such as polystyrene. The material is supplied as cylindrical pellets with a typical density of 1.04 g/cm³ under ISO 1183-1. The manufacturer’s published technical datasheet reports a melt mass-flow rate of 40 g/10 min at 220 °C with a 10 kg applied load under ISO 1133-1. This fluidity is obtained by controlling the molecular weight of the styrene–acrylonitrile continuous phase rather than by external plasticizer addition, allowing the grade to retain a notched Izod impact strength of 18 kJ/m² at 23 °C under ASTM D256. The material is not flame-retardant and is typically classified UL 94 HB at 3.0 mm.

Representative data from public technical literature for AF-312C are shown in the following table. These values are typical lot-average values, not maximum or minimum specification limits, and should be confirmed against the current manufacturer’s datasheet for production acceptance.

What Distinguishes AF-312C From General-Purpose and High-Impact ABS Grades?

The principal difference between AF-312C and a general-purpose high-impact grade such as HI-121H is the melt-flow-to-impact trade-off. Under ISO 1133-1 at 220 °C/10 kg, HI-121H is reported at approximately 6 g/10 min, while AF-312C exhibits 40 g/10 min. The higher melt flow reduces viscous heating during filling, lowers injection-pressure demand, and shortens cycle time in complex tools. Conversely, notched Izod impact under ASTM D256 at 23 °C declines from 35 kJ/m² for HI-121H to 18 kJ/m² for AF-312C. The selection boundary is therefore clear: AF-312C is specified when mould-filling constraints dominate, not when the moulding must absorb repeated high-energy impact in service.

Within the AF-312 series, AF-312C shifts further toward fluidity than AF-312A. The following comparison, compiled from public grade data, illustrates the relative position of the product.

Compared with 20 wt% glass fibre-reinforced ABS, AF-312C has lower flexural modulus, lower heat deflection temperature, and substantially higher melt fluidity. Glass-filled ABS grades generally report flexural modulus values above 5,000 MPa under ISO 178, whereas AF-312C is reported at 2,300 MPa. Consequently, AF-312C is specified where surface appearance, mould filling, and cycle time govern part design, while glass-filled grades are used when structural stiffness and dimensional stability under load are the controlling criteria.

Pre-drying of AF-312C is mandatory when pellets have been exposed to ambient relative humidity above 60% RH. Residual moisture above 0.1% by weight produces splay, silver streaking, and reduced weld-line strength. A desiccant dryer with a dew point of −20 °C or lower and a bed temperature of 80 °C for 2–4 h is normally sufficient. Over-drying beyond 6 h at 90 °C may deplete processing antioxidants and increase yellowing at hot-runner tips. Dried pellets should be conveyed with dry air and used within 30 min of discharge from a hopper outlet exposed to plant air above 55% RH.

On a 25 mm diameter reciprocating screw with an L/D ratio of 20:1 and a compression ratio of 2.5:1, barrel set-points are typically held at 170–190 °C in the rear, 190–210 °C in the centre, and 210–230 °C in the front, with a nozzle set-point of 220–240 °C. Mould temperature is normally maintained between 30 °C and 50 °C. Shot size should occupy 25–70% of barrel capacity. Back pressure between 0.5 MPa and 1.5 MPa and screw surface speed below 100 rpm limit accumulative shear heating in the melt. At hot-runner tips, local melt temperature should not exceed 250 °C; residence time above 240 °C should be limited to 5 min to suppress thermal yellowing and polybutadiene degradation.

Regrind addition up to 20% by weight is common in non-appearance-critical parts, provided the regrind is dried and free of contamination. Higher regrind levels increase melt-viscosity variability and can reduce notched impact by 5–15%. Any production lot containing regrind should be evaluated under the end-use mechanical test protocol because the impact reduction is sensitive to particle size, dust fraction, and thermal history.

When Thin-Wall Housings and Multi-Cavity Tools Demand High Melt Fluidity

Typical application areas for AF-312C include non-flame-retardant electronic enclosures, display bezels, vacuum cleaner housings, small appliance consoles, and interior trim components where wall thickness falls between 1.0 mm and 2.0 mm and where flow path relative to thickness is high. The grade is not recommended for transparent components, outdoor load-bearing parts without UV stabilization, or direct food-contact articles unless a specific certified lot is supplied. In multi-cavity tools, the fluidity of AF-312C permits cavity-to-cavity moulded-mass variation below 2% when runner systems are geometrically balanced and gate land lengths are maintained between 0.8 mm and 1.5 mm.

In thin-wall moulding, the practical process boundary is the pressure required to fill the cavity. At a wall thickness of 1.0 mm, gate diameters below 0.6 mm can produce jetting and surface flow marks. Published pressure-limited flow-length data for AF-312C in sub-1 mm walls is limited; mould-filling simulation should therefore use shear-viscosity data from the manufacturer’s material database and be verified by short-shot trials on the production tool. Vent depths of 0.02–0.04 mm along the parting line are used to prevent burn marks without creating flash. For clamp-force estimation on hydraulic injection machines, cavity pressures of 40–60 MPa are typical for filled thin-wall parts; a 120-ton machine is generally required when total projected area approaches 200 cm² at a wall thickness of 1.2 mm.

Production-scale failure modes observed in high-flow ABS tools include short shots at low injection speed, gate blush at injection speeds above 250 mm/s, and burn marks from insufficient gas venting. Filling trials on thin-wall moulds have shown that hold-pressure transfer should occur at 95–98% of visual part fill, not at theoretical complete fill, to avoid overpacking at the gate. Screw-recovery time should be less than cooling time in automated cycles; otherwise, the next shot is delayed by melt preparation.

Mechanical and Thermal Response Under Standard Test Protocols

Under ISO 527-2, AF-312C reports a tensile stress at yield of 42 MPa and nominal strain at break of 15%. Flexural modulus under ISO 178 is 2,300 MPa, and flexural strength is 64 MPa. The heat deflection temperature under ISO 75-2/A at 1.82 MPa is 85 °C, and the Vicat softening temperature under ISO 306/B50 is 96 °C. These values place AF-312C in the standard unfilled ABS range, with lower stiffness and heat resistance than glass-filled ABS but higher melt fluidity and better surface replication.

The practical upper service temperature under load is normally 10–15 °C below the heat deflection temperature. Parts designed for continuous exposure above 70 °C should be prototype-tested under actual loading conditions because creep resistance and dimensional stability are load-dependent and cannot be inferred from single-point heat deflection data. Linear mould shrinkage under ISO 294-4 is 0.4–0.7% depending on flow direction, wall thickness, and gate morphology. Dimensional audits should be conducted after conditioning at 23 °C and 50% RH for 24 h under ISO 291, because post-mould shrinkage continues during the first day after ejection.

Evaluating Chemical Resistance and Regulatory Compliance Boundaries

AF-312C is generally specified to comply with REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU as amended by Delegated Directive (EU) 2015/863. Compliance must be confirmed through the supplier’s certificate for the specific lot because custom colour masterbatches or recycled feedstock can introduce restricted substances. The standard grade is not formulated for direct food-contact use under 21 CFR; a separate certified lot is required if food-contact compliance is necessary.

Aromatic solvents, ketones, esters, and chlorinated hydrocarbons can induce environmental stress cracking in ABS mouldings. Acetone and toluene must not be used for cleaning stressed parts; even isopropyl alcohol can initiate cracking if moulded-in stress is high. The resin should be purged with high-density polyethylene or polypropylene before and after moulding runs. Contamination with acetal or PVC residues can generate acidic decomposition products that corrode screw and barrel surfaces and degrade the polybutadiene rubber phase. For outdoor weatherable applications, ASA or ASA/PC grades are preferred because unfilled ABS undergoes photo-oxidation and embrittlement unless heavily stabilized; AF-312C does not carry a long-term xenon-arc weathering rating under ISO 4892-2 as a standard unfilled ABS grade.