In material selection for injection-moulded and extruded components, LG Chem ABS SG-173 is an acrylonitrile-butadiene-styrene terpolymer supplied in pellet form. Typical values reported by the manufacturer include a density of 1.04 g/cm³ when tested to ISO 1183-1:2019, a melt flow rate of 4.0 g/10 min at 220 °C/10 kg when measured in accordance with ISO 1133-1:2022, a tensile yield stress of 42 MPa under ISO 527-2:2012, and a flexural modulus of 2,050 MPa under ISO 178:2019. The notched Izod impact value is reported as 32 kJ/m² at 23 °C using ISO 180:2000, while the Vicat softening temperature is 95 °C under ISO 306:2022 method B50 and the heat deflection temperature is 86 °C at 1.8 MPa under ISO 75-2:2013. Mould shrinkage is reported in the range 0.4–0.7% when measured according to ISO 294-4:2018. The figures are material-selection values and are not binding lot-specific specifications.

The molecular structure of SG-173 consists of a continuous styrene-acrylonitrile phase and dispersed polybutadiene rubber particles. The polybutadiene domain size and graft ratio are not published in the commercial datasheet; however, ABS grades of this class generally contain 15–25 wt% polybutadiene, which contributes to the notched impact response at 23 °C. Tensile elongation at break is typically 10–15% under ISO 527-2:2012, with exact values depending on mould temperature and cooling rate. Because the SAN continuous phase is amorphous, the moulding exhibits no crystalline melting transition; the heat deflection temperature is governed by the stiffness of the SAN phase and the rubber particle volume fraction. This morphology positions SG-173 for appliance housings, automotive interior trim panels, electrical enclosure frames, and structural components with wall thicknesses of 1.5–3.0 mm.

Before melt processing, the granulate is dried at 80–90 °C for 2–4 h in a desiccant-bed dryer with a dew point below −30 °C. Residual moisture must remain below 0.05 wt% when determined by ISO 15512:2019. Conveying lines exceeding 30 m in length or containing more than 5 bends with radius-to-diameter ratios below 10:1 can produce fines that increase moisture pickup; central vacuum systems operating at 0.6–1.2 bar conveying pressure generally maintain pellet breakage below 0.3 wt%. Processing trials with general-purpose screws of 20:1–24:1 L/D and compression ratios of 2.2:1–3.0:1 on 80–140 ton hydraulic injection moulding machines show that failure to maintain the drying limit produces silver streaking at melt temperatures above 230 °C.

What Tooling and Thermal Conditions Govern Injection Moulding of SG-173?

Process stability is maintained within a melt-temperature window of 210–240 °C and a mould-temperature window of 40–80 °C. At mould temperatures below 40 °C, uneven gloss and injection pressures above 100 MPa appear in parts with wall thickness below 2.0 mm. Back pressure is set between 0.5 and 1.5 MPa during screw recovery to homogenize melt without excessive shear heating. A cushion volume of 3–6 mm is maintained on machines with screw diameters of 35–50 mm; cushions below 2 mm are associated with hold-pressure variation and sink marks at rib intersections. Hot-runner manifold temperatures are kept below 250 °C, and total residence time at melt temperature is limited to 5 min or less to reduce yellowing from thermal oxidation of the polybutadiene phase. Vent depths of 0.02–0.03 mm are used on moulds for unfilled ABS; deeper vents permit flash, while shallower vents produce gas burn at end-of-fill.

Capillary rheometry on a 1.0 mm diameter capillary at 220 °C indicates shear-thinning behavior typical of ABS: apparent viscosity decreases from approximately 1,800 Pa·s at 100 s⁻¹ to 300–500 Pa·s at 1,000 s⁻¹. Injection velocities above 100 mm/s generate gate shear rates of 1,000–5,000 s⁻¹; in this range the viscosity is low enough for thin-wall filling but still high enough to limit flash. Nozzle melt pressure typically ranges from 60–120 MPa depending on flow length and wall thickness. In comparison, high-flow ABS grades can require 80–100 MPa lower nozzle pressure for the same part because of reduced melt viscosity. For a 2.0 mm wall section at a mould temperature of 60 °C, gate freeze time is approximately 3–5 s; hold pressure must be maintained beyond this period to prevent sink marks at bosses and rib junctions.

When SG-173 Is Substituted for Medium-Flow ABS in Thin-Wall Housings

In thin-wall enclosures with nominal walls of 1.8–2.5 mm, the substitution of a high-flow ABS with melt volume-flow rate above 20 cm³/10 min by SG-173 requires a melt temperature increase to 230–235 °C and an injection velocity increase to 100–140 mm/s. A single edge gate can fill a flow length-to-wall thickness ratio below 120:1; the lower flow rate is partially offset by higher melt strength, which reduces jetting and gate blush. Where the flow path exceeds 180 mm at 1.2 mm wall thickness, published data for this specific configuration is limited, and mould-filling simulation is required because the processing window contracts to approximately ±5 °C around 235 °C. Sequential valve gating is preferred over direct edge gating for those configurations because SG-173 does not contain the high-flow modifier package of grades with melt volume-flow rate above 20 cm³/10 min. The difference in flow performance is most visible in multi-cavity tools with more than 8 cavities; reductions in melt flow rate increase cavity-to-cavity fill imbalance unless runner balancing is verified by short-shot studies at 85% fill volume.

Sulphuric-Chromic Acid Etching Alters Surface Tension for Electroplating

Surface finishing operations on SG-173 use an ABS pre-plate sequence of alkaline soak cleaning at 60–70 °C, neutral rinse, chromic acid etching at 68–72 °C for 8–15 min, and palladium-tin activation. Peel adhesion on electroplated plaques is evaluated by ASTM B533-85; peel strengths of 50–80 N/25 mm are obtainable only when the cavity surface is polished to SPI A2 finish or better. Surface roughness values above 0.05 µm Ra reduce peel uniformity and can produce blistering after thermal cycling between −30 °C and 80 °C for 10 cycles. SG-173 is also used in painted or as-moulded applications in which adhesion primers are applied at 5–10 µm dry film thickness after solvent wipe with isopropanol. Contact with aromatic hydrocarbons, ketones, and esters should be avoided because these solvents can induce environmental stress cracking in the SAN phase. Long-term outdoor exposure without UV stabilisation is not recommended; black pigmented or painted parts exhibit less surface chalking than unpigmented natural grades under ISO 4892-2:2013 accelerated weathering, but published data for this specific grade is limited.

Mechanical Property Benchmarks and Comparative Position Against High-Flow and High-Impact Grades

The mechanical envelope of SG-173 places it between high-flow ABS and high-impact ABS. High-flow ABS grades with melt volume-flow rates of 25–35 cm³/10 min typically exhibit notched Izod values of 12–18 kJ/m² at 23 °C and flexural moduli near 2,300 MPa; high-impact grades often achieve 35–45 kJ/m² but with melt flow rates below 6 g/10 min and flexural moduli near 1,900 MPa. SG-173 is therefore specified for appliance housings, trim panels, and electronic enclosures with wall thicknesses above 1.5 mm. The difference from other products is primarily a flow-impact trade-off rather than a chemical incompatibility. The table below summarises the typical class envelope; values for adjacent grades are not manufacturer guarantees and should not be used for final moulding validation without a lot-specific certificate of analysis.

Regulatory documentation supplied with each lot includes confirmation that the material does not contain restricted substances above the thresholds set in 2011/65/EU as amended by (EU) 2015/863; analytical screening is performed using IEC 62321-7-1:2015 and related parts. REACH communication under Regulation (EC) No 1907/2006 is updated against the SVHC candidate list; as supplied, no SVHC is intentionally added at a concentration above 0.1 wt%. Flammability classification is HB under UL 94 at 3.0 mm, which excludes direct use in electrical enclosures requiring V-0 ratings. The grade is not supplied as a food-contact material; FDA 21 CFR compliance should not be assumed unless specifically confirmed by the supplier for a defined formulation and use temperature. Processing waste from unfilled ABS can be reground at up to 20 wt% in virgin material without loss of notched Izod impact beyond 10%, provided the regrind is dried to the same moisture specification and is free of contamination; higher regrind fractions lower impact and increase lot-to-lot viscosity variation.