LG Chem ABS SG-175 is an acrylonitrile-butadiene-styrene injection-moulding grade supplied as natural or precoloured pellets. The material is designed for high-flow thin-wall applications and is often specified where a medium-impact ABS would require excessive injection pressure to fill projected areas with wall sections below 1.5 mm. The grade is based on a continuous mass-polymerisation process with a bimodal butadiene rubber particle distribution. This morphology retains notched impact resistance while lowering melt viscosity under high shear. Typical processing is by reciprocating-screw injection moulding with a desiccant-dried feedstock. Compliance documentation is generally available under RoHS 2011/65/EU and REACH Regulation 1907/2006, but the grade is not marketed as a food-contact material.

Material Identity and Representative Property Data

Supplier technical data for SG-175 position the grade between general-purpose ABS and higher-flow ABS grades used for office automation and display enclosures. Representative values below are typical lot averages; they are not guaranteed minimum values. Testing follows the specified standard conditions and specimen thicknesses shown in the method column.

The combination of 33 g/10 min melt mass-flow rate and 230 J/m notched Izod at 23°C is significant. Medium-flow ABS grades typically require a higher packing pressure to fill the same thin-wall geometry. The heat deflection temperature of 85°C under 1.82 MPa is a load-bearing boundary rather than a use temperature limit; for ribbed structural parts with continuous load, design should remain below 70°C unless creep data are generated separately.

What Processing Constraints Govern Thin-Wall Fill and Surface Appearance?

Melt temperature control is more critical for SG-175 than for low-flow ABS. The grade flows readily at 200–240°C, so increasing barrel temperature to reduce viscosity is generally unnecessary. Supplier processing guidance and production-scale moulding practice recommend the following conditions for screw diameters from 30 mm to 50 mm.

At melt temperatures above 250°C, the butadiene phase begins thermal degradation. Common field indicators are yellowing, gloss variation, and silver streaking even when the feedstock moisture is within specification. On hot-runner tools, gate tip temperatures above 245°C produce similar surface defects. Direct-gated hot tips with separate temperature control and insulated flow channels are preferred for multi-cavity tools running thin-wall display components.

When SG-175 is substituted for a medium-flow ABS in a 1.2 mm-thick monitor bezel with a 500 mm long axis, a mould-temperature difference greater than 10°C between the stationary and moving halves has been observed to increase bow along the long axis by approximately 0.3 mm. The distortion mechanism is differential solidification shrinkage across thickness. Moulds should therefore be operated with turbulent water at 10–12 L/min per circuit and a setpoint of 50°C to hold cavity surface temperature within 5°C of the target. Weld-line impact retention is also geometry-sensitive; at a 0.8 mm gate and a flow ratio above 140:1, notched Izod on weld-line specimens can fall to 40–60% of the non-weld-line value.

Differences from High-Heat, Flame-Retardant and Glass-Reinforced ABS Grades

SG-175 is not a high-heat ABS. Its 85°C heat deflection temperature at 1.82 MPa is lower than the 95–105°C range typical of high-heat ABS grades containing α-methylstyrene or maleimide comonomers. High-heat ABS grades usually require melt temperatures above 240°C, have lower flow, and are more prone to yellowing in hot-runner systems. SG-175 should be selected only when the thermal load permits an HDT below 90°C.

Compared with flame-retardant ABS rated UL 94 V-0 at 1.5–3.0 mm, SG-175 carries a UL 94 HB classification at 1.6 mm. Flame-retardant ABS grades have higher density, generally 1.16–1.20 g/cm³, and narrower processing windows because brominated or phosphorus-based additives increase melt viscosity and can generate mould deposits. The absence of flame-retardant additives in SG-175 reduces plate-out in the tool and permits lower injection pressure for thin-wall parts, but it also eliminates the ability to pass a V-0 flame rating.

Glass-reinforced ABS grades have flexural moduli of 4000–6000 MPa, which is two to three times the 2050 MPa modulus of SG-175. That stiffness advantage is accompanied by higher melt viscosity, lower notched impact, higher abrasion on screw and barrel surfaces, and anisotropic shrinkage. Glass-filled grades often show mold shrinkage of 0.1–0.3% in the flow direction and 0.4–0.6% transverse to flow. SG-175 is more isotropic, with mould shrinkage of 0.4–0.7%, and provides better weld-line appearance and surface gloss than glass-reinforced ABS in visible housing applications.

Chemical resistance of SG-175 is consistent with general-purpose ABS. Ketones, esters, and chlorinated hydrocarbons soften the material. Acetone or methyl ethyl ketone contact can cause stress cracking when surface tensile stress exceeds 10–20% of the yield stress. Dilute mineral acids and alkylbenzene sulfonate-based detergents are acceptable for short-term contact at 23°C. Phthalate plasticisers migrating from overmoulded soft-touch polymers should be avoided because they lower heat deflection temperature and increase surface tack.

Why Does Notched Impact Testing Require Conditioning Before Comparison?

Specimens for notched Izod and tensile testing are conditioned at 23±2°C and 50±5% relative humidity for a minimum of 40 h unless otherwise specified. Conditioning time shorter than 24 h can bias notched Izod values because absorbed moisture alters the stress state at the initial notch tip. The effect is usually less than 12% compared with dry-as-moulded specimens. For low-temperature impact testing at -30°C, specimens should be held at the test temperature for at least 1 h per 2 mm of thickness before striking.

Compliance Verification and Handling Boundaries

Lot-level documentation for SG-175 is generally aligned with RoHS 2011/65/EU Annex II maximum concentration values in homogeneous materials. Lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE contents are below the relevant thresholds. REACH SVHC status is supplier-specific and should be confirmed through the manufacturer’s information system. For food-contact applications, compliance with 21 CFR 177.1020 is not implied and must be verified separately. Storage should be in sealed bags in a dry area at ambient temperature; opened material exposed to relative humidity above 60% should be re-dried before moulding.