LG Chem ABS HG-173 is a general-purpose acrylonitrile-butadiene-styrene terpolymer supplied as a natural, high-gloss injection moulding grade. The product is positioned within the high-flow ABS segment, with a published melt flow index of 20–30 g/10 min at 220 °C under 10 kg load when tested according to ISO 1133-1:2022. The material combines a styrene-acrylonitrile continuous phase with a dispersed butadiene rubber phase. The reduced rubber content relative to high-impact ABS grades contributes to elevated gloss, reduced melt viscosity, and easier filling of thin sections, while limiting notched impact resistance. Typical applications include non-structural appliance trims, personal-care housings, cosmetic packaging elements, office equipment covers, and electronic display bezels where surface definition and rapid cycling are primary requirements. The grade is not formulated as a flame-retardant material, outdoor weathering grade, or load-bearing structural resin unless specified service conditions have been qualified through part testing.

Morphologically, the high-gloss designation is associated with a lower rubber-phase fraction and controlled elastomer particle sizing, which suppresses surface light scattering and raises melt fluidity. This same morphology reduces energy absorption under high-speed impact relative to impact-modified ABS grades such as LG Chem HI-121H. The pelletized material is intended for injection moulding; it is not recommended for profile extrusion, blow moulding, or thermoforming because its low melt strength does not support stable parison or sheet formation. Processors handling the grade in central conveying systems should maintain consistent pellet feed and avoid bridging in hoppers by using mass-flow hoppers with polished internal surfaces.

How Does HG-173's Rheology Compare with High-Impact ABS During Thin-Wall Filling?

Flow-length behaviour in thin-wall tools is governed by shear viscosity and solidification rate. HG-173 exhibits a comparatively low viscosity under high shear, which promotes complete filling of ribs, bosses, and snap features at wall thicknesses below 1.0 mm. In contrast, high-impact ABS grades such as HI-121H require higher injection pressure or wider flow channels because their higher rubber content raises viscosity and lowers melt flow index. The practical consequence is that HG-173 can usually be moulded at lower hydraulic pressure and shorter fill time, but this advantage is achieved at the expense of notched impact energy. Under ISO 180/A testing at 23 °C, HG-173 typically reports notched Izod impact values of 18–24 kJ/m², whereas high-impact ABS grades commonly fall in the range of 30–40 kJ/m². That separation reflects the structural trade-off between gloss and impact tolerance.

Capillary rheometry of general-purpose ABS with melt flow index in the 20–30 g/10 min range shows a shear-thinning profile that supports short injection cycles but also narrows the safe process window for holding pressure and gate freeze. In multi-cavity tools with long flow paths, pressure loss in the runner must be estimated from the grade's viscosity curve. For HG-173, a practical starting point for flow analysis is a melt viscosity at 1000 s⁻¹ and 230 °C of approximately 80–120 Pa·s, with the understanding that filled, coloured, or regrind-containing lots may deviate. Published data for this specific configuration is limited; mold-filling simulation should be calibrated with on-press short-shot trials rather than relying solely on generic ABS viscosity data.

The following representative property ranges are assembled from publicly available technical datasheet values and polymer database entries for natural-grade LG Chem ABS HG-173. Coloured lots, regrind-containing batches, and moisture-exposed material may shift these values.

Thermal history cannot be separated from surface aesthetics.

Pre-drying is mandatory for moisture-sensitive surface quality, particularly in components with polished or high-gloss surfaces. ABS absorbs atmospheric moisture, and even small quantities convert to steam during plasticating, producing splay, silver streaks, and loss of gloss. Supplier processing guidance for ABS HG-173 recommends desiccant drying at 80 °C for 2–4 h, with a dew point below −30 °C and a target residual moisture level below 0.05 wt% as determined by ISO 15512:2019. In high-humidity environments above 60% RH, sealed hopper systems are preferred because dried pellets reabsorb water within minutes when exposed to ambient air. Failure to dry this grade properly is commonly observed on production lines as gate-blush, inconsistent gloss across the cavity, and jetting marks near the sprue.

Thermal degradation must also be controlled. Melt temperatures for HG-173 are typically maintained between 210 °C and 240 °C, with occasional short excursions up to 250 °C in hot-runner drops. Prolonged residence time above 250 °C causes yellowing, gas generation, and loss of impact due to thermo-oxidative degradation of the butadiene phase. Shot sizes below 25% of barrel capacity increase residence time and should be avoided unless a reduced melt temperature and short holding time are validated. Screw geometries with L/D between 20:1 and 25:1, compression ratio of 2.5:1 to 3.0:1, and non-return valves with low shear accumulation are suitable for processing this grade. Back pressure is generally set at 0.5–1.5 MPa to ensure melt homogeneity without excessive frictional heating.

Mould surface temperature exerts a controlling influence on gloss replication. HG-173 develops its highest visual gloss when tool surfaces are polished to SPI A-1 or SPI A-2 finishes and maintained at 60–80 °C. Lower mould temperatures of 40–50 °C reduce cycle time but produce matte or uneven surfaces because the polymer skin freezes before full contact with the cavity topography occurs. In thin-wall parts with wall thickness below 1.5 mm, injection speed should be set high enough to prevent premature solidification at the flow front; values of 50–150 mm/s are typical starting conditions depending on gate size and flow length. Holding pressure should be optimized using gate-seal studies rather than fixed time. A clamp force requirement of 0.4–0.6 t/cm² of projected area is a practical first-order estimate for thin-wall multi-cavity molds running HG-173.

When thin-wall electronics housings require high gloss without secondary coating, HG-173 is selected as a direct-moulded surface solution. The material fills complex geometry under high shear, reduces the need for post-mould painting, and supports high-throughput production in energy-efficient moulding cells. Treated surfaces such as in-mould labels, pad printing, and solvent bonding are possible if surface tension is raised by plasma or corona treatment. However, intentional adhesion must be validated because the high-gloss surface has low wetting energy. In applications where textured surfaces are specified, chemical etching or laser texturing of the cavity is preferred because the smooth flow front of HG-173 reproduces tool details with high fidelity.

Comparative positioning of HG-173 against other ABS products is important for grade substitution decisions. Relative to high-impact ABS such as HI-121H, HG-173 exchanges low-temperature ductility for melt flow and gloss. The notched Izod impact energy under ISO 180/A is roughly 40–50% lower, while the melt flow index may be higher by a factor of approximately 2.0–3.0. Relative to an extrusion-grade ABS such as ER-461, HG-173 has lower melt strength and is not suitable for continuous profile, sheet, or pipe extrusion because melt draw-down and sagging become uncontrollable. Relative to flame-retardant ABS grades, HG-173 does not contain the halogenated or phosphorus-based additive systems required for UL 94 V-0 classification at thicknesses of 1.5 mm or below. Electrical enclosure parts requiring glow-wire ignition resistance under IEC 60695-2-10 should therefore be produced from a specifically flame-retardant ABS or PC/ABS grade rather than HG-173. Relative to heat-resistant ABS grades, HG-173 has lower heat deflection temperature of 85–90 °C under ISO 75-2/A, which limits continuous service in proximity to heat sources above approximately 75 °C.

Chemical resistance boundaries in lubricated and solvent-exposed assemblies are determined by environmental stress cracking rather than simple dissolution. Aromatic hydrocarbons, ketones, esters, and chlorinated solvents can reduce the critical strain for craze formation in general-purpose ABS. Exposure to certain oils, greases, cosmetic emollients, and cleaning agents may cause stress cracking in moulded parts that contain high residual stress near gates, snaps, or insert metal. The bent-strip test method described in ISO 22088-3 provides a comparative ranking of environmental stress cracking resistance. For HG-173, compatibility with each contact fluid should be tested using production-representative molded specimens at maximum service strain and temperature. Published data for this specific grade under all potential lubricant, adhesive, and household chemical combinations is limited; therefore, chemical compatibility is best treated as application-specific rather than inferred from generic ABS resistance tables. Regrind incorporation should be limited to ≤20 wt% in high-gloss visible parts, with dried regrind sorted free of contamination and retained to similar particle size. Higher regrind fractions may produce gloss variation, colour shift, and batch-to-batch differences in melt flow index that exceed narrow process control limits.