LG Chem ABS HF-380G is an injection-molding grade of acrylonitrile-butadiene-styrene copolymer formulated for high-flow filling of thin-wall, appearance-critical parts. The product model designation HF-380G identifies a high-flow ABS with controlled rubber-phase morphology; melt index under ISO 1133-1:2022 condition Z (220 °C, 10 kg) is typically 38 g/10 min, and density is 1.04 g/cm³ under ASTM D792-20. The grade is supplied as cylindrical pellets for conventional reciprocating-screw injection molding machines with general-purpose screws having an L/D ratio of 18:1 to 22:1 and a compression ratio of 2.5:1 to 3:1. Typical application segments include appliance trim, consumer electronics housings, small automotive interior components, and non-food-contact equipment enclosures in which filling of ribs, bosses, and snap-fit features must occur without weld-line cracking.

What Distinguishes HF-380G From High-Impact and Standard General-Purpose ABS Grades?

The main process distinction is rheological. HF-380G presents a melt flow index approximately 19 g/10 min higher than high-impact ABS grade HI-121H under identical conditions, while its notched Izod impact at 23 °C is lower by approximately 56 J/m under ASTM D256-23. This inverse relationship between flow and impact reflects the expected trade-off in graft-rubber morphology; the grade uses a controlled rubber particle-size distribution to maintain practical impact retention in thin sections. Compared with standard general-purpose ABS grades, the G configuration is intended to provide tighter melt-viscosity consistency and lower lot-to-lot variation during fast injection cycles. However, published flow-length and weld-line data specific to the G designation remain limited compared with standard HF-380 grades; processors should confirm lot-specific melt-flow index and impact values through the certificate of analysis before tool commissioning.

Tooling, Drying, and Injection-Molding Parameter Ranges

Predrying in a desiccant dryer at 80 °C for 2–4 h reduces moisture content below 0.05 wt%. Blower air dew point should remain below −20 °C, and airflow capacity should be at least 0.5 m³/h per kg/h of polymer throughput. Moisture above 0.1 wt% before melting causes splay, surface delamination, and reduced weld-line strength under fast injection. Barrel zone settings typically span 180–200 °C at the rear, 200–230 °C at the center, 210–240 °C at the front, and 210–230 °C at the nozzle. Measured melt temperature should not exceed 240 °C; at melt temperatures above 240 °C, total residence time should not exceed 5 min. Mold temperature 40–60 °C is conventional for thin-wall filling; the higher half of this range is used when gate freeze-off limits packing.

Injection pressure requirements are typically 60–120 MPa, with holding pressure between 60 and 80 MPa for parts with nominal wall sections of 1.0–1.5 mm. Screw recovery is conducted with back pressure 5–10 bar and circumferential screw speed 0.2–0.4 m/s to avoid excessive shear heating. Decompression 3–5 mm prevents nozzle drool. High-flow ABS grades are more sensitive to screw-recovery heating than to high-speed injection heating; therefore, screw speed should not be increased to compensate for short cycle time without monitoring melt temperature.

In production-scale hot-runner tools, filling imbalance becomes a measurable defect mechanism for high-flow grades. Multi-cavity tools should use geometrically balanced runners, valve-gate actuation where possible, and identical cooling-circuit pressure drop across all cavities. A variation of ±0.5 °C in mold surface temperature can shift the flow front length by more than 1 mm in a 1.0 mm wall. When edge gates are unavoidable, gate thickness below 0.8 mm freezes before packing is complete; this produces sink marks opposite ribs and bosses. Hot-runner nozzle tips should be profiled for amorphous styrenic melts to minimize dead zones and material hang-up.

Venting is a further boundary condition in high-flow ABS. Vent depth should be limited to 0.02–0.03 mm and vent width 5–10 mm, with perimeter venting placed at the last areas to fill. Insufficient venting causes burn marks and lowers weld-line strength; excessive vent depth creates flash because of the low melt viscosity. For thin-wall parts with wall thickness 1.0 mm, cavity pressure at the end of fill may peak between 40 and 60 MPa; clamp-force requirements should be calculated from projected area and cavity pressure, not from material viscosity alone.

Residence time at melt temperature controls degradation. At 230 °C, the butadiene-rich phase undergoes oxidative crosslinking and chain scission; visible failure modes are brown streaking, weld-line embrittlement, and melt-index drift greater than 5 %. In machines with shot size below 25 % of barrel capacity, residual melt remains in the plastication zone longer than the nominal cycle time. Production trials should include a cold-start purge and short-shot study after the material has been held in the barrel for 15 min without injection to confirm surface quality before extended runs.

When HF-380G Is Applied to Thin-Wall Electronic Housings, Which Dimensional Control Measures Apply?

Mold shrinkage for unfilled ABS is typically 0.4–0.7 % in the flow direction under ASTM D955-08(2014), with transverse shrinkage up to 0.9 %. Molded parts with nominal wall thickness 1.2 mm and holding pressure 70 MPa show post-mold dimensional change of 0.1–0.3 % after 24 h at 23 °C and 50 % RH. For bosses, a wall thickness-to-boss diameter ratio of 0.6:1 and a root radius of 0.3 mm reduce sink. Beryllium copper or conformal cooling inserts in isolated heat-load regions reduce differential shrinkage and warpage.

Weld lines occur where flow fronts converge around core pins and apertures. In this grade, weld-line tensile strength is controlled by flow-front temperature above 120 °C and by holding pressure. Simulation with Cross-WLF viscosity parameters and measured pressure-volume-temperature data is recommended before tooling because published weld-line strength data specific to HF-380G are limited. If gate-to-weld-line distance exceeds 80 mm in a 1.0 mm section, hot-runner valve-gate sequencing or multiple drop locations should be evaluated.

Gate geometry should avoid direct impingement on core pins or cavity walls. A fan gate with thickness 0.8–1.2 mm and width 2–4 mm is used for flat housings; pin gates below 0.5 mm produce high shear and may degrade the rubber phase around the gate. For high-gloss surfaces, the gate land angle should be 15–20 ° to reduce gate blush. The mold surface finish controls part gloss. Diamond-polished cavity surfaces with average roughness Ra ≤ 0.05 µm are required for high-gloss surfaces; spark-eroded surfaces with Ra > 1.0 µm produce low-gloss textured finishes. The high melt flow of HF-380G improves replication of microtexture but also increases the risk of visible flow lines if the melt front cools unevenly.

HF-380G resists aqueous acids, alkalis, and many aliphatic hydrocarbons at room temperature, but prolonged contact with esters, ketones, chlorinated solvents, and aromatic hydrocarbons induces environmental stress cracking, especially in molded parts with high residual stress. Mold releases, cleaning agents, and adhesive systems containing such solvents should be validated by ASTM D543-21 immersion testing before production. The grade is typically recognized as UL 94 HB at 1.5 mm thickness. It is not normally supplied as a food-contact formulation; compliance with FDA 21 CFR 177.1020 must be confirmed with the supplier for the exact pigment and additive package. RoHS declarations are available under EU 2015/863, and REACH SVHC status should be checked against the date-stamped supplier safety data sheet. Processing fumes contain styrene monomer; exhaust extraction and workplace exposure monitoring are required.

Does Regrind Reincorporation Require a Modified Drying Protocol?

Regrind from sprues and runners can be re-introduced at 10–20 wt% into virgin HF-380G, provided particle size remains below 8 mm and fines are screened. Regrind increases moisture uptake because of increased surface area; predrying time should be extended to 4 h at 80 °C when regrind fraction exceeds 15 wt%. At regrind fractions above 20 wt%, melt viscosity may shift by more than ±2 g/10 min, and appearance-critical surfaces may exhibit silver streaks and gloss variation. Melt flow index should be checked under ISO 1133-1:2022 at least once per 8 h shift, and injection peak pressure should be logged as a stability indicator.

Compared with high-impact polystyrene, HF-380G offers higher tensile strength and chemical resistance to aliphatic hydrocarbons; compared with styrene-acrylonitrile, it provides improved impact resistance but lower transparency. Against ASA, HF-380G has lower outdoor UV retention and is not recommended for unpainted exterior parts. When flame-retardant performance is required, halogen-free flame-retardant ABS or PC/ABS blends should be evaluated because HF-380G is not formulated for V-0 classification. Compared with PC/ABS blends, HF-380G has a heat deflection temperature at 1.82 MPa typically 20–30 °C lower under ASTM D648-18, lower notched impact, and lower density. It is selected where thin-wall filling, chemical resistance to dilute acids and alkalis, and lower part mass are primary constraints. It should not be specified where continuous service above 80 °C, steam sterilization, transparency, or prolonged outdoor UV exposure is required without additional stabilization or validation.