LG Chem ABS HF-380 is an acrylonitrile-butadiene-styrene injection molding grade designed for high-speed filling of thin-wall and complex-flow-path components in which cycle time, dimensional replication, and surface appearance control processing economics. The grade is supplied as natural or colored pellets with a melt flow rate of 38 g/10 min at 220 °C under a 10 kg load according to ISO 1133-1:2022. This flow level is higher than the 15–18 g/10 min range typical of medium-impact ABS grades in the same product family. Representative ISO test specimen data include a tensile yield stress of 46 MPa per ISO 527-2/1A, flexural modulus of 2350 MPa per ISO 178, Izod notched impact strength of 20 kJ/m² at 23 °C per ISO 180/1A, heat deflection temperature of 84 °C at 1.82 MPa per ISO 75-2/A, and UL 94 HB rating at 1.6 mm. The main applications are vacuum cleaner housings, small appliance bodies, telephone handsets, office equipment enclosures, and toys where high flow permits filling of ribs, bosses, snap-fit arms, and thin wall sections that would otherwise require higher injection pressure or higher melt temperature. The product differs from general-purpose ABS grades in that it trades some notched impact reserve and solvent stress-cracking resistance for a lower viscosity envelope and better replication of fine mold features. Selection should therefore favor ambient-temperature impact requirements over sub-zero impact resistance. The high-flow character also demands stricter control of melt residence time because thermal degradation can occur above 250 °C.

Melt Rheology and Hot-Runner Pressure Drop in Thin-Wall Molds

The practical advantage of the high melt-volume rate appears as lower injection pressure and lower hot-runner pressure drop in multi-cavity tools. In a hot-runner system using 0.8 mm valve-gate tips and a manifold at 220 °C, the pressure required to fill a 1.2 mm thick plaque from a 32-cavity layout depends on the apparent shear rate at the gate. At an apparent shear rate near 10⁴ s^-1, HF-380 behaves as a pseudoplastic melt with viscosity well below the plateau value at 10² s^-1. The exact viscosity curve should be obtained from the supplier in Cross-WLF or Carreau-WLF format for injection molding simulation; published data for this specific configuration is limited, and simulation users should request the current Moldflow UDB file. The grade is more sensitive to melt temperature than to back pressure. A practical melt temperature range is 200–240 °C. Above 250 °C, thermal degradation of the butadiene phase can generate conjugated unsaturated species that increase yellowness, reduce notched impact strength, and elevate volatile condensation on the mold surface. Below 190 °C, the melt pressure needed to fill thin sections may exceed the clamp force available on smaller machines. Screw recovery should use low back pressure, typically 0.5–1.0 MPa, because high-flow ABS does not require high shear input to reach melt homogeneity. Melt flow index is a single-point test and is not sufficient to predict filling behavior; pressure-volume-temperature and shear-viscosity data are required for accurate mold-filling simulation.

For molders without simulation capability, spiral flow length under ISO 294-1 can provide a rough comparative ranking, but it is not a material constant because the value depends on mold temperature, injection speed, and hold pressure. A capillary rheometer operating at 220 °C and 230 °C with Bagley-corrected shear viscosity data is more useful for estimating gate pressure drop. When the melt becomes too hot, the window between adequate flow and visible degradation narrows, and barrel residence time should be kept below 5–8 min where possible, depending on shot size and cycle time. Nozzle temperature should not exceed 240 °C, and hot-runner manifold channels should be sized to keep shear rate below 10⁵ s^-1 at the gate; shear heating in small gates can raise local melt temperature above the barrel set point and produce silver streaks or burn marks. Equipment with closed-loop injection control and sensor-based mold temperature monitoring is preferred for consistent thin-wall filling.

What Distinguishes HF-380 from Medium-Impact ABS Grades When Flow Length and Impact Toughness Conflict?

The selection between HF-380 and a medium-impact ABS grade should be made on a flow length versus notched impact chart. HF-380 delivers longer flow length under equivalent injection pressure, but its Izod notched impact at 23 °C is approximately 20 kJ/m², whereas many medium-impact grades range from 28 kJ/m² to 34 kJ/m². At −30 °C, the difference widens because the polybutadiene content and morphology are adjusted toward lower viscosity rather than low-temperature cavitation resistance. This is the central trade-off: the grade is not intended for components that require high crack initiation energy in cold environments. For indoor appliance housings, the typical impact mode is accidental drop at ambient temperature, and HF-380 is generally adequate when nominal wall thickness remains above 1.5 mm. For structural snap-fit bosses, local stress concentration at the boss root should be evaluated by tensile impact or instrumented puncture testing, because the single-point Izod test does not capture injection molded skin-core orientation effects. Comparisons with high-heat ABS grades show that HF-380 has a lower Vicat softening temperature, near 96 °C under ISO 306/B50, and is not recommended for continuous exposure above 80 °C. Against flame-retardant ABS grades, HF-380 is not a substitute because it is only UL 94 HB at 1.6 mm, not V-0. This grade should therefore be viewed as a viscosity class shift rather than a general-purpose replacement for all ABS types.

In dehumidifying hopper dryers, the material should be dried at 80 °C for 2–4 h to reach a moisture content below 0.05 %, particularly when ambient relative humidity exceeds 60 %. ABS is hygroscopic enough to pick up surface moisture during storage; the effect on molded parts is generally not as severe as in polyamide or polycarbonate, but excess moisture can produce splay marks and reduce surface gloss. Drying air should have a dew point of −20 °C or lower, and hopper capacity should match throughput to avoid bridging or segregation. A validated loss-on-drying moisture analyzer operating at 120 °C is recommended for lot acceptance. High-flow grades can show slightly higher sensitivity to moisture-induced splay in thin-wall parts because the lower melt viscosity allows vapor nucleation to propagate rapidly from the melt front; a closed conveying system and immediate bag sealing reduce variability.

Thermal History of the Melt Controls Surface Gloss and Weld-Line Integrity in High-Shear Filling

Surface finish on HF-380 moldings is governed by melt temperature, injection velocity, and mold surface replication. For glossy appliance housings, the nozzle melt temperature should be 220–230 °C, and the mold surface should be polished to SPI-A2 or finer. Lower mold temperatures of 40–50 °C increase cooling rate and reduce cycle time, but they can produce jetting and flow marks if injection velocity is too high; profiled injection with moderate initial filling reduces shear heating and improves gloss uniformity. The high flow rate permits lower packing pressure than medium-flow grades, but holding pressure must still be optimized against gate freeze time. On a direct edge gate, gate freeze typically occurs within 1–3 s at a wall thickness of 2.0 mm; small-diameter hot-runner tips may freeze earlier. Weld-line strength in complex multi-gated housings should be tested on specimens cut from the molded part, because ABS weld lines are sensitive to melt temperature and packing. Higher melt temperature improves molecular diffusion across the weld line, but excessive temperature above 250 °C may degrade the rubber phase and increase the yellow index. Mold temperatures above 80 °C are usually unnecessary for this grade and may lengthen cycle time without proportional impact improvement. Cooling channels should maintain a cavity-to-cavity mold temperature variation of less than ±5 °C to prevent asymmetric shrinkage and visible warpage in large flat appliance panels.

Typical machines for this grade range from 80-ton to 350-ton clamp force depending on projected area and cavity count; screw L/D ratios of 20:1 to 24:1 are standard. The non-return valve should seal completely during injection because low-viscosity melt can back-flow and reduce pack pressure. A nozzle shut-off valve is recommended for high-speed sequential filling of multi-cavity hot-runner tools. Injection pressure at the machine gauge should not be used as a direct comparison across machines because hydraulic pressure and intensification ratio differ; the actual melt pressure at the nozzle or cavity sensor is the transferable variable. Cavity pressure at transfer from fill to pack should be reproducible within ±5 % lot-to-lot, and cushion size should be maintained at 2–4 mm to provide stable packing. When using a hot runner, purge after color change with a purging compound rated for ABS and verify that all previous material is removed before restart.

Because of its high melt flow rate, the grade is used in multi-cavity production of vacuum cleaner housings, small appliance bodies, and electronic enclosures where nominal wall thickness is between 1.2 mm and 2.5 mm and rib-to-wall ratio does not exceed 0.6. In such parts, the material provides adequate stiffness and ambient-temperature impact resistance, but it is not intended for load-bearing brackets exposed to continuous torque. The high flow also reduces the injection pressure needed to fill long flow paths in office automation equipment. Textured surfaces should maintain a draft angle of at least 1° per 0.025 mm of texture depth to prevent ejection drag; this guideline is independent of grade but becomes more critical at low mold temperatures. Color masterbatch must be dried and, when used, the final melt flow rate and impact properties should be rechecked because pigment carriers can shift viscosity.

When Regrind Ratios Rise Above 20 % in Production Lines

Regrind use in HF-380 follows standard ABS practice but requires tighter control because high-flow design is more susceptible to viscosity shift after repeated thermal-mechanical degradation. The recommended regrind fraction is 20 % or less for appearance and impact-critical parts. Higher fractions, up to 30 %, may be acceptable when the sprue and runner system is clean and the regrind is uniform in particle size. Above 30 %, molders should monitor melt flow rate and impact retention on injection-molded specimens. A shift from 38 g/10 min toward values below 30 g/10 min after repeated processing indicates excessive chain scission or crosslinking and requires lower melt temperature or reduced regrind percentage. The material should not be blended with polycarbonate-based regrind, PVC, or flame-retardant ABS without full separation, because contamination can alter flammability rating and mechanical integrity. Regrind exposed to high humidity before molding should be dried at 80 °C for 2–4 h. Size reduction should use a granulator with a screen hole diameter of 6–8 mm; finer fluff may increase feeding instability in the extruder throat.

Incoming lot acceptance should include melt flow rate and impact verification because batch-to-batch variation in high-flow ABS can alter cavity pressure and part weight. A tensile bar cavity with ASTM D638 Type I or ISO 527-2 Type 1A geometry is sufficient for periodic mechanical property monitoring. Retained samples should be conditioned at 23 °C and 50 % relative humidity for 40 h according to ISO 291 before testing unless the part specification requires dry-as-molded testing. Shrinkage after molding is anisotropic; the supplier datasheet value is usually a range of 0.4–0.7 % under ISO 294-4, but actual mold shrinkage depends on wall thickness, gate location, and holding pressure. Dimensional checks on critical snap-fit features should be performed after 24 h because post-molding shrinkage continues after ejection.

For regulatory records, natural-grade HF-380 is typically supplied with a REACH statement and RoHS directive compliance for the standard global application scope; however, end-use compliance must be verified against the exact color masterbatch and additive package because pigments, flame retardants, and processing aids can introduce reportable substances. The general-purpose grade is not automatically suitable for food-contact applications under FDA 21 CFR 181.32 or EU 10/2011 without grade-specific certification. Under ISO 175 chemical resistance testing, ABS is generally resistant to dilute aqueous acids and alkalis but is attacked by ketones, esters, aromatic hydrocarbons, and some chlorinated solvents. The grade should not be specified for housings that are routinely wiped with strong solvent cleaners or exposed to fuel vapors. Ultraviolet resistance of unpigmented HF-380 is limited; outdoor use without UV-stabilized color or coating leads to chalking, embrittlement, and color shift, and published data for this specific configuration under extended UV weathering is limited. The operational boundary for continuous load-bearing service is typically below 60 °C, and short-term exposure should remain below 80 °C, because creep modulus declines with temperature.