LG Chem LUPOS ABS AT-553 is a pelletized acrylonitrile-butadiene-styrene copolymer classified as an antistatic grade within the LUPOS product family. The product is intended for injection-molded articles requiring controlled electrostatic charge dissipation without the fixed black coloration and brittleness of carbon-filled conductive thermoplastics. Typical production applications include semiconductor wafer carriers, IC handling trays, hard disk drive packaging, and cleanroom tote boxes in which surface resistivity between 10¹⁰ Ω/sq and 10¹² Ω/sq is specified under IEC 61340-5-1 ESD protected-area packaging rules. The grade differs from general-purpose ABS not by a change in the butadiene rubber phase alone, but by a migratory antistatic additive system that modifies surface electrical behavior after molding. The following data are representative manufacturer-published values for injection-molded test plaques conditioned at 23 °C and 50 % RH.

Representative property data from the manufacturer’s technical datasheet

These values are single-point representatives, not guaranteed specification limits. Batch-to-batch variation in the antistatic additive package may shift surface resistivity by one decade within the stated range without moving mechanical properties beyond normal production tolerances.

Drying is not a peripheral recommendation. ABS absorbs 0.2 wt% to 0.45 wt% moisture at saturation at 23 °C and 50 % RH. Before injection molding, LUPOS ABS AT-553 should be dried in a desiccant dryer with a dew point no higher than -40 °C at 80 °C for 2 h to 4 h, to a residual moisture level below 0.10 wt%. At ambient relative humidity above 60 %, drying time is extended to 4 h to 6 h because pellet surfaces re-adsorb moisture rapidly. Insufficient drying produces splay, silver streaking, and nonuniform surface resistivity after molding. Vented barrels with vacuum venting reduce volatile load but do not replace pre-drying. Drying equipment should include a dew-point sensor on the regeneration loop. If the desiccant bed cannot maintain -40 °C dew point, drying time is not sufficient and splay defects persist. Hopper capacity should not exceed 4 h of material consumption to avoid extended residence in a non-drying hopper at high ambient humidity.

The melt-temperature window for the antistatic additive system is narrower than for unfilled general-purpose ABS. Barrel set points from rear to nozzle should be 190 °C to 210 °C, 210 °C to 230 °C, 220 °C to 240 °C, and 220 °C to 235 °C, respectively. Mold temperature is normally held between 40 °C and 70 °C. Higher mold temperature increases the migration of the antistatic additive to the part surface and lowers local resistivity, but it also increases cycle time and can produce gloss variation on textured trays. Screw peripheral speed should remain between 30 m/min and 60 m/min, and back pressure between 0.3 MPa and 0.7 MPa. Residence time at melt temperature should not exceed 5 min; longer residence causes yellowing, brown specks, and partial loss of static-dissipative performance due to additive degradation. This conflict is specific to antistatic ABS and is not observed in standard LUPOS general-purpose grades.

A general-purpose screw with compression ratio 2.0:1 to 2.5:1 and L/D 20:1 to 25:1 is adequate. High-shear mixing sections are not required and can mechanically degrade the butadiene phase or over-disperse the antistatic additive, causing surface resistivity to climb above the upper target. Hot-runner manifold and nozzle temperatures should not exceed 240 °C. Valve-gated hot runners can produce localized overheating at the gate; surface resistivity should therefore be measured at the gate and at the end of fill during mold validation. The injection unit should be sized so that shot weight is between 30 % and 80 % of barrel capacity. Smaller shot sizes increase residence time and additive degradation; larger shot sizes reduce plasticating consistency and create unmelt particles. Cushion distance should be held constant between 2 mm and 5 mm to maintain pack pressure stability.

For thin-wall articles with nominal wall thickness below 1.0 mm, the flow length-to-wall-thickness ratio should be evaluated because high shear heating can locally degrade the antistatic additive. Mold-filling simulation with shear-rate data measured according to ISO 11443 is used to keep shear rates below the point at which surface resistivity becomes nonuniform. Weld lines in antistatic ABS are a frequent production defect. At the junction of two melt fronts, the additive-rich surface layer is disrupted, and local surface resistivity can be one to three decades higher than the bulk surface. Weld-line tensile strength is tested according to ISO 527-2:2012 using an injection-molded double-gated plaque, and acceptable strength retention is typically above 70 % of the single-gate tensile strength. Mold design should place gate welds away from snap-fit features and provide overflow tabs where weld lines cannot be moved.

Why does relative humidity shift the antistatic response?

The antistatic mechanism in AT-553 is not independent of ambient moisture. Migratory antistatic additives function by forming a charge-dissipating layer at the molded surface; continuity of that layer depends on adsorbed water. At 23 °C and 50 % RH, surface resistivity is typically 10¹⁰ Ω/sq to 10¹² Ω/sq. Below 15 % RH, resistivity commonly increases by two to three decades and may exceed 10¹³ Ω/sq, outside the upper bound for dissipative packaging materials under IEC 61340-5-1. Parts used in dry-air cleanrooms below 20 % RH therefore require verification under actual use conditions. The grade is not a permanent conductive material and should not be specified where surface resistance below 10⁶ Ω/sq is mandatory.

Static decay time from 5000 V to 50 V is typically below 2.0 s at 50 % RH when measured per IEC 61340-2-3; at 12 % RH the decay time can exceed 10 s. The antistatic additive can also be depleted by repeated washing or solvent wiping; prolonged immersion in isopropanol should be avoided because it extracts surface-active additives and raises resistivity. For recycled regrind, addition of clean sprues and runners up to 20 wt% is generally tolerated provided the regrind has not been exposed to high humidity and has not exceeded 5 min total melt residence time. Higher regrind fractions may reduce surface resistivity uniformity because the antistatic additive already migrated to the previous part surface and is partially depleted.

Positioned against standard, high-impact, and conductive ABS materials

Compared with LG Chem LUPOS ABS HI-121H, a high-impact grade with notched Izod impact near 30 kJ/m² under ISO 180:2019 but no intentional surface-conductivity control, AT-553 trades impact strength for static dissipation. The AT-553 notched Izod value of approximately 21 kJ/m² remains sufficient for ESD trays and carriers but is below the level expected for heavy-walled housings or snap-fit assemblies subject to repeated impact. Compared with LUPOS ABS GP-2100, a general-purpose grade, AT-553 adds an antistatic function but is more sensitive to drying, residence time, and shear history.

Against carbon-filled conductive ABS, AT-553 avoids the permanent black color and brittle failure modes associated with high carbon-black loading. Conductive ABS typically has surface resistivity from 10³ Ω/sq to 10⁶ Ω/sq and notched Izod impact from 8 kJ/m² to 12 kJ/m², but colorability is limited to black and mechanical rigidity is higher. AT-553 retains natural colorability and better melt flow, but its antistatic performance is relative-humidity-dependent and cannot provide shielding-level conductivity. Selection should follow ANSI/ESD S541 for packaging that requires consistent charge dissipation below 100 V within 2 s.

RoHS compliance is assessed under Directive 2011/65/EU Annex II, and the grade is not formulated with polybrominated biphenyls or polybrominated diphenyl ethers. REACH SVHC declarations should be obtained for each production lot. Flammability classification is UL 94 HB at 3.0 mm; this is not a flame-retardant ABS. The product does not provide food-contact approval under FDA 21 CFR 177.1020 unless a specific lot certification is issued by the supplier.

In semiconductor wafer-carrier molding, the interaction between the antistatic additive and the part surface is evaluated by measuring surface resistance after 24 h conditioning at 23 °C and 50 % RH. Because shrinkage of unfilled ABS is typically 0.4 % to 0.7 % in the flow direction, tooling for carriers is cut with the same shrinkage allowance as other unfilled LUPOS ABS grades. However, the antistatic additive can alter pack pressure requirements; short shots and sink marks at boss locations require holding pressure profiles developed with pressure-transducer-equipped tools. Published data for this specific configuration is limited, so mold trials are required for end-use qualification.