Lotte Chemical ABS MP-2110 is an electroplating-grade acrylonitrile-butadiene-styrene resin sold under the Starex ABS trade name. The grade is designed for chromic acid/sulfuric acid etch and electroless nickel/chromium plating rather than paint-first or chrome-free PVD decoration. Representative natural-grade material data are presented in Table 1; the values are single-point determinations and do not constitute lot-release minima.

Lot-to-lot variation in rubber-phase gel content can shift the optimal etch time. Incoming lots should be screened for melt mass-flow rate, ash content, and moisture before release. For critical exterior programs, a three-level etch study at 5 min, 7.5 min, and 10 min is recommended because ASTM B533 peel adhesion often peaks sharply at intermediate etch intensity.

Where MP-2110 Sits Within Lotte Chemical’s ABS Electroplating Portfolio

Within the Starex ABS range, MP-2110 is positioned as a medium-flow electroplating grade rather than a general-purpose molding resin. Its melt mass-flow rate of 22 g/10 min at 220°C/10 kg is lower than high-flow electronics grades; this preserves the polybutadiene particle size during filling and reduces gate-area rubber deformation. Compared with general-purpose grades, MP-2110 exhibits a tighter polybutadiene particle-size distribution and higher gel content, which narrows the etch pit population after chromic acid attack to the 0.5–1.5 µm range and improves adhesion uniformity when tested by ASTM B533. Compared with high-impact ABS grades, the notched Izod impact at 23°C is lower—approximately 22 kJ/m² by ISO 180/A—because the rubber morphology is tuned for etch-pit formation rather than maximum energy absorption. Compared with heat-resistant ABS, MP-2110 carries a heat deflection temperature of 88°C under 1.82 MPa by ISO 75-2:2013 method A, which excludes continuous use above that threshold. Compared with a PC/ABS plating grade, MP-2110 etches more readily at 65–70°C in a 400 g/L chrome trioxide bath, but it is more sensitive to over-etching when immersion exceeds 10 min.

Pre-drying is mandatory at ambient relative humidity above 60%. A desiccant-wheel hopper dryer should be held at 80°C for 3–4 h, with an inlet dew point no higher than -30°C. Feed-throat moisture should remain below 0.02% when measured by ISO 15512:2019. Barrel temperatures should be profiled from 240°C at the rear zone to 250°C at the nozzle, with an upper melt limit of 260°C. Mold temperature should be kept between 40°C and 80°C; temperatures above 80°C can raise ASTM B533 peel adhesion but also extend cycle time and increase sink-mark risk. Table 2 summarizes the recommended molding window.

Shot-to-shot variation in melt density caused by worn check-ring clearances can appear as skip plating after etch. Injection molding machines with closed-loop process control and melt temperature verification by immersion thermocouple are specified. Screw assemblies with L/D 20:1 to 25:1 and compression ratio 2.0:1 to 2.5:1 are acceptable; high-shear mixing sections are not recommended because they can degrade the polybutadiene phase and widen etch pit distribution. At mold temperatures below 40°C, frozen-in orientation at the surface reduces etch rate in the flow direction and creates streaky plate appearance. At melt temperatures above 260°C, oxidative degradation of the polybutadiene phase releases volatile compounds that can cause silver streaks and alter etch pit distribution.

Low levels of regrind are allowed. For exterior plated parts, regrind is typically limited to 20% by weight; higher ratios narrow the rubber-phase particle size distribution and lower ASTM B533 peel adhesion after thermal cycling. In-line granulation with closed-loop vacuum conveying is preferred; fines and dust increase etch bath sludge, which shifts etch rate and raises maintenance frequency. Each regrind ratio change should be validated by mold-filling pressure and a three-point etch study.

What Limits Plating Adhesion When Etch Bath Parameters Drift?

Chromic acid/sulfuric acid etching removes butadiene-rich domains from the molded skin, leaving microvoids with diameters typically between 0.5 µm and 1.5 µm. If bath temperature falls below 60°C, pit depth and density are insufficient, and adhesion by ASTM B533 can fall below 0.5 kN/m. If temperature exceeds 70°C or immersion time exceeds 10 min, pits coalesce into voids above 2 µm, weakening the substrate surface and producing peel failure at the nickel-to-substrate interface. The microvoid depth should be validated by scanning electron microscopy on molded plaques before production etching. A pit diameter larger than 2 µm indicates over-etch; a surface dominated by smooth resin with scattered pits below 0.5 µm indicates under-etch. Etch bath turnover and hexavalent chromium concentration should be monitored by titration at intervals no longer than 4 h; trivalent chromium accumulation above 30 g/L slows etch rate.

The chromic acid/sulfuric acid ratio must remain within the line-specific control band because sulfate depletion accelerates resin oxidation and creates chalky surfaces with poor electroless nickel initiation. Sulfuric acid concentration should be maintained at 350 g/L ± 20 g/L; chrome trioxide at 400 g/L ± 20 g/L. The absence of mineral fillers is deliberate; filler particles act as etch obstacles and disrupt uniform pit geometry. Amine-containing mold-release residues are incompatible because they neutralize the acidic etch front and create localized skip-plating defects.

When Chromic Acid Etching Replaces Mechanical Abrasion

When chromic acid etching replaces mechanical abrasion as the adhesion-promoting step, the plating line becomes an extension of the material specification. A standard ABS plating sequence for MP-2110 includes alkaline soak cleaning, chromic acid/sulfuric acid etch at approximately 400 g/L chrome trioxide and 350 g/L sulfuric acid, immersion at 65–70°C for 5–10 min, neutralization, palladium-tin activation, electroless nickel at 0.25–0.5 µm, copper strike, semi-bright nickel, bright nickel, microporous nickel, and chromium. Neutralization in sodium bisulfite after etch is required to remove hexavalent chromium residues from micropits; incomplete neutralization reduces electroless nickel adhesion and creates skip plating. Palladium-tin activation should produce a uniform brown color on the part surface; color variation indicates uneven etch or molded-in stress. Racked parts should be tested by ASTM B533 peel adhesion and ASTM B604 for decorative electroplated coatings. Optimized ABS plating lines typically achieve peel values above 0.8 kN/m; published data for MP-2110-specific peel values are limited and should be established on production plaques with three etch times. A water-break test after neutralization is a rapid line check; a continuous water film indicates acceptable surface energy, while water beading indicates residual organic contamination or incomplete neutralization.

Electroplated exterior components—radiator grilles, wheel covers, door handle cups, tailgate garnish, and emblem surrounds—are the primary production-scale uses for MP-2110. For a grille with projected area 0.12 m² and cavity pressure of 35 MPa, clamp force must be at least 4,200 kN; smaller handle-cup tools typically operate between 1,200 kN and 1,800 kN. Multi-cavity tools with sequential valve gates are specified to prevent weld lines in visible plate areas, because weld-line regions etch at a different rate under 400 g/L chromic acid at 65°C and can produce visible adhesion defects after chromium deposition. Edge gates should be 1.5–2.0 mm in diameter and subgates 0.8–1.2 mm; undersized gates cause high shear heating and rubber-phase degradation near the gate. Mold shrinkage before plating is typically 0.4–0.6% in the flow direction and 0.3–0.5% cross-flow by ISO 294-4; after plating, dimensional growth can be 0.3–0.5% depending on plate thickness and rack position.

MP-2110 is not a heat-resistant ABS, a flame-retardant ABS, or a PC/ABS plating grade. Continuous service above 88°C under load is outside the intended thermal boundary. Vicat softening temperature of 98°C permits plating-line rack drying up to 90°C for short cycles; prolonged exposure above 95°C can relax molded-in orientation and alter part dimensions. Chrome-plated parts using MP-2110 require RoHS review for hexavalent chromium in the applied coating under Directive 2011/65/EU Annex III; the resin itself is not formulated with intentionally added cadmium, lead, mercury, or chromium VI, but lot certification to IEC 62321-1 should be requested. For chrome-free PVD or paint-first decorative work, general-purpose or high-gloss ABS grades are usually selected instead. Unopened bags should be stored below 30°C and 60% relative humidity; opened containers should be re-dried before use.