Product literature identifies SABIC ABS EX39—also referenced as CYCOLAC EX39 in some regional documentation—as an unfilled extrusion-grade acrylonitrile-butadiene-styrene resin. The material is classified under ISO 2580-1:2015 as an ABS for extrusion; its styrene-acrylonitrile matrix supplies rigidity, dimensional stability, and surface hardness, while the dispersed polybutadiene phase supplies low-temperature impact. Compared with high-flow injection-molding ABS grades, EX39 is positioned for sheet and profile extrusion where melt strength, web stability, and controlled low gloss are controlling. The product is not a UV-stabilized weatherable grade; outdoor parts require pigmentation, coextruded cap layers, or a separate UV protection strategy because extended ultraviolet exposure oxidizes the butadiene phase and reduces impact. Accelerated weathering evaluations should use ISO 4892-2:2013 or ASTM D2565 because natural exposure data for this specific grade are limited.

Pre-drying is mandatory for EX39 sheet extrusion. Moisture content above 0.1% by weight in ABS granules can generate splay marks, surface pitting, and die-lip deposits because water vaporizes during plastication. A dehumidified-air dryer set to 80°C for 2 h to 4 h with a dew point below −30°C is the standard starting condition for unfilled ABS. For high-humidity storage environments above 60% RH, the drying time should be shifted to the upper end of the range or the granulate should be transferred directly from sealed containers to the dryer hopper to avoid re-adsorption.

What Specification Values Govern EX39 Grade Selection in Extrusion Applications?

The EX designation in the SABIC ABS range is associated with extrusion-oriented flow characteristics: lower melt-flow values than the injection-molding MG or GPM series, higher melt strength, and a surface finish tuned for sheet formability. The following single-point values are reported for comparative characterization, not as design allowables.

These single-point property values are not design allowables. The Charpy notched values under ISO 179-1/1eA:2010 are measured on centrally notched prismatic bars and are sensitive to notch machining quality; a dull cutter can reduce apparent impact by more than 15%. Tensile values obtained under ASTM D638-14 on Type I specimens are not directly comparable to ISO values because of different specimen widths and strain rates. The melt-flow data at 220°C/10 kg may differ from ASTM D1238 values at 230°C/3.8 kg; conversions without capillary rheometry are not reliable. Low melt-flow results at 220°C/10 kg reflect the high melt strength required for sheet take-off; high-flow injection grades are specified under the same method but are typically an order of magnitude higher. The actual value for a lot is reported on the certificate of analysis and should be used for extruder speed calculations.

When Thermoforming Demands a Stable Melt Web Across a 40 mm Draw Depth

Thermoforming of EX39 sheet requires a temperature window of 140°C to 180°C at the sheet surface. Infrared pyrometers should map the sheet surface to within ±5°C before forming because nonuniform preheat produces thickness variation in plug-assisted forming. For plug-assisted positive molds, plug temperature should be held between 90°C and 120°C, and the plug should be coated with a release surface to prevent premature cooling of the sheet. Forming pressures from 0.6 bar to 1.0 bar are typical for vacuum and low-pressure air forming; high-pressure processes above 4 bar are uncommon for thin ABS sheet because excessive strain rate can tear the hot web at draw ratios above 3:1. The mold temperature should not exceed 80°C for gloss control and part ejection; higher mold temperatures can increase cycle time and produce sticking.

Capillary rheometry under ISO 11443:2021 at 230°C is used to map the shear-thinning behavior of EX39. Apparent viscosity is higher at low shear rates, which supports the melt web, but decreases as the material passes through the die lip; die designers should use a shear rate in the range of 100 s⁻¹ to 1000 s⁻¹ for lip design calculations. The flow channel should be streamlined because the butadiene phase can create stagnant regions at abrupt cross-sectional changes, causing degraded material to accumulate and release as black specks. A die land length 10 to 20 times the lip gap is typical for ABS sheet to obtain stable flow; shorter lands can produce melt fracture at high line speeds.

Sheet extrusion on a single-screw extruder requires a barrier screw with a compression ratio of 2.5:1 to 3.0:1 and a length-to-diameter ratio of at least 24:1. A 60 mm screw may use a feed-section channel depth of 8 mm to 12 mm, but screw design should be matched to the expected throughput and sheet gauge. Barrel temperatures typically range from 190°C to 210°C in the feed zone and 220°C to 235°C in the metering zone; the melt should not exceed 250°C because the butadiene phase undergoes thermal degradation that produces yellowing, loss of impact, and volatile compounds. Screen packs of 80/120/80 mesh protect the die from gels; the pressure differential across the screen pack should be recorded and the screens changed when the differential rises more than 25% above the clean-run value. Roll-stack temperatures between 80°C and 100°C are used to set sheet thickness and surface finish; the center roll should be adjusted to avoid calender shrinkage and edge curl.

On production-scale sheet lines, the most commonly observed defect for extrusion-grade ABS is gloss variation caused by roll-stack temperature drift. If the center roll falls below 80°C while the edges run hotter, the sheet develops differential shrinkage and surface defects that are not correctable by die-lip adjustment. Batch-to-batch variation in rubber particle size distribution can shift notched Charpy impact even when melt flow remains within the certificate limits; incoming lots should therefore be checked by notched impact and capillary rheometry under ISO 11443:2021 rather than by melt-flow index alone.

A primary difference between EX39 and high-flow injection-molding ABS grades appears in the melt volume-flow rate. High-flow injection grades can show MVR values from 20 cm³/10 min to 50 cm³/10 min at 220°C/10 kg, while extrusion-grade EX39 remains at the low-flow end to maintain melt strength. This divergence changes tool design and cycle economics: a high-flow grade fills a multi-cavity mold quickly but cannot maintain a stable melt web during sheet take-off. Conversely, EX39 produces uniform sheet with controlled gloss but is unsuitable for tightly packed hot-runner molds with wall thickness below 2.0 mm, where shear heating and pressure drop become limiting. In notched impact testing under ISO 179-1/1eA:2010, EX39 generally exceeds high-flow injection ABS because the butadiene phase is retained at a higher content and sheet extrusion produces less shear-induced rubber particle orientation. The tensile modulus, however, remains close to unfilled injection ABS; the grade difference is primarily in flow, impact retention, and surface appearance, not in room-temperature rigidity.

Chemical Resistance Boundaries and Regulatory Compliance Checklist

ABS is not resistant to esters, ketones, chlorinated solvents, or concentrated oxidizing acids. The acrylonitrile phase provides resistance to dilute aqueous acids and alkalis at room temperature, but environmental stress cracking can occur under load in the presence of organic solvents. Stress-cracking evaluations for ABS parts should use ISO 22088-3:2013 for bent-strip testing or ISO 22088-2:2013 for constant tensile load; the exact test depends on the end-use stress state. When direct food contact is claimed, only the specific grade, color, and production site listed in the supplier’s written declaration should be used under FDA 21 CFR 177.1520 or the applicable EU food-contact regulation. For electrical and electronic equipment, flammability evaluation should follow UL 94 at final thickness and color. A natural ABS sheet is usually classified HB; flame-retardant claims require a specific FR grade and should not be transferred to EX39. For automotive interior applications, many OEMs require odor, fogging, and volatile organic compound testing under their own specifications; published data for EX39 are available only on a case-specific basis from SABIC.

Application literature for EX39 points toward thermoformed refrigerator liners, automotive interior trim panels, luggage shells, and appliance covers where low surface gloss and high crack resistance are more relevant than rapid injection cycles. Sheet lines with 90 mm or larger single-screw extruders have demonstrated the need for stable roll-stack temperatures between 80°C and 100°C to control thickness and surface finish. The material can be colored by masterbatch or precolored by the compounder; color concentrates can shift the flow and impact properties, so the exact color-matched formulation should be re-qualified under the same test methods used for the natural grade. Because published data for specific configurations is limited, pilot-scale trials on the intended production equipment are required before committing to multi-cavity thermoforming tools.