SABIC ABS EX39F is a pelletized acrylonitrile-butadiene-styrene copolymer supplied under the commercial resin designation SABIC CYCOLAC EX39F. The grade is positioned for sheet extrusion and subsequent thermoforming rather than primary injection moulding. Processors specify this product where the combined requirements of controlled melt viscosity, high melt strength during radiative sheet heating, retained low-temperature impact, and resistance to stress cracking in appliance interiors must be satisfied. Typical published melt volume-flow rate using ISO 1133-1 at 220 °C under a 10 kg load is approximately 5.0 cm³/10 min; density measured by ISO 1183 is approximately 1.04 g/cm³. These values are representative and do not supersede lot-specific certificates of analysis.

What Limits the Discoloration Threshold During High-Temperature Sheet Extrusion?

Thermal degradation of the polybutadiene phase controls the upper processing boundary. Sheet lines running SABIC ABS EX39F maintain a melt temperature of 205 °C to 240 °C; excursions above 260 °C initiate oxidation of the elastomer phase, producing yellowing, black speck formation, and a shift in melt flow rate outside the supplier-controlled range. The lower boundary is constrained by insufficient plastication. Melt temperatures below 195 °C increase screw torque, produce unmelts, and reduce gloss transfer in the polishing stack. Venting is required because ABS is hygroscopic. Pre-drying at 80 °C to 85 °C for 3 h to 4 h reduces residual moisture to below 0.1%; at relative humidity above 60%, additional drying time is required. Drying temperature must not exceed 90 °C, because polymer particles can fuse in desiccant hoppers.

Production-scale sheet extrusion is commonly run on vented single-screw extruders with screw diameters of 75 mm to 120 mm and an L/D ratio of 24:1 to 36:1. A 90 mm extruder with 30:1 L/D, vacuum venting, and screw speed of 45 rpm to 65 rpm is representative for producing 1.5 mm to 2.0 mm sheet. Three-roll polishing stack temperatures are set at 80 °C to 100 °C; higher roll temperatures improve gloss transfer but increase plate-out. Screen packs of 60/120/60 mesh are typically installed to raise melt pressure and remove gel particles.

The representative property set and a comparison with general-purpose injection-moulding ABS are shown in the following table.

When EX39F Replaces Standard Injection-Moulding ABS in Deep-Draw Liners

The substitution is driven primarily by melt strength rather than absolute toughness. General-purpose injection-moulding ABS grades often display melt volume-flow rates above 15 cm³/10 min under the same ISO 1133-1 condition, whereas EX39F operates near 5 cm³/10 min. The lower flow rate corresponds to higher melt elasticity, which reduces non-uniform sag across a heated sheet. In deep-draw refrigerator liner tools with draw ratios exceeding 1.0:1 in corner regions, this prevents excessive thinning. The trade-off is that EX39F must be processed through sheet extrusion rather than high-cavitation injection moulding. Injection-moulding clamp force and fast fill are not the governing parameters; sheet surface-temperature uniformity, plug-assist speed, and vacuum bleed rate control wall-thickness distribution.

Refrigerator interior liners represent the largest documented application. The resin is extruded into sheet and subsequently thermoformed into liners for domestic and commercial refrigeration cabinets. Compatibility with cyclopentane and HFC blowing-agent residues is critical because rigid polyurethane foam insulation is injected behind the formed liner. Crazing in thermoformed corners occurs if residual stress from forming exceeds the stress-cracking resistance of the ABS. Processors reduce this by maintaining sheet surface temperature at 170 °C to 190 °C during forming and by using ceramic heating elements with spectral output matched to ABS sheet absorption. Published data for specific foam-agent and lot combinations is limited; converter validation under production conditions is required.

Regrind management introduces a production-scale conflict. Closed-loop recovery of trim scrap is economically necessary, yet repeated heat history increases melt volume-flow rate and lowers notched Izod impact at -30 °C. Typical refrigerator-liner operations limit regrind to 30 wt% in virgin/regrind blends. At 40 wt% regrind, sheet sag during heating may increase by 8% to 12%, and reject rates for corner-thinning defects rise. Gravimetric blending with two-component feeding is used to maintain consistency, and regrind particle size is controlled below 4 mm by screen classification. Without such control, batch-to-batch variation in regrind bulk density produces visible thickness banding in thermoformed parts.

Comparative Regulatory, Drying, and Recycle Limits

Regulatory status depends on the additive package and end-use condition. As normally supplied, the grade is assessed against Directive 2011/65/EU and the amending Delegated Directive (EU) 2015/863; it does not rely on PBDE or PBB flame retardants. Under REACH Regulation (EC) No 1907/2006, Article 33 communication is required only if candidate-list substances exceed 0.1 wt%. For food-contact applications in the United States, the converter must verify that the finished article meets 21 CFR 177.1020 for the intended temperature and food-type conditions. For EU food contact, Regulation (EU) No 10/2011 applies only with validated overall migration testing. The grade is not inherently UV-stabilised for long-term outdoor exposure.

Compared with flame-retardant ABS extrusion grades, EX39F does not contain low-molecular-weight brominated additives, which reduces polish-roll plate-out but limits the material to UL 94 HB. Compared with high-heat ABS, the Vicat softening temperature of approximately 96 °C is lower; thermoformed parts are therefore not specified for continuous service above 70 °C under load or hot-air impingement above 80 °C. Secondary uses include bath panels, spa shells, luggage shells, and recreational-vehicle interior trim, where wide forming latitude and low-temperature impact are more important than high gloss.

Operational boundaries must be observed. Pre-drying is mandatory at relative humidity above 60%. The polymer is incompatible with ketone, ester, and chlorinated solvent exposure, which can induce environmental stress cracking in formed parts. Amine-based purge compounds should be avoided where residues can accelerate surface oxidation. Processing above 260 °C melt temperature generates gel particles and yellowing; processing below 195 °C increases screw torque and degrades sheet quality. The material is not recommended for direct ultraviolet exposure without a coextruded cap layer or UV-stabilised coating. Published data for twin-screw recompounding of contaminated post-industrial scrap is limited; each reclaim stream must be qualified on the intended production line.