Kumho Petrochemical ABS XT-560 is supplied as a natural pelletized acrylonitrile-butadiene-styrene terpolymer intended for sheet extrusion and downstream thermoforming. The grade is positioned within the producer’s ABS range by a rheological package that combines a low melt-flow rate, high melt strength, and stable draw-down behavior. The resin is typically processed on single-screw or twin-screw sheet lines with melt filtration, then converted by vacuum forming, pressure forming, or die cutting. Representative datasheet values obtained under standard test methods are shown in Table 1; the values are for natural unpigmented resin conditioned at 23 °C and 50 % relative humidity according to the cited methods.

For sheet producers running a co-rotating twin-screw line with L/D 36:1 and atmospheric venting, the melt temperature should be measured at the die adapter with an immersion probe. A 90 mm extruder producing 1.5 mm sheet is often adjusted to maintain a melt pressure of 120–160 bar at the breaker plate. Pressures above that band indicate low melt temperature, excessive regrind, or screen blockage. The use of a melt pump between the extruder and die reduces pressure surge and permits thickness tolerances of ±0.05 mm on 3.0 mm sheet. Incoming lot acceptance should record melt-flow rate and notched Izod impact on retained specimens; because ABS is a terpolymer, batch-to-batch variation in polybutadiene particle size and grafting can shift the notched Izod value by ±15 J/m even when the melt-flow rate remains within specification. A control chart keyed to ASTM D1238-20 and ASTM D256-23 is therefore more instructive than a single property check.

The tensile yield stress of 46 MPa and flexural modulus of 2.3 GPa provide cut-sheet rigidity for flat-bed die cutting. The notched Izod impact value of 340 J/m at 23 °C reflects the rubber-phase morphology retained by the low-flow molecular architecture. Heat deflection temperature of 90 °C at 1.82 MPa permits short-term exposure to warm wash-down in domestic appliance housings, but continuous load-bearing service above that threshold requires derating of stress and fastener span because the flexural modulus decays with service temperature.

What Limits Regrind Incorporation in XT-560 Sheet Stock?

Sheet extrusion operations often route trim scrap and thermoforming skeletons back into the feed stream. In XT-560, the practical limit is controlled by the thermal history of the butadiene rubber phase. Reclaimed sheet that has passed through one or more heat cycles contains oxidized polybutadiene domains and gel particles. When regrind content exceeds 25 wt%, the notched Izod impact value measured under ASTM D256-23 may fall by 10–15 %, and the melt pressure before a 80/120 mesh screen changer rises. This pressure rise is more pronounced on single-screw lines with L/D 32:1 because the barrel residence time is long enough to propagate thermo-oxidative crosslinking. Operators should monitor pressure upstream of the screen pack and set an alert when the pressure deviation exceeds 15 % of the virgin-material baseline. The extruder barrel should be purged with fresh virgin material before shutdown; stagnant melt in dead zones generates black specks that require screen changes and die-lip cleaning.

Regrind should be pre-dried separately before feeding to avoid bridging at the feed throat. A desiccant dryer with a dew point of -40 °C or lower can reduce residual moisture to below 0.02 wt% when run at 80 °C for 2–4 h. Mixing regrind with virgin pellets in the feed hopper without separate drying creates moisture pockets that appear as splay in the sheet. In practice, a regrind fraction maintained below 15 wt% typically preserves more than 90 % of the original notched Izod value; above 25 wt%, the converter should expect more frequent die-lip deposit and reduced deep-draw consistency.

A low melt-flow rate configured for high melt-strength extrusion

High-flow injection ABS grades commonly exhibit melt flow rates above 20 g/10 min under 220 °C/10 kg, which permits short filling times in thin-wall tools. XT-560 operates near 3.0 g/10 min under the same load and temperature. The lower melt-flow value is a direct indicator of high molecular weight and reduced chain mobility. During sheet extrusion, the higher melt viscosity stabilizes the web between the die and roll stack and reduces sag-induced thickness variation. During injection-style flow, the same property would require higher holding pressure and can produce surface blush in ribs. A converter moving from an injection grade to XT-560 should not substitute it directly into a mold designed for high-flow material without rheology simulation; published data for the specific configuration of XT-560 in high-speed injection form is limited.

Compared with a general-purpose injection ABS, XT-560 also contains a more impact-oriented polybutadiene phase. The trade-off is a lower melt flow, higher notched Izod impact, and a slightly softer flexural response. In sheet extrusion, these attributes support sag resistance and post-forming toughness rather than hard-surface cosmetic fill. In applications where optical clarity is required, a transparent MABS or clear ABS grade is more appropriate because XT-560 is opaque due to rubber-particle scattering.

When a producer runs XT-560 sheet against a high-gloss coextruded cap layer, the gloss difference between the cap and the substrate is not relevant because the cap is on the exposed surface. However, the substrate must accept the cap melt at the feedblock without interfacial shear instability. The low flow rate of XT-560 can create a viscosity mismatch against a high-flow cap resin; feedblock temperature should be held within ±5 °C to minimize waviness. In converters that previously ran a higher-flow substrate, the feedblock design may require a revised selector plate.

For vacuum forming operations that pull XT-560 sheet at a surface temperature of 150–180 °C, the grade maintains enough elastic strength to form deep draws without local thinning. Typical applications include refrigerator inner cabinets, coolers, bath and wash-basin panels, automotive door-trim substrates, and luggage shells. The sheet is heated on both sides until the core temperature reaches a uniform state; infrared pyrometer readings that vary by more than 5 °C across the sheet can cause corner bridging and nonuniform wall thickness. In production, a 3.0 mm sheet is often draped by vacuum at -0.8 bar with a plug assist speed below 300 mm/s to avoid chilling the sheet before final draw. Formed parts can be trimmed with router bits at 18000–24000 rpm; frictional heating above 220 °C causes melting and smearing at the cut edge.

Sheet thickness selection for refrigerator inner liners is typically between 2.0 mm and 4.5 mm; at these thicknesses the outer skin establishes a low-gloss surface while the core retains rubber-phase toughness. When the liner is welded at corners by hot-plate welding at 190–210 °C, the weld factor measured as weld strength divided by parent tensile strength should be checked on weld coupons under ASTM D638-14. Weld factors below 0.70 indicate contamination, excessive moisture, or an insufficient melt phase in the formed sheet.

When the sheet line processes XT-560 below 1.0 mm gauge

Thin-gauge extrusion of XT-560 below 1.0 mm shifts the dominant variable from melt strength to melt fracture and die-lip deposit. The grade’s high molecular weight creates elevated die entrance pressure; reducing the die gap below 0.7 mm without raising melt temperature can cause sharkskin at the web edges. In such conditions, the barrel temperatures should be maintained at 210–230 °C and the die temperature at 225–240 °C. A melt temperature exceeding 250 °C causes visible yellowing from polybutadiene oxidation, while a melt temperature below 205 °C increases drive load and may leave unmelts. The operational window is therefore narrow; thermocouple calibration drift of ±3 °C is enough to create visible edge-viscosity change.

Drying before thin-gauge extrusion must be executed in a desiccant dryer with a dew point of -40 °C or lower for 2–4 h at 80 °C; residual moisture above 0.02 wt% produces splay and microvoids. At 0.5 mm sheet thickness, the same moisture load leads to bubble defects that cannot be re-melted out. The chill roll temperature should be increased gradually from 70 °C to 95 °C as sheet thickness decreases to avoid freeze-off and excessive orientation. If the sheet is intended for lamination or coextrusion, corona treatment is generally required no more than 24 h before adhesive application; surface energy should be checked by dyne test according to ASTM D2578.

Verifying raw-material traceability and regulatory compliance

Raw-material traceability for XT-560 should originate from production lot documentation retained by the compounder. Converter incoming inspection can verify melt flow rate using ISO 1133-1:2022 and density using ASTM D792-20. Regulatory documentation for ABS typically includes a supplier declaration concerning REACH SVHC content and RoHS 2011/65/EU as amended by (EU) 2015/863; the heavy metals and brominated flame retardants covered by the RoHS annex are normally below the maximum concentration values in natural virgin material. UL 94 classification at 1.5 mm is HB; this is a burning-rate class, not a fire-proof rating.

Because XT-560 contains a butadiene rubber phase, it is not inherently UV-stable. Outdoors or UV-exposed parts require a co-extruded cap layer or UV-stabilized pigmentation; uncoated natural sheet will yellow and lose surface integrity after long xenon-arc exposure exceeding 1000 h depending on cycle irradiance. Contact with ketones, esters, and aromatic hydrocarbons can induce environmental stress cracking under load; chemical compatibility in actual clamped or bonded assemblies should be evaluated according to ISO 4599:2002 or equivalent internal protocol. In coextrusion, tie-layer selection should be confirmed by peel testing under ASTM D903 on the actual total structure; published data for XT-560 in all possible capstock configurations is limited.

Storage conditions in an uncontrolled warehouse can shift the processing behavior. Polyethylene-lined containers or sealed bulk bags should be kept away from direct sunlight and from condensate cycles that raise the moisture content of the pellets. If bags remain open above 60 % relative humidity for more than 8 h, re-drying is required before extrusion. The grade should not be blended with external lubricants, mold releases, or amine-containing additives without plant validation, because such additives can migrate to the sheet surface and reduce thermoforming adhesion or weld strength. Unloading, blending, and conveying equipment should be grounded and purged with dry air, and regrind should be pre-dried separately before feeding to avoid bridging at the feed throat.