LG Chem ABS XR-407E is an amorphous acrylonitrile-butadiene-styrene extrusion resin formulated for flat-die sheet, low-stress thermoforming, and formed interior liners. The grade belongs to the manufacturer’s heat-resistant XR series and is commonly referenced for refrigerator inner liner sheet, automotive interior trim panels, and edge-protective profiles where the semifinished sheet must retain dimensional stability at elevated forming temperatures. Under ISO 2580-1:2014 designation practices for ABS materials, the product is reported using ISO 10350-1 single-point data conventions. Typical values used in preliminary tool design include a melt mass-flow rate of approximately 4.0 g/10 min at 220°C and 10.0 kg load per ISO 1133-1, a tensile yield stress in the range of 45 MPa to 50 MPa under ISO 527-2/1A/50, and a deflection temperature under load near 104°C at 1.82 MPa per ISO 75-2/A. These values should be verified against the lot-specific certificate of analysis because polymerization and compounding line variation produces batch-to-batch shifts of up to ±5% in melt-flow and notched impact properties. For design purposes, the material is best treated as a heat-resistant ABS whose utility depends on the interaction between melt rheology, thermal history, and forming stress rather than on any single property. The polymer matrix consists of a styrene-acrylonitrile continuous phase with a dispersed butadiene-based rubber phase. The molecular weight distribution and rubber particle size are adjusted by the manufacturer to increase melt strength during vertical sheet draw while retaining flow through a flat die. In practice, this means the material occupies a processing window above that of general-purpose ABS grades and below that of higher-heat XR-409H material. The balance is most visible in melt-flow behavior: lower melt-flow resins resist sheet sag but increase extruder head pressure, while higher-flow resins process easily but exhibit excessive drawdown in deep-cavity thermoforming. XR-407E is therefore specified where a sheet surface temperature of 160°C to 180°C is required at the forming station and where heat deflection after demolding is a critical quality variable.

What Happens to Sheet Gloss Uniformity When Melt Temperature Exceeds 250°C?

On a production-scale single-screw extruder with a 30:1 to 36:1 L/D ratio and a barrier feed section, XR-407E is typically processed with a flat barrel profile from 180°C in the feed zone to 230°C in the metering zone. The die lip is normally held at 230°C to 240°C, and the melt temperature at the screw tip or melt-pump inlet is maintained at 230°C to 250°C. When the melt temperature exceeds 250°C for prolonged residence periods, the butadiene-rich rubber phase begins thermo-oxidative degradation. The first visible indication is a loss of 60° specular gloss uniformity measured per ISO 2813. Low-gloss textured sheet becomes patchy because degraded rubber domains produce local viscosity fluctuations in the die lip region. Additional evidence includes an increase in yellowness index of more than 2.0 units per ASTM E313-20 and a reduction in notched Izod impact strength of more than 10% relative to material processed at 235°C, measured per ISO 180/A. Published data for this specific degradation threshold is limited, but production records on 75 mm extruders indicate that melt temperature excursions above 255°C for more than 5 min correspond to surface splay, gel formation on breaker-plate screen packs, and increased melt-pressure oscillation. The pressure instability is typically observed as a shift from ±0.5 MPa to more than ±1.5 MPa at the breaker plate. To preserve gloss uniformity, the barrel zone set points, screw speed, and melt-pump suction pressure are trimmed so that residence time above 250°C remains below 4 min. When low-temperature impact retention is critical, the melt temperature should be held at 235°C to 245°C, and the die gap should be adjusted to maintain a sheet thickness tolerance of ±5% across the web. Melt rheology measurements under ISO 11443 at 220°C and shear rates from 10 s⁻¹ to 1000 s⁻¹ provide a better indication of die-lip behavior than single-point melt-flow data. The material is shear-thinning, and the apparent viscosity decreases with increasing shear rate. In deep thermoforming, high shear history in the die can reduce melt strength and increase sag. For this reason, the extruder is commonly operated with a melt pump after the screw and a screen pack of 50/100/50 mesh, which stabilizes die throughput and limits short-duration pressure spikes. Where XR-407E diverges from general-purpose injection-molding ABS such as LG Chem HI-121H is in the balance between heat deflection and melt flow. General-purpose ABS grades typically operate in the 85°C to 92°C HDT range at 1.82 MPa and exhibit melt-flow rates above 5.0 g/10 min at 220°C and 10.0 kg. XR-407E typically maintains a lower melt mass-flow rate near 4.0 g/10 min, which supports higher melt strength during vertical sheet draw but requires greater extruder drive load. The grade also differs from XR-409H, another heat-resistant ABS in the series, in that XR-409H literature reports a higher heat deflection range near 108°C to 112°C with a correspondingly lower flow range near 3.0 g/10 min. XR-407E is therefore selected when the thermoforming tool requires elevated sheet temperature but the extrusion line cannot tolerate the higher screw torque and die pressure of a lower-flow heat-resistant grade. The table below summarizes the differentiation in ranges typically referenced for preliminary material selection. The values are not lot-specific and should be confirmed from the manufacturer’s technical datasheet or certificate of analysis.

Property	Test method	XR-407E typical range	General-purpose ABS reference
Melt mass-flow rate at 220°C, 10 kg	ISO 1133-1	3.5–4.5 g/10 min	5.0–8.0 g/10 min
Deflection temperature under load, 1.82 MPa	ISO 75-2/A	100–106°C	85–92°C
Notched Izod impact, 23°C	ISO 180/A	25–35 kJ/m²	20–28 kJ/m²
Tensile yield stress	ISO 527-2/1A/50	45–50 MPa	43–48 MPa
Vicat softening temperature, B/50	ISO 306/B50	105–112°C	95–100°C

Injection-molding applications require a different set of clamp-force and gate considerations. General-purpose ABS flows more readily into thin-wall sections but exhibits lower hot-part stiffness after ejection. XR-407E is not optimized for high-speed injection molding because its lower melt-flow characteristic increases fill pressure in multi-cavity tools. When molded, the resin may require a melt temperature at the upper end of 240°C to 255°C and a mold temperature of 50°C to 70°C to reproduce textured surfaces. Published data for this specific configuration is limited because the grade is primarily an extrusion product.

Chemical Resistance Boundaries Under Constant Tensile Load

ABS XR-407E is not recommended for continuous contact with ketones, esters, chlorinated hydrocarbons, or aromatic hydrocarbon solvents under stress. Environmental stress cracking can occur when a formed part retains a tensile strain above 0.5% and is exposed to plasticizing contaminants such as methyl ethyl ketone, ethyl acetate, or dioctyl phthalate. The failure mode is not simple dissolution but localized crazing at surface defects, followed by crack propagation. The performance boundary can be evaluated using constant-strain environmental stress-cracking methods described in ISO 22088-3, with flexural strain strips exposed for 24 h at 0.5% and 1.0% strain. A loss of notched Izod impact of more than 20% after exposure is a practical rejection criterion. The grade resists dilute aqueous acids, alkalis, aliphatic hydrocarbons, and many vegetable-oil-based contact fluids. In refrigerator-liner applications, formed XR-407E sheet exhibits acceptable resistance to milk, vegetable oils, and mild household cleaners at ambient temperature, but the specific cleaning-agent concentration and service temperature must be validated. Contact with ketone-based adhesives or paint-stripping solvents should be avoided. If a secondary operation such as hot-plate welding or ultrasonic welding is planned, the surface must be free of mold release, oil, and plasticizing contaminants because these agents alter fusion quality and reduce weld strength. For food-contact applications, manufacturers and converters should request the specific European Union compliance declaration under EU Regulation 10/2011 and applicable national migration limits. Under FDA 21 CFR, ABS copolymers intended for food-contact use must comply with the applicable sections for acrylonitrile copolymers; the specific grade formulation, color concentrate, and regrind source must be addressed because compliance is recipe-dependent. Under UL 94 test protocols, ABS grades are commonly rated HB in sections above 1.5 mm, but the exact thickness-dependent rating for XR-407E must be confirmed from the supplier’s yellow card. The manufacturer typically certifies conformance to Directive 2011/65/EU on the restriction of hazardous substances and Regulation (EC) No 1907/2006 under REACH for the supplied compound lot.

When Co-extruded PMMA Cap Layers Are Used Over XR-407E

When co-extruded PMMA cap layers are applied to increase surface hardness, the interfacial viscosity ratio between XR-407E and the acrylic cap must be controlled below approximately 3:1 at the die lip. PMMA typically has a melt viscosity higher than ABS under the same shear rate, so the cap layer is usually fed through a separate extruder with a melt temperature of 240°C to 260°C. Interfacial delamination under vacuum forming is observed when the cap layer thickness falls below 30 µm or when the XR-407E core sheet temperature drops below 160°C at the forming station. In production, this configuration is used for high-gloss black refrigerator door panels where the acrylic cap provides chemical resistance and surface hardness while the ABS core provides impact strength and sag resistance. Rheological data from capillary tests per ISO 11443 at 220°C and 100 s⁻¹ should be obtained for each lot because moisture contamination in the acrylic layer and ABS core above 0.05% by weight produces micro-voids at the interface. The co-extrusion feedblock and die design must maintain layer encapsulation so that the PMMA cap does not migrate to the trim edges. If edge trim is reground into the XR-407E core at concentrations exceeding 5%, the acrylic contamination produces surface haze and local viscosity inhomogeneity. Published data for this specific regrind configuration is limited, but production experience indicates that a separate regrind stream is required when tight gloss specifications are in effect. Maintaining a melt pump downstream of the co-extrusion feedblock reduces pressure pulsations and prevents cap-layer thickness variation above ±10%. Predrying is required before extrusion. ABS XR-407E absorbs atmospheric moisture; wet material above 0.05% moisture by weight produces surface splay, internal bubbles, and melt viscosity instability at the die. Desiccant dryers with a dew point of −30°C to −40°C and a set point of 80°C for 2 h to 4 h are standard. Hopper residence time should not exceed 6 h. Regrind rates are generally limited to 20% to 30% by weight for sheet goods where surface gloss or low-temperature impact is a specification variable. On a 65 mm single-screw extruder with 30:1 L/D, regrind above 30% increases melt-pressure variability from a typical ±0.5 MPa to more than ±1.5 MPa at the breaker plate, which corresponds to visible transverse thickness variation. The material is not compatible with polyoxymethylene or PVC melt streams; separate purging with a high-viscosity acrylic or commercial ABS purging compound is required before shutdown. If the material is to be used in food-contact or potable-water components, the specific grade formulation, color concentrate, and regrind source must be cleared under the end-use regulatory standard such as EU Regulation 10/2011 or FDA 21 CFR 181.32 for ABS copolymers. The processing table below consolidates the recommended operating bands for dryers, extrusion zones, and melt-quality checks.

Process variable	Operating range	Measurement or equipment basis
Moisture content after drying	< 0.05% by weight	Karl Fischer or thermogravimetric moisture balance
Desiccant dryer set point	80°C	Hopper dryer with −30°C dew point
Barrel temperature profile	180°C to 230°C	30:1–36:1 L/D single-screw extruder
Melt temperature	230°C to 250°C	Melt probe at screw tip or melt-pump inlet
Die temperature	230°C to 240°C	Flat sheet die with adjustable lip gap
Thermoforming sheet surface temperature	160°C to 180°C	Infrared pyrometer or thermocouple contact probe

In thermoforming, the sheet must be heated uniformly to the processing range without allowing surface degradation. Uneven sheet temperature produces wall-thickness variation in deep-draw parts and can alter local gloss. Tooling with plug assist should use a plug temperature below the ABS melting range to prevent sticking. The formed part should be cooled below 80°C before trimming to avoid edge deformation. Dimensional stability after forming is influenced by the high heat deflection of XR-407E, but retained forming stress can still produce shrinkage if the part is exposed to temperatures above the annealing threshold. If close-tolerance trimming is required, a post-forming annealing step at 70°C to 85°C for 30 min may be used to reduce residual forming stress, provided the specification allows cycle-time extension.