The amorphous styrene-acrylonitrile copolymer INEOS Styrolution Luran SAN 358N is positioned at the high-flow end of the Luran SAN injection-moulding portfolio. Under ISO 1133-1:2022 the melt volume-flow rate is 22 cm³/10 min at 220 °C under 10 kg load; density determined to ISO 1183-1:2019 is 1080 kg/m³; tensile modulus in accordance with ISO 527-2:2012 is 3600 MPa; tensile stress at yield is 72 MPa; flexural modulus to ISO 178:2019 is 3600 MPa; Vicat softening temperature VST/B/50 by ISO 306:2013 is 106 °C; Charpy notched impact strength by ISO 179-1:2010 is 2.0 kJ/m² at 23 °C; and light transmittance by ISO 13468-2:2021 is approximately 90% at 2 mm wall thickness. The grade is used for transparent, stiff mouldings with complex geometry, multi-cavity tooling, and wall thickness below 2 mm, including cosmetic packaging, household appliance reservoirs, measuring cups, and diagnostic or medical housings when end-use compatibility is validated. The material differs from lower-flow styrene-acrylonitrile grades such as Luran SAN 368R and Luran SAN 378P in that its higher melt volume-flow rate shortens fill time and reduces residual gate pressure; this benefit carries a lower heat-resistance ceiling and lower melt strength for extrusion or blow moulding. Compared with transparent ABS and Luran S ASA, the absence of a butadiene-based rubber phase raises hardness and light transmittance but lowers notched impact and ductility.

The amorphous nature of the polymer means processing is governed by glass transition and viscous flow rather than a crystalline melting point. Mould shrinkage values for general-purpose SAN typically fall between 0.4% and 0.7% according to ISO 294-4:2018; for Luran SAN 358N, published datasheet values may vary with gate type, wall thickness, and hold pressure. The refractive index for styrene-acrylonitrile copolymer is typically 1.57. In applications where total light transmittance above 92% is required, PMMA or optical polycarbonate is normally substituted; in applications where high flow and moderate heat resistance are required, Luran SAN 358N is selected over PMMA because of the lower melt viscosity and over polycarbonate because of the lower melt temperature and lower density of 1080 kg/m³.

Regulatory status and the applicable test designations

Material qualification for Luran SAN 358N is normally conducted against the current product datasheet and the regulatory letter for the supplied lot. Because food-contact and medical status are application-specific, components should be qualified by the converter under the relevant national or regional instrument. The references listed in the compliance matrix are the usual starting points for verifying the grade.

The property values shown are typical values from published commercial data, not minimum specification limits. Lot-specific certificates of analysis should be used for release of critical dimensions or compliance limits.

Processing of Luran SAN 358N begins with moisture control. The pellets are hygroscopic enough to require desiccant drying to 0.05 wt% residual moisture, typically at 80 °C for 2–4 h with a desiccant-bed dryer dew point of −30 °C or lower. On an 80 t hydraulic injection-moulding machine with a 3-zone general-purpose screw of L/D 20:1 and compression ratio 2.4:1, barrel settings are commonly programmed from 210 °C at the feed throat to 245 °C at the nozzle. Mould temperature is maintained between 40 °C and 60 °C; lower mould temperatures preserve cycle time but reduce surface gloss and increase moulded-in stress. For thin-wall sections under 1.2 mm, linear injection speeds of 80–120 mm/s are used to prevent premature gate freeze-off, while screw rotation is held at 80–120 rpm and back pressure at 5–8 bar hydraulic to limit shear heating. Residence time is kept below 5 min; melt temperatures above 250 °C or hot spots in the compression zone produce yellowing, silver streaks, and a measurable drop in notched Charpy impact. Regrind of this transparent grade is usually restricted to 20 wt% for critical optical parts because each heat history raises haze and lowers light transmittance. Incoming lot-to-lot MVR variation is normally controlled within ±10%; when a lot arrives at the high MVR limit, the same tool may require 1–2 mm more cushion or 0.2–0.5% lower part weight to hold dimensional limits.

Shear-rate and temperature interactions create the practical processing window. Published capillary rheometry data for high-flow styrene-acrylonitrile grades indicate pseudoplastic behaviour with apparent viscosity at 230 °C falling by approximately one order of magnitude between 100 s⁻¹ and 10,000 s⁻¹; grade-specific curves for Luran SAN 358N should be obtained from the supplier for use in injection-moulding simulation. Below 200 °C, viscosity increases steeply, so thin-wall fills below 1.0 mm become susceptible to short shot. Above 250 °C, the practical limit is no longer viscosity but degradation; this conflict defines the narrow thermal operating range. When melt temperature is held at 230 °C and mould temperature at 50 °C, capillary-rheometer and simulation data can be correlated with actual short-shot studies to determine the minimum injection pressure for a given gate and runner geometry.

Surface replication on Luran SAN 358N is constrained by the same viscosity and mould-temperature interplay. For high-gloss optical surfaces, tool polish of SPI/SPE A-1 or A-2 and mould temperature of at least 50 °C are required; lower mould temperatures quench the melt before full replication of micro-texturing occurs. Textured surfaces for consumer housings should specify draft angles above 1.5° per side at depths of 25–35 µm because SAN is harder and less elastic than ABS; demoulding from deep textures can generate stress whitening or micro-cracks. A production-scale method for eliminating gate blush is to reduce injection velocity through the gate to 20–40 mm/s for the first 0.2–0.5 s and then increase to the required filling velocity; this velocity profile requires controlled acceleration segments on the injection unit and is not available on all hydraulic machines.

How does Luran SAN 358N compare with Luran SAN 368R, Luran SAN 378P, transparent ABS, and PMMA?

Within the same product family, grade selection is governed by melt-volume-flow rate, heat deflection under load, and ductility. Luran SAN 358N is the high-flow general-purpose injection-moulding grade; the 22 cm³/10 min MVR at 220 °C/10 kg permits lower cavity pressures than those required by lower-flow styrene-acrylonitrile grades when filling identical tools. The trade-off is that the Vicat VST/B/50 of 106 °C places Luran SAN 358N below high-heat SAN types in continuous temperature capability. Luran SAN 368R is specified where a higher heat-resistance margin is required at the expense of longer fill time; Luran SAN 378P is selected when higher melt strength is needed for sheet, profile, or thick-wall mouldings. Direct substitution of Luran SAN 358N for these grades without revalidation is not recommended because shrinkage, gate sealing time, and moulded-in stress differ with molecular weight distribution. Compared with ABS, Luran SAN 358N has no butadiene rubber phase; therefore its notched Charpy impact of 2.0 kJ/m² is significantly below that of medium-impact ABS but its ~90% light transmittance and hardness are higher. Compared with PMMA, Luran SAN 358N has lower melt viscosity for thin-wall filling and lower density of 1080 kg/m³, but PMMA offers higher surface hardness, higher total light transmittance above 92%, and better resistance to outdoor UV exposure. For products where contact with ethanol, cleaning agents, or cosmetics formulations is expected, SAN stress-cracking resistance is lower than that of polyolefins and may be lower than that of specific PMMA grades; the selection should be tested under the actual load condition rather than from generic tables alone.

Chemical compatibility data for Luran SAN 358N is dependent on the applied stress, reagent concentration, temperature, and contact time. The resin is generally resistant to water, dilute aqueous acids, alkaline solutions, alcohols, and aliphatic hydrocarbons at ambient temperature; it is not recommended for continuous contact with ketones, esters, aromatic hydrocarbons, chlorinated hydrocarbons, or concentrated oxidizing acids. In closure and packaging applications, environmental stress cracking must be evaluated under the final formulation. Static immersion per ISO 175:2010 or ASTM D543-21 at 23 °C and 40 °C for 7 days is a common screening method; for aqueous ethanol, cracking can occur above 20 vol% ethanol depending on orientation and hoop stress. Moulded parts with high orientation near gates and weld lines are more susceptible to stress cracking. When the chemical compatibility of this specific grade in a particular solvent is not available, qualification should use the actual production part under torque, load, or assembly stress rather than unstrained immersion.

Closure torque retention is a common failure mode in cosmetic packaging. Parts moulded from Luran SAN 358N with high gate stress or inadequate hold pressure can lose torque after contact with ethanol-based formulations within 24–72 h at 40 °C. A validation protocol should therefore combine moulding trials at two melt temperatures, 225 °C and 245 °C, and two hold pressures to create different stress levels, followed by contact testing under ISO 175:2010 with the filled product. If cracking is observed, options include reducing gate size to minimize packing pressure near the gate, raising mould temperature to relax molecular orientation, or switching to a toughened or higher-molecular-weight SAN grade.

When melt temperatures exceed 250 °C, residence time and hot-runner design govern colour shift

Hot-runner processing of Luran SAN 358N is possible only when the system is maintained inside the grade's thermal window. Manifold and nozzle setpoints above 245 °C may reduce viscosity enough to improve fill, but the same setpoints accelerate chain scission and oxidation at the hot-runner wall. On an 8-cavity hot-runner tool with externally heated manifolds, melt residence time below 3–5 min at 230–245 °C typically produces no visible yellowing, whereas operation at 260 °C even for 5 min can increase yellowness index by more than 2 units under ASTM E313-20. The critical control variables are shear heating in restricted nozzles, dead spots in manifold corners, and recirculation zones associated with improper valve-gate settings. Purging from polycarbonate or polyamide to Luran SAN 358N requires a dedicated styrenic purging compound and a temperature reduction step; direct contact between residual polyamide and styrene-acrylonitrile at high temperature can generate black specks and deposits. If hot-runner setpoints cannot be reduced below 250 °C because of a shared system with polycarbonate, Luran SAN 358N is not the appropriate grade; a higher-heat styrene-acrylonitrile or another amorphous resin with a broader thermal window should be evaluated.

Application design with Luran SAN 358N favours wall stocks between 0.8 mm and 2.5 mm. Transparent appliance reservoirs, blender jars, measuring cups, and cosmetic closures are representative industrial uses. In dishwasher-exposed parts, the material's heat distortion temperature under 1.8 MPa should be checked against the continuous wash temperature; published data for this specific grade under hot-water mechanical load is limited, so creep testing per ISO 899-2 is required before use above 80 °C under load. For diagnostic or medical housing applications, sterilisation compatibility must be established by the manufacturer; gamma or e-beam radiation doses above 25 kGy can alter colour and impact, while ethylene oxide exposure requires residue validation. The absence of a butadiene phase means the material does not show the impact strength of ABS; designs with snap arms, living hinges, or high assembly strain should be rethought for SAN's lower ductility. With adequate drying, thermal control, and chemical compatibility testing, Luran SAN 358N provides consistent mould filling and surface replication for transparent, stiff parts.