Luran SAN 348Q Crystal Clear 77850 is an unfilled amorphous styrene-acrylonitrile copolymer supplied by INEOS Styrolution as cylindrical pellets for injection moulding. The designation 348Q identifies a high-flow grade within the Luran SAN series, while 77850 identifies a crystal-clear colour formulation intended for transparent parts. The polymer is classified under ISO 11469 as SAN, and its published density is 1080 kg/m³ when measured under ISO 1183-1. The melt volume-flow rate is 25 cm³/10 min at 220 °C with a 10 kg load under ISO 1133-1.

Because the copolymer is amorphous, shrinkage is lower and more uniform than that of semi-crystalline polyolefins. However, the published tensile elongation at break of 3.0% under ISO 527-2 indicates limited ductility. Load-bearing snap-fits and hinged closures therefore require generous radii, low moulded-in stress, and case-specific mechanical testing. The grade is supplied without impact modification.

Before melt processing, the pellets require drying in a dehumidified hopper dryer at 80 °C for 4 h. A drying-air dew point of -40 °C or lower is used to bring residual moisture below 0.02%. The moisture limit is a processing boundary rather than a nominal recommendation; exceeding it produces splay, silver streaks, and optical haze because entrained water vapour expands at the flow front and can contribute to surface defects in transparent parts.

Moisture-related defects are amplified in hot-runner systems with long melt-residence zones. In such configurations, water in the melt promotes yellowness and hydrolysis-related molecular weight loss at elevated temperature. Closed-loop drying with dew-point control is preferred for uninterrupted runs exceeding 24 h. The dried pellets should be conveyed with dry air and should not be exposed to ambient plant humidity for more than 30 min before entering the feed throat.

The melt temperature is normally controlled between 230 °C and 260 °C, and the mould temperature between 60 °C and 80 °C. Operation above 270 °C for more than 10 min barrel residence time can produce yellowing, black specks, and a measurable drop in molecular weight. General-purpose three-zone injection screws with an L/D ratio of 20:1 and a compression ratio of 2.5:1 are adequate when screw peripheral speed is kept from 0.1 m/s to 0.3 m/s. Hydraulic back pressure is maintained between 5 bar and 10 bar to homogenise the melt without excessive shear heating.

What Limits the Melt-Temperature Window in Transparent Part Production?

For clear parts, the lower melt-temperature boundary is determined by filling behaviour rather than by melting point. At 230 °C, the melt exhibits higher viscosity than at 250 °C; in wall sections below 1.2 mm, injection velocity must be increased to avoid premature freeze-off. Elevated injection velocity raises shear heating and can produce gate blush at small pin-point or tunnel gates. The upper boundary is governed by thermal degradation and chromophore formation in the acrylonitrile-containing copolymer. Melt temperatures above 260 °C should be limited to short residence times and should be confirmed by colour measurements on transparent plaques.

When moulding transparent household articles, the nozzle is normally set 5–10 K below the highest barrel zone to reduce drool and thermal shock. Hot-runner manifold zones are controlled within ±5 °C of the nozzle set-point. Larger deviations create colour streaks because partially degraded melt from the manifold can enter the cavity at a different temperature. In production-scale mould trials, manifold zones are adjusted using air shots and pressure-drop measurements because thermocouple readings alone do not capture shear heating in the drops.

Thermal and Optical Benchmarks for Part Design

The values in Table 1 are consolidated from published technical data for dry-as-moulded specimens at 23 °C unless otherwise noted. They are used for preliminary part design and mould-flow simulation.

The 101 °C VST/B/50 value is a single-point softening measurement under a 50 N load and 50 K/h heating rate. It is not a continuous-service temperature. The HDT/A of 98 °C under 1.8 MPa flexural stress provides a comparative design value but does not account for chemical exposure, creep, or long-term thermal ageing. Optical values measured on 2 mm plaques do not automatically transfer to parts with weld lines, hot-runner valve marks, or thickness gradients.

Shrinkage parallel to flow is typically 0.3–0.5% for a 2 mm wall, while transverse shrinkage is 0.4–0.6%. These ranges depend on gate geometry, packing pressure, and cavity temperature. Shrinkage anisotropy can cause warpage in flat transparent lids if the flow front is not balanced. For transparent circular parts, a centrally located diaphragm gate or a hot-runner valve gate reduces ovality, while edge gating tends to increase differential orientation and residual stress near the weld line.

The High-Flow Grade Shifts the Balance Away From Heat Resistance in the Luran SAN Portfolio

Luran SAN 348Q is differentiated from lower-flow grades such as Luran SAN 368R by its melt volume-flow rate. The MVR of 25 cm³/10 min permits filling of long flow paths at lower injection pressure and reduces cycle time in multi-cavity thin-wall moulds. The trade-off appears in thermal resistance. The published VST/B/50 of 101 °C is lower than that of high-viscosity SAN grades specified for applications involving sustained hot-water contact near 85–90 °C. In such cases, a lower-flow SAN grade with a higher Vicat softening point is usually selected after application-specific testing.

Compared with general-purpose polystyrene, the 348Q grade provides approximately 10–15 K higher VST/B/50 and improved resistance to oils and aliphatic hydrocarbons. General-purpose polystyrene stress-cracks in contact with many fats and petroleum-based hydrocarbons; SAN reduces this failure mode but does not eliminate it. Compared with polymethyl methacrylate, the SAN grade has lower surface hardness and lower long-term outdoor UV resistance, but it offers better flow for thin-wall injection and lower equilibrium water absorption than many PMMA formulations. The lower water absorption reduces pre-drying time relative to some acrylic moulding compounds and improves dimensional stability in humid service environments.

Compared with opaque acrylonitrile-butadiene-styrene grades, 348Q offers transparency and higher stiffness but substantially lower impact strength. ABS notched impact values in household appliance parts often exceed 15 kJ/m² under ISO 179-1/1eA, whereas 348Q publishes 2.0 kJ/m². The two materials are therefore not interchangeable when impact failure is a risk. The SAN grade is chosen when clarity, chemical resistance, and predictable shrinkage are controlling; ABS is selected when ductility and toughness dominate.

When Contact With Oily Formulations Demands Stress-Crack Screening

The grade resists dilute acids, alkalis, aliphatic hydrocarbons, and many household detergents at room temperature. Environmental stress cracking can occur under tensile stress in contact with polar solvents such as ketones, esters, and aromatic hydrocarbons. Pre-production screening is required for cosmetic emollients, sunscreen esters, and concentrated fruit oils because these fluids can plasticise the amorphous matrix and reduce tensile strength under moulded-in stress. A screening protocol based on ISO 22088-2 places injection-moulded bars at 0.5% outer fibre strain in the candidate fluid at 60 °C for 72 h. Retained tensile stress at break below 70% of the untreated reference is interpreted as a high stress-cracking risk for the application.

Ethanol and high-proof alcohol are aggressive toward SAN. Clear containers or closures for alcoholic formulations above 40% ethanol are generally outside the recommended use envelope unless moulded-in stress is very low and service testing demonstrates compatibility. The material is also not recommended for outdoor unpainted applications unless UV-stabilised because long-term UV exposure produces yellowing, surface microcracking, and gloss loss. These limitations must be evaluated against the actual formulation and exposure conditions rather than inferred from initial optical clarity of the moulded part.

Published data for this specific configuration is limited for high-concentration synthetic ester emollients and for hot-fill products above 80 °C. In such cases, aged-part testing under simulated distribution conditions is required before converting from glass or acrylic. The test should include the effect of moulded-in stress, closure torque, and hot-fill headspace vapour, because vapour-phase contact can be more aggressive than liquid immersion.

The table below summarises the regulatory declarations commonly associated with the base resin. Application-specific confirmation is required because final part compliance depends on pigments, mould release, processing aids, and subsequent assembly steps.

In cosmetic packaging, 348Q is applied to transparent caps, jars, and overcaps with wall sections between 1.0 mm and 2.5 mm. The melt-flow rate allows six- to eight-cavity cold-runner or hot-runner moulds to fill without excessive clamp force. For a 1.5 mm nominal wall, melt temperature of 250 °C and injection velocity of 100–150 mm/s are used to advance the flow front through polished cavity surfaces without jetting. The low moisture absorption and predictable shrinkage allow cylindrical closures to maintain ovality within 0.1 mm when venting is sufficient and the gate is centrally located.

In household appliance lenses and display windows, the grade is used where transparency and chemical resistance to cleaning agents are required but impact resistance is secondary. The 2.0 kJ/m² Charpy notched impact strength requires careful handling of drop heights and avoidance of sharp corners. For a 2 mm flat lens, the gate should be positioned at the edge or in a fan configuration to reduce weld-line haze. Mould temperature uniformity is more important than the absolute setting; a variation of ±10 °C across the cavity surface can create differential gloss and internal stress that later becomes visible when the part is exposed to detergent vapour.

In transparent laboratory housings and point-of-sale display fixtures, the grade replaces acrylic where chemical exposure and part cost favour SAN. However, the low mar resistance of SAN means that dry wiping with cloth or paper can produce micro-scratches. High-touch transparent surfaces may require a protective coating or antistatic treatment; antistatic additions are separate products and can reduce transparency. The unfilled 348Q grade is neither antistatic nor flame-retardant, and its electrical surface resistivity remains in the insulating range typical of styrenics. Ultrasonic welding is feasible with shear joints at 20 kHz and amplitude of 20–30 µm, but bond strength decreases if the parts are moulded with high residual stress near the joint.