INEOS Styrolution Luran SAN VLN is an amorphous styrene-acrylonitrile copolymer supplied for high-speed injection moulding of transparent, thin-wall components. The designation VLN identifies a low-viscosity, high-flow variant within the Luran SAN family. Representative data from the current manufacturer’s technical datasheet include a melt volume-flow rate of 55 cm³/10 min under ISO 1133-1 at 220 °C with 10 kg load, a density of 1.08 g/cm³ under ISO 1183-1, a Vicat softening temperature VST/B/50 of 96 °C under ISO 306, and a tensile modulus of 3600 MPa under ISO 527-2. The natural grade exhibits a light transmittance of 90 % at 3 mm plaque thickness under ISO 13468-2 and haze below 1.0 % under ISO 14782. Because property values are representative and can shift with colourant loading, regrind content, and production lot, the current revision of the supplier datasheet and the certificate of analysis remain the controlling specification documents.

The notched impact strength of 2.0 kJ/m² under ISO 179/1eA places the grade below many medium-impact ABS products. Component designs that include snap-fits, clips, or thin cantilever features should use generous radii and avoid sharp transitions because the material exhibits limited ductile energy absorption at high strain rates. Typical application contexts include thin-wall cosmetic packaging, transparent appliance lenses, office-equipment covers, and household goods where the nominal wall is below 2.0 mm. The grade is not intended for exterior glazing or load-bearing components exposed to continuous stress above 85 °C without a validated heat-resistance review.

Comparative Melt-Viscosity and Heat-Resistance Data for SAN Grade Selection

Within the INEOS Styrolution Luran SAN family, the VLN grade occupies the high-flow end. Lower-flow grades such as Luran SAN 368R, 378P, and 388S retain higher Vicat temperatures but impose higher injection-pressure requirements in identical cavities. Table 2 lists nominal melt volume-flow rates and Vicat softening temperatures reported under ISO 1133-1 and ISO 306.

For a wall thickness of 1.2 mm, replacing Luran SAN 368R with VLN in mould-filling simulation generally reduces required injection pressure by 15–25 %, although the exact reduction depends on gate diameter, runner layout, and hot-runner pressure drop. The trade-off is a Vicat reduction of approximately 5 °C versus 368R. Components requiring continuous load-bearing service above 85 °C should therefore select a lower-flow SAN grade or an alternative amorphous polymer with higher heat resistance.

Compared with PMMA, Luran SAN VLN provides lower density—1.08 g/cm³ versus 1.19 g/cm³ under ISO 1183-1—and a higher melt volume-flow rate, which benefits thin-wall filling. However, PMMA supplies higher surface hardness and superior outdoor weathering retention under ISO 4892-2 exposure. Luran SAN VLN is therefore not recommended for exterior lenses requiring prolonged UV exposure unless a protective coating or capstock is used. Compared with transparent ABS, this SAN grade offers measurable transmission and low haze, but the notched impact strength of 2.0 kJ/m² is roughly an order of magnitude below many transparent ABS grades. Designs undergoing high-rate impact should not depend on ductile energy absorption in unsupported thin sections.

What Limits Flow-Length-to-Wall-Thickness Ratio in Thin-Wall Moulding?

The low melt viscosity of VLN permits filling of flow lengths that general-purpose SAN cannot achieve without gas traps or overpacking. In practice, the limiting parameter is the flow-length-to-wall-thickness ratio, which is runner and gate dependent. For wall thicknesses between 0.8 mm and 1.5 mm, flow-length ratios up to 150:1 are commonly evaluated in mould-filling simulation. For wall thickness below 0.6 mm and flow lengths above 120 mm, published injection-pressure data for this specific configuration is limited; cavity filling should be verified with short-shot studies on the production tool.

High-flow SAN grades require balanced hot-runner manifolds and adequate gate diameters. Pinpoint gates below 0.8 mm in diameter can raise shear rates above 100 000 1/s, increasing local melt temperature and producing gate blush or yellowing. On single-stage reciprocating-screw machines with three-zone screws of 20:1–25:1 L/D, injection speed should be set in the range 100–250 mm/s depending on part volume; screw-back pressure between 1–3 MPa is typically sufficient for natural-grade homogenisation. Cavity-pressure sensors with holding-pressure transfer based on cavity pressure rather than screw position reduce short-shot variation in multi-cavity tools.

Mould-filling simulation for the high melt volume-flow rate of 55 cm³/10 min should use Cross-WLF viscosity coefficients fitted to capillary rheometry data, not generic SAN parameters. The shear-thinning slope becomes significant at shear rates above 10 000 1/s; incorrect viscosity coefficients under-predict pressure drop in thin-wall cavities. A capillary rheometer with a 1 mm die and temperature range of 220–260 °C provides the required viscosity data. If public simulation libraries do not contain grade-specific coefficients, custom characterisation is required before production tooling is cut.

When Regrind Incorporation and Colour Masterbatch Are Specified

Regrind from sprues and runners can be reincorporated at levels up to 20 % without documented loss of tensile strength, provided the regrind is dried identically and does not contain degraded material from hot-runner hold-up. Higher regrind levels are possible but should be qualified by tensile testing per ISO 527-2 and Charpy impact testing per ISO 179/1eA on production-representative plaques or specimens. Dust and fines from granulation must be limited because fine-particle oxidation can produce visible black specks at melt temperatures above 240 °C.

For critical optical parts, precoloured compound is preferred over dry colour masterbatch because local refractive-index discontinuities can increase haze. If masterbatch is used, the carrier should be SAN-compatible and melt-mixed with a mixing screw or static mixer in the machine nozzle. Masterbatch let-down ratios above 5 % should be verified for haze, transmission, and mechanical property retention because high carrier levels can dilute the base molecular weight and reduce tensile modulus.

Pre-drying is required when hopper moisture or ambient humidity exceeds 60 % RH; undried material causes silver streaks and splay at melt temperatures above 240 °C. A desiccant dryer with an inlet air dew point of -30 °C or lower and a resin temperature of 80 °C for 2–4 h reduces residual moisture below 0.05 %. Moisture analysis by Karl Fischer titration or a moisture balance with 0.01 % resolution supports incoming resin control. Hopper dryers without desiccant beds are not adequate at ambient relative humidity above 60 %.

Melt temperature should be maintained between 220 °C and 260 °C; mould temperature between 40 °C and 80 °C controls surface gloss and post-mould shrinkage. In hot-runner systems, manifold temperature is preferably held near 240 °C. Hold-up time at 260 °C should be limited to 10 min to avoid visible yellowing; temporary line stops require barrel retraction and hot-runner temperature reduction.

Because the grade is amorphous, mould shrinkage is relatively isotropic. Post-mould shrinkage can continue for up to 24 h at 23 °C, with typical linear mould shrinkage in the range 0.3–0.7 % depending on wall thickness, gate location, and holding pressure. Dimensional checks should be performed after conditioning at 23 °C and 50 % RH for at least 24 h per ISO 291, with shrinkage measured in accordance with ISO 294-4. Haze and transmission are also influenced by mould polish, melt homogeneity, and contamination. Textured surfaces and hot-runner hot spots can increase haze above 2 %; regrind levels above 20 % can reduce transmittance and shift the colour coordinate.

Chemical resistance follows the SAN polymer class. Continuous contact with ketones, esters, chlorinated solvents, and aromatic hydrocarbons is not recommended because these media cause environmental stress cracking or surface attack. Resistance to aliphatic hydrocarbons, paraffinic oils, dilute acids, and dilute alkalis is generally acceptable at 23 °C; however, moulded-in stress magnifies stress-cracking susceptibility. Parts intended for cosmetic emulsions, alcohol-based hand sanitisers, or household cleaning agents should be tested under service conditions per ISO 175 or the manufacturer’s stress-cracking protocol. For continuous contact with ethanol or isopropanol above 60 °C, published data for this specific configuration is limited; use of lower-flow grades or stress-relief annealing may be required.

Regulatory suitability must be confirmed for the specific grade, colour, and region. Luran SAN VLN is supplied with a safety data sheet and supplier product regulatory information. For food-contact, medical, or toy applications, the candidate colour and regrind content must be evaluated against the applicable regional instrument—EU 10/2011, FDA 21 CFR, or EN 71-3—using the supplier’s confirmation letter, not generic polymer-class statements. Electrical and electronic housing compliance with RoHS Directive 2011/65/EU and registration status under REACH should be verified in the current supplier declaration for the specific product code.