INEOS Styrolution Luran SAN HD 20 is a styrene-acrylonitrile copolymer supplied as cylindrical pellets for injection moulding of transparent, dimensionally stable technical components. The grade is positioned within the Luran SAN range around a nominal melt volume-flow rate of 20 cm³/10 min when measured in accordance with ISO 1133-1 at 220 °C under a 10 kg piston load. That flow level corresponds to a low-to-medium-viscosity SAN that can fill thin-wall sections while retaining rigidity and surface hardness. The polymer comprises styrene and acrylonitrile comonomer units; the acrylonitrile fraction raises heat resistance, tensile strength, and environmental stress cracking resistance relative to general-purpose polystyrene, but the exact comonomer ratio is not disclosed in standard product literature. Density is typically 1.08 g/cm³ (ISO 1183-1), water absorption after 24 h is approximately 0.2 % (ISO 62), and the material is naturally transparent with light transmission near 90 % through a 3 mm plaque (ASTM D1003). The designation HD 20 does not denote high density; density is governed by the acrylonitrile content and remains essentially constant across unfilled SAN grades.

The material is commonly used where transparent parts require a balance of heat resistance, surface hardness, and resistance to oils, detergents, and cosmetic vehicles. Typical end uses include transparent caps, jars, air-flow meters, washing-machine control panels, vacuum-cleaner windows, kitchen appliance housings, and stationery components. In these applications, the grade is selected primarily when general-purpose polystyrene lacks adequate chemical or thermal performance, but full impact-modified ABS is not required.

What Limits the Processing Window for Luran SAN HD 20 in Thin-Wall Injection Moulding?

On production-scale injection moulding machines with clamp forces from 500 kN to 2,500 kN, the practical melt-temperature window is 230–260 °C. Lower temperatures increase melt pressure and create flow lines and high residual orientation; higher temperatures above 260 °C accelerate thermal decomposition of the acrylonitrile phase, visible as a shift in yellowness index b* and surface splay. The material should be dried to residual moisture below 0.05 % using a desiccant dryer at 80 °C for 4 h when storage humidity has exceeded 60 % RH. A dryer dew point of −30 °C to −40 °C is recommended. Drying temperatures above 85 °C should be avoided because pellet agglomeration can occur.

In a single-screw reciprocating injection unit with a three-zone screw of L/D 20–25 and compression ratio 2.0–2.5, back pressure of 5–10 bar and screw speed of 80–150 rpm provide adequate homogenization without excessive shear heating. The material is not shear-sensitive in the manner of rigid PVC, but frictional heat in small-diameter screws can lift melt temperature by 10–20 °C above barrel set point. For hot-runner systems, externally heated manifolds with minimum dead spots are preferred; valve-gated drops reduce stringing. Residence time at melt temperature should remain below 10 min, and shutdown purging with acrylic or polystyrene purging compound is required if the barrel will sit at temperature for extended periods.

The high melt-volume rate of the grade is a process advantage but reduces melt strength and weld-line robustness. Weld-line strength is lower than the uninterrupted tensile strength, and component design should avoid placing weld lines in highly stressed areas or around snap-fit features. Where weld lines cannot be avoided, the use of higher melt and mould temperatures within the specified window can improve molecular diffusion at the knit line, but the gain is limited and must be balanced against yellowing. Injection speed and pack pressure should be set to obtain a cavity-pressure decay profile without sink marks. The glass-transition temperature is approximately 107 °C, so the material solidifies quickly and is suited to thin sections rather than large, thick-walled parts with long cooling requirements.

Representative physical and mechanical properties are listed below. The values are typical for an unfilled, unpigmented injection-moulding grade and are not release limits; certificates of analysis should be requested for the specific lot and colour.

The mechanical data show a rigid, glassy polymer with a tensile modulus close to 3,700 MPa. The material behaves as a linear elastic solid at room temperature and will fail in a brittle manner under tensile overload. The unnotched Charpy impact value of 15 kJ/m² should not be interpreted as toughness in sharp-notched components; Charpy notched impact strength at 23 °C is typically below 3 kJ/m². Snap-fit assemblies, threaded closures, and pressed interconnections therefore require generous radii, low insertion forces, and controlled assembly torque. The Vicat softening temperature of 106 °C permits short-term contact with hot water or steam condensate, but continuous load-bearing service above 70 °C is not recommended.

From a regulatory perspective, the base resin is generally consistent with European REACH registration obligations and can be selected for RoHS-compliant applications because it does not contain the restricted heavy metals or brominated flame retardants at levels above the maximum concentration values. UL 94 classification is usually HB at 1.5 mm and 3.0 mm; a yellow card should be verified for the specific colour and grade. Direct food-contact approval is not automatic and must be confirmed for the final article under the intended conditions of use.

Chemical resistance and environmental stress cracking set the outer boundary for continuous service.

The performance of Luran SAN HD 20 in household, cosmetic, and appliance applications is constrained less by its mechanical strength than by environmental stress cracking. The acrylonitrile comonomer improves resistance to mineral oils, vegetable oils, detergents, and many cosmetic vehicles relative to polystyrene. However, ketones such as acetone, aromatic hydrocarbons such as toluene, esters such as ethyl acetate, and chlorinated solvents can attack SAN and should be excluded from contact or cleaning operations. Alcohols show concentration-dependent behaviour: ethanol and isopropanol can be tolerated in brief wipe tests, but continuous contact with high-water alcohol formulations can produce haze or stress cracking at moulded-in stress. The resin is also incompatible with plasticized PVC components because phthalate plasticizer migration can induce environmental stress cracking in stressed transparent parts. Chemical compatibility is commonly screened by immersion under ASTM D543 or by constant-strain tests using bent strips; the latter is more severe because it superimposes mechanical strain on chemical exposure. Moulded-in stress from excessive packing or abrupt wall-thickness changes will reduce the critical strain for environmental stress cracking.

For food-contact and personal-care packaging, the converter must verify compliance with the relevant national implementation of EU 10/2011 or FDA 21 CFR 177.1040 for styrene-acrylonitrile copolymers, including migration limits for acrylonitrile monomer. Published data for the specific formulation and colour concentrate are usually supplied on request; a certificate of analysis should be matched to the actual grade and lot.

When unfilled SAN replaces GPPS in cosmetic packaging and appliance covers

When unfilled SAN replaces GPPS in cosmetic packaging and appliance covers, the primary benefits are higher heat resistance and better resistance to oils and detergents, but the processor must accept a higher melt viscosity and greater sensitivity to moulded-in stress. The high-flow version is suited to multicavity tools with long flow paths and wall thicknesses down to 1.2 mm. In a 16-cavity hot-runner mould for a transparent cosmetic jar wall of 1.5 mm, the grade can fill from a single sprue with balanced fill within 1.0 s at an injection pressure of 80–120 MPa. These figures are machine- and tool-dependent; published data for this specific configuration is limited. For parts requiring sustained transparency, the mould surface should be polished to SPI A-1 or ISO 1302 N1, and external mould release should be limited because release agents reduce gloss and increase surface haze.

Colour concentrates based on styrene-acrylonitrile or methacrylate carriers are compatible; polyolefin-based masterbatches can create visible delamination and reduce weld-line strength. Regrind can be incorporated at up to 20 % for opaque parts; for high-clarity items, regrind use should be validated for shift in yellowness index and haze. The material is not stabilized for long-term exterior UV exposure; if used in outdoor applications, a UV-stabilized SAN or a capstock with UV absorber is required.

Grade differentiators and rheological positioning against GPPS, ABS, and other Luran SAN types

Within the INEOS Styrolution Luran SAN family, Luran SAN HD 20 is distinguished by its flow length rather than by maximum heat or chemical resistance. Lower-flow grades such as Luran SAN 368R provide higher melt strength and may be preferred for extrusion or thick-wall moulding. Luran SAN 378P is positioned for more aggressive detergent and cosmetic contact, while Luran SAN 388S provides higher heat resistance for applications near 100 °C service. Compared with general-purpose polystyrene such as Styrolution PS 165N, Luran SAN HD 20 has higher tensile modulus, higher Vicat softening temperature by roughly 15–20 °C, and better resistance to fatty oils and detergents, but lower light transmission and a slightly higher density. Compared with ABS, the absence of a butadiene rubber phase gives Luran SAN HD 20 transparency and better surface gloss retention, but substantially lower notched impact strength and reduced low-temperature toughness. For components that must survive drop impact at −20 °C, ABS or an impact-modified SAN should be evaluated. Compared with polymethyl methacrylate, Luran SAN HD 20 offers lower surface hardness and lower resistance to outdoor UV, but better resistance to some detergent and oil formulations and lower density.

In appliance control panels where transparent windows are integrated with opaque SAN or ABS frames, two-component moulding or insert moulding is used. Luran SAN HD 20 can be over-moulded onto opaque SAN grades if the interface temperature is kept above the Vicat point; for ABS combinations, adhesion is limited by the absence of butadiene in the hard phase. On a production line using a 1,200 kN injection moulding machine and a 2+2 stack mould, cycle times for 2.0 mm transparent covers are typically governed by cooling time at a mould temperature of 50 °C; raising the mould temperature to 80 °C improves surface gloss and reduces stress cracking but increases cooling time by approximately 15–20 %. Cavity pressure sensors are recommended to maintain switchover reproducibility within 50 bar of the set point, because variation in switchover pressure can alter residual stress and subsequent chemical resistance.