LyondellBasell Hiloy SAN 243 is a glass-fibre-reinforced styrene-acrylonitrile copolymer injection-moulding grade. The designation belongs to the legacy Hiloy compounding portfolio integrated into LyondellBasell Advanced Polymer Solutions after the 2018 acquisition of A. Schulman. It is supplied as pelletized feedstock with a nominal glass-fibre loading of 20% by weight. The matrix is a random styrene-acrylonitrile copolymer; the reinforcement is short chopped glass fibre. Published product summaries place the material in the dimensionally stable, high-stiffness SAN class rather than in an impact-modified or elastomer-containing system. Because the glass fibres orient during mould filling, mechanical properties and mould shrinkage are anisotropic. Published data for this specific configuration are limited in open literature; grade-specific release values must be obtained from the current LyondellBasell technical data sheet and lot certificate of analysis.

What Distinguishes a 20% Glass Fibre-Reinforced SAN from Unfilled and Impact-Modified Styrenics?

The defining difference in this product class is the replacement of a portion of the SAN matrix with chopped glass fibre. The result is not a new polymer but a multiphase compound in which fibre length distribution, fibre-matrix sizing, and fibre orientation dominate stiffness, strength, and warpage. The table below gives class-reference data for unfilled SAN and 20% glass-reinforced SAN. It is not a certificate of analysis; the values are drawn from public polymer science literature and supplier screening data for glass-reinforced styrenics and should be verified against the grade-specific data sheet.

Compared with unfilled SAN, the 20% glass reinforcement raises tensile modulus by approximately 80–100%, raises flexural modulus by a similar order, and lowers the coefficient of linear thermal expansion by roughly half. The heat deflection temperature under 1.8 MPa load moves from approximately 83°C to approximately 102°C. The notched Charpy impact value increases only modestly and remains below 6 kJ/m², which means the material is not an alternative to glass-filled ABS or polycarbonate/ABS when impact tolerance is the controlling requirement. Against a lower glass loading such as 10%, the 20% grade provides higher modulus and lower CLTE but has higher melt viscosity and a greater tendency for anisotropic shrinkage. Against a 30% glass-reinforced SAN, the 20% grade normally exhibits lower warpage tendency and better surface appearance, but lower tensile and flexural stiffness. Changing from unfilled SAN to glass-reinforced SAN reduces elongation at break to roughly 2–3%, which is typical for the class; design strain should be kept below this level for static components. The absence of an elastomeric impact modifier should be considered as an operational limitation rather than a defect: snap-fit and living-hinge designs that rely on large strain to failure are generally not recommended.

Within the Hiloy family, product codes with higher numerical designations may not necessarily follow a simple glass-content progression; some codes reflect carrier resin, stabilization package, or colour platform. Product selection should therefore be made against the specific LyondellBasell grade datasheet rather than an assumption based on nomenclature. If a similar stiffness is required with improved impact, a glass-reinforced ABS or polycarbonate/ABS compound should be evaluated. If chemical resistance is the governing requirement, a glass-reinforced polypropylene may be compared for aliphatic fluid environments, but with lower heat deflection temperature. Such substitutions alter mould shrinkage and thermal expansion and cannot be made as drop-in replacements without tooling changes.

Processing Constraints in High-Shear Injection Moulding

Before conversion, the pellets should be dried in a desiccant dryer to a residual moisture level below 0.05%. A drying temperature of 80°C for 4 h is common in processing guides for glass-reinforced SAN; if the granulate has been stored in humid conditions at relative humidity above 60%, dwell time should be extended. A closed-loop dryer dew point of -30°C or lower is recommended because the glass sizing layer is hydrophilic and surface moisture can attack the fibre-matrix interface during melting.

The melt temperature measured by a needle pyrometer should be maintained between 230°C and 260°C. Barrel setpoints should not be used as a substitute for direct melt measurement because shear heating from glass fibres can raise melt temperature above the setpoint. At the upper limit, cumulative residence time should be kept below 5 min; thermal degradation of the SAN matrix releases styrene monomer and causes yellowing. When interruptions occur, the barrel front zone and nozzle should be cooled or purged.

A general-purpose screw with an L/D of 20:1 to 24:1 and a compression ratio of 2.5:1 to 3.0:1 is suitable. Because the glass filler is abrasive, the screw, check ring, and barrel should have hardened surfaces. The check ring should be inspected for wear at intervals shorter than unfilled SAN service intervals; a worn check ring reduces shot-to-shot consistency and increases cushion variation. For a multicavity appliance housing with wall sections of 2.0–3.0 mm, specific injection pressure is often in the range 80–120 MPa at the nozzle. Cavity pressure near the gate can exceed 40–60 MPa, and clamp force should be selected from projected area with an appropriate safety factor for glass-filled materials.

Mould temperatures in the range 60–80°C are typically used. Higher mould temperatures reduce orientation stress and improve knit-line strength but increase cycle time and may reduce gloss. Lower mould temperatures accelerate skin freezing and can produce exposed glass fibres at the surface. Injection speed should be set in the moderate-to-fast range for thin-walled sections because a slow fill front freezes before pack and produces gate-area voids. Excessive injection speed, however, raises shear heating and can degrade the matrix. Packing pressure and gate-seal time should be determined by gate-seal study; short glass fibre compounds often seal early, and additional pressure after gate freeze has no effect on cavity dimensions.

Under ISO 1133-1:2022, glass-reinforced SAN of this class is commonly characterized at 220°C and 10 kg, with melt volume-flow rate values in the range 6–12 cm³/10 min. This range is not a processing window by itself; the shear rate in the runner and gate is a stronger predictor of fill pressure. Fibre attrition during plasticating reduces average fibre length from the as-supplied 3–4 mm chopped fibre to a moulded part length typically between 0.2 mm and 0.5 mm. The final fibre length distribution depends on back pressure, screw speed, and check ring clearance. Laboratory tensile bars should not be used as the sole source of design allowables for production parts because fibre orientation in a bar differs from orientation in a multi-gated component.

Runner and gate design should follow the short-flow-length logic used for highly filled amorphous materials. Gate diameters below 1.0 mm are not recommended for parts thicker than 2.0 mm because the higher viscosity and abrasive filler increase pressure loss and gate wear. Edge gates, fan gates, and valve gates are preferred over pinpoint gates when dimensional control is critical. A cold runner with a length-to-thickness ratio above 200:1 is likely to require excessive injection pressure; the runner should be full-round or trapezoidal with polished surfaces to reduce shear heating. Hot-runner systems should include a leak-free manifold and open-pipe channels; dead spots in the manifold increase residence time and lead to dark specks.

Regrind of glass-reinforced SAN can be incorporated at levels up to 25% by weight without eliminating the dimensional stability of the neat grade, but the regrind must be dust-free and dried with the same schedule. Higher regrind fractions reduce fibre length and increase shot-to-shot density variation. For appearance parts, regrind levels above 15% may produce visible glass-fibre bundles at the surface.

The glass content of incoming pellets can be checked by thermogravimetric analysis or by ignition loss according to ISO 3451-1. A 20% nominal glass content should be confirmed against the certificate of analysis because the final ash residue includes glass and any mineral flow enhancer; the ash value is not identical to the glass content if the formulation contains noncombustible additives. Melt flow rate testing under ISO 1133-1:2022 is a useful incoming-check tool but does not detect fibre length distribution. For critical parts, a laboratory moulding trial with a standardized tool is the most reproducible way to compare lots.

When Fibre Orientation Controls Shrinkage and Warpage

Dimensional stability in Hiloy SAN 243 is not isotropic. The coefficient of linear thermal expansion parallel to flow may be approximately 25–35×10⁻⁶ K⁻¹, while the cross-flow value can be 45–60×10⁻⁶ K⁻¹. Mould shrinkage follows the same directionality: shrinkage parallel to fibre orientation is lower than shrinkage perpendicular to it. A flat part with a single edge gate will therefore tend to bow unless the gate location is selected so that the flow front is nearly uniform and the packing pressure is delivered along the longest flow path. Differential shrinkage between thick and thin sections remains a source of warp even in reinforced materials; packing pressure cannot correct a section that freezes before pressure arrives.

Weld lines are the limiting mechanical feature. Published data for short-glass thermoplastics indicate that weld-line tensile strength is commonly between 40% and 60% of the datasheet value because fibres at the weld line align along the plane of the knit line rather than across it. In a glass-reinforced SAN without an impact-modifying phase, the weld line is also brittle. Multi-gated parts should therefore be designed so that weld lines are located in low-stress regions, not in snap-fit arms or around bearing bores. If weld-line position is fixed by part geometry, a hot runner valve-gate sequence or a flow leader can shift the knit line.

The flatness of long components can be verified with a fixture that constrains one datum face and measures deviation over a 200 mm span. Published data for this specific configuration is limited, so the supplier moulding guidelines and prototype shrinkage trials are required for tolerances tighter than ±0.1 mm. When moulding a part with ribs, bosses, or fixing points, the transition radius should be increased relative to unfilled SAN because the glass fibres create local stress concentrations at sharp internal corners.

Chemical resistance of the compound remains matrix-dominated. The styrene-acrylonitrile copolymer resists aliphatic hydrocarbons, mineral oils, and many aqueous detergent solutions but is attacked by aromatic hydrocarbons, ketones, esters, and chlorinated solvents. The glass reinforcement does not change the matrix solubility parameters; it can nevertheless create a wicking path along the fibre-matrix interface after surface damage or at exposed fibre ends. Continuous immersion in hot aqueous glycol mixtures above 60°C should be validated because published data for this specific configuration are limited. For electrical and electronics applications, the grade is normally assessed under UL 94 HB; applications requiring V-2 or better require a flame-retardant grade. RoHS Directive 2011/65/EU and REACH Regulation 1907/2006 declarations should be requested from the supplier for the specific batch.

Electrical enclosures, small appliance structural frames, and HVAC vanes are representative application zones. For these components, the dimensionally stable character of the 20% glass-reinforced SAN is used to maintain snap-fit engagement, bearing bores, and connector spacing. The maximum continuous operating temperature under load should be below the heat deflection temperature, with a design margin determined by creep data; for general unloaded parts, a continuous service temperature of 70–80°C is frequently used as a screening value, but grade-specific data must control. Parts exposed to outdoor weathering require UV stabilization because the SAN matrix yellows and loses surface integrity under prolonged ultraviolet radiation. The glass reinforcement may improve dimensional stability but does not provide UV protection.

Pump housings and filter bowls in non-pressurized mineral-oil systems may be considered because of matrix resistance to aliphatic oil. They are not recommended for hot water, steam, or glycol environments above 60°C unless long-term pressure testing is performed. Glass-fibre compounds in such applications should be evaluated for extraction of sizing components if the fluid is potable or medical. Batch-to-batch fibre content should be verified by ignition loss according to ISO 3451-1 when incoming inspection is required. If lot-specific colour or additive packages are used, the release documentation should state the exact glass content and the test method used.