LyondellBasell Hiloy SAN 246 is a glass-fibre-reinforced styrene-acrylonitrile injection-moulding compound supplied in pellet form for structural thermoplastic applications. The grade is commonly described as a 20 % glass-fibre-reinforced SAN material, although the current supplier certificate of analysis remains the controlling specification for filler content because colour concentrates, regrind ratios, and lot-specific compounding can shift the final reinforcement fraction. The product identification combines the Hiloy filled-polymer platform with an SAN matrix designation and the numeric grade code 246. Representative physical-property summaries place the density near 1.22 g/cm³ when tested under ISO 1183-1, which is consistent with a 20 wt% short-glass loading in a styrene-acrylonitrile matrix having an unfilled density of approximately 1.08 g/cm³. The reinforcement shifts the material out of the neat SAN property envelope: stiffness, tensile strength, and heat deflection temperature increase, while unfilled transparency is lost and melt-flow length at the same injection pressure decreases. These trade-offs define the grade’s application window and separate it from unfilled SAN, mineral-filled SAN, and glass/mineral hybrid styrenic compounds.

The material is evaluated for load-bearing components that require better dimensional stability than unfilled SAN but do not require the upper-use-temperature range of glass-filled polyamide or polycarbonate. Typical candidate components include appliance structural bases, electrical enclosures, coil bobbins, fan shrouds, power-tool housings, and pump bodies. In those applications, the glass network reduces mould shrinkage and increases apparent creep resistance, but the moulded part is opaque because of refractive-index mismatch between the glass fibre and the SAN matrix. The material is not a transparent-cover or light-transmitting-panel solution. Designers specifying the grade for visible transmission applications are outside the intended use envelope. The glass content is normally verified by a burn-off test under ISO 3451-1 or ASTM D5630, and the reinforcement is generally a short glass fibre with a residual length after compounding that is material-specific and affected by both compounding screw design and subsequent injection-moulding history.

Does the 20 % Glass Loading Change the Property Profile Compared with Unfilled SAN?

Table 1 consolidates representative comparative data for Hiloy SAN 246 and general-purpose unfilled SAN ranges. The values are compiled from public material summaries and are not a substitute for the current LyondellBasell technical datasheet or lot-specific certificate of analysis. Specimen preparation and test condition differences can produce systematic offsets between ISO and ASTM data sets.

The modulus change is the primary design differentiator. Under ISO 527-2, typical tensile modulus values for Hiloy SAN 246 are reported near 7400 MPa, whereas unfilled SAN typically falls in the 3300–3800 MPa range. This produces a stiffer load path but also a lower tensile failure strain and a sharper notch-sensitivity envelope. Notched impact tested under ISO 179/1eA at 23 °C may show a value near 5.0 kJ/m², but that value is sensitive to gate location, weld-line position, and fibre-length distribution. The heat deflection temperature under 1.80 MPa load tested according to ISO 75-2/A is reported near 102 °C; however, HDT is a single-point thermal-mechanical property and should not be used as a continuous-use temperature rating under load. Compared with mineral-filled SAN, the glass fibre provides greater tensile strength and modulus at equivalent filler loading but introduces more flow-direction/cross-flow anisotropy and higher machine-surface abrasion. Compared with glass-filled polystyrene, the SAN matrix generally provides better resistance to aliphatic hydrocarbons and stress cracking in selected environments, although specific chemical exposure must be validated under final end-use conditions.

Before melt processing of Hiloy SAN 246, moisture control must be addressed as a process boundary, not as a cosmetic recommendation. SAN matrices are hygroscopic, and absorbed moisture at ambient relative humidity above 60 % can produce surface splay, flow lines, and local reductions in weld-line strength. A dehumidifying dryer with a dew point of -20 °C or lower is typically used, with an air temperature of approximately 80 °C and a dwell time of 4 h. The target residual moisture is below 0.05 wt%. Tray drying at the same temperature may be insufficient in high-humidity production halls unless surrounding air is conditioned. Pellets should not be left open in the machine throat for more than 30 min at high relative humidity because glass sizing can promote surface moisture adsorption. On production-scale machines with screw diameters from 40 mm to 80 mm, the presence of short glass fibre raises the practical lower limit of injection pressure and makes check-ring sealing surfaces more sensitive to wear. General-purpose screws with short compression zones can fracture fibre bundles before complete matrix melting, producing resin-rich regions that exhibit local strength loss. Hardened check-ring non-return valves and cylinder liners are preferred. Back pressure in the range of 5–15 bar hydraulic is commonly used to homogenise the melt and maintain a stable cushion; above 20 bar, the additional shear work can reduce fibre length and lower tensile strength. The compounding history of the pellet is equally relevant. Co-rotating twin-screw extruders with L/D ratios between 32:1 and 44:1 are widely used for such glass-reinforced styrenics, but fibre attrition during compounding and subsequent moulding means that datasheet values are only representative if the specimen preparation history matches the intended production route.

Injection-Moulding Parameter Boundaries and Gate Freeze Considerations

Mould-wall temperature is a first-order control on surface appearance, fibre show, and frozen-in stress. Mould temperatures in the range of 60–80 °C are typical for a glass-reinforced SAN grade, with the upper half of that range used where finer surface detail or reduced gate blush is required. Thin-wall sections below 2.0 mm may require mould temperatures above 70 °C and fast injection speeds to avoid premature solidification. However, fast injection intensifies flow-induced fibre orientation and increases the difference between flow-direction and cross-flow shrinkage. Holding pressure and gate freeze time must therefore be balanced. A gate that freezes too early produces sink marks and elevated mould shrinkage; a gate held open too long can overpack the cavity and increase moulded-in stress near the gate. The processing window is bounded at one end by short-shot and freeze-off formation and at the other by polymer degradation, splay, and yellowing. Melt-temperature settings are generally selected between 220 °C and 260 °C, with the nozzle kept below 270 °C. At higher melt temperatures or extended residence times, styrene-acrylonitrile copolymers undergo yellowing and can release styrene monomer; the practical maximum residence time at the upper barrel set point is often limited to 8 min. Injection machines with large shot-to-barrel volume ratios may require reduced set-point temperature or a smaller barrel to avoid holding thermally degraded material in the cushion. Regrind should be limited to a controlled percentage because each heat history reduces fibre length. High-regrind ratios are not represented by virgin-property datasheet values and should be validated on the actual production tool.

When Fibre Orientation Converts Shrinkage Data into Warpage Risk

Glass-fibre-reinforced SAN does not shrink isotropically. In injection-moulded plaques, the shell layer fibres are highly oriented in the flow direction by the propagating flow front, while the core layer may contain more transverse orientation depending on cavity thickness and melt-temperature profile. Because glass fibres constrain thermal contraction along their axes, mould shrinkage in the flow direction is typically lower than shrinkage in the cross-flow direction. Table 1 reports flow-direction mould shrinkage of 0.2–0.4 % under ISO 294-4, but cross-flow values can be higher. The resulting differential shrinkage is a primary source of warpage in box-like housings and flat electrical-enclosure lids. Gate location changes the warpage pattern because it defines the principal flow direction. A single edge gate feeding a long flat part in the width direction can produce a cylindrical bow along the flow axis. Multiple gates or a diaphragm gate can create radial flow that reduces the flow/cross-flow shrinkage asymmetry but may introduce weld lines. Weld lines are mechanically weak in glass-reinforced materials because fibres align parallel to the weld plane instead of bridging it. In unfilled SAN, weld-line tensile-strength retention is generally higher than in the glass-filled analogue. Published data for this specific grade under weld-line conditions is limited; therefore, moulders should generate weld-line specimens under ISO 527-2 and compare them with unwelded specimens rather than relying on datasheet values. Test plaques should be prepared under ISO 294-1, and anisotropic shrinkage should be measured across a range of hold pressures because packing stress directly changes the flow/cross-flow shrinkage ratio. For parts requiring flatness over a length greater than 150 mm, tool trials with pressure-sensitive film or strain-gauge monitoring are more informative than databook mould-shrinkage references.

For applications involving continuous contact with organic solvents, aromatic hydrocarbons, ketones, or chlorinated fluids, the chemical resistance of Hiloy SAN 246 must be confirmed by testing under ISO 175 or ASTM D543. Styrene-acrylonitrile matrices are vulnerable to environmental stress cracking when an external load is combined with solvent exposure. The glass reinforcement reduces thermal expansion and mould shrinkage but does not inherently change the solvent resistance of the SAN phase. Continuous load testing at elevated temperature should reference ISO 899-2 or ISO 22088 for stress cracking rather than assuming that room-temperature tensile strength is a reliable predictor. Regulatory review should be based on the latest supplier documentation. The compound may be covered under EU 2011/65/EU RoHS declarations and EC 1907/2006 REACH registration obligations in the current production form. Flammability ratings are highly part-thickness dependent; any claim of UL 94 class must be confirmed with the current yellow-card file and the exact wall thickness. No food-contact or medical-grade status is implied unless specified in a written certification under the relevant standard. Avoid blending the material with engineering polymers that require melt temperatures above 270 °C, because the SAN phase will degrade and the resulting property loss cannot be recovered by adjusting moulding parameters.