INEOS Styrolution Absolan SAN+GF20% 23GF20% is a short-glass-fibre reinforced styrene-acrylonitrile copolymer compound supplied as pellets for injection moulding of dimensionally stable structural parts. The designation identifies a nominal glass-fibre loading of 20% by mass in a SAN matrix, while the numeric prefix 23 is interpreted through ISO 19062-1 as a melt-volume-flow-rate class for acrylonitrile-styrene materials. Published data for this specific configuration is limited; therefore lot-specific values for density, MVR, ash content, and mechanical properties should be obtained from the manufacturer certificate of analysis. Under ISO 1183-1, short-glass SAN grades of this fibre content typically exhibit density in the range 1.22–1.28 g/cm³. The product is intended for technical housings, brackets, electrical enclosures, and appliance components in which unreinforced SAN lacks tensile modulus and creep resistance, while polyolefins lack heat deflection and surface hardness. Because the fibres orient during flow, the compound is anisotropic: the modulus along the dominant melt-flow direction is higher than across it, and warpage is governed by orientation gradients rather than simple differential shrinkage alone.

What does the 23GF20% designation communicate in the ISO 19062-1 classification system?

ISO 19062-1 defines designation blocks for styrene-acrylonitrile materials; a code such as 23GF20% is read as melt-volume-flow-rate class 23 and glass-fibre content 20%. The fibre content is verified by ash determination under ISO 3451-1, and the melt-volume-flow-rate class is linked to ISO 1133-1 measurement conditions for SAN at 220°C and 10 kg applied mass. The class is a bracketing system, not an exact MVR value; two products classified as class 23 can differ within the class boundaries. For highly filled compounds, the measured MVR is also strongly influenced by fibre length, fibre length distribution, and moisture. The melt-density correction in the MVR calculation therefore matters when comparing filled and unfilled grades. The designation does not state whether an elastomeric impact modifier, lubricant, mould-release agent, or UV stabiliser is present; those additives must be confirmed from the product datasheet or infrared spectrum.

This classification issue has direct process relevance. A compound with the same nominal 20% fibre content can exhibit large differences in spiral-flow length if the fibre length distribution is degraded during compounding. When transferring a mould from one SAN GF20 source to another, a spiral-flow test under fixed barrel temperature and injection pressure is recommended before tool modifications are approved. Because the melt is shear-sensitive, the MVR class should not be used alone to predict cavity pressure.

Mechanical Property Profile and Thermal Load Limits

Short-glass SAN compounds at 20 wt% fibre loading are substantially stiffer than unreinforced SAN. The modulus increase is not uniform through the part: fibres aligned in the flow direction produce a flow-direction tensile modulus that may exceed the transverse modulus by 30–50%. Tensile tests under ISO 527-2 report values averaged over the specimen gauge length; they do not capture local orientation differences across ribs, weld lines, or abrupt thickness changes. Typical ranges for this class are shown in Table 1.

The thermal limits are matrix-dominated. Heat deflection temperature under 1.8 MPa bending stress is commonly 100–110°C for dry as-moulded specimens tested after conditioning to ISO 291 atmosphere. Under low load, maximum short-term service temperature may be higher, but long-term exposure above 85°C can shift part dimensions, alter fibre-matrix adhesion, and reduce impact strength; validation under actual load and environment is required. Glass transition of the SAN matrix is usually above 100°C, but the complex modulus decreases gradually between 80°C and the glass transition. Creep under load must therefore be evaluated by ISO 899-2 rather than inferred from HDT alone.

On injection-moulding lines equipped with a general-purpose three-zone screw with an L/D ratio of 20:1–25:1 and compression ratio of 2.0:1–2.5:1, the compound is processed at a melt-temperature window of 230–260°C and a mould temperature of 60–80°C. Pre-drying in a desiccant dryer at 80°C for 2–4 h is required when moisture content exceeds 0.05%; splay and silver streaks appear if residual moisture is not removed. The cylinder temperature profile is reverse or flat to avoid overheating at the feed zone. Screw rotation is limited to a peripheral speed below 0.3 m/s; high screw speed reduces fibre length and decreases tensile modulus and impact strength. Back pressure of 2–5 MPa hydraulic pressure improves melt homogenisation but must not be raised to the point that fibre breakage becomes measurable. Injection speed and hold pressure are part-dependent; hold pressures of 60–100 MPa on the melt are used for technical housings. Cushion consistency should be held within 2–4 mm because screw decompression can draw air into the melt and create surface defects.

Shrinkage is anisotropic: flow-direction shrinkage is usually 0.1–0.3%, while cross-flow shrinkage is 0.4–0.6%; thick sections may exhibit a broader differential. Gates should be located to orient flow along the direction of maximum tensile stress. Fan gates or edge gates with a land length of 0.8–1.2 mm are preferred over central sprue gates for flat parts. Vent depths of 0.02–0.05 mm prevent burn marks from fibre volatiles. Weld lines formed behind cores or multi-gate junctions are the most serious structural weakness: fibres align parallel to the weld plane and do not bridge the interface, so weld-line tensile strength retention can fall to 50–65% of the oriented material. Moving weld lines to low-stress areas, increasing local melt temperature, or using sequential valve-gating is required for pressure-containing or load-bearing parts.

Fibre accumulation in hot-runner dead spots produces black specks and intermittent wall-thickness variation. Hot-runner systems for this material require fully open gates, polished channels, and no stagnation zones. The compound abrades screws, barrels, and non-return valves; nitrided or bimetallic components are used for series production. Drying and conveying systems should be stainless steel to avoid moisture re-uptake and abrasion from glass fibres.

Chemical resistance and dimensional stability in humid environments

SAN matrices resist aliphatic hydrocarbons, diesel fuel, motor oil, detergents, dilute acids, and dilute alkalis at room temperature better than polyolefins. The glass reinforcement does not change the chemical resistance of the matrix, but it can accelerate stress-cracking because fibre ends act as local strain concentrators. Water absorption after 24 h immersion under ISO 62 is typically 0.2–0.3%, producing dimensional changes usually below 0.1% in indoor applications. In hot water above 80°C, the glass-fibre sizing layer can hydrolyse and reduce interfacial adhesion faster than the resin matrix alone would suggest; long-term immersion is not recommended.

Polar solvents including methyl ethyl ketone, acetone, esters, and chlorinated hydrocarbons soften or craze SAN. The product is not suitable for continuous vapour contact with these fluids or for immersion. Stress-cracking resistance must be screened under ISO 22088-2 when the part is exposed to a detergent or oil under mechanical load. For UV-exposed outdoor parts, a pigmented or UV-stabilised grade is required; glass reinforcement does not provide UV protection and may increase surface roughening after weathering.

When 20% glass-fibre SAN replaces ABS or polypropylene in structural housings

Compared with ABS GF20, the SAN-based compound has higher resistance to cooking oils and commercial detergents and lower moisture sensitivity, but lower notched impact strength and greater susceptibility to environmental stress cracking under biaxial load. ABS GF20 typically has a notched Charpy impact strength in the range 8–15 kJ/m² at 23°C, whereas SAN GF20 is closer to 5–10 kJ/m²; the difference widens below 0°C. In return, SAN GF20 offers lower rubber-phase odour, better resistance to yellowing by detergents, and lower coefficient of linear thermal expansion than many ABS grades.

Compared with PP GF20, the SAN+GF grade has higher heat deflection under load, higher surface hardness, better dimensional stability, and paint adhesion without plasma pretreatment. However, PP GF20 has lower density, better low-temperature impact strength, and better resistance to strong bases and battery acid. PP GF20 can reach higher HDT/A values under 1.8 MPa in homopolymer reinforced grades, often 130–150°C, but modulus and creep resistance at room temperature are lower than those of SAN GF20. The choice is therefore driven by the combination of temperature, load, chemical exposure, and impact at sub-zero temperature.

Compared with unfilled SAN, the reinforced grade raises tensile modulus by about a factor of 2 and increases HDT/A by 15–25 K. The melt becomes more viscous, and the surface shifts from glossy to a matte glass-fibre texture that is difficult to brighten without a post-coating. Tool shrinkage allowances must be revised because unfilled SAN shrinkage is more isotropic and often larger in both directions.

Quality-control release for glass-fibre reinforced SAN is based on ISO 3451-1 ash content to confirm the 20% fibre weight fraction, on ISO 1133-1 melt flow measurement, and on mechanical tests under ISO 527-2. Because fibre content increases melt viscosity and lowers MVR, a mould trial with a spiral-flow tool is recommended before tool release. Screw and barrel wear is higher than with unreinforced resins; nitrided or bimetallic barrels and hardened screws are used for long production runs. Hot-runner systems require fully open gates and polished flow channels with no dead spots. Regrind use above 30% is generally not recommended for dimensional stability because fibre length reduction and residence-time degradation shift shrinkage and impact values. When the material is changed from ABS or PP, purging with a high-viscosity SAN or acrylic-based purge compound is performed at the rated processing temperature; residual PP can cause delamination and optical defects.

The product is not inherently flame-retardant unless a specific flame-retardant package is present. Without additional additives, the material is expected to fall into UL 94 HB; electrical enclosures requiring V-0 require a different flame-retardant grade. RoHS Directive 2011/65/EU and REACH SVHC compliance must be confirmed from the supplier for each production lot. Published data for this specific configuration under IEC 60695-2-11 glow-wire testing is limited; therefore end-product testing is required for unattended appliance applications.