LG Chem LUPOS SAN+GF30% GP2305A is a 30% by weight glass-fibre-reinforced styrene-acrylonitrile copolymer supplied as pelletised feedstock for injection moulding. The amorphous SAN matrix contains acrylonitrile units distributed along a styrene backbone, while the glass-fibre phase consists of chopped E-glass fibre with silane sizing that promotes load transfer at the fibre-matrix interface. Manufacturer technical literature identifies the grade as a high-rigidity, dimensionally stabilised SAN compound rather than an engineering thermoplastic. The 30% fibre fraction elevates tensile strength and flexural modulus above unfilled SAN, lowers mould shrinkage, and introduces anisotropic flow-direction mechanical properties. Typical applications include electrical housing components, bobbins, terminal blocks, power-tool casings, interior automotive brackets, and HVAC fan shrouds. The grade is selected where unfilled SAN exhibits insufficient creep resistance or where glass-filled polyamide and polyester alternatives impose excessive moisture absorption, density, or post-moulding warpage.

What Property Shifts Are Introduced by the 30% Glass-Fibre Phase?

Relative to unfilled SAN, the addition of 30% discontinuous glass fibre changes the property envelope in three directions: tensile and flexural modulus increase, mould shrinkage decreases, and mechanical behaviour becomes anisotropic. Representative data for GP2305A, reported in supplier literature under standard injection-moulded test plaque conditions, cluster around the following ranges: density 1.28–1.30 g/cm³ per ISO 1183-1, tensile strength 105–125 MPa per ISO 527-2/1A/5, flexural modulus 7,800–9,200 MPa per ISO 178, notched Charpy impact 5–8 kJ/m² per ISO 179-1/1eA, and heat deflection temperature under 1.8 MPa of 100–110 °C per ISO 75-2/A. These values are typical screening figures rather than specification limits; lot-specific certificates and moulded-plaque data must be obtained before tool design.

Dry-as-moulded plaques are typically conditioned at 23 ± 2 °C and 50 ± 5 % relative humidity for 40 h according to ISO 291 before mechanical testing. Glass-fibre orientation in the skin-core structure generates higher modulus in the shell and lower modulus in the core; reported values therefore represent plaque averages rather than local part stiffness. The notched impact range is quoted at 23 °C. At sub-zero temperatures, matrix embrittlement in SAN reduces notched impact energy, and sharp internal corners become more vulnerable to crack initiation.

Pre-Drying, Screw Design, and Injection Moulding Parameters

Pre-drying is required above ambient-equilibrium moisture conditions. Desiccant drying at 80 °C for 3–4 h to a residual moisture content below 0.05% by weight is the recommended conditioning window, with hopper desiccant air maintained at a dew point of ≤ -30 °C. Glass-filled SAN does not hydrolyse as rapidly as polyamide, but surface moisture on pellets produces splay, silver streaks, and weak weld-line appearance. Production-scale machines with general-purpose three-zone screws are suitable for GP2305A when the screw L/D ratio is 20:1 to 24:1 and the compression ratio is 2.0:1 to 2.5:1. Bimetallic barrel lining and hardened screw surfaces reduce screw-body and check-ring wear caused by glass-fibre attrition. Melt temperature at the nozzle should be held between 220 °C and 240 °C, with the front zone at 220–240 °C, middle zone at 210–230 °C, and feed zone at 190–210 °C. Mould temperature between 40 °C and 80 °C controls surface finish and fibre bloom; higher mould temperatures improve knit-line consolidation but extend cycle time. Screw back pressure of 0.3–0.7 MPa and screw speed of 40–80 rpm on a 30–50 mm screw are typical process windows. For a nominal 2.5 mm wall, filling pressure of 70–100 MPa is typical. Gate diameters between 0.8 mm and 1.5 mm, runner diameters of 4–8 mm, and vent depths of 0.02–0.03 mm reduce gas entrapment and fibre-resin separation.

Process capability studies on injection moulding machines with clamp force between 800 kN and 2,000 kN indicate that GP2305A is best processed at shot sizes between 20% and 80% of maximum barrel capacity. Excessive residence time in the barrel causes thermal degradation of the SAN matrix and a yellowing shift in colour. Residence time should not exceed 5 min at melt temperature above 230 °C; start-up purging with unfilled SAN or acrylic purging compound prevents glass-fibre accumulation in dead zones. Screw decompression after dosing should be limited to 3–5 mm to avoid air entrapment.

Glass-fibre length retention is sensitive to screw speed and back pressure. Pelletised glass fibre in 30% by weight compounds typically enters the feed throat as 3.0–4.5 mm chopped strand bundles. After plastication, mean fibre length is reduced by shear to 0.3–1.2 mm; higher screw speed and lower melt temperature increase fibre fracture. The ratio of number-average to weight-average fibre length influences tensile strength more than modulus. Reducing back pressure to the minimum needed for a homogeneous melt and avoiding restrictive non-return valve geometries preserve fibre length. Hot-runner systems require free-flow nozzle geometries; valve-gate hot runners with small clearances may shear fibres and create resin-rich streaks at gate areas. Fibre breakage is not recoverable after injection, so the property potential of GP2305A is process-limited.

When Dimensional Stability and Creep Resistance Are Primary Acceptance Criteria

When dimensional stability and creep resistance are primary acceptance criteria, GP2305A is specified over unfilled SAN because the glass-fibre phase reduces mould shrinkage and improves long-term dimensional retention under sustained mechanical load. Mould shrinkage measured per ISO 294-4 is roughly one-third to one-half that of unfilled SAN. Typical unfilled SAN shrinkage is 0.4–0.7%, whereas the 30% glass-filled compound shrinks 0.15–0.30% in the flow direction and 0.25–0.50% transverse to flow. This anisotropy is process-dependent: higher injection speed, thicker wall sections, and cold moulds increase solidification-rate differences across the wall and raise warpage in flat panels. Creep resistance under continuous static load is governed by the glass phase at strains below 0.5%; deflection under a sustained flexural stress of 20 MPa at 23 °C is lower than unfilled SAN, but published creep curves for this exact grade are limited and must be obtained from the manufacturer for long-term design. For parts that require precise bearing bores or gear centres, post-mould annealing at 70–80 °C for 2 h can reduce residual stress, although it may slightly increase thickness-direction shrinkage. A minimum wall thickness of 1.5 mm should be specified to allow glass-fibre flow and avoid surface delamination. Ribs should be limited to 60% of the nominal wall to reduce sink marks and fibre-orientation discontinuities. Weld lines in glass-reinforced SAN may retain only 40–60% of the parent tensile strength, depending on melt temperature and fibre length, so weld lines should not be placed at load-bearing locations.

Production experience with 30% glass-fibre SAN shows that the grade is used in electrical enclosures, terminal blocks, and power-tool housings where stiffness is required at moderate temperatures and the part must survive repeated assembly torque without cracking. In bobbins and coil forms, the material maintains winding tension over time because the glass phase reduces creep; however, weld-line strength is lower than unfilled SAN, and gates should be placed so that weld lines are moved away from high-stress regions. Interior automotive brackets and HVAC fan shrouds benefit from low moisture-induced expansion; measured linear moisture expansion is far lower than that of polyamide equivalents. The material is not intended for continuously painted exterior body panels or glazing because unprotected SAN matrix undergoes UV-induced surface discoloration and gloss loss. For applications requiring UL 94 V-0 flame retardance, grade-specific flame-retardant SAN products should be substituted unless the part operates at low voltage or inside a non-flammable enclosure; published data for this specific configuration is limited. Short glass fibre in GP2305A creates flow-direction stiffness and transverse-direction weakness; finite-element modelling of anisotropic mechanical properties is necessary for accurate warpage and failure prediction.

Compared with glass-fibre-reinforced ABS or ASA, GP2305A generally has higher rigidity and lower rubber-phase toughening. ABS GF30 and ASA GF30 may show higher notched impact because the butadiene or acrylate rubber phase dissipates energy; SAN GF30 lacks this elastomeric phase and therefore exhibits lower ductility. This distinction is relevant in power-tool housings where impact loads occur. Conversely, the SAN matrix may provide different resistance to household cleaners and lower resin cost at a given glass loading than some ASA grades; ASA is preferred for outdoor UV stability. The selection between GF SAN and GF ABS/ASA is therefore driven by the impact-versus-stiffness requirement and chemical exposure profile.

Moisture Uptake, Chemical Resistance, and Thermal Bounds Restrict the Application Envelope

Moisture uptake, chemical resistance, and thermal bounds restrict the application envelope. Under ISO 62 immersion at 23 °C, SAN absorbs approximately 0.2–0.3% water by mass, while glass-filled grades typically absorb 0.10–0.20%; this is approximately one-tenth of the equilibrium moisture uptake of 30% glass-fibre polyamide 66 at 50% relative humidity. The practical consequence is that GP2305A retains a larger fraction of its dry-as-moulded flexural modulus in humid environments than polyamide 66, although its absolute heat resistance is lower. Heat deflection temperature under 1.8 MPa is in the 100–110 °C range, below PBT GF30 and PA66 GF30 grades that typically exceed 200 °C under the same test. Continuous-use temperature for dry-air service is generally bounded below 70–85 °C for SAN matrices; prolonged exposure above this range can produce embrittlement and surface discoloration even when the short-term HDT-A value is higher. Chemical resistance is governed by the SAN matrix: aromatic hydrocarbons, esters, ketones, and chlorinated solvents attack the polymer, and stress cracking may occur in the presence of certain plasticising additives or solvent vapours. The grade is not suitable where repeated contact with polar solvents or strong acids occurs; dilute acids and alkalis at room temperature are tolerated only for short exposure. Glass-fibre reinforcement does not eliminate the UV degradation route of SAN; outdoor service requires an opaque coating or a UV-stabilised variant. Where these thermal, chemical, and environmental bounds are acceptable, GP2305A offers lower density and lower moisture sensitivity than glass-filled polyamide and polyester alternatives; where temperatures exceed the SAN matrix limit, the part should be converted to PBT GF30, PA66 GF30, or PPS GF30 depending on the chemical environment.