Chimei KIBISAN SAN PN-107 L125FG is a rigid transparent styrene-acrylonitrile copolymer supplied as natural pellets. The grade belongs to the high-flow segment of the PN-107 series and is intended for injection moulding where a melt volume-flow rate of 12.5 cm³/10 min under ISO 1133-1 at 200°C/5 kg supports rapid filling of multi-cavity and thin-wall tools. The polymer combines the transparency and surface hardness of SAN with better resistance to aliphatic hydrocarbons than general-purpose polystyrene. It is not a toughened grade; the notched impact response is characteristic of unmodified styrene-acrylonitrile copolymers.

The suffix L125FG is a supplier flow-class identifier. FG may appear in commercial documentation as a food-contact associated designation, but regulatory status is not conferred by the grade name alone. Food-contact suitability requires validation of the finished article, including colourants, masterbatch carriers, mould release, and regrind content. A certificate of analysis and supplier regulatory statement are the controlling documents.

Material Identity and Grade Designation

Styrene-co-acrylonitrile resins are statistical copolymers in which the acrylonitrile repeat units raise the glass transition temperature, increase polar solvent resistance, and contribute to the inherent rigidity of the polymer matrix. Public datasheets for the PN-107 series position the material as a high-clarity SAN grade. Typical acrylonitrile contents for high-clarity styrene-acrylonitrile copolymers fall in the 24–28 wt% range, but the exact comonomer ratio for any specific lot is generally treated as proprietary and should not be inferred as a specification limit. The continuous mass polymerisation route used for this product class produces a resin with low residual emulsifier content compared with emulsion SAN grades, which is relevant where low haze and low extractables are required.

The physical profile of the PN-107 L125FG flow class is summarised in the following representative data set. The values are typical publication values for the PN-107 SAN family and should not be read as lot-specific maximum or minimum limits unless stated on the supplier certificate of analysis.

Storage and pre-processing conditions are not part of the specification values but are decisive for surface cosmetics. Pellets exposed to relative humidity above 60% or blended with more than 25% regrind are usually dried at 80°C for 2–4 h in a desiccant dryer with a dew point below -20°C. Residual moisture above 0.1% can produce splay, silver streaks, and localised haze in thick bosses. On production-scale injection lines using hopper loaders with open granulate transfer, moisture uptake in humid geographic regions has been observed to affect part weight consistency when dryers are bypassed; the failure mode is not gross degradation but surface defect formation in high-gloss applications.

What melt-processing limits follow from the L125FG flow designation?

The flow class imposes both opportunities and constraints. Melt temperature should be maintained between 230°C and 250°C; temperatures above 260°C accelerate chain scission and can produce yellowing and plate-out on mould cores. Barrel profiles from rear to nozzle are typically set at 210°C, 220°C, 230°C, 235°C, and 235°C for general-purpose screws with 20:1–25:1 L/D and compression ratios of 2.4:1–2.8:1. Mould temperature is usually held in the 40–70°C range; higher mould temperatures improve knit-line strength and surface gloss but increase cycle time. Injection pressure is normally adjusted to give a fill time of 0.5–2.0 s for thin-wall parts; hold pressure is set by gate-seal studies, often in the range of 60–80 MPa hydraulic pressure on 80–120 tonne toggle-clamp equipment. The use of ISO 294-1 test plaque moulding conditions reduces variability in comparative work but may not reproduce cooling gradients in production parts.

Hot-runner systems should be designed to avoid dead spots and long residence times. At melt temperatures above 250°C, residence time should be limited to less than 5 min when possible. Production-scale trials have shown that colour shift and deposit formation often begin at hot-runner drop tips or at sharp transitions in the manifold, rather than uniformly through the melt stream. The preferred intervention is to reduce manifold temperature and raise shear heating only where flow hesitation is observed, rather than increasing nozzle temperature uniformly. Venting is also material-specific: SAN does not produce the same level of volatile emission as ABS, but insufficient venting can generate surface blemishes when volatile degradation products accumulate at the cavity end.

The high-flow character of L125FG permits shorter injection times, but the low melt elasticity can reduce the tolerance for excessive injection velocity at thick-to-thin transitions. Gate freeze-off must be confirmed for consistent part mass. In multi-cavity tools with eight or more cavities, cavity-to-cavity mass variation should be checked by automatic weighing or statistical process control, because flow imbalance cannot be corrected by raising melt temperature without entering the degradation-sensitive zone.

When PN-107 L125FG is specified for transparent thin-wall packaging

Transparent cosmetic jars, spice closures, food-service articles, and water-filter housings are typical application classes because the grade combines melt flow sufficient for wall thicknesses down to 1.0 mm with acceptable impact behaviour at room temperature. Food-contact status must be confirmed for the finished article under the intended migration testing regime. For EU applications, the material is normally evaluated under Regulation (EU) No 10/2011; overall migration limits of 10 mg/dm² apply to the final article or, for low-volume containers, to equivalent area-to-volume ratios. In the US context, styrene-acrylonitrile copolymers intended for food-contact use are assessed under 21 CFR 181.32 and must be supported by end-use testing for residual acrylonitrile and total non-volatile extractives. For thin-wall snap-fit closures, the low notched impact strength of SAN requires generous radii and live hinges that operate below the yield strain; sharp gates and cold sprue drops can initiate brittle fracture.

The dimensional stability of SAN is useful in threaded closures because the material shows lower creep in warm air than GPPS and better resistance to vegetable oil stress cracking. Moulded threads should be truncated with radii of at least 0.3 mm at the root. High-gloss packaging surfaces are sensitive to mould temperature and packing pressure; gloss reduction is more likely from underpacking than from final mould temperature within the 40–70°C window. For hot-fill or microwaveable applications, the grade is generally not appropriate above 75–85°C under load because of the heat deflection temperature of 98°C at 1.82 MPa. The material should not be specified for direct exposure to boiling water or for repeated steam sterilisation unless the end user has validated the specific part geometry and residual stress level.

Against GPPS, PN-107 L125FG offers higher tensile and flexural strength, improved resistance to aliphatic hydrocarbons, and reduced stress cracking in contact with vegetable oils, but it has a higher melt processing temperature and a narrower operating window. Against transparent ABS, this SAN grade has lower haze and lower density but much lower notched impact strength; ABS should be selected when drop-impact resistance at cold temperatures is dominant. Against PMMA, the SAN grade has better chemical resistance to common cosmetics and better flow at equivalent molecular weight, but lower UV weathering resistance and lower surface scratch resistance. Within the KIBISAN SAN range, the L125FG flow class is used where high-speed injection of multi-cavity closures or thin-wall packaging governs; lower-flow grades are used for thick-wall injection or profile extrusion where melt strength is essential.

Thermal ageing and chemical exposure constrain the service window

Continuous service temperature is not a single material property; it depends on load, environment, and time. The Vicat softening temperature of 104°C under ISO 306/B50 and heat deflection temperature of 98°C under ISO 75-2/A at 1.82 MPa indicate that parts under mechanical load should not be specified for continuous exposure above approximately 75–85°C. Published creep-rupture data for this exact L125FG configuration is limited; long-duration structural parts should be validated by end-user testing under the actual load and thermal profile. In hydrocarbon environments, the resin resists aliphatic solvents, petrol, and many cosmetic esters, but it is attacked by ketones, chlorinated solvents, esters, and concentrated oxidising acids. Stress-cracking behaviour is dependent on moulded-in orientation; parts moulded with high hold pressure and abrupt transitions can show accelerated environmental stress cracking in contact with phthalate plasticisers or vegetable oils at elevated temperature.

The material is normally rated UL 94 HB at thicknesses of 1.5–3.0 mm, but the exact listing is supplier-specific and colour-dependent. Outdoor exposure leads to yellowing and gloss loss; UV-stabilised grades should be specified if exterior use is required. When assembled with gaskets, seals, or labels, compatibility of the adhesive and plasticiser system should be tested under ASTM D543 or an equivalent immersion or contact method. Failure from environmental stress cracking in SAN frequently appears as a delayed craze network at gate areas or sharp corners, not as uniform dissolution. The operational boundary is therefore set not only by chemical class but by local stress concentration, processing orientation, and service temperature.