KIBISAN SAN PN-106 is a transparent, non-rubber-modified styrene-acrylonitrile random copolymer supplied by Chi Mei Corporation as cylindrical pellets. The styrene-acrylonitrile matrix retains optical clarity and surface hardness while offering better resistance than crystal polystyrene to aliphatic hydrocarbons, vegetable oils, and aqueous detergent solutions. The acrylonitrile comonomer content of general-purpose SAN resins typically falls between 20 wt% and 30 wt%; this polar comonomer raises the glass transition temperature and improves resistance to environmental stress cracking relative to polystyrene, but it also increases hygroscopicity compared with acrylonitrile-free aromatic vinyl polymers. Published data for the exact comonomer sequence distribution in PN-106 are limited; however, the grade is classified as a medium-flow injection moulding resin with melt flow rate measured under ASTM D1238 at 200 °C/5 kg reported at 6 g/10 min in manufacturer technical literature. Specific gravity is 1.06 g/cm³ per ASTM D792. Because no polybutadiene rubber phase is present, the product shows lower notched impact strength than medium-impact ABS; notched Izod values under ASTM D256 are typically below 2 kJ/m² at 23 °C. This property profile directs PN-106 toward transparent cosmetic packaging, clear appliance lenses, household articles, audio equipment windows, and precision stationery components where gloss, dimensional stability, and chemical stress-crack resistance are more important than impact toughness.

What Drying, Melt-Temperature, and Residence-Time Limits Control Moulding Quality?

Moisture removal is the first production bottleneck. SAN resins absorb atmospheric moisture, and melt-phase hydrolysis or volatilisation produces silver streaks and surface splay that cannot be removed by mould-temperature adjustment alone. Desiccant drying at 80 °C for 2–4 hours to a dew point below -30 °C is specified for KIBISAN SAN PN-106. The target moisture content is below 0.1 wt%; higher moisture content creates optical defects and may reduce molecular weight during plastication. Pellets should not remain in the drying hopper for more than 24 hours at 80 °C, because prolonged thermal exposure can increase yellowing. In production-scale machines, barrel temperature set points are established from feed throat to nozzle at 180–210 °C, 200–220 °C, 210–230 °C, and 200–220 °C for a general-purpose screw with L/D ratio 20:1 to 24:1 and compression ratio 2.2:1 to 2.8:1. Melt temperature measured by an air-shot probe should remain between 200 °C and 240 °C; sustained melt temperature above 250 °C can initiate acrylonitrile cyclization and chain scission, resulting in yellowing, free monomer generation, and reduced tensile strength. Back pressure is limited to 0.5–1.5 MPa, and screw rotation speed is normally set between 60 rpm and 120 rpm depending on screw diameter; excessive shear heating from high back pressure or screw speed contributes to gate blush and material degradation. Mould temperature should be maintained at 40–80 °C, with the upper region used for high-gloss surfaces and thin sections. A cavity-pressure study during start-up establishes the packing-pressure profile; holding pressure is commonly 60–80 % of peak injection pressure, and packing time is set at gate-seal time plus 0.5–1.0 seconds to minimise sink marks and warpage.

Regrind reincorporation is constrained by optical quality. Transparent mouldings should normally be produced from virgin pellet; however, 10–20 wt% of clean, dry, same-grade regrind may be acceptable in coloured or non-optical components if fines are below 0.5 wt% and contamination with ABS or polycarbonate is excluded. Contamination with polycarbonate at even 1–2 wt% can produce visible delamination and haze because of viscosity mismatch and interfacial tension. Hot-runner processing is permissible, but manifold and nozzle temperatures must stay within the melt-temperature window; internal hot-runner volumes should be purged when changing colour or shutting down. The first 20–30 shots after start-up should be inspected for black specks, splay, flow marks, and gate blush before high-volume production is authorised. Mould clamp force should be calculated from projected area; for SAN grades of this flow class, a first approximation is 30–50 MPa of projected area for thin-wall parts with wall thickness below 2 mm. Mould shrinkage is typically 0.4–0.7 % along flow and 0.5–0.8 % transverse to flow; the exact value depends on gate geometry, packing pressure, wall thickness, and mould temperature. Initial tool cut using 0.5 % shrinkage should be adjusted after first-article dimensional audit under ISO 294-4.

Property Benchmarks Against Crystal Polystyrene and Medium-Impact ABS

The grade is frequently evaluated as a replacement for crystal polystyrene when chemical stress-crack resistance must improve, or as a transparent alternative when ABS impact strength is not required. The following table shows representative property envelopes for unfilled, non-rubber-modified SAN, crystal polystyrene, and medium-impact ABS. The values are not a substitute for the current Chi Mei product datasheet; they are compiled from public technical literature and standard test methods.

Optical performance is measured on injection-compression moulded plaques because surface finish and stress affect transmitted light. Luminous transmittance for SAN grades in this class is typically 88–90 % at 3 mm thickness under ASTM D1003; haze is generally below 2 % for well-polished mould surfaces but can increase to 5–10 % if mould texture or internal voiding is present. Gloss retention after abrasion is better than crystal polystyrene but lower than polymethyl methacrylate; abrasion testing under ASTM D4060 with CS-10 wheels and 500 g load is used to compare candidate materials. For cosmetic packaging, the material is often selected for clarity after contact with emollients and alcohol-water mixtures; however, fragrance oils containing terpenes or high aromatic content can induce stress cracking. Compatibility testing of the final formulation on moulded containers under load is mandatory. The absence of rubber particles also means that the grade exhibits lower moulded-in colour shift during regrind than ABS, but multiple heat histories can still raise yellowness index by more than 1 ΔYI after three moulding cycles. Published data for PN-106-specific optical fatigue under UV exposure are limited; external UV stabilisation is required for outdoor use because unmodified SAN yellows and embrittles after prolonged solar exposure. For indoor lighting applications, UV-stabilised grades or coatings should be specified; the general-purpose PN-106 is not formulated for continuous outdoor weathering.

The absence of a polybutadiene disperse phase is the defining morphological difference between KIBISAN SAN PN-106 and ABS. In ABS, rubber particles with diameters typically between 0.1 µm and 2.0 µm cavitate or initiate shear yielding under impact, leading to notched Izod values above 15 kJ/m² at room temperature. PN-106, lacking that phase, behaves as a brittle glassy polymer under high-rate impact and should not be used for snap-fit closures or load-bearing structural parts without impact testing under ISO 179-1 or ASTM D256. Compared with crystal polystyrene, the acrylonitrile comonomer increases intermolecular polar interactions, producing higher tensile strength and better resistance to aliphatic hydrocarbon stress cracking. This difference is measurable by tensile strength at yield: SAN grades in this class report 68–72 MPa under ASTM D638-14, whereas crystal polystyrene typically reports 45–55 MPa. Flexural modulus is also higher, in the range 3500–3700 MPa for SAN versus 2800–3300 MPa for crystal polystyrene. The trade-off is processability: the polar comonomer increases melt viscosity and requires more careful moisture control. The product also exhibits higher yellowness index than optical-grade methacrylate polymers; polymethyl methacrylate may be selected when light transmittance above 92 % and surface hardness are paramount, but PMMA has lower chemical resistance to some cosmetic solvents and lower impact strength than SAN in many practical mouldings. Published PN-106-specific comparisons to PMMA haze and colour shift are limited; instrumented colour and transmission tests under ASTM D1003 and ASTM E313 should be performed on moulded plaques before final specification.

When Chemical Resistance and Dimensional Stability Become the Dominant Specification Drivers

KIBISAN SAN PN-106 is specified for components that contact cosmetic emulsions, soap solutions, and household detergents at room temperature. The resin is not a barrier polymer; oxygen and water vapour transmission rates are higher than those of polyethylene terephthalate or oriented polypropylene, and the material should not be used for oxygen-sensitive packaging requiring an oxygen transmission rate below 1 cm³/(m²·day·atm). It is also not suitable for continuous service with aromatic hydrocarbons, ketones, esters, or halogenated solvents; these agents can swell or stress-crack the moulded part. Chemical compatibility should be evaluated under ISO 175 or ASTM D543 on stressed plaques, not solely by unstressed immersion. Dimensional stability is governed by moulded-in orientation and moisture uptake. Conditioning at 23 °C/50 % RH for 48 hours is standard before mechanical testing. The coefficient of linear thermal expansion for unfilled SAN in this class is approximately 70–80 × 10⁻⁶ K⁻¹ per ISO 11359-2, lower than polypropylene and polyethylene but higher than glass-filled engineering resins. Continuous use under load should be limited to temperatures below 85 °C; heat deflection temperature under 1.82 MPa is reported in the range 85–90 °C for the grade. For food-contact articles, compliance is not automatic and must be verified lot-by-lot. SAN copolymers may be evaluated under FDA 21 CFR 177.1040 for repeated-use articles and under Commission Regulation (EU) No 10/2011 for overall and specific migration limits. The grade is generally supplied with REACH product stewardship documentation and is not formulated with halogenated flame retardants; therefore, it does not meet UL 94 V-0 at 1.6 mm or 3.2 mm without external flame-retardant modification. Electrical applications require independent testing under IEC 60243-1 for dielectric strength and IEC 62631-3-1 for volume resistivity because PN-106-specific published dielectric data are limited. The material should not be used as primary electrical insulation without component qualification at the intended operating temperature and field strength.

Production-scale failure modes associated with KIBISAN SAN PN-106 mirror those of other transparent SAN grades. Silver streaks and surface splay indicate inadequate drying or gas entrapment; the corrective action is to verify dew point and drying time rather than to increase melt temperature. Gate blush and localised yellowing at the gate suggest excessive melt temperature or shear heating; reducing back pressure and screw speed usually resolves the defect more effectively than raising mould temperature. Weld lines in transparent parts are visible as slight optical discontinuities and are minimised by relocating the gate or increasing mould and melt temperature within the safe window. Sink marks and warpage arise from insufficient packing; a cavity-pressure study should be used to set holding pressure and time. Black specks can originate from degraded material lodged in dead spots, hot-runner channels, or check-ring assemblies; purging with a commercial SAN-compatible purging compound and inspecting non-return valve clearances are required. Batch-to-batch variation in melt flow rate should be monitored by a 4-point melt-flow sampling routine per shift under ASTM D1238; shifts greater than ±15 % from the nominal value can indicate raw-material lot variation or contaminant introduction. In-line colour measurement of moulded plaques at D65/10° should be performed when transparent articles must meet tight yellowness limits; published tolerances for PN-106 colour are limited and should be agreed with the supplier before production. The grade is not recommended for processes requiring long melt residence times above 15 minutes, such as large accumulator-head blow moulding or very large injection shots with oversized barrels, unless the melt-temperature upper limit is strictly controlled.