Chimei KIBISAN SAN PN-117C is a styrene-acrylonitrile random copolymer supplied in pellet form for injection moulding. The resin belongs to the KIBISAN SAN family produced by Chi Mei Corporation. The acrylonitrile comonomer, typically present in commercial transparent SAN at 24–30 wt%, confers resistance to aliphatic hydrocarbons, oils, and dilute aqueous chemicals while retaining an amorphous, rigid, transparent solid. Published grade-specific data for this specific configuration is limited; therefore, preliminary engineering should use the class-typical ranges below and replace them with the manufacturer’s certificate of analysis before tool design. The grade is positioned for transparent rigid parts requiring better chemical resistance and dimensional stability than general-purpose polystyrene, but where opaque impact-modified materials such as ABS are unnecessary.

The grade is classified as a styrene-acrylonitrile copolymer according to ISO 1043-1. The resin is amorphous; it has no crystalline melting point, and solidification is determined by the glass transition temperature rather than a crystallization exotherm. Thermal analysis of commercial SAN typically shows a glass transition in the range 100–110°C, although the exact value depends on acrylonitrile content and measurement rate by differential scanning calorimetry. The material has a density of approximately 1.06–1.08 g/cm³ and a melt viscosity that is shear thinning; both attributes influence part weight control and injection pressure requirements.

In the absence of a polybutadiene rubber phase, PN-117C and similar SAN grades exhibit lower notched impact strength than ABS but higher tensile and flexural modulus. The material is suitable for parts that are not subjected to repeated impact or extreme cold-temperature loading. Snap-fit features and threaded inserts require generous radius design because the polymer is more brittle than standard-impact ABS. Compared with poly(methyl methacrylate), SAN has lower melt viscosity and better resistance to aliphatic hydrocarbons, but lower light transmission and lower surface hardness. Compared with polycarbonate, SAN has lower impact strength and lower continuous-service temperature, but better melt processability and lower material cost.

The values in the following table are representative of transparent SAN injection moulding grades, not a PN-117C specification. They are provided as preliminary design guidance and must be superseded by the supplier’s certificate of analysis.

What separates PN-117C from unmodified polystyrene and opaque ABS grades?

The primary molecular difference is the acrylonitrile comonomer. In unmodified polystyrene the pendant phenyl group creates a relatively nonpolar chain with a glass transition near 100°C and limited resistance to vegetable oils and aliphatic solvents. In SAN the nitrile group raises intermolecular cohesion and the glass transition to approximately 100–110°C, while improving stress-crack resistance. Opaque ABS contains a discrete butadiene rubber phase that absorbs impact energy; this phase eliminates transparency and lowers tensile modulus to approximately 2.0–2.6 GPa. PN-117C therefore retains transparency and rigidity with improved chemical resistance relative to GPPS, but it does not provide the low-temperature impact performance of ABS.

Within the KIBISAN SAN family, grade selection is primarily influenced by melt flow and heat resistance. A higher-flow SAN is used for thin-wall or long flow-path parts, while a higher-heat SAN is used where short-term exposure to hot aqueous solutions or adjacent metal inserts occurs. PN-117C is generally presented as a general-purpose injection moulding grade; converters should not substitute grades without verifying melt-flow condition and heat deflection limits. Single-point melt flow rate is not a substitute for a viscosity curve. Values reported at 220°C / 10 kg and 200°C / 5 kg are not directly interchangeable, and melt flow rate alone does not capture shear-thinning or gate freeze-off behaviour. Grade-specific spiral-flow data are preferred for long thin-wall tools.

Light transmission through a 3 mm plaque is commonly 88–91% when measured by ISO 13468 or ASTM D1003. Haze below 1.5% is achievable with polished cavity surfaces, but hot-runner dead spots, mould release contamination, and moisture-induced splay can increase haze locally. Chemical resistance should be validated by immersion testing under ASTM D543 or ISO 22088 using the actual stress state and exposure time. Short-term contact with mineral oil, white spirit, and dilute acids is generally acceptable for SAN; ketones, esters, ethers, and aromatic hydrocarbons can attack the matrix. Alcohols and some surfactant-based cleaners may induce environmental stress cracking when parts are under continuous tensile stress.

When the melt is processed above 240°C, residence time becomes the critical variable

The melt-temperature window for SAN injection moulding is 200–240°C. Barrel set points are typically flat or mildly increasing from rear to nozzle: rear 180–200°C, middle 200–220°C, front 210–230°C, nozzle 220–240°C. Measured melt temperature should not exceed 240°C for more than 5 minutes cumulative residence time. Prolonged exposure at higher temperatures causes thermal degradation visible as yellowing, reduced melt viscosity, and surface splay from decomposition volatiles. Barrels should be purged with GPPS or a commercial styrenic purge compound before shutdown; prolonged idle at high barrel settings may require barrel cooling to 180°C.

Production-scale equipment behaviour is sensitive to shear history. On machines below 120 tons clamp force, small pin gates below 0.8 mm have produced jetting and surface haze in transparent SAN parts; increasing gate diameter to 1.0 mm or reducing injection velocity commonly resolves the defect. Screws with compression ratio 2.5:1 to 3.5:1 and free-flowing nonreturn valves are used for styrenics. Low-shear metering screw geometry is preferred for optical parts because it reduces frictional heating and melt-temperature variation. Hot-runner systems should be externally heated and fully open-gated; insulated runner tips can create stagnant zones that degrade into yellow specks. Valve-gated hot runners improve gate vestige control but raise shear heating, and temperature controllers should be tuned to prevent overshoot above the setpoint.

Fill speed is set to achieve a cavity pressure of 80–120 MPa. Excessively high injection velocity at small gates may exceed the critical shear rate and produce jetting or gate blush. Hold pressure is typically 50–80% of injection pressure. Mould temperature is held at 45–65°C; higher values improve surface gloss and reduce moulded-in stress, while temperatures below 40°C can generate flow marks and increase warpage. Venting is critical in transparent SAN parts to avoid gas marks. Vent depths of 0.02–0.05 mm and land lengths below 1.0 mm are typical for SAN. In blind features, ejector-pin vents or porous metal inserts may be required.

Predrying in a desiccant dryer at 80°C for 2–4 hours is required when pellets have been stored in conditions above 60% relative humidity. The target residual moisture is below 0.02%. A hopper-mounted dry-air system with dew point below -30°C is used where intermittent operation causes long hopper residence times. If splay appears despite drying, the source is usually gas entrapment at blind ribs or overheating in the compression zone; raising back pressure to 5–10 bar and reducing screw speed may eliminate melt discontinuities. Regrind from sprues and runners can be incorporated at up to 20 wt% in non-critical parts; optical parts often use 100% virgin pellets to maintain haze and yellowness index. Repeated recycling increases yellowness index and decreases notched impact strength because of chain scission.

Dimensional stability limits and chemical exposure boundaries

Mould shrinkage for SAN injection grades is typically 0.4–0.7% in the flow direction and slightly lower across flow. Coefficient of linear thermal expansion is approximately 6–8 × 10⁻⁵ K⁻¹, lower than common polyolefins but higher than glass-reinforced materials. Post-mould dimensional movement is governed by residual stress and thermal/chemical exposure. Annealing at 70–80°C for 2–4 hours can reduce asymmetrical stress relaxation but adds cost. Dimensional tolerances for unfilled SAN are sensitive to flow orientation, wall thickness variation, and gate location; tool compensation should be based on measured shrinkage on a production-representative machine, not on laboratory plaques alone.

Heat deflection temperature under 1.80 MPa for general-purpose SAN is commonly 83–94°C by ISO 75-2. Continuous load-bearing service above approximately 80°C is not recommended because creep modulus declines and moulded-in stress relaxes asymmetrically. Vicat softening temperature by ISO 306 is approximately 98–108°C; Vicat values do not define load-bearing temperature limits. For applications with short-term steam exposure or hot-water contact, the part must be evaluated under the actual stress and exposure cycle.

Chemical exposure must be assessed under actual load. SAN resists dilute acids, bases, alcohols, aliphatic hydrocarbons, and greases. It is attacked by concentrated oxidizing acids, ketones, esters, ethers, and some chlorinated solvents. Environmental stress cracking is possible with certain surfactants and plasticizers; components under continuous tensile stress should be tested with the production cleaning or sterilization regimen. Test reports should state the method, strain level, and exposure time when reporting environmental stress cracking results. Ultraviolet exposure can cause yellowing and surface microcracking unless a stabilised formulation is specified; standard SAN grades are not recommended for long-term exterior weathering without protective coating or UV stabilisation.

Compliance boundaries are article-level determinations. The polymer as supplied is not a finished food-contact article. REACH registration obligations apply to monomers and additives even where the polymer itself is exempt. RoHS 2011/65/EU applies to the finished electrical or electronic product. Food-contact suitability must be confirmed under EU Regulation (EU) No 10/2011 and the applicable FDA 21 CFR section for the specific article and migration conditions. Flammability classification, such as UL 94, is thickness- and color-dependent and must be obtained from the supplier for the exact formulation. The material is not inherently antistatic; surface static charging can attract dust on optical parts, and antistatic additives may reduce transparency.

Applications reported for transparent SAN injection grades include cosmetic packaging, appliance indicator lenses, water filter housings, battery cases, and laboratory ware. These applications use the balance of clarity, chemical resistance, and dimensional stability. For impact-dominated parts at low temperature or for autoclave-resistant components above 120°C, opaque ABS or polycarbonate grades are evaluated instead. High-gloss parts are produced with polished mould surfaces and valve-gated hot runners; direct sprue gating can produce visible gate vestige and increased local stress. Optical-quality parts require clean-room handling of pellets and closed conveying systems to prevent dust contamination.