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ASA

Acrilonitrilo Estireno Acrilato-Nitrilo

ASA·Polystyrenes·Amorphous

ASA (Acrylonitrile-Styrene-Acrylate) is basically "the ABS that survives the sun" — same terpolymer structure but with the butadiene elastomer phase replaced by ethyl-butyl acrylate, the component that gives it its superpower: native UV resistance that maintains color, stiffness and impact for years outdoors. You know it by brands like Luran S (BASF / INEOS Styrolution, global leader), Geloy (SABIC), Centrex (DSM, the original). Application #1: automotive exterior parts — radiator grilles, mirror housings, drip rails, roof antennas, front splitters, all those matte black components you see in the sun.

The trick is chemistry: ABS's polybutadiene has C=C double bonds that UV attacks → yellowing and embrittlement in 12–18 months in the sun. ASA's polyacrylate is a saturated ester with no vulnerable double bonds → retains >90% impact after 2000 hours of Xenon arc (~3-4 years of real sun), vs ABS that loses 40–60%. Here we have compiled the reference ranges from the PDS, plus the questions that come up over and over on the shop floor: ASA vs ABS for outdoor, ASA-PC blends, drying, signage/furniture, FDM 3D printing.

Share your experience in the comments — ranges vary by manufacturer and grade, and collective discussion is what gets us out of trouble on the floor.

The ranges shown in these data tables were compiled by the MVPS team from various parameter sheets and literature, integrating the lower and upper limits for each material type.

This information must be carefully reviewed when developing injection molding processes. Final ranges and processing tolerances are the responsibility of the engineer in charge.

These ranges are not recommended for developing specific process tolerances. MVPS always recommends requesting and consulting the supplier's data sheet.

General Properties

Chemical StructureAmorphous
Specific Gravity (Density)1.12:1
L/D Ratio15 – 22
Compression Ratio1.5 – 3
Tonnage Factor3.86 – 5.41kN/cm²
Thermal Diffusivity0.1442mm²/s
Max Shear Rate20,0001/s
Shrinkage0.4 – 0.7%
Regrind20%
Heat Deflection (HDT) @ 1.82 MPa80°C
Glass Transition (Tg) @ 10°C/min103°C
Vicat Softening @ 50N105°C

Drying

Drying Temperature77 – 82°C
Drying Time3 – 4h
Recommended Moisture0.05%
Recommended Dryer TypeDesiccant
Dew Point-40°C

Temperatures

Melt202 – 229°C
Nozzle210 – 221°C
Front210 – 221°C
Middle191 – 210°C
Rear179 – 202°C
Demolding57 – 91°C
Mold (Cooling)41 – 79°C
Feed Throat35 – 79°C

Processing

Back Pressure3.1 – 14.5bar
Screw Speed40 – 70RPM
Injection SpeedMedium
Barrel Occupancy35 – 75%
Injection Pressure700 – 1,400Pbar
Holding Pressure175 – 1,120Pbar
Cushion6.4 – 12.7mm

Mold

Runner Diameter4.57 – 9.14mm
Gate Diameter1.02 – 2.03mm
Gate Area0.81 – 3.24mm²
Wall Thickness1.19 – 5.08mm

Venting

Depth (Vent Depth)0.0203 – 0.0508mm
Land (Vent Land)0.508 – 1.02mm
Width (Vent / Clearance)3.05 – 5.08mm
Relief (Relief Channel)0.254 – 0.381mm

Frequently asked questions

ASA is an amorphous terpolymer synthesized by copolymerizing acrylonitrile + styrene + acrylate — analogous to ABS but replacing the butadiene (B) component with acrylate (A, typically n-butyl or ethyl-hexyl acrylate). The acrylate elastomer phase is dispersed as small particles in the SAN (styrene-acrylonitrile) matrix, identical to ABS's structure but with a different elastomer. Density ~1.07 g/cm³, transparent only in special grades (most are pigmented opaque).
Problem chemistry: ABS's polybutadiene has unsaturated C=C double bonds in the chain. UV radiation (290–400 nm wavelength) has enough energy to break these bonds, generating free radicals that oxidize the chain → yellowing, embrittlement, white surface chalking. Solution chemistry: ASA's polyacrylate is a saturated ester (–C(=O)–O–R) — no UV-vulnerable double bonds. Testing result: ASA retains >90% impact + delta-E <2 after 2000 h Xenon arc; ABS loses 40–60% impact + delta-E >8 (visibly yellow). UV-stabilized ABS with HALS improves but doesn't match ASA without stabilization.
Automotive exterior: radiator grilles, mirror housings (including electric folding ones), roof drip rails, aerodynamic front splitters, air intake ducts, shark-fin antennas, emblems, bumper trims. Outdoor furniture: quality garden chairs, tables, plastic balustrades. Outdoor signage: light boxes for ads, outdoor advertising displays, letter signs. Outdoor HVAC: split AC outdoor housings, heat pumps. Sports: kayaks, outdoor equipment. FDM 3D printing: outdoor functional parts (drone parts, weather sensors).
Depends on grade and region: (1) Standard outdoor grade (Luran S 778, Geloy XP4034): 5–10 years in temperate climates maintaining >80% properties. (2) Premium grade (Luran S 957, with extra UV): 10–15+ years. (3) Carbon black grade (automotive black): 15–20 years. (4) Extreme climates (Arizona, Australia, Sahara): reduce life expectancy 30–40%. The main degradation is color (increasing delta-E) more than mechanical — impact holds much better than appearance. For 10-year outdoor automotive warranties, OEMs specify Luran S tested to SAE J1960 (Xenon arc) for 2500–5000 hours.
The ASA + Polycarbonate blend (typically 60/40 or 50/50) combines the best of both: from ASA the UV resistance and processability, from PC the higher service temperature (HDT +30°C), better low-temperature impact (–30°C) and higher rigidity. Applications: outdoor electronics housings (electrical boxes, solar controllers), automotive exterior parts seeing impacts (bumpers, splitters), premium structural exterior. Brands: Luran S KR 2861/1 (BASF), Bayblend (Bayer, PC/ABS though also PC/ASA version). More expensive than neat ASA (~20–30%) but much less than neat PC.
Yes, ASA is slightly hygroscopic — absorbs 0.2–0.4% at equilibrium. Without proper drying, you'll see silver streaks on polished surfaces and internal microbubbles. Conditions: desiccant dryer (ideally) or hot air, 80–85°C for 2–4 hours, dew point ≤–20°C, target ≤0.05% moisture before injection. In tropical climate or if material is open >1 day, drying mandatory. Never above 90°C because you can start yellow oxidation on pellet surface.
The PDS marks 41–79°C — similar to ABS. Hot (60–75°C) = better gloss, better mold detail reproduction, less residual stress, longer cycle. Cold (45–55°C) = short cycle and high throughput, but worse surface and more frozen stress. For visible automotive exterior parts (where surface finish and color consistency are critical): 60–75°C ideal, ideally with fine mold polishing + controlled temperature uniformity. For internal or non-cosmetic functional parts: 45–60°C.
Shrinkage 0.4–0.7%, similar to ABS, isotropic (amorphous, no significant directionality). This is an advantage vs semi-crystallines like PP (1.5–3% directional, warps). ASA holds tight tolerances and precise dimensions — key for automotive parts that must fit exactly with the body. Minimal after-shrinkage (~0.1%) if well processed. For large flat parts (grilles, panels): multiple gates, uniform walls, balanced cooling are fundamental.
ASA is the #1 FDM filament for outdoor functional parts: drone bodies, weather sensors, mailboxes, signage, plant tags, outdoor lampshades. Reasons: (1) native UV resistance (vs ABS, PLA, PETG that yellow in the sun), (2) mechanical properties similar to ABS (rigid, tough, post-processable with acetone), (3) printable on standard FDM machines (240–270°C nozzle, 80–100°C bed, enclosed chamber recommended), (4) cosmetic surface finish. Downsides: emits volatile styrene during printing (ventilation needed), warping if bed isn't well adhered. Popular filament brands: Bambu Lab ASA, Polymaker PolyMax ASA, 3DXTech ASA-GF (with glass fiber).
(1) Difficult demolding: ASA has high surface affinity and can stick to the mold — use appropriate silicone release agents or mold surface treatments (hard chrome, PVD). (2) Visible weld lines: because ASA is matte opaque, weld lines are more obvious than in glossy plastics — use fast injection + well-designed venting. (3) Material sensitive to overheating: long residence times above 280°C → yellowish degradation. If you'll stop 15+ min, lower barrel temperature or purge with standard ABS. (4) Mixing with ABS regrind: never use ABS regrind in ASA — you immediately lose the lot's UV resistance. Pure ASA regrind: up to 25% no problem.

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