ABS Injection Moulding: Properties, Uses & Design Guide
ABS (Acrylonitrile Butadiene Styrene) is the workhorse engineering thermoplastic of injection moulding. It combines rigid stiffness with solid impact resistance, processes across a broad temperature window, and accepts almost any surface finish. For product housings, enclosures, and structural consumer goods it is usually the first material to put on the shortlist.
What are the mechanical and thermal properties of ABS?
ABS is a two-phase polymer: a rigid SAN (styrene-acrylonitrile) matrix reinforced by dispersed butadiene rubber particles. The rubber phase absorbs impact energy; the SAN matrix provides stiffness and surface quality. This structure gives ABS all-round, predictable performance that neither PP nor PS can match at the same price point.
| Property | Typical Value | Test Standard |
|---|---|---|
| Tensile Strength | 40–50 MPa | ISO 527 |
| Flexural Modulus | 2,000–2,700 MPa | ISO 178 |
| Izod Impact (notched) | 200–400 J/m | ISO 180 |
| Rockwell Hardness | R100–115 | ASTM D785 |
| Heat Deflection Temp (0.45 MPa) | 88–100°C | ISO 75 |
| Vicat Softening Point | 95–110°C | ISO 306 |
| Density | 1.02–1.06 g/cm³ | ISO 1183 |
| Mould Shrinkage | 0.4–0.7% | ISO 294-4 |
| Water Absorption (24 h) | 0.2–0.4% | ISO 62 |
HDT varies significantly by grade. High-heat ABS grades produced by blending with maleic anhydride copolymers can push HDT to 110°C; standard commodity grades sit at the lower end of the range.
Where is ABS injection moulding used?
ABS is the default when no extreme requirement — high temperature, chemical exposure, or optical clarity — rules it out. Its processability, finishing options, and cost make it the rational starting point for most opaque housings and structural consumer goods.
Consumer electronics: Laptop casings, keyboard keycaps, remote control shells, and printer bodies. ABS delivers the dimensional accuracy needed for snap-fit assemblies and the surface quality needed for painted or textured aesthetics.
Automotive interior trim: Dashboard panels, pillar covers, door pockets, and bezel components. Automotive grades commonly include flame retardants or UV stabilisers.
Medical device housings: Diagnostic equipment enclosures, monitor bezels, and trolley shells. Medical-grade ABS can be formulated to meet ISO 10993 biocompatibility requirements — confirm grade-specific data at DFM.
Power tool bodies and industrial enclosures: ABS handles the combination of rigidity and impact resistance well for hand-held tools. UL 94 V-0 flame-retardant grades are available for electrical enclosures.
Toys and consumer goods: LEGO bricks are the canonical example — ABS's tight dimensional tolerances and paint adhesion make it the obvious choice for high-precision, high-cosmetic-quality consumer goods.
What are the moulding characteristics of ABS?
ABS is forgiving to process. Relative to nylon or PC it is tolerant of moisture variation and has a wide processing window, which reduces startup scrap and keeps cycle times predictable.
Melt temperature: 220–270°C. Higher-flow grades process at the lower end; high-heat grades require the upper end.
Mould temperature: 40–80°C. Higher mould temperatures improve surface gloss and reduce internal stress; lower temperatures speed cycle time. For high-gloss parts, 60–80°C is the practical target.
Injection pressure: 50–150 MPa. ABS is shear-sensitive at high injection rates; gradual fill profiles reduce jetting and weld-line weakness.
Drying: 2–4 hours at 80°C in a dehumidifying dryer before processing. Inadequate drying causes surface splay, silver streaks, and reduced impact strength. ABS is more moisture-tolerant than nylon or PC, but drying is still non-negotiable for cosmetic parts.
Shrinkage: 0.4–0.7%. Flow-direction shrinkage is marginally lower than transverse shrinkage — this anisotropy must be accounted for in asymmetric parts.
Draft angles: Minimum 1° on unpainted surfaces; 2–3° on textured surfaces to avoid drag marks during ejection.
Sink and warp: ABS warps less than PP due to lower shrinkage. Sink marks appear at walls thicker than 4 mm or at rib-to-wall junctions where the rib thickness exceeds 60% of nominal wall.
Which ABS grades and variants should you consider?
ABS grade selection should be driven by the application's dominant requirement — not defaulted to the cheapest commodity option.
| Grade / Variant | Key Modification | Typical Use |
|---|---|---|
| Standard ABS | Baseline | General housings, enclosures |
| High-impact ABS | Higher rubber content | Handles, brackets |
| High-heat ABS | SAN copolymer blend | Automotive, appliances |
| Flame-retardant ABS (V-0) | Halogenated or halogen-free FR | Electrical enclosures |
| UV-stabilised ABS | Hindered amine + UV absorbers | Outdoor / signage |
| Medical-grade ABS | Low extractables, ISO 10993 | Medical device shells |
| ABS + PC blend | PC matrix | High-impact, elevated temp |
| ABS + GF (10–30%) | Glass fibre | Structural, dimensional stability |
Glass-filled ABS offers a substantial stiffness increase (flexural modulus up to 6,000 MPa at 30% GF) but degrades surface finish. Where aesthetics matter, a standard unfilled grade is preferable.
ABS advantages and limitations
Advantages:
- All-round balance of stiffness, impact resistance, and processability — few materials match the combination at this price
- Low shrinkage and good dimensional stability
- Accepts painting, electroplating, chrome, and UV-curing lacquers
- Wide grade range covering heat, flame, and UV requirements
- Lower processing temperatures and pressures than PC reduce tooling wear and cycle energy
Limitations:
- Moderate chemical resistance — acetone, MEK, and esters attack it aggressively
- Poor UV stability in standard grades; yellows outdoors within months
- Not suitable for continuous service above 90°C in standard grades
- Lower stiffness than PC or POM for precision mechanical parts
- Not intrinsically food-safe; specific food-contact grades required
When to choose ABS over alternatives
ABS vs PP: Choose ABS when tighter tolerances, better surface quality, or snap-fit stiffness are required. PP is preferred for chemical resistance, living hinges, or where cost per kilogram is the main driver.
ABS vs PC: Choose ABS when optical transparency or service above 90°C is not needed. PC costs more per kilogram and is harder to process; ABS is the standard default for opaque housings.
ABS vs POM: Use ABS for housings and aesthetic parts. Use POM for precision sliding contact, high fatigue life, or low-friction requirements.
ABS vs ASA: For parts exposed to direct sunlight or outdoor weathering, ASA is the direct weatherable alternative — near-identical processing, almost identical mechanical properties, substantially better UV stability.
Is ABS recyclable?
ABS carries resin code 7 (Other) and is not widely collected in municipal streams. Mechanically recycled ABS is commercially available and used in automotive and electronics sectors, typically blended with virgin resin to maintain impact performance. Halogenated FR grades have more restricted recycling pathways; halogen-free FR grades are preferable where end-of-life recyclability is a product requirement.
Frequently asked questions
What is the shrinkage rate of ABS in injection moulding?
ABS typically shrinks 0.4–0.7% during injection moulding. This is lower than PP and more predictable than PC, making it reliable for dimensionally critical housings. Nordmould accounts for exact shrinkage in tool design based on the specific grade selected.
What wall thickness should I use for ABS injection moulding?
A wall thickness of 1.5–3.5 mm is recommended. Walls thinner than 1.2 mm risk incomplete fill; walls thicker than 4 mm increase the risk of sink marks and voids. Wall thickness is reviewed during the free DFM process.
Can ABS be used for outdoor parts?
Standard ABS has limited UV resistance and will yellow or embrittle with prolonged outdoor exposure. For outdoor use, UV-stabilised ABS grades or a switch to ASA — the direct weatherable alternative — is advisable. Nordmould can source UV-stabilised grades on request.
What surface finishes are possible with ABS?
ABS accepts matt, glossy, and textured finishes well. It paints, chrome-plates, and electroplates readily, making it a common choice for consumer products requiring decorative surfaces. High-gloss finishes require polished steel tooling.
Is ABS food-safe for injection moulding?
Standard ABS is not certified food-safe. Food-contact applications require specific FDA- or EU-regulation-compliant grades. Confirm material compliance during the DFM review stage.
How does ABS compare to PC/ABS blends?
PC/ABS blends offer higher impact strength and heat resistance than pure ABS, at higher material cost. Plain ABS is sufficient for most general-purpose housings and is easier to process. Nordmould can advise on whether a blend is warranted for your application.
What is the minimum order quantity for ABS parts at Nordmould?
Nordmould's minimum order quantity is 100 pieces, applicable to all standard materials including ABS. Tooling starts from €3,000, with aluminium bridge tooling available for low-to-mid volume runs.
Send your STEP file to Nordmould for a free DFM review and written quote — typically returned within one business day.