The short answer
ABS is stiffer, stronger, holds tighter tolerances and takes paint, glue and plating, so it suits housings and appearance parts. Polypropylene is lighter, cheaper, far more chemical resistant and makes living hinges, so it suits containers, caps, chemical-contact and cost-driven parts.
PP and ABS are two of the most common injection molding resins, and buyers often weigh one against the other on cost. They behave very differently in the mold and in service, so a straight swap rarely works without checking the part.
Side by side
| Property | Polypropylene (PP) | ABS |
|---|---|---|
| Structure | Semi-crystalline polyolefin | Amorphous styrenic (rubber-toughened) |
| Density | ~0.90–0.91 g/cm³ | ~1.03–1.06 g/cm³ |
| Tensile strength | ~25–38 MPa | ~38–50 MPa |
| Flexural modulus | ~1.0–1.8 GPa | ~2.0–2.6 GPa |
| Impact strength | Low (homopolymer) to high (impact copolymer) | High |
| Heat deflection, 1.8 MPa | ~50–65°C | ~80–100°C |
| Chemical resistance | Excellent: acids, bases, alcohols, many solvents | Fair: ketones, esters and some aromatics attack it |
| Mold shrinkage | ~1.0–2.5% | ~0.4–0.7% |
| Drying | Not needed | Needed |
| Surface | Waxy; hard to paint or glue without treatment | Glossy; paints, glues and plates well |
| Living hinges | Excellent | Not suitable |
| Relative cost | Lower | Higher |
Typical ranges for unfilled general-purpose grades; individual grades vary. Filled grades change the picture: glass-filled PP is much stiffer than unfilled PP.
Choose PP when
- The part touches acids, bases, alcohols or detergents
- It needs a living hinge or snap-fit flexibility
- Weight and cost matter most
- Containers, caps, closures, battery cases, automotive under-hood parts
Choose ABS when
- The part needs stiffness and a glossy, durable finish
- It will be painted, glued, plated or ultrasonically welded
- Tight tolerances and low warp matter
- Housings, enclosures, consumer products, interior trim
Switching between PP and ABS
- Check the mold: the shrinkage difference is large, so plan on resizing the cavity.
- Check stiffness: unfilled PP flexes more; ribs, thicker walls or a filled grade may be needed.
- Check heat: PP softens sooner under load.
- Check decoration and assembly: PP needs surface treatment for paint, printing and adhesives.
- Check cold impact: PP homopolymer turns brittle in the cold; impact copolymer is the usual choice for cold service.
- Trial first and measure parts after they have fully cooled.
See also PP homopolymer vs. impact copolymer, glass-filled PP vs. nylon and the shrinkage calculator in our molding calculators.
Grades we source
We source polypropylene (homopolymer, impact and random copolymer, filled grades) and ABS for injection molding and extrusion, from one gaylord up, with a COA on every lot, tested to ASTM or ISO methods. See polypropylene and ABS.
Common questions
Is polypropylene stronger than ABS?
No. ABS is stronger and stiffer than unfilled polypropylene and holds its shape better under load. Polypropylene wins on chemical resistance, fatigue (living hinges), low weight and cost. Glass-filled PP can match or beat ABS in stiffness.
Which is cheaper, PP or ABS?
Polypropylene is usually cheaper per pound, and because it is about 13% lighter, a part uses fewer pounds of resin for the same volume.
Can PP replace ABS?
Sometimes, as a cost-down, when the part does not need ABS's stiffness, gloss, paintability or tight tolerances. Check stiffness, heat, finish and how the part is assembled or decorated first.
Can I run PP in an ABS mold?
Usually not without changes. PP shrinks about 1.0–2.5% while ABS shrinks about 0.4–0.7%, so parts come out smaller and may warp. Most switches need a resized or new cavity.
Which is better for painting and gluing?
ABS. It paints, glues and plates easily. Polypropylene has a low-energy, waxy surface that needs flame, plasma or primer treatment before paint or adhesives will hold.
Which has better chemical resistance?
Polypropylene. It resists most acids, bases, alcohols and many solvents. ABS is attacked by ketones, esters and some aromatic solvents, and can stress-crack with some oils and cleaners.
Tell us the grade you run now
A polymer chemist reviews every request, then matches your grade or finds a qualified equivalent and prices it.
What to send for an accurate quote
- The grade name, from any supplier, or a data sheet
- Color (natural, black or a custom match)
- Fill type and percentage, if any
- Melt flow, if you know it
- Quantity for this order and what you use in a year
- Ship-to city and state or province