Polypropylene vs. ABS: A Detailed Comparison Guide

Polypropylene (PP) and Acrylonitrile Butadiene Styrene (ABS) are two of the most widely used thermoplastics in modern manufacturing. Both are affordable, recyclable, and work well with CNC machining, injection molding, and industrial 3D printing. Despite their similarities, PP and ABS differ significantly in chemical structure, mechanical properties, and environmental performance. This guide provides a detailed, side-by-side comparison to help you choose the right plastic for your specific application.

What Is Polypropylene (PP)?

Polypropylene (PP) is a semi-crystalline thermoplastic polymer with the chemical formula (C3H6)n, produced through the polymerization of propylene monomers. It is naturally semi-transparent to milky white, depending on its grade and processing. PP has a low density and is highly resistant to acids, bases, and many organic solvents. It offers excellent fatigue resistance, good impact strength, and very low moisture absorption. With a relatively high melting point , PP can withstand intermittent high temperatures without deformation.

Polypropylene (PP) is commercially available in two main types:

• Homopolymer (PP-H): A general-purpose grade made purely from propylene monomers in a semi-crystalline form. It provides higher stiffness and better heat resistance.
• Copolymer (PP-C): Produced by incorporating ethylene comonomers—either as random grades (1–7 % C₂) for clarity and moderate toughness gains, or as impact grades (15–18 % C₂) for maximum toughness and low-temperature performance.

What Is Acrylonitrile Butadiene Styrene (ABS)?

Acrylonitrile Butadiene Styrene (ABS) is an amorphous thermoplastic polymer, typically opaque with an ivory appearance. It is most commonly produced via an emulsification process and is composed of three monomers—acrylonitrile, butadiene, and styrene—each contributing distinct characteristics:

• Acrylonitrile imparts strength, stiffness, and chemical resistance.
• Butadiene adds toughness, impact resistance, and flexibility.
• Styrene enhances rigidity and processability, while giving ABS its glossy surface finish.
  

ABS has no fixed melting point due to its amorphous nature, but it softens at around 105°C (glass transition temperature). Its heat resistance can be improved through the addition of heat-resistant modifiers. ABS offers excellent mechanical strength, impact resistance, and dimensional stability. While it is not naturally transparent, ABS can be easily modified to produce vibrant, colorful parts. It also supports post-processing techniques,such as painting, plating, and adhesive bonding, for a wide range of aesthetic and functional treatments.

What’s the Difference Between PP and ABS?

PP vs. ABS: Composition

PP is a semi-crystalline polymer synthesized from the single monomer propylene (C₃H₆). It offers high stiffness, very low moisture absorption, and excellent chemical resistance. Commercial grades sometimes incorporate up to 5% ethylene comonomer to improve impact strength.

ABS is an amorphous terpolymer consisting of 15–35% acrylonitrile, 5–30% butadiene, and 40–60% styrene. This engineered blend delivers balanced strength, dimensional stability, and a high-quality surface finish, making it highly suitable for applications requiring tight tolerances and a premium appearance.

PP vs. ABS: Properties Comparison Table

The table below compares typical material properties of these two plastics:

PP vs. ABS: Density

PP is notably lightweight; with a density below 1 g/cm³, it is one of the few commercial thermoplastics（along with PE）that are less dense than water. But PP offers higher stiffness, better heat resistance, and excellent fatigue life compared to PE.

ABS has a higher density of 1.03–1.07 g/cm³, which results in heavier parts, increased material usage, and no buoyancy.

PP vs. ABS: Thermal Properties

• Melting Point & Glass Transition Temperature

PP has a melting point of 160–170 °C, which allows it to retain its solid form at relatively high temperatures. This makes PP suitable for applications like boiling sterilization and microwave-safe containers. However, its glass transition temperature (Tg) is around −10 °C, so it may become brittle at temperatures near or below freezing. In contrast, ABS does not have a true melting point. Instead, it gradually softens above its Tg of about 105 °C, and its mechanical properties deteriorate significantly.

• Heat Deflection Temperature (HDT)

HDT reflects a material’s ability to retain shape under load. ABS typically resists deformation up to 95–105 °C, while PP has a lower HDT of around 50–70 °C, depending on crystallinity and formulation. Although PP’s melting point (160–170 °C) is much higher, its lower modulus causes it to deform under load at lower temperatures. In applications without mechanical stress, PP can tolerate short-term temperatures up to ~130 °C, making it suitable for hot-fill packaging and microwave-safe containers.

PP vs. ABS: Mechanical Properties

ABS generally outperforms PP in stiffness and tensile strength, with higher values for tensile strength (40–50 MPa vs. 30–40 MPa) and flexural modulus (1800–2300 MPa vs. 1200–1600 MPa). As a result, ABS is more rigid and better suited for structural applications that require load-bearing capacity and shape retention. While PP is slightly lower in strength, it offers a high strength-to-weight ratio and is often used as a lightweight alternative to heavier engineering plastics.

In terms of impact resistance, ABS performs exceptionally well and maintains toughness at low temperatures down to around −40 °C. In contrast, PP becomes increasingly brittle at temperatures near or below its glass transition temperature of −10 °C.

However, PP stands out in fatigue resistance and repeated flexing; for example, PP living hinges can endure hundreds of open-and-close cycles without breaking. ABS, by contrast, is more prone to cracking when bent repeatedly.

PP vs. ABS: Chemical Properties

PP has excellent chemical stability; it resists most common acids, bases, and a wide range of organic solvents, even under prolonged exposure. This makes PP a safer and more reliable choice for applications such as chemical-reagent containers, outdoor products, and components frequently in contact with grease or oil.

ABS has more limited chemical resistance; it can be attacked or dissolved by certain organic solvents like acetone, methyl ethyl ketone (MEK), and ethyl acetate. But ABS remains stable in most daily environments, such as freshwater, mild acids and bases, and alcohols. So ABS is still suitable for general household, consumer, and electronic applications; it should, however, be kept away from highly corrosive substances.

Another key factor is water absorption. PP is virtually impermeable to water, so its dimensions and mechanical strength remain stable even when submerged. By contrast, ABS is slightly hygroscopic (0.2–0.4% absorption); while modest, prolonged exposure to high-humidity environments may cause minor dimensional changes and slight degradation in electrical performance.

PP vs. ABS: Processability

Both PP and ABS are commonly used in injection molding: ABS has moderate melt viscosity, excellent mold-filling ability, and low shrinkage, making it easy to produce complex, precision parts. PP, by comparison, shrinks more on cooling—if mold design and processing parameters aren’t carefully controlled, parts can warp and lose dimensional accuracy. Because PP’s crystallization is exothermic and it cools quickly, thick-walled sections often crystallize unevenly and distort, so ABS is generally preferred for high-precision components or large, flat panels.

In 3D printing, ABS prints readily in a controlled environment, delivering good dimensional accuracy and strength, whereas PP’s high shrinkage and poor adhesion to standard build platforms make parts prone to warping and detachment.

Both materials can be extrusion-blown into hollow shapes, but PP excels in fiber spinning (e.g., woven sacks, carpet fibers) and thin-film extrusion (such as food-packaging films)—applications beyond ABS’s reach. Conversely, ABS machines well with standard cutting tools, while PP’s high toughness often causes tool deflection, heat buildup, and material sticking, making precision machining more challenging.

PP vs. ABS: Surface Treatment & Aesthetics

ABS offers far greater aesthetic versatility. It supports painting, electroplating, and adhesive bonding with ease, and can achieve a wide range of surface finishes—from matte to high gloss. ABS also accepts pigments well during molding, allowing for consistent coloration and visually appealing parts.

In comparison, PP has a waxy, low-surface-energy texture that resists painting and bonding unless it undergoes surface treatments such as flame, corona, or plasma activation. While PP can be colored during compounding, its surface is not well suited for secondary finishing, limiting its use in applications that require refined appearance or decorative finishes.

PP vs. ABS: Material Cost

PP is a widely produced commodity plastic with a very low unit cost. Among common plastic resins, PP typically costs much as ABS—though this can vary with market fluctuations. This makes PP a highly cost-effective option for large-scale production.

ABS is considered a general-purpose engineering plastic. It offers better overall performance but comes at a higher price. The cost increases further for high-performance grades such as flame-retardant or reinforced ABS, but it remains acceptable for enhanced mechanical or aesthetic performance.

In summary:

Conclusion

PP’s low cost, chemical and moisture resistance, and excellent fatigue life make it ideal for high-volume, flexible-use applications such as packaging, fluid reservoirs, medical disposables, and outdoor products. ABS, with its superior strength and surface-finish quality, is the go-to material for structurally critical or visually demanding parts, including automotive interiors, electronics housings, appliances, and precision-molded components.

At Chiggo, we do more than material comparison. We help you turn material advantages into real-world manufacturing success. With over a decade of CNC plastic machining experience, we provide not just parts, but precision, performance, and partnership. Reach out today to get started!