ENGINEERING MATERIAL

Polypropylene (PP)

A highly versatile and cost-effective thermoplastic known for its exceptional chemical resistance, fatigue resistance, and ability to form integral living hinges.

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Colorful toy car shells, a common application for injection molded Polypropylene

The Champion of Chemical Resistance

Polypropylene is a semi-crystalline thermoplastic belonging to the polyolefin family. It is one of the most widely produced plastics in the world due to its excellent balance of properties and low cost. Its resistance to a wide range of acids, bases, and chemical solvents makes it an indispensable material for containers, lab equipment, and automotive components.

Excellent Fatigue Resistance

PP is famous for its ability to withstand repeated bending and flexing without breaking. This makes it the only material suitable for creating integral "living hinges," such as the lid on a reusable container.

High Chemical Resistance

PP is highly resistant to moisture and a broad spectrum of chemicals at room temperature, making it ideal for fluid containers, chemical tanks, and laboratory ware.

Lightweight & Low Cost

With one of the lowest densities among all commodity plastics, PP provides a lightweight and highly cost-effective solution for a huge range of consumer and industrial products.

Manufacturing with Polypropylene

PP Injection Molding

This is the most common method for processing Polypropylene. Its low melt viscosity allows it to flow easily, filling complex mold cavities. It is the go-to process for producing everything from automotive bumpers and dashboards to food storage containers and bottle caps. We mold various grades, including copolymers for enhanced impact strength and glass-filled grades for higher stiffness.

The housing for a portable power station, a typical injection molded PP application

CNC Machining PP

While its softness can make it more challenging to machine than harder plastics like Delrin or PEEK, PP can be effectively CNC machined to create prototypes and low-volume parts. It is often chosen for machined prototypes when the final part will be molded in PP, allowing for testing with the exact end-use material. Special attention is paid to tooling and feed rates to achieve a good surface finish and avoid melting.

A complex machined part, representing the CNC process for plastics like PP

Polypropylene (PP) FAQ

What is the difference between PP Homopolymer and Copolymer?

PP Homopolymer is stiffer and has a higher strength-to-weight ratio. PP Copolymer is formulated to be softer, with much better impact strength, especially at low temperatures. Copolymer is often used for applications like bumpers that need to absorb energy.

Is it difficult to glue or bond Polypropylene?

Yes, PP has a low surface energy, which makes it very difficult for most common adhesives and glues to form a strong bond. Bonding PP typically requires specialized surface treatments (like flame or plasma treatment) and industrial-grade structural adhesives.

Can Polypropylene be 3D printed?

While PP filaments for FDM 3D printing do exist, they are notoriously difficult to print with due to extreme warping and poor bed adhesion. For 3D printed parts requiring similar properties like chemical resistance and durability, we typically recommend SLS Nylon as a more reliable alternative.