Polypropylene (PP) is a versatile and cost-effective thermoplastic polymer known for its exceptional chemical resistance, fatigue strength, and low density. Its excellent balance of properties makes it a “workhorse” material in countless industries. While often associated with injection molding, PP is also an excellent candidate for CNC machining, allowing for the rapid production of prototypes, custom one-off parts, and low-volume components with complex geometries that would be costly or impossible to mold. CNC machining PP delivers parts with the material’s inherent benefits, bypassing the need for expensive tooling.
KEY BENEFITS
CNC machining unlocks the full potential of Polypropylene, offering a unique set of advantages for engineered components.
| Benefit | Description |
|---|---|
| Superior Chemical Resistance | Highly resistant to a wide range of acids, alkalis, and solvents, making it ideal for fluid handling and corrosive environments. |
| Excellent Fatigue Resistance | Can be repeatedly flexed without failing, perfect for living hinges, snap-fit closures, and other dynamic components. |
| Low Friction & Good Wear Properties | Provides a smooth, low-coefficient surface suitable for bearings, gears, and wear pads. |
| Lightweight | One of the lightest commercially available plastics, reducing part weight for applications where mass is a critical factor. |
| High Impact Strength | Maintains toughness and ductility even at low temperatures, resisting impact and shock loading. |
| Excellent Moisture Resistance | Acts as an exceptional moisture barrier, absorbing virtually no water, which ensures dimensional stability in humid conditions. |
| Cost-Effective | As a commodity plastic, PP is one of the most economical material choices for both raw material and machining time. |
How PP Compares to Other Plastics:
| Property | PP | ABS | Nylon (PA6) | Acetal (POM) |
|---|---|---|---|---|
| Chemical Resistance | Excellent | Good | Fair | Good |
| Impact Strength | High | High | Very High | Fair |
| Moisture Absorption | Very Low | Low | High | Low |
| Fatigue Resistance | Excellent | Good | Good | Excellent |
| Cost | Low | Low | Medium | Medium |
APPLICATIONS
The unique properties of CNC-machined PP make it the material of choice for a diverse range of applications across multiple industries.
| Industry | Typical CNC Machined PP Parts |
|---|---|
| Chemical Processing | Tank liners, fluid manifolds, valve bodies, pump components, laboratory equipment, and chemical-resistant jigs. |
| Automotive | Washer fluid tanks, battery cases, interior trim clips, low-stress gears, and protective covers. |
| Food & Beverage | Conveyor components, food-grade containers, processing fixtures, and packaging machine parts that require FDA-compliance. |
| Medical & Laboratory | Single-use fluidic connectors, cassette housings, specimen container racks, and non-critical housings that require biocompatibility. |
| General Industrial | Living hinges, low-load bearings, wear strips, electrical insulators, and custom jigs & fixtures. |
| Consumer Products | Prototypes for containers, caps, toys, and household items where flexibility and durability are key. |
TECHNICAL SPECIFICATIONS
The following table provides key technical data for standard Homopolymer Polypropylene, which is the most common grade used for CNC machining.
| Property | Value / Description | Test Method |
|---|---|---|
| General Properties | ||
| Material Type | Thermoplastic Polypropylene (PP-H) | – |
| Mechanical Properties | ||
| Tensile Strength | 30 – 40 MPa | ASTM D638 |
| Flexural Modulus | 1.5 – 2.0 GPa | ASTM D790 |
| Impact Strength (Izod Notched) | 20 – 80 J/m | ASTM D256 |
| Hardness (Rockwell R) | 80 – 110 | ASTM D785 |
| Thermal Properties | ||
| Melting Point | 160 – 165 °C | – |
| Continuous Service Temperature | 100 – 120 °C | UL 746B |
| Heat Deflection Temp (HDT) @ 0.45 MPa | 100 – 120 °C | ASTM D648 |
| Electrical Properties | ||
| Dielectric Strength | 20 – 28 kV/mm | ASTM D149 |
| Physical Properties | ||
| Density | 0.90 – 0.91 g/cm³ | ASTM D792 |
| Water Absorption (24hr) | < 0.01% | ASTM D570 |
| Machining Notes | ||
| Machinability | Excellent. Machines easily but requires sharp tools and appropriate feeds/speeds to avoid melting or stringing. | – |
| Finishing | Can be easily milled, turned, and drilled. Produces a smooth, semi-matte finish. | – |