In our previous article “Can Plastics Replace Metal Parts?“, we discussed the growing trend of replacing metal parts with plastics in manufacturing, driven by rising steel and aluminum prices, tariffs, and increasing logistics costs. Many companies are now exploring “plasticification” to reduce weight, cut costs, and simplify assembly.
That article focused on the why and when plastics can replace metals—but it left an important question open: which types of plastics are actually suitable for taking on metal’s role?
In this article, we’ll dive into the what and how: exploring common engineering plastics—Nylon (PA), POM, PC, PPS, and PEEK—their strengths, limitations, and applications. This will help you decide which material is the right fit for your parts and operating conditions.
Advantages and Challenges of Plastic Substitution
Before swapping a metal bracket, gear, or housing for plastic, it’s essential to understand the benefits and limitations of the change.
Advantages:
- Lightweight: Plastics typically weigh one-sixth of steel or half of aluminum, significantly reducing overall machine weight.
- Flexible molding: Complex geometries can be injection molded in one step, reducing assembly operations.
- Corrosion resistance: Most plastics perform better in acidic, alkaline, or salt-spray environments.
- Cost potential: For large-volume production, the cost per piece after amortizing mold expenses can be lower than metal parts.
Challenges:
- Strength differences: Even reinforced plastics may approach aluminum’s strength, but they still lag behind steel.
- Temperature limitations: Plastics vary widely in heat resistance, ranging from 80°C to over 250°C.
- Creep: Long-term loads may cause plastic parts to deform, requiring compensation in design.
The feasibility of substitution depends on the match between the part’s operating conditions and material performance.
Comparing Common Engineering Plastics
| Material | Key Properties | Typical Metal Parts Replaced | Limitations | Cost Level |
|---|---|---|---|---|
| PA (Nylon) | Strong, wear-resistant, good toughness; glass fiber reinforced | Intake manifolds, bearing housings, gears | High moisture absorption; dimensional instability in humid conditions | Low-Medium |
| POM (Acetal) | Low friction, high dimensional precision | Sliders, sprockets, precision gears | Limited heat resistance (<100°C) | Low-Medium |
| PC (Polycarbonate) | High toughness, impact resistant, transparent | Protective covers, housings, some brackets | Scratches easily; creep under long-term load | Medium |
| PPS (Polyphenylene Sulfide) | High strength, heat-resistant (>200°C), chemical resistant | Automotive pump housings, electrical connectors | Shrinkage during molding; demanding processing requirements | Medium-High |
| PEEK (Polyether Ether Ketone) | Exceptional strength, high temperature (>250°C), chemical resistant | Aerospace engine parts, medical implants | Expensive; high processing cost | High |
As the table shows, PA and POM are suitable for general-purpose replacements, offering a balance of strength and cost, whereas PPS and PEEK are reserved for high-temperature or extreme-condition applications.
Industry Applications
Automotive: A German automaker replaced an aluminum intake manifold with PA66+GF (glass-fiber reinforced nylon), cutting weight by 30% and simplifying assembly. Nylon and POM are widely used for gears, bearings, and pump housings, while PEEK is making its way into high-end powertrain components.
Electronics and Electrical Equipment: Apple uses PPS in MacBook connectors to ensure heat resistance and electrical stability during soldering. PPS and PEEK are suitable for electrical connectors and heat-resistant brackets, whereas PC is used for transparent covers and housings.
Medical Devices: PEEK is used in spinal implants, replacing titanium, reducing weight and avoiding metal allergy risks. It’s also gradually replacing stainless steel in sterilizable surgical instruments.
Industrial Machinery: POM gears substitute for metal ones in automation equipment, reducing noise and lubrication requirements. POM has become a standard replacement for medium and low-load transmission components.
How to Choose the Right Plastic
- Operating temperature: Above 120°C? Consider PPS or PEEK.
- Load requirements: Long-term stress? Check for creep resistance.
- Environmental factors: Humidity or chemical exposure? Select moisture-resistant or chemically stable materials.
- Budget constraints: For limited budgets, start with PA or POM for prototyping, then consider PPS or PEEK for high-performance needs.
In short: prototype first, scale later; begin with mid-range materials, upgrade to high-performance plastics as needed.
Conclusion
Plastic substitution isn’t about replacing strong metals with weaker materials—it’s about leveraging different material properties to reduce weight, cut costs, and optimize designs. From routine use of Nylon and POM to high-end applications of PPS and PEEK, this trend is gaining traction in automotive, electronics, and medical industries.
If you’re considering switching metal parts to plastic, a practical approach is to prototype small batches first, test actual performance, and then decide on full-scale substitution. With our expertise in CNC machining, injection molding, and engineering material validation, we can help you quickly assess and validate solutions, minimizing trial-and-error costs.
Continue Reading:
5 Design Pitfalls to Avoid When Switching Metal Parts to Plastic
Can Plastics Really Replace Metal Parts?
CNC Machining vs. Injection Molding for Plastic Parts: How to Choose
