Acetal Plastic: What You Need to Know

Are you looking for a strong plastic that works in tough situations? Acetal plastic might be the answer. This guide breaks down everything about acetal – from what it is to how to use it, in simple terms.

What is Acetal Plastic?

Acetal plastic, also called POM (Polyoxymethylene), is a high-performance thermoplastic that engineers love. When you need parts that stay the same size and shape even when conditions change, acetal delivers.

Acetal comes in two main types:

• Homopolymer (like Delrin®)
• Copolymer (like Celcon®)

Both types are strong, but they have small differences that matter for certain jobs.

Key Properties of Acetal

You can also get acetal in special grades:

• UV-stable (for outdoor use)
• Glass-filled (for extra strength)
• FDA-compliant (for food and medical use)

7 Major Benefits of Acetal

Acetal plastic shines in many ways that make it better than other materials:

1. Stays the same size and shape – Even when temperature changes, acetal parts keep their dimensions.
2. Self-lubricating – Parts slide against each other without needing oil or grease.
3. Resists water and chemicals – Doesn’t soak up water and stands up to most fuels, solvents, and mild acids.
4. Lighter than metal – About 70% lighter than brass, making machines more efficient.
5. Easy to machine – Can be cut precisely with the right tools, great for CNC turning parts and other plastics.
6. Handles constant force – Doesn’t bend slowly over time (low creep) when under pressure.
7. Cost-effective for high-wear parts – Lasts a long time in moving parts, saving money.

Top Industrial Applications

Acetal’s unique mix of properties makes it perfect for many industries:

Automotive

Car makers use acetal for:

• Fuel system parts
• Gears and bearings
• Seatbelt mechanisms
• Door handles

These parts need to work perfectly for years, through hot summers and cold winters.

Medical Devices

With FDA-approved grades, acetal works well for:

• Surgical tools
• Drug delivery devices
• Implant parts that don’t stay in the body

The medical field values acetal because it’s safe, strong, and can be cleaned thoroughly.

Consumer Goods

Look around your home, and you’ll find acetal in:

• Zippers (over 1 billion units yearly!)
• Pen clips
• Kitchen appliance gears
• Shower heads

Industrial Equipment

Factories rely on acetal for:

• Conveyor belt parts
• Pump components
• Bearings and bushings

One factory found that switching metal valves to acetal reduced maintenance costs by 40%. This shows how acetal can save money while working better.

How to Work with Acetal

Whether you’re machining acetal with CNC or molding it, knowing the right way to work with this material is key.

Machining Tips

When cutting acetal:

• Use carbide tools for best results
• Set speeds around 500-800 SFM when milling
• Make sure chips clear out (acetal melts if it gets too hot)
• Allow for cooling between cuts

Acetal’s excellent properties make it a favorite for precision machined parts, similar to how CNC plastic machining is valued for tight tolerances.

Injection Molding

If you’re making many identical parts:

• Melt temperature: 190–230°C
• Mold shrinkage: 2.1–2.9%
• Dry material before molding
• Use hot runners for best flow

Post-Processing

After making an acetal part:

• Annealing reduces internal stress
• Light sanding creates smooth edges
• Sonic welding works for joining parts
• Avoid strong glues (they often don’t stick well)

Limitations of Acetal

While acetal is great, it’s not perfect for every job. Know these weaknesses:

1. Poor UV resistance – Standard acetal breaks down in sunlight unless you use special UV-stable grades.
2. Problems with strong chemicals – Strong acids and bases can damage acetal.
3. Not flame-retardant – Burns more easily than some other plastics unless modified.
4. Higher cost – More expensive than basic plastics like polyethylene.

A manufacturing study showed that unstabilized acetal loses about 50% of its strength after one year of outdoor exposure.

Acetal vs. Competing Materials

How does acetal stack up against other materials? Let’s compare:

Acetal vs. Nylon

Acetal wins for:

• Better dimensional stability – Nylon absorbs more moisture (up to 8% vs. acetal’s 0.3%)
• Better wear resistance – Acetal’s lower friction makes it last longer in moving parts
• More consistent properties – Less affected by humidity changes

Nylon wins for:

• Better impact resistance
• Generally lower cost
• Higher heat resistance

Acetal vs. PTFE (Teflon)

Acetal wins for:

• Much higher strength
• Better rigidity
• Lower cost

PTFE wins for:

• Better chemical resistance
• Lower friction
• Higher temperature range

Acetal vs. Metal

Acetal wins for:

• No corrosion
• Quieter operation (dampens vibration)
• Lighter weight
• Lower production cost for complex shapes

Metals win for:

• Higher strength
• Better heat resistance
• Lower cost for simple shapes

Sourcing Acetal Plastic

When you need acetal, you have several options:

Leading Suppliers

• Ensinger
• BASF
• Mitsubishi

Custom Fabricators

• Xometry (great for prototyping)
• Laird Plastics (offers cut-to-size sheets and rods)

Cost Guide

Expect to pay between $5–$15 per pound, depending on:

• Grade (FDA-approved costs more)
• Quantity (bulk discounts apply)
• Form (sheets, rods, or custom shapes)

Many suppliers offer both Delrin® (DuPont’s acetal homopolymer) and various copolymer brands. The difference matters for certain applications.

Common Questions About Acetal

Conclusion

Acetal plastic stands out for precision parts that need strength, durability, and low friction. Its excellent dimensional stability and chemical resistance make it ideal for gears, bearings, and other moving parts.

When you need parts that:

• Keep their shape
• Move smoothly against other parts
• Resist water and chemicals
• Last for years

Acetal should be high on your list of materials to consider. While it costs more than basic plastics, its performance often justifies the investment.

For precision applications, consider partnering with specialists in precision CNC milling who understand how to get the best results from acetal.

With the right design and manufacturing approach, acetal can help your products perform better and last longer.