When selecting a high-performance polymer for CNC machining, Delrin is often a top choice. It is a strong, stiff, and low-friction plastic that is easy to machine. However, when you look at a supplier’s catalog, you quickly face a choice: Delrin 100 or Delrin 150?
They look and feel almost identical. So, what is the difference? And which one is the right choice for your project?
This guide will give you a clear comparison. We will look at their core differences, compare their technical data, and show you which applications are best for each. This article will help you make the right material choice with confidence.
What is Delrin? A Quick Overview
First, let’s understand what Delrin is. Delrin® is the brand name from the company DuPont for a material called acetal homopolymer, also known as Polyoxymethylene (POM-H).
It is a semi-crystalline thermoplastic known for its excellent properties:
- High Mechanical Strength and Stiffness: It can handle heavy loads without bending.
- Excellent Machinability: It cuts cleanly, producing smooth surfaces and holding tight tolerances.
- Low Friction and High Wear Resistance: It is perfect for moving parts like bearings and gears.
- Great Dimensional Stability: It does not easily change shape with temperature or humidity changes.
- Good Chemical Resistance: It resists solvents, fuels, and other common chemicals.
Both Delrin 100 and 150 share these great qualities. Their differences come from a small change in their molecular structure.
The Key Difference: Crystallinity
The primary difference between Delrin 100 and Delrin 150 is their crystallinity.
- Delrin 100 has a higher degree of crystallinity. Think of its molecules as being very tightly and neatly packed together. This dense structure gives it higher stiffness, strength, and resistance to creep (deformation under long-term stress).
- Delrin 150 has a slightly lower degree of crystallinity. Its molecular chains are a little less ordered. This structure gives it better impact strength (toughness) and slightly more elongation (the ability to stretch before breaking).
This single difference in crystallinity creates a trade-off: Strength vs. Toughness. Let’s see how this looks in the technical data.
Head-to-Head: Mechanical Properties Comparison
Data sheets provide the best way to compare these two materials. The numbers clearly show the strengths and weaknesses of each. Below are typical values for Delrin 100 and 150.
Note: The exact values can vary slightly based on the manufacturer and testing conditions.
Key Mechanical Properties at Room Temperature (23°C / 73°F)
| Ejendom | Delrin 100 | Delrin 150 | Unit | What it Means for Your Part |
|---|---|---|---|---|
| Trækstyrke | 75.8 MPa (11,000 psi) | 69 MPa (10,000 psi) | MPa (psi) | Winner: Delrin 100. Better for parts under constant tension or load. |
| Bøjningsmodul | 3100 MPa (450,000 psi) | 2830 MPa (410,000 psi) | MPa (psi) | Winner: Delrin 100. Stiffer and less likely to bend under load. |
| Forlængelse ved brud | 30% | 40% | % | Winner: Delrin 150. Can stretch more before failing. Better for snap-fits. |
| Notched Izod Impact | 80 J/m (1.5 ft·lb/in) | 120 J/m (2.2 ft·lb/in) | J/m | Winner: Delrin 150. Tougher and better at resisting sudden impacts. |
| Hardness, Rockwell M | M94 | M94 | vægt | Tie. Both have excellent surface hardness. |
Analysis:
The data confirms the theory. Delrin 100 is stronger (higher tensile strength) and stiffer (higher flexural modulus). Delrin 150 is tougher (higher impact strength) and more ductile (higher elongation).
Physical and Thermal Properties
Beyond strength, other properties like heat resistance and water absorption are important for many applications.
Thermal and Physical Properties
| Ejendom | Delrin 100 | Delrin 150 | Unit | Importance |
|---|---|---|---|---|
| Heat Deflection Temp. | 124 °C (255 °F) | 118 °C (244 °F) | °C (°F) | Winner: Delrin 100. Holds its shape better at higher temperatures under load. |
| Tæthed | 1.43 g/cm³ | 1.42 g/cm³ | g/cm³ | Almost Identical. This difference is negligible for most projects. |
| Water Absorption (24hr) | 0.22% | 0.25% | % | Winner: Delrin 100. Absorbs slightly less water, offering marginally better dimensional stability in wet environments. |
Analysis:
The differences here are smaller but still follow the same trend. The more crystalline structure of Delrin 100 gives it slightly better performance at high temperatures and in water. However, both materials have very low water absorption compared to other plastics like Nylon.
CNC Machining Considerations: The Practical View
For a machinist, the “better” material is often the one that is more stable and predictable on the mill or lathe.
- Delrin 150: The Machining Standard
Delrin 150 is often called the “general purpose” or “standard” machining grade of Delrin. Its slightly lower internal stress makes it more dimensionally stable during machining. When you remove large amounts of material, it is less likely to warp or bow. It also has a lower risk of “centerline porosity,” which are tiny voids that can sometimes be found in the center of thicker acetal rods. For these reasons, many machine shops prefer Delrin 150 as their default choice. - Delrin 100: For Maximum Performance
Delrin 100 machines very well, producing an excellent surface finish. However, its higher internal stress requires more care. If you are machining a thin, complex part from a large piece of Delrin 100, you might see some movement after machining. This can sometimes be managed by using annealed (stress-relieved) stock, but that adds cost. You choose Delrin 100 when you absolutely need its superior strength and stiffness, and you are prepared to manage its machining behavior.
Machinability At-a-Glance
| Funktion | Delrin 100 | Delrin 150 | The Takeaway |
|---|---|---|---|
| Overall Machinability | Fremragende | Fremragende | Both are top-tier plastics for machining. |
| Overfladefinish | Fremragende | Fremragende | Both produce a smooth, clean finish. |
| Dimensionel stabilitet | Meget god | Fremragende | 150 is often more predictable and less prone to warping. |
| Risk of Porosity | Lav | Very Low | 150 is generally considered safer for parts where internal voids are a concern. |
| Værktøjsslid | Very Low | Very Low | Both are non-abrasive and easy on cutting tools. |
Applications: Where Does Each Material Shine?
The best way to choose is to match the material’s strengths to your application’s needs.
Use Delrin 100 For:
Parts that require maximum strength, stiffness, and creep resistance.
- High-Load Gears: Where tooth strength and stiffness prevent deformation.
- Structural Components: Small frames, supports, or brackets under constant load.
- High-Performance Insulators: Where stiffness and temperature stability are key.
- Parts for High-Temperature Environments: When the part must maintain its shape close to its heat deflection temperature.
Use Delrin 150 For:
A wide range of general-purpose and impact-prone applications.
- Bushings and Bearings: Excellent low-friction properties and general durability.
- Rollers and Wear Strips: Its toughness and wear resistance make it very durable.
- Snap-Fit Enclosures: The higher elongation allows the tabs to bend without breaking.
- Medical and Food-Grade Parts: Specific grades of Delrin 150 are compliant with FDA, NSF, and USP Class VI regulations.
- General Prototypes and Jigs: It is the reliable, all-around performer.
How to Choose: A Simple Decision Guide
Still not sure? Ask yourself these questions.
| Ask Yourself… | If You Answer Yes, Choose… | Why? |
|---|---|---|
| Is my part a structural component under constant, high load? | Delrin 100 | You need the highest stiffness and tensile strength. |
| Will my part experience sudden shocks or impacts? | Delrin 150 | You need its superior toughness (impact strength). |
| Does my part have a “snap-fit” feature? | Delrin 150 | You need the higher elongation so it can bend without breaking. |
| Am I machining a large, complex part and worried about it warping? | Delrin 150 | It is generally more stable during machining. |
| Is this a general-purpose moving part like a bushing or roller? | Delrin 150 | It is the industry standard and offers the best balance of properties. |
| Do I need the absolute best performance at elevated temperatures? | Delrin 100 | It has a higher heat deflection temperature and better creep resistance. |
Conclusion: Which is Better for CNC Machining?
There is no single “better” material. The better material is the one that fits your specific needs.
- Delrin 150 is the better choice for most general CNC machining applications. It offers a fantastic balance of toughness, strength, and excellent machinability, making it the reliable workhorse. If you are unsure which to pick, Delrin 150 is almost always a safe and effective choice.
- Delrin 100 is the better choice for specialized, high-performance applications. When your design demands the highest possible strength, stiffness, and creep resistance, and you can manage its machining characteristics, Delrin 100 delivers that extra level of performance.
By understanding the trade-off between the strength of Delrin 100 and the toughness of Delrin 150, you can look beyond the spec sheet. You can select the perfect material to ensure your CNC machined parts are strong, reliable, and perfectly suited for their job.
