Complete Guide to PEI (Polyetherimide) Engineering Plastic

Understanding PEI Ultem Material Grades

Ultem 1000 is the standard unfilled grade of PEI plastic, offering the best balance of properties for general-purpose applications. This natural polyetherimide provides maximum electrical insulation properties, transparency to microwave radiation, and excellent surface finish when machined. The material's amber color is characteristic of pure PEI resin without additives.

For applications requiring enhanced stiffness and dimensional stability, glass-filled PEI grades like Ultem 2300 (30% glass fiber) increase flexural modulus by 40% while maintaining excellent thermal properties. Carbon fiber-reinforced PEI offers superior wear resistance and thermal conductivity for bearing applications and heat dissipation components.

PEI vs PEEK: Making the Right Material Choice

When comparing PEI vs PEEK for high-temperature applications, PEI often provides the best value for applications below 170°C. While PEEK offers higher temperature resistance (250°C continuous), PEI polyetherimide costs 40-60% less and provides adequate performance for most applications. PEI's superior electrical properties and transparency to microwave radiation make it preferable for electronic and microwave applications.

The key advantages of PEI over PEEK include lower cost, better electrical insulation, inherent flame resistance without additives, and easier machinability. PEEK excels in extreme chemical environments and temperatures above 170°C, but for most aerospace, medical, and electronic applications, PEI Ultem provides the optimal balance of performance and cost.

CNC Machining PEI: Best Practices and Guidelines

Successfully machining PEI plastic requires understanding its unique characteristics. The material's high glass transition temperature (217°C) allows aggressive cutting parameters without melting. Use sharp carbide tools with positive rake angles for optimal chip evacuation. Recommended cutting speeds range from 500-1000 SFM for milling operations.

When drilling PEI sheets or rods, use standard HSS or carbide drills with 118-135° point angles. Pecking cycles prevent heat buildup and ensure clean holes. For threading, single-point thread milling produces superior results compared to tapping, especially for fine pitches. Coolants improve surface finish and extend tool life, though many machinists successfully cut PEI dry with compressed air chip evacuation.

PEI Processing Techniques and Considerations

Thermoforming PEI sheets requires heating to 180-200°C, just below the glass transition temperature. Pre-drying at 150°C for 2-4 hours removes moisture that could cause surface defects. Vacuum forming and pressure forming both work well, with male molds providing better dimensional control for deep draws.

For injection molding PEI, melt temperatures of 350-400°C and mold temperatures of 135-165°C produce optimal results. The material's low shrinkage (0.5-0.7%) ensures excellent dimensional accuracy. Proper venting prevents burn marks, while generous radii prevent stress concentrations.

Derations for PEI Components

When designing with PEI plastic, consider the material's anisotropic properties and low shrinkage rates. Wall thickness variations should be minimized to prevent warpage. For CNC machined PEI parts, design with generous radii (minimum 0.5mm) to prevent stress concentrations. Threaded features should have minimum 2× diameter engagement length for optimal strength.

PEI's excellent creep resistance makes it ideal for snap-fit assemblies and living hinges. Design snap-fits with 1-2% strain maximum to prevent failure. For high-temperature applications, account for thermal expansion (56 ppm/°C) when designing tight-tolerance assemblies.

Why Choose BeePlastic for PEI Solutions?

With over 20 years specializing in high-performance plastics, BeePlastic has developed extensive expertise in PEI processing. Our state-of-the-art CNC machining centers, combined with experienced engineers, ensure your PEI components meet the most demanding specifications. We maintain substantial inventory of PEI sheets, PEI rods, and PEI tubes for rapid turnaround.

Our capabilities span from prototype development through high-volume production. Whether you need PEI plastic cut to size, complex 5-axis machined components, or technical guidance on material selection, BeePlastic delivers comprehensive solutions. Our commitment to quality, competitive pricing, and responsive customer service makes us your ideal partner for all PEI polyetherimide plastic needs.