Polyamide vs Polyimade

Polyamide vs Polyimide

Updated 10/02/2026

Polyamide and Polyimide are both polymers formed from repeating monomer units, but despite their similar names, they exhibit very different mechanical, thermal, and chemical properties. These differences arise primarily from their molecular structure, which directly influences performance in engineering applications.

Understanding where each material excels is critical when selecting the right polymer for demanding industrial environments.

Mechanical and Thermal Property Comparison

The table below compares typical properties of Polyamide 6 (dry) and Polyimide. These values are intended for reference and comparison purposes only and may vary depending on grade, processing method, and test conditions.

Property Polyamide 6 (Dry) Polyimide
Specific Gravity 1.14 1.43
Tensile Strength (MPa) 85 86.2
Elongation at Break (%) 70 7.5
Heat Deflection Temperature 75 °C 360 °C
Water Absorption (23 °C, 24 hr) (%) 0.3 0.24
Water Absorption @ Equilibrium (23 °C, 50% RH) (%) 3.0 1.15
Flammability (UL94) HB V0

Key takeaway:
Polyamide offers toughness and flexibility, while Polyimide provides exceptional thermal stability and flame resistance.

What Is Polyamide?

The most well-known polyamide is Nylon. Polyamides are typically semi-crystalline thermoplastics known for their toughness, good fatigue resistance, and ease of processing.

Common engineering grades include:

  • Nylon 6

  • Nylon 66

  • Nylon 6.12

Key Characteristics of Polyamides

  • High toughness and impact resistance

  • Good wear properties

  • Good resistance to oils, fuels, and many chemicals

  • Susceptible to moisture absorption, which can affect dimensional stability

  • Limited performance at elevated temperatures

  • Vulnerable to attack by strong acids

Polyamides can be compounded with glass fibre, oil, or solid lubricants to enhance stiffness, wear resistance, or frictional performance.

Typical Applications of Polyamides

Polyamides are widely used in:

  • Electrical switches and connectors

  • Sensors and ignition components

  • Support rollers and guide wheels

  • Cable sheaves

  • Automotive motor and throttle components

  • General moulded engineering parts

How Polyamides Are Made

Polyamides are produced through the polymerisation of diamines and dicarboxylic acids, forming long molecular chains linked by amide groups.

What Is Polyimide?

Polyimide (often abbreviated as PI) is a high-performance polymer formed from imide monomers. It is regarded as an advanced engineering plastic due to its exceptional thermal, mechanical, and chemical resistance.

Polyimides are commonly used in extreme environments where conventional engineering plastics fail.

Key Characteristics of Polyimides

  • Outstanding thermal stability (continuous use at very high temperatures)

  • Excellent chemical resistance

  • Very low creep

  • Inherent flame resistance

  • Good dimensional stability

  • High radiation resistance

Polyimide Variants

Several high-performance polymers fall under the polyimide family, including:

  • Polyetherimide (PEI)

  • Polyamideimide (PAI)

These materials contain the imide functional group and are often classified as aromatic polyimides because they are derived from aromatic diamines and anhydrides. Their molecular structure contributes to their high thermal and mechanical performance.

How Polyimides Are Made

Polyimides are formed through:

  • The reaction between a dianhydride and a diamine, or

  • The reaction between a dianhydride and a diisocyanate

Radiation Resistance of Engineering Polymers

Polyimides also perform exceptionally well in radiation-rich environments. The table below compares typical gamma radiation resistance across several high-performance polymers.

Material Gamma Dose (rad) Performance
PEEK 4 × 10⁹ Very Good
Polyimide 2 × 10⁹ Very Good
PVDF 5 × 10⁷ Good
ECTFE & PCTFE 3 × 10⁷ Good
ETFE 1 × 10⁷ Good
PFA & FEP 5 × 10⁵ Okay
PTFE 5 × 10⁴ Poor

Polyimide ranks second only to PEEK in radiation resistance, making it suitable for aerospace, nuclear, and high-energy applications.

Thermosetting Polyimides

Among polyimides, thermosetting grades are particularly valued for:

  • Excellent thermal stability

  • Good chemical resistance

  • High mechanical strength

These materials are often identifiable by their characteristic yellow colour and are commonly used in high-temperature aerospace and electrical insulation applications.

Polyamide vs Polyimide: Summary

Although polyamides and polyimides are often confused due to their similar names, they are fundamentally different materials:

  • Polyamides are tough, versatile, and cost-effective engineering plastics suitable for moderate temperatures and general-purpose applications.

  • Polyimides are high-performance materials designed for extreme heat, radiation, and chemically aggressive environments.

Selecting the correct material depends on operating temperature, mechanical demands, environmental exposure, and long-term performance requirements.

To find out how we can help with your latest project, please contact info@fluorocarbon.co.uk.

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