Key Difference – Polyamide vs Polyimide
Polyamide and polyimide are high-temperature-resistant thermoplastic elastomers with a wide range of applications. The major difference between polyamide and polyimide is in their chemical structures; polyamide has the amide (-CONH-) linkages in their polymer backbone, while polyimide has imide group (-CO-N-OC-) in their polymer backbone.
These two polymers are also known for their excellent electrical and physical properties in addition to high thermal stability.
CONTENTS
1. Overview and Key Difference
2. What is Polyamide
3. What is Polyimide
4. Side by Side Comparison – Polyamide vs Polyimide in Tabular Form
5. Summary
What is Polyamide?
Polyamides are high-performance thermoplastic elastomers characterized by their high service temperature, good heat aging, and solvent resistance. In addition, polyamides have high modulus and impact properties, low coefficient of friction, and high abrasion resistance. Although polyamides are developed to have a wide range of properties, they all consist of amide (-CONH-) linkages in their polymer backbone. Nylon is the most common and widely used type of polyamide; this was one of the earliest polymers developed by Carothers. Today nylon is among one of the most important and widely consumed polymers in the United States.
The amide group is a polar group, which allows polyamides to build hydrogen bonds between chains, thus improving the interchain attraction. This enhances the mechanical properties of polyamide. In nylon, the flexible aliphatic carbon groups in the chain improve the processability of the material by reducing the melt viscosity. The strength and stiffness can be reduced by increasing the number of carbon atoms between the amide linkages. Therefore, the length of the hydrocarbon backbone is a key property that determines the performance of polyamide material. Due to the polarity of the amide group, polar solvents, mainly water, can affect polyamides.
There are two types of polyamides: aliphatic and aromatic polyamides. Nylon can be either an aliphatic or semi-aromatic polyamide. The main applications of polyamides include radiator header tanks in cooling systems, switches, connectors, ignition components, sensors and motor parts in auto electrical systems, wheel trims, throttle valves, engine covers, heat resistant under-bonnet components, airbrake tubing, etc.
