Thermoplastic vs. Thermosetting Polymers Explained

The principal differences between the two fundamental polymer systems used in the advanced composites industry, thermoplastic and thermosetting polymers, are based on how they are formed to make a solid polymer resin and the presence, or lack of, cross-linking molecular groups connecting the long chain polymer repeating molecules.

 
The tables below show the basic differences between thermoplastic and thermosetting polymers:

 

Thermoplastic vs. Thermosetting Polymers Explained - ThermoplasticThermoplastic vs. Thermosetting Polymers Explained - Thermosetting

 

Illustration of the lack of, or presence of, long chain polymer cross links can be shown as follows, where the figure on the left represents a thermoplastic polymer and the one on the right represents a thermosetting polymer.

 

 
Know Your Materials - ThermoplasticsKnow Your Materials - Thermosets
In thermoplastic polymers specifically, and occasionally in thermosetting polymers, we see regions of crystalline and amorphous molecules patterns. The crystalline regions are developed where the molecules become layered and structured, in the amorphous regions there is no regular or layered pattern (chaotic positioning of the molecules). Crystallinity produces improvements in physical and structural performance of the polymer.
 

Basically, thermosetting polymers have covalent or ionic bonds between the cross-linking molecule and the long chain polymer molecules. These covalent or ionic bonds form a strong and irreversible attachment to the long chain polymer.

 
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