What defines thermoplastic materials?

Thermoplastic materials are primarily characterized by their molecular structure, which features weak secondary bonds, specifically van der Waals forces, between polymer chains. This type of bonding allows thermoplastics to be easily reshaped and reprocessed when heated. The weak nature of these bonds means that when heat is applied, the chains can slide past each other more readily, enabling the material to soften and become moldable, and then harden as it cools again. This property makes thermoplastics versatile for various applications, including in manufacturing and product design.

On the other hand, strong primary bonds between chains would describe thermosetting materials better, which cannot be remolded once cured. Complex molecular structures can be found in many materials, but they do not specifically define thermoplastics. High resistance to heat is not a defining characteristic of thermoplastics, as many of them can soften at relatively low temperatures compared to other materials.