3911.90.91.10 - Thermoplastic

This HTS classification, 3911.90.91.10, covers thermoplastic resins and other products that are not specifically listed or included elsewhere within Chapter 39, as further defined by Note 3 to this chapter. These materials, when presented in their primary forms, fall under the broader category of petroleum resins, coumarone-indene resins, polyterpenes, polysulfides, and polysulfones. The sub-classification "Other" under this heading signifies materials that do not fit into more specific subheadings within this group.

Distinguishing this category from its sibling, 3911.90.91.50 ("Thermosetting"), is the fundamental difference in their behavior when subjected to heat. Thermoplastic materials, as classified here, are capable of repeatedly softening when heated and hardening when cooled, allowing them to be molded or reshaped multiple times. In contrast, thermosetting materials undergo an irreversible chemical change during curing and cannot be remelted or reshaped.

As this is a leaf node, there are no further subcategories. Therefore, classification within 3911.90.91.10 hinges on the material meeting the general description of certain specialized resins and polymers, exhibiting thermoplastic properties, and not being specifically enumerated in other headings or subheadings within Chapter 39 or the broader classification notes. Examples could include specific grades of thermoplastic polymers not otherwise classified, or mixtures of resins that fall under the purview of Note 3 and behave as thermoplastics.