3902.90.00 - Other

This HTS classification, 3902.90.00, encompasses "Other" polymers of propylene or other olefins, in primary forms, that do not fall under the more specific preceding headings within Chapter 3902. This category is a residual classification, meaning it captures materials that meet the general definition of polymers of propylene or other olefins but are not specifically classified as polypropylene (3902.10), polyisobutylene (3902.20), or propylene copolymers (3902.30). It is crucial to examine the chemical structure and monomer composition to ensure a material is not classifiable under a more specific subheading.

To distinguish this category from its siblings, classification hinges on the absence of the defining characteristics of those categories. Polypropylene, as the name suggests, is solely polymerized propylene. Polyisobutylene is derived from isobutylene monomers. Propylene copolymers, on the other hand, explicitly involve the polymerization of propylene with one or more other olefinic monomers. If a polymer consists of propylene or other olefins but does not fit these specific definitions, it will likely be classified under this "Other" heading.

Within the "Other" classification, further distinctions are made. Subheading 3902.90.00.10 specifically addresses polybutylene, a polymer derived from butylene monomers. The remaining materials that are polymers of propylene or other olefins, and do not fit the definitions for polypropylene, polyisobutylene, propylene copolymers, or polybutylene, are then classified under the residual subheading 3902.90.00.50, also designated as "Other." This hierarchical structure ensures that all polymers of propylene or other olefins, in primary forms, are accounted for within Chapter 3902.