Polypropylene homopolymer (390210) consists essentially of propylene repeat units, while propylene copolymers (390230) contain a significant proportion of another monomer—commonly ethylene—incorporated into the polymer chain. The producer's certificate of analysis showing monomer composition is the primary classification document; impact copolymers and random copolymers both fall under 390230 when the ethylene or other comonomer content is sufficient to alter the polymer's classification.

Polypropylene resins are consumed across automotive components, rigid and flexible packaging, nonwoven fabrics, and medical devices. End-use sector does not by itself change the tariff classification or duty rate, but certain downstream applications may qualify for duty drawback or manufacturing bonded warehouse treatment if the resin is further processed before export.