The distinction is whether a plasticizer has been compounded into the PVC mixture. Nonplasticized PVC (390421) is rigid and contains no significant plasticizer content, while plasticized PVC (390422) has had a plasticizer—such as a phthalate or adipate ester—incorporated to impart flexibility. The producer's formulation data or a plasticizer content test is the standard basis for classification.

PTFE and related fluoropolymers are industrial materials and do not trigger mandatory admissibility review by FDA or USDA. However, importers should be aware that certain per- and polyfluoroalkyl substance (PFAS) regulations are evolving at both the federal and state level, and some downstream applications of fluoropolymers may face end-use restrictions. Classification accuracy is also important because fluoropolymer lines may carry different duty rates than standard PVC lines.