3907.91.20.00 - Allyl resins, uncompounded

This HTS classification covers allyl resins that are uncompounded and presented in their primary forms. Allyl resins are a subclass of unsaturated polyesters, characterized by the presence of allyl groups in their molecular structure. These resins are typically thermosetting, meaning they cure or harden irreversibly upon heating or exposure to a catalyst. Examples include diallyl phthalate (DAP) resins, which are valued for their excellent electrical properties, heat resistance, and dimensional stability, making them suitable for applications in electrical connectors, molded parts, and high-performance laminates.

While this specific category is for "Allyl resins," its sibling category, 3907.91.40.00, covers "Other" unsaturated polyesters. This distinction is crucial: 3907.91.20.00 is exclusively for resins where the unsaturated functionality is derived from allyl groups. The "Other" category would encompass unsaturated polyesters with different types of unsaturated functional groups, such as vinyl or acrylate groups, that do not fall under the specific definition of allyl resins. Therefore, the presence and nature of the unsaturated group are the primary distinguishing factors.

As a leaf node in the HTS structure, this classification (3907.91.20.00) does not have further subcategories. All eligible uncompounded allyl resins in primary forms fall directly under this code. When classifying, it's important to confirm that the resin is indeed an allyl resin, meaning it contains allyl ester linkages, and that it is in an uncompounded state, meaning it has not been mixed with fillers, pigments, or other additives that would alter its primary resinous form.