3911 - Petroleum resins, coumarone-indene resins, polyterpenes, polysulfides, polysulfones and other products specified in note 3 to this chapter, not elsewhere specified or included, in primary forms:

Heading 3911 encompasses a diverse group of synthetic resins and polymers that are not specifically classified elsewhere within Chapter 39. This category primarily includes petroleum resins, coumarone-indene resins, polyterpenes, polysulfides, and polysulfones. These materials are characterized by their specific chemical structures and are often used as binders, modifiers, or components in the manufacture of various articles, including adhesives, coatings, and printing inks. The key distinguishing feature of goods classified under 3911 is their composition and origin as specifically outlined in Note 3 to Chapter 39, ensuring they are not inadvertently placed under broader polymer headings.

When classifying products within Chapter 39, it is crucial to differentiate heading 3911 from other headings that may also describe polymeric materials. For instance, while heading 3901 through 3910 cover specific types of polymers based on their monomeric units or general characteristics (e.g., polyacetals, polyethers, polycarbonates), heading 3911 is reserved for those synthetic resins and polymers that do not fit neatly into those more defined categories, particularly those derived from petroleum or characterized by their indene or terpene components, or the polysulfide and polysulfone structures.

The subcategories under heading 3911 provide further specificity. Subheading 3911.10.00.00 distinguishes petroleum resins, coumarone, indene or coumarone-indene resins, and polyterpenes, often recognized by their tackifying or adhesive properties. The remaining products, which include polysulfides, polysulfones, and other resins not elsewhere specified, are broadly grouped under the "Other" subheading 3911.90, requiring careful analysis of their chemical composition and application to ensure accurate classification.