Chemical and Plastic Tariff Classification: How the Chapter Notes Decide

How are chemicals and plastics classified under the HTS?

Chemicals and plastics are classified by the section and chapter notes first, and by the heading text only after the notes have spoken. The notes to Chapters 28, 29, 38 and 39 decide whether a product is a defined compound, a preparation, a polymer in primary form, or an article, and that one decision sets the heading.

What decides between Chapter 29, Chapter 38 and Chapter 39?

Three questions decide most cases: is it a separate chemically defined compound, was anything added on purpose that makes it fit a specific use, and is it a polymer, and in what form. CROSS rulings show how CBP has answered those questions on specific facts, and each ruling applies to its own facts.

TL;DR: For a coatings, resin or specialty chemical importer working through a 200-SKU product master, most classification errors happen at chapter boundaries, not at the 10-digit level. A pure compound stays in Chapter 28 or 29. A deliberate mixture, or a compound treated for a purpose, usually moves to Chapter 38, often heading 3824. A polymer in a liquid, paste, powder, granule or flake goes to headings 3901 to 3914, sorted by the comonomer that predominates by weight. Shaped plastics go to the article headings, or out of Chapter 39 entirely. TSCA certification runs alongside, as a separate entry requirement. GingerControl's HTS Classification Researcher works through those notes as questions before it proposes a code, and you can start with one SKU.

Last updated: October 2026

Which HTS chapter governs a chemical product?

Section VI of the HTS covers "products of the chemical or allied industries," Chapters 28 to 38. Section VII covers plastics and rubber, Chapters 39 and 40. Under General Rule of Interpretation 1, classification is determined "according to the terms of the headings and any relative section or chapter notes." In this part of the schedule, the notes carry most of the weight.

The table below maps the chapters a chemical or plastics importer meets most often, with the note that does the sorting. All note references are to the HTS Revision 20 (2026) chapter files published by the USITC, read on 8 October 2026.

Chapter	What it holds	The note that decides
28	Inorganic chemicals, plus compounds of precious metals, rare earths and isotopes	Note 1: separate chemical elements and separate chemically defined compounds, with limited permitted additions
29	Organic chemicals	Note 1: separate chemically defined organic compounds, isomer mixtures, and listed exceptions; Note 3: if two headings in the chapter fit, the last in numerical order wins
38	Miscellaneous chemical products, including heading 3824	Note 1(a): excludes separate chemically defined compounds, with five listed exceptions
39, headings 3901 to 3914	Plastics in primary forms	Notes 3, 4 and 6: synthetic polymers, copolymer predominance, and the definition of primary forms
39, headings 3915 to 3926	Waste, semi-manufactures and articles of plastics	Note 2: a long list of exclusions to other chapters

Bottom line: For a chemical importer classifying a new SKU from a technical data sheet, the first question is never "which heading sounds right." It is "which chapter note does this product satisfy," because Section VI and Chapter 38 Note 1 lock the answer before any heading comparison starts.

Pharmaceutical preparations are out of scope here. They raise Chapter 30 questions covered in our guide to pharma HS classification.

What makes a product a separate chemically defined compound?

Note 1 to Chapter 29 says the chapter's headings apply only to "separate chemically defined organic compounds, whether or not containing impurities," and a short list of permitted variations. Note 1 to Chapter 28 does the same for inorganic compounds. The permitted variations are where most disputes start:

1. Impurities. Allowed. CBP, quoting the Explanatory Notes in HQ H273388, limits "impurities" to substances whose presence "results solely and directly from the manufacturing process."
2. Dissolved in water. Allowed.
3. Dissolved in another solvent. Allowed only if the solution is "a normal and necessary method of putting up these products adopted solely for reasons of safety or for transport," and the solvent "does not render the product particularly suitable for specific use rather than for general use."
4. Stabilizers and anticaking agents. Allowed when "necessary for their preservation or transport."
5. Anti-dusting agents, colorants, odorants or emetics added for identification or safety. Allowed, on the same condition that the product is not made particularly suitable for specific use.

Read those five together and a pattern appears. Every permitted addition serves storage, transport, identification or safety. None serves performance. The moment an addition is there to make the product work better in a customer's process, the compound has usually become a preparation.

Chapter 29 adds a tie-breaker that surprises engineers. Note 3 says goods that fit two or more headings of the chapter go to "that one of those headings which occurs last in numerical order." Note 5 adds specific rules for esters, salts and coordination compounds. A molecule with two functional groups is not classified by its more important group. It is classified by the rule.

Quotable insight: In Chapters 28 and 29, every addition the notes permit serves storage, transport, identification or safety. None serves performance. That gives a single test that sorts most 29 versus 38 disputes: if a component was added to make the product work better in the customer's process, rather than to keep it stable, safe or identifiable, the product has usually left the defined-compound chapters and become a preparation.

When does a mixture fall to Chapter 38 instead?

Note 1(a) to Chapter 38 excludes "separate chemically defined elements or compounds," apart from five listed exceptions such as artificial graphite and put-up pesticides of heading 3808. The two chapters are built as mirror images. Outside those five exceptions, if a product qualifies under Note 1 to Chapter 28 or 29, Chapter 38 is closed to it. If it fails, heading 3824 is often where it lands: "chemical products and preparations of the chemical or allied industries (including those consisting of mixtures of natural products), not elsewhere specified or included."

Two CROSS rulings show the boundary on their own facts.

Worked example 1: treated fumed silica, HQ H273388 (14 November 2016). The goods were fumed silica whose surfaces had been treated with organosilicon compounds to make them more water-repellent. The question was whether they remained silicon dioxide of heading 2811 or became a preparation of heading 3824. CBP followed the Federal Circuit's reasoning in Degussa and held that the deliberately introduced hydrocarbon groups made the product non-stoichiometric, so it was not a separate chemically defined compound under Note 1 to Chapter 28. CBP also rejected the "mixtures of two or more inorganic compounds" subheading because the treated silica contained carbon, adding that "in the absence of any kind of carbon content threshold for organic substances, it is immaterial that the molecular weights of these carbon atoms are relatively low." The ruling classified the goods in heading 3824 at the residual "other" subheading. Read HQ H273388 on CROSS.

Worked example 2: denatonium benzoate in propylene glycol, HQ H072379 (7 July 2014). The product was 25% denatonium benzoate, a bittering agent, in 75% propylene glycol. The importer had sought classification as an amide of heading 2924. CBP had already held, in HQ 968018, that the product was a chemical preparation of heading 3824 and not a separate chemically defined compound. HQ H072379 kept that heading analysis, found the earlier residual "other" subheading in error, and revoked HQ 968018 and the New York ruling it had affirmed. Because denatonium benzoate contains a benzene ring, the solution was a mixture containing 5% or more by weight of an aromatic substance under Additional U.S. Note 2(a) to Section VI, and it went to the aromatic mixtures subheading by GRI 1 and GRI 6. Read HQ H072379 on CROSS.

Both rulings carry a second lesson. They cite subheadings under 3824.90, and the current HTS no longer has a 3824.90. In Revision 20 (2026), the residual provisions of heading 3824 sit under 3824.99. The heading reasoning in an older ruling can still apply, but the subheading number it cites has to be checked against today's schedule before it goes on an entry. For more on reading rulings this way, see our guide on how to use CROSS for tariff classification.

How do you classify plastics in primary forms under Chapter 39?

Chapter 39 splits into two halves: headings 3901 to 3914 for plastics in primary forms, and headings 3915 to 3926 for waste, semi-manufactures and articles. Four notes do the work.

Note	What it says	What it means in practice
Note 3	Headings 3901 to 3911 cover synthetic polymers with an average of at least five monomer units, silicones, resols and other prepolymers	Note 2(c) also excludes "separate chemically defined organic compounds" from Chapter 39
Note 4	A copolymer is any polymer in which no single monomer contributes 95% or more by weight; copolymers and blends go to the heading of the comonomer unit that "predominates by weight over every other single comonomer unit"	Units falling in the same heading are added together. If none predominates, the last heading in numerical order among those equally meriting consideration applies
Note 5	Chemically modified polymers, where only appendages to the main chain were changed, go with the unmodified polymer	Graft copolymers are excluded from this rule
Note 6	Primary forms means only liquids, pastes, dispersions, solutions, irregular blocks, lumps, powders, granules, flakes and similar bulk forms	Pellets and resin solutions are primary forms. A sheet, film, profile or molded part is not

Bottom line: For a resin or compounding importer bringing in pellets, liquids or powders, the decisive document is the formulation sheet with weight percentages by monomer. Without it, Note 4 cannot be applied and the heading is a guess.

Worked example 3: a phenolic and urea resin blend in water, NY N211517 (27 April 2012). The product was 35-45% phenol formaldehyde resin, 5-15% urea formaldehyde polymer and 40-50% water, used to make coatings for aluminum fins in automotive air-conditioning units. Both resins fall in heading 3909. CBP applied Note 4 to keep the blend in heading 3909, then Subheading Note 1, which classifies a blend "in the same subheading as polymers of the same monomer units in the same proportions." Because the phenol formaldehyde component predominated by weight, the ruling classified the blend as phenolic resins in primary forms, subheading 3909.40.0000. The ruling also notes that the merchandise "may be subject to the requirements of the Toxic Substances Control Act (TSCA)." Read NY N211517 on CROSS.

Watch the solvent threshold elsewhere in the chapter. Note 2(e) to Chapter 39 sends polymer solutions in volatile organic solvents to heading 3208 when the solvent exceeds 50% of the solution's weight. The blend in N211517 was carried in water, which that exclusion does not name. The same resin, dissolved in a volatile organic solvent above that threshold, would change chapters.

Once a plastic has been shaped, Note 2 to Chapter 39 takes over. It excludes, among others, machines and electrical apparatus of Section XVI, vehicle parts of Section XVII, furniture and lighting of Chapter 94, and toys of Chapter 95. A molded polypropylene housing is an article of plastics only if no exclusion claims it first. If the product combines plastic with other materials, see our guide to GRI 3(b) and the Carborundum factors.

How do the GRIs apply to chemicals and plastics?

The rules apply in order, and in this part of the schedule most products are decided at GRI 1 because the notes are so specific. The table shows where each rule tends to bite.

Rule	Where it applies to chemicals and plastics
GRI 1	Headings plus notes. Decides most cases: Chapter 28 and 29 Note 1, Chapter 38 Note 1(a), Chapter 39 Notes 2 to 6
GRI 2(b)	A reference to a material includes mixtures with other materials, and sends mixed goods to GRI 3. In practice, the chapter notes usually settle mixtures before GRI 2(b) is needed
GRI 3(a) and 3(b)	Rarely decisive for bulk chemicals, because the notes and heading 3824 already give a place for preparations. More common for kits and composite goods
GRI 3(c)	Echoed inside the chapters: Chapter 29 Note 3 and Chapter 39 Note 4 both use "last in numerical order" tie-breakers
GRI 6	Applies the same logic at subheading level, together with subheading notes, such as Chapter 39 Subheading Note 1

Section VI Note 3 and Section VII Note 1 add a rule for sets. Separate constituents put up together to be mixed into a Section VI or VII product, such as a two-part epoxy, are classified in the heading for the mixed product. This holds only if they are clearly put up to be used together without repacking, entered together, and identifiable as complementary to one another.

Bottom line: For a compliance team auditing 50 to 100 chemical classifications a quarter, the GRI review is mostly a chapter-notes review. A file that records which note was satisfied, and why, defends better than one that records only the final 10 digits. Our walkthrough of the HS code classification process covers the GRIs in general.

Where does TSCA certification fit at entry?

The Toxic Substances Control Act sits beside classification, not inside it. CROSS rulings on chemicals, including N211517, point importers to the EPA, which administers TSCA. CBP's own regulations set the import certification. Under 19 CFR 12.121, text current as of 1 October 2026, the importer or its authorized agent of "a TSCA chemical substance in bulk form or as part of a mixture" must file one of two statements:

• Positive certification: "I certify that all chemical substances in this shipment comply with all applicable rules or orders under TSCA and that I am not offering a chemical substance for entry in violation of TSCA or any applicable rule or order thereunder."
• Negative certification, for TSCA-excluded chemicals not clearly identified as such: "I certify that all chemicals in this shipment are not subject to TSCA."

The certification is filed in writing or electronically in ACE "prior to release of the shipment," with the certifier's name, phone number and email address. Chemicals contained in articles need certification only "if required to do so by a rule or order issued under TSCA."

Classification and TSCA interact in two practical ways. First, the same chemistry that decides the chapter, meaning the CAS number, the composition and whether the product is a defined compound or a mixture, is what the person signing the certification must know. Second, TSCA carries its own definitions, so an HTS answer, such as primary form versus article under Chapter 39, does not settle a TSCA question. The two are separate legal tests.

Our view: chemical importers should build the classification file and the TSCA file from the same composition data, reviewed once, so the two cannot drift apart.

What does a defensible chemical classification file contain?

Pulling the notes and rulings together, a chemical or plastics classification is defensible when the file answers these questions with evidence:

1. Identity: CAS number, chemical name and the supplier's composition by weight, including solvents and additives.
2. Defined compound or not: which item of Note 1 to Chapter 28 or 29 is satisfied, or why none is.
3. Purpose of every addition: storage, transport, identification or safety, or performance.
4. Polymer data: monomer weight percentages, whether the polymer is chemically modified or a graft copolymer, and the physical form under Note 6.
5. Exclusions checked: Chapter 39 Note 2 for plastics, and Section VI Notes 1 and 2, which send goods described in headings 2844 and 2845 (radioactive elements and isotopes) to those headings and certain retail or dosed put-ups, such as 3808 pesticides, to their own headings.
6. Precedent: the CROSS rulings relied on, with a note on how the facts match and confirmation that each cited subheading still exists.
7. Entry requirements: the TSCA certification type, and who signs it.

Material choices made at design time also move these outcomes. Our piece on material composition and tariff impact covers that side.

Putting chapter-note reasoning into your chemical SKU review

When a technical data sheet leaves the chapter open, the answer turns on facts the description does not state: why an additive is there, what carries the polymer, which monomer predominates. GingerControl asks about those points before assigning a classification, reads relevant CROSS rulings during the reasoning, and returns a report grounded in the Section and Chapter Notes.

GingerControl is an HTS Classification Researcher. It follows the same reasoning process a licensed customs broker uses, meaning GRI analysis, Section and Chapter Note review, and CROSS ruling research, but the final classification decision benefits from professional judgment. GingerControl produces documentation that supports the classification decision; it does not provide legal advice or replace licensed customs expertise, and it does not file TSCA certifications or entries.

Classify a chemical or plastics SKU with GingerControl

References

1. U.S. International Trade Commission. Harmonized Tariff Schedule of the United States, Revision 20 (2026), General Rules of Interpretation. GRI text on hts.usitc.gov. Read 8 October 2026.
2. U.S. International Trade Commission. HTS Revision 20 (2026), Section VI Notes and Chapter 28 Notes. Chapter 28 file. Read 8 October 2026.
3. U.S. International Trade Commission. HTS Revision 20 (2026), Chapter 29 Notes. Chapter 29 file. Read 8 October 2026.
4. U.S. International Trade Commission. HTS Revision 20 (2026), Chapter 38 Notes and heading 3824. Chapter 38 file. Read 8 October 2026.
5. U.S. International Trade Commission. HTS Revision 20 (2026), Section VII Notes and Chapter 39 Notes. Chapter 39 file. Read 8 October 2026.
6. U.S. Customs and Border Protection. HQ H273388, 14 November 2016, treated fumed silicas. CROSS.
7. U.S. Customs and Border Protection. HQ H072379, 7 July 2014, denatonium benzoate, 25% in propylene glycol. CROSS.
8. U.S. Customs and Border Protection. NY N211517, 27 April 2012, phenol formaldehyde and urea formaldehyde resin blend. CROSS.
9. Electronic Code of Federal Regulations. 19 CFR 12.121, TSCA reporting requirements, as amended by CBP Dec. 16-28, 81 FR 94985 (27 December 2016). eCFR. Text current as of 1 October 2026.