U.S. exports of Other Styrene Polymers in Primary Forms (NESOI) (HS 390390) totaled $52.8M in August 2026.
Importers of Other Styrene Polymers in Primary Forms (NESOI) paid $1.6M in duties in August 2026, an average duty rate of 9.41% — duty actually collected as a share of the imports that cleared customs, not the published tariff schedule.
Last updated: August 2026 dataBeyond the named polystyrene and copolymer subheadings, this residual category captures specialty styrene-based polymers in primary forms, including methyl methacrylate-butadiene-styrene (MBS) copolymers — a key impact modifier for PVC — classified at 3903901000, and other miscellaneous styrene polymers at 3903905000. MBS is a technically distinct impact modifier used heavily in rigid PVC pipe and profile extrusion, and its classification here rather than under heading 3904 is a common point of confusion for importers. South Korea and Japan are among the leading suppliers, reflecting deep petrochemical integration in those markets.
AI-written summary of the official U.S. Census Bureau trade figures on this page — verify before relying on it.
416 import shipments a month
MBS (methyl methacrylate-butadiene-styrene) is classified under heading 3903 because it is a copolymer in which styrene is a principal constituent monomer, placing it within the styrene polymers heading. It is not a vinyl chloride polymer and does not belong under 3904, even though its primary commercial use is as an impact modifier for PVC compounds.
These polymers are typically imported as pellets, granules, powders, or dispersions — all qualifying as 'primary forms' under Chapter 39 Note 6. The physical form does not change the heading classification, but it may affect packaging, handling, and Customs entry documentation, particularly for powders that may require additional safety data sheet review.
Subheading 1 of 5 in heading 3903
Subheading 390390 · $52.8M of $108.0M
ImportsExports
Imports
$17.3MYoY · free account
Exports
$52.8MYoY · free account
12-mo low · imports
Low · free accountOver the twelve months to August 2026, the U.S. imported $194.6M of Other Styrene Polymers in Primary Forms (NESOI) and exported $606.6M.
Through August 2026. Source: U.S. Census Bureau.
HS10 import codes under this HS6 parent, each with its own page. Source: U.S. Harmonized Tariff Schedule.
| Code | Description | Imports for consumption | Average duty rate | Dutiable Share | Duty Collected |
|---|---|---|---|---|---|
| 3903905000 | Polymers of Styrene, In Primary Forms, NESOI | $15.3M | 8.45% | 66.82% | $1.3M |
| 3903901000 | Methyl Methacrylate-Butadiene-Styrene(Mbs)Copolymr | $1.3M | 20.88% | 100.00% | $270K |
HS10 export codes under this HS6 parent, each with its own page. Source: U.S. Schedule B export classification.
| Code | Description | Export Value |
|---|---|---|
| 3903900000 | Polymers of Styrene, In Primary Forms, NESOI | $52.8M |
Import lines come from the U.S. Harmonized Tariff Schedule and export lines from Schedule B. The two are numbered by different agencies, so the same 10-digit code can appear in both tables describing a different product.
Exports · August 2026
destination
Mexico and China together take 52% of it.
customs district
origin
entry
rate provision · imports
29.3% enters free of duty; duty collected equals 9.41% of imports for consumption.
Trade Directory
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