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HSChapter 39
U.S. imports of other styrene polymers in primary forms (nesoi) (HS 390390) totaled $19.0M in April 2026, traded with 29 countries.
Importers of Other Styrene Polymers in Primary Forms (NESOI) paid $2.2M in duties in April 2026 — an effective duty rate of 15% on $14.4M in dutiable value, based on actual customs collections rather than the published tariff schedule. Other Styrene Polymers in Primary Forms (NESOI) imports of $19.0M in April 2026 ran 22% above the year-to-date monthly average of $15.6M.
Last updated: April 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.
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.
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Monthly import values over time
| Country | Imports | Exports | Balance |
|---|---|---|---|
| MEXICO | $4.3M | $19.0M | +$14.7M |
| CHINA | $859K | $7.5M | +$6.6M |
| JAPAN | $1.9M | $4.4M | +$2.6M |
| KOREA, SOUTH | $4.6M | $972K | -$3.6M |
| CANADA | $322K | $4.6M | +$4.3M |
HS10 import codes under this HS6 parent. Source: U.S. Harmonized Tariff Schedule.
| Code | Description | Import Value | Effective Tariff % | Duty Collected |
|---|---|---|---|---|
| 3903905000 | POLYMERS OF STYRENE,IN PRIMARY FORMS,NESOI | $18.1M | 15.41% | $2.1M |
| 3903901000 | METHYL METHACRYLATE-BUTADIENE-STYRENE(MBS)COPOLYMR | $932K | 13.95% | $114K |
POLYMERS OF STYRENE,IN PRIMARY FORMS,NESOI
METHYL METHACRYLATE-BUTADIENE-STYRENE(MBS)COPOLYMR
HS10 export codes under this HS6 parent. Source: U.S. Schedule B export classification.
| Code | Description | Export Value |
|---|---|---|
| 3903900000 | POLYMERS OF STYRENE, IN PRIMARY FORMS, NESOI | $48.9M |
POLYMERS OF STYRENE, IN PRIMARY FORMS, NESOI
14.6M kg
ARTICLES OF PLASTICS, NESOI
HS 392690
FLOOR, WALL, ETC COVERS, VINYL CHLORIDE POLYMERS
HS 391810
TABLEWARE AND KITCHENWARE OF PLASTICS
HS 392410
SACKS & BAGS (INCL CONES) OF POLYMERS OF ETHYLENE
HS 392321
HOUSEHOLD AND TOILET ARTICLES NESOI OF PLASTICS
HS 392490
PLATES, SHEETS ETC, NON-CELL ETC, POLYMER
HS 392010
| Port | Imports | Exports | Balance |
|---|---|---|---|
| LAREDO, TX | $2.6M | $11.9M | +$9.3M |
| HOUSTON, TX | $378K | $5.1M | +$4.8M |
| SAVANNAH, GA | $1.7M | $3.0M | +$1.3M |