# HS code 3913.90: Natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms

> HS code 3913.90 covers natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms, other than those classified in 3913.10. It sits in heading 39.13 (natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms) in chapter 39 (plastics and articles thereof). Other goods of heading 39.13 are classified under 3913.10 (alginic acid, its salts or esters). National tariff lines under 3913.90 are live on border.bot for the United States (4 lines, also used by 1 other country).

Source: https://border.bot/hs-codes/391390
Last updated: 11 October 2026

[HS codes](https://border.bot/hs-codes) / [Chapter 39](https://border.bot/hs-codes/39) / [39.13](https://border.bot/hs-codes/3913) / [3913.90](https://border.bot/hs-codes/391390)

## Key facts

- HS code: 3913.90
- Covers: Natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms
- Heading: [39.13: Natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms](https://border.bot/hs-codes/3913)
- Chapter: [39: Plastics and articles thereof](https://border.bot/hs-codes/39)
- Edition: HS2022
- Duty in the United States: [See its 4 lines](https://border.bot/countries/united-states/hs-codes/391390)

## What this code covers

HS code 3913.90 covers natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms, other than those classified in 3913.10.

The legal text of the subheading is “Other”, in HS2022.

## What it doesn’t cover

Other goods of heading 39.13 are classified under 3913.10 (alginic acid, its salts or esters).

- [3913.10](https://border.bot/hs-codes/391310) Alginic acid, its salts and esters

## How it is structured

3913.90 is a six-digit subheading. Its first two digits, 39, are the chapter; the first four, 3913, are heading 39.13; the last two, 90, identify the subheading within the heading.

Countries add their own digits after these six for their national tariff lines.

- Chapter 39: Plastics and articles thereof
- Heading 39.13: Natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms
- Subheading 3913.90: Other

## In other countries

National tariff lines under 3913.90 are live on border.bot for the United States (4 lines, also used by 1 other country).

- [United States](https://border.bot/countries/united-states/hs-codes/391390): 4 lines, used by 1 other country

- Previous subheading: [3913.10](https://border.bot/hs-codes/391310) Alginic acid, its salts and esters
- Next subheading: [3914.00](https://border.bot/hs-codes/391400) Ion-exchangers based on polymers of headings 39.01 to 39.13, in primary forms

## Frequently asked questions

### What does HS code 3913.90 cover?

HS code 3913.90 covers natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms, other than those classified in 3913.10.

### Which heading and chapter is HS code 3913.90 in?

HS code 3913.90 is in heading 39.13 (natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms) in chapter 39 (plastics and articles thereof).

### Where are goods of heading 39.13 classified when 3913.90 doesn’t fit?

Other goods of heading 39.13 are classified under 3913.10 (alginic acid, its salts or esters).

### Which countries’ tariffs list national lines under HS code 3913.90?

National tariff lines under 3913.90 are live on border.bot for the United States (4 lines, also used by 1 other country).

## Sources and updates

The Harmonized System legal text comes from border.bot release 2 (edition HS 2022), imported from a file, and has been live since 11 October 2026.

This page was last updated on 11 October 2026.

Guidance from published tariff data, not a binding ruling. For a decision customs must follow, apply to the destination’s customs authority for a binding tariff ruling.

Machine-readable: https://border.bot/hs-codes/391390.json