HS Code 39.13 – Natural polymers (e.g. alginic acid) and modified natural polymers (e.g. hardened proteins, chemical derivatives of natural rubber), n.e.c. or included, in primary forms

HS code 3913 is a 4-digit heading in the Harmonized System that covers: Natural polymers (e.g. alginic acid) and modified natural polymers (e.g. hardened proteins, chemical derivatives of natural rubber), n.e.c. or included, in primary forms. Heading 3913 covers natural polymers and modified natural polymers, not elsewhere specified or included, in primary forms. This classification is vital for materials derived from natural sources that undergo chemical modification but are not cellulose derivatives (which fall under 3912) or synthetic polymers (3901-3911). The 'primary forms' criterion means the goods are in bulk states like liquids, pastes, powders, granules, flakes, blocks, or lumps, ready for further processing, not yet shaped into finished articles. This heading includes a diverse range of biopolymers and their altered states, such as alginic acid, its salts and esters (alginates), hardened proteins, and chemical derivatives of natural rubber. Examples include casein derivatives, chitosan, carrageenan, and cyclized or chlorinated natural rubber. The scope is critical for industries like food processing, pharmaceuticals, cosmetics, and specialty chemicals, where these natural and modified biopolymers serve as gelling agents, thickeners, stabilizers, binders, or film-forming agents. For instance, alginates are extensively used in food and medical applications, while hardened proteins find use in adhesives and coatings. Accurate classification under 3913 ensures proper customs duties, regulatory compliance, and eligibility for trade benefits. It differentiates these specialized natural-based polymers from both raw natural materials (e.g., natural rubber latex 4001, starches 1108, unmodified proteins 3504) and wholly synthetic plastics within Chapter 39, reflecting their unique position as processed natural substances with enhanced properties.

Alginic acid powder, Sodium alginate granules, Calcium alginate powder, Propylene glycol alginate, Carrageenan powder, Chitosan flakes, Hardened casein, Caseinates, Chemically modified starch (not cellulose-based), Chlorinated natural rubber, Cyclized natural rubber, Hydrochlorinated natural rubber, Grafted natural rubber, Oxidized natural rubber, Depolymerized natural rubber, Shellac derivatives, Gellan gum, Xanthan gum (if chemically modified natural origin), Gum Arabic derivatives, Agar-agar derivatives, Pectin derivatives, Modified soy proteins, Modified gelatin, Modified albumin, Protein hydrolysates (if hardened or chemically modified)

Traders often confuse Heading 3913 with unmodified natural products, such as raw natural rubber (4001), unmodified starches (1108), or basic proteins (3504), failing to recognize the 'modified' aspect required for 3913. Another common error is to classify cellulose derivatives (e.g., HPMC, CMC) under 3913 instead of the more specific 3912. Conversely, some might incorrectly classify highly processed or compounded forms of these materials, or finished articles, under 3913 when they should be in other headings within Chapter 39 or even other chapters depending on their final form and use.

In 2025, the top exporters of HS code 3913 in UN Comtrade data were Sweden ($1.1B, 30% of world exports), China ($803M) and the United States ($356M). World exports came to about $3.7B, adding countries' reported figures and partner-based estimates for those that did not report (UN Comtrade data). Countries that did not report 2025 data are estimated from partner records, which can understate them.

In 2025, the top importers of HS code 3913 in UN Comtrade data were the United States ($465M, 12% of world imports), South Korea ($428M) and Japan ($271M). World imports came to about $4.0B, adding countries' reported figures and partner-based estimates for those that did not report (UN Comtrade data). Countries that did not report 2025 data are estimated from partner records, which can understate them.

HS code 3913 is a 4-digit heading under Chapter 39 of the Harmonized System. The first 2 digits (39) identify the chapter, and digits 3-4 (13) specify the heading. This code contains multiple 6-digit subheadings for precise product classification.