Semua Tentang Nitrocellulose: Jenis, Pelapis Kayu Hibrida NC-PU & Pemilihan Pengeras (Panduan 2026)

For specific TDI hardener options compatible with NC lacquer systems, see also our TDI Trimer Hardener Selection Guide for Indoor Wood Coatings.

What is Nitrocellulose?

Nitrocellulose (NC), also called cellulose nitrate, is an organic polymer produced by the nitration of cellulose with a mixed acid of nitric acid (HNO₃) and sulfuric acid (H₂SO₄). Its general chemical formula is (C₆H₇N₃O₁₁)_n, with the exact degree of substitution depending on how many hydroxyl (–OH) groups on each glucose unit are replaced by nitrate ester (–ONO₂) groups.

In its dry state, nitrocellulose appears as white or pale-yellow cotton-like fibers, flakes, or chips with no distinct odor. It dissolves readily in organic solvents such as acetone, ethyl acetate, butyl acetate, methyl ethyl ketone (MEK), and aromatic hydrocarbons, while remaining insoluble in water. NC is resistant to dilute acids, water, and weak alkalis — but it is highly flammable, and the higher the nitrogen content, the faster and more energetic the combustion.

Discovered by Henri Braconnot in France (1832) and refined by Christian Schoenbein in Switzerland (1845), nitrocellulose was first used as an explosive ("guncotton"). After the First World War, lower-nitrogen grades (10.5–12.2 % N) found enormous application in the coatings industry — particularly automotive finishes and, later, wood lacquers — because of their fast solvent release, high gloss, and easy sanding.

Types of Nitrocellulose: Nitrogen Content & Viscosity Grades

Industrial nitrocellulose is classified by two parameters that together determine which application it suits.

1. By Nitrogen Content (Degree of Nitration)

Nitrogen content (% N) controls solubility, flammability, and end use:

• Low-nitrogen NC (10.7–11.2 % N) — "AS" / E-grade: Best alcohol solubility; used in flexographic and gravure printing inks, leather coatings, and ink binders. Often called "ester-soluble" NC.
• Mid-nitrogen NC (11.8–12.2 % N) — "SS" / A-grade: Balanced solubility in esters, ketones, and aromatic hydrocarbons. The workhorse for wood lacquers, nail polish, and general decorative coatings.
• High-nitrogen NC (12.6–13.5 % N) — H-grade / propellant grade: Lower coating solubility; used in smokeless powders, propellants, and military explosives. Not relevant to the coating industry.

2. By Viscosity Grade

Within each nitrogen class, NC is further graded by its solution viscosity (typically measured in a standard 12.2 % toluene/ethanol solution):

• Low viscosity (¼ sec, ½ sec): High solids loading, easy spraying, used in high-build wood lacquers and clear topcoats.
• Medium viscosity (1 sec, 5 sec): Balanced flow and film strength, the standard for furniture lacquers and sealers.
• High viscosity (15 sec, 30 sec, 60 sec): Stronger film cohesion, slower solvent release, used in lacquer topcoats requiring superior toughness.

For NC-PU hybrid wood coating systems, formulators typically select mid-nitrogen (A-grade) NC at medium viscosity (1–5 sec), then cross-link with a TDI adduct or HDI trimer hardener to lift hardness and chemical resistance.

How Nitrocellulose Is Manufactured

Two industrial processes dominate global NC production: batch and continuous.

Batch Production Process

Defatted cotton linter (or refined wood pulp) is fed into a nitrator and treated with a controlled mixture of nitric and sulfuric acids. Sulfuric acid absorbs the water generated during nitration, keeping the reaction equilibrium pushed toward higher substitution. Once the target nitrogen content is reached, the slurry undergoes acid removal, boiling stabilization, pressurized viscosity adjustment, dewatering, and final blending with a wetting agent (ethanol, isopropanol, or butanol). The commercial product is typically 70 % NC plus 30 % wetting alcohol for safe transport.

Continuous Production Process

Cellulose and mixed acid are dosed continuously into a nitration reactor. The slurry then enters a sectional centrifugal separator: spent acid is recovered in the first stage, replaced by progressively weaker acids, and finally washed with water. Continuous lines yield more uniform nitrogen distribution and lower acid consumption — preferred for large-volume coating-grade NC.

NC Lacquer vs NC-PU Hybrid vs 2K PU: Side-by-Side Comparison

The biggest formulation question wood-coating manufacturers ask is whether to stay with pure NC lacquer, upgrade to an NC-PU hybrid, or switch entirely to a 2K polyurethane system. Here's how the three systems compare across the parameters that matter most on the production floor:

What Is Nitrocellulose Used For?

Nitrocellulose's combination of fast solvent release, hardness, and gloss makes it relevant across five major industries:

1. Wood & Furniture Coatings

The largest single end use. NC lacquers and NC-PU hybrids dominate furniture finishing in Asia because they sand easily, polish to a high gloss, and forgive humid factory conditions. Browse our wood & furniture hardener lineup for the paired PU crosslinkers most commonly used in NC-PU formulations.

2. Printing Inks

Low-nitrogen NC (E-grade) is the standard resin binder for flexographic and gravure inks on flexible packaging. It provides fast drying, sharp print definition, and excellent pigment wetting.

3. Nail Polish & Cosmetic Films

Mid-viscosity NC is the film-former in most nail polishes — it dries fast, builds gloss, and does not damage skin.

4. Adhesives

NC-based solvent adhesives bond paper, leather, and certain engineering plastics where a fast-tack, removable bond is required.

5. Explosives & Propellants

High-nitrogen NC (>12.6 % N) remains a core ingredient in smokeless powder and military propellants. This grade is outside the coatings industry and is tightly regulated worldwide.

NC-PU Hybrid Wood Coating Systems: Why and How

Pure NC lacquer dries fast and sands beautifully — but it falls short on hardness, chemical resistance, and long-term yellowing. The fix that most professional furniture and cabinet manufacturers use today is the NC-PU hybrid system: an NC lacquer formula is cross-linked with a polyisocyanate hardener, combining NC's processability with PU's durability.

How the chemistry works

Nitrocellulose itself does not carry enough free –OH groups for full PU cure. In a hybrid formulation, the resin blend typically includes:

• Nitrocellulose (mid-nitrogen, medium viscosity) — the primary film-former
• An OH-functional resin (alkyd, hydroxy-acrylic, or polyester polyol) — provides the –OH groups the isocyanate reacts with
• A polyisocyanate hardener — TDI adduct, TDI trimer, or HDI trimer/biuret, depending on drying speed and yellowing tolerance
• Plasticizer, solvent blend, matting agent as required

The NCO groups on the hardener react with the OH groups on the polyol, building a cross-linked PU network that locks the NC film in place. The result: a coating that still sands like NC but resists water, alcohol, and household chemicals like PU.

Choosing the right Dongsen hardener for your NC-PU system

• Premium indoor furniture clear topcoat: DL-75 (TDI Trimer, NCO 13 %, free TDI ≤ 0.4 %) — low free-monomer, excellent transparency, the go-to standalone hardener for high-end NC-PU lacquers.
• Fast-drying matte topcoat modifier: HDX-50BA — pale-color modifier engineered to be blended at 5–50 % with a TDI adduct base to control sheen drift and accelerate dry time.
• Non-yellowing NC-PU finish (light woods, white stains, outdoor furniture): step up to aliphatic — HDX-175MPX (HDI trimer, 75 % solids) for general-purpose work, or HDX-100 (100 % solids HDI) for high-performance topcoats.
• Full aliphatic option range for non-yellowing systems: see our aliphatic polyisocyanate hardeners.

If you are already running an NC line and want to know exactly which Dongsen hardener to drop in without reformulating from scratch, our technical team can match your existing NC viscosity and OH-resin chemistry to a starting-point hardener. See also our Blocked Isocyanate Crosslinker Selection Guide if you are evaluating one-component baking-finish alternatives.

Nitrocellulose vs Cellulose: What’s the Difference?

Although their names sound nearly identical, cellulose and nitrocellulose behave very differently in industrial use.

Property	Cellulose	Nitrocellulose
Origin	Natural plant polymer	Chemically modified (nitrated) derivative
Formula	(C6H10O5)n	(C6H7N3O11)n
Solubility	Insoluble in water and most organic solvents	Soluble in acetone, esters, ketones
Flammability	Burns slowly	Highly flammable; can detonate at high N content
Industrial Use	Paper, textiles, biomaterials, viscose fibers	Coatings, inks, adhesives, propellants

In short: cellulose is the natural starting material; nitrocellulose is the engineered derivative that became a backbone of the global coatings industry.

Frequently Asked Questions

What is the difference between nitrocellulose and cellulose?

Cellulose is a natural plant polymer (C₆H₁₀O₅)_n that is insoluble in water and most solvents. Nitrocellulose is the chemically nitrated derivative (C₆H₇N₃O₁₁)_n, which is soluble in esters and ketones, highly flammable, and used as a film-former in coatings, inks, and adhesives.

Why add a PU hardener to a nitrocellulose lacquer?

Pure NC lacquer dries fast and sands well but is soft and yellows over time. Adding a polyisocyanate hardener cross-links an OH-resin component in the formula to build a PU network, giving the film significantly better hardness, water resistance, and chemical resistance without losing NC's fast-drying processability.

What nitrogen content is best for wood coatings?

Mid-nitrogen nitrocellulose (11.8–12.2 % N), often called A-grade or SS, is the standard for wood lacquers. It dissolves well in the ester, ketone, and aromatic solvent blends used in furniture coatings and balances film strength with sanding behavior.

Which Dongsen hardener should I use with my NC lacquer?

For premium indoor furniture clear topcoats, DL-75 (TDI trimer) is the most common standalone choice. For fast-drying matte finishes, HDX-50BA is engineered to be blended with a TDI adduct base to control sheen drift. For non-yellowing finishes on light woods or outdoor furniture, switch to aliphatic options like HDX-175MPX or HDX-100.

Is nitrocellulose safe to ship and store?

Commercial NC for coatings is supplied wet with about 30 % alcohol (ethanol, isopropanol, or butanol) as a wetting agent to prevent fire risk. It must be stored in sealed metal drums away from heat, direct sunlight, and ignition sources. Keep the wetting alcohol level above the specified minimum at all times.

Can I switch from a pure NC lacquer to a 2K PU system on the same line?

Yes, but the formulation, dosing equipment, and pot-life management will change. An NC-PU hybrid is often used as a transition step — it keeps spraying and sanding behavior close to a familiar NC line while introducing the durability of PU. Our technical team can advise on the simplest migration path.