🎨 Coatings & Inks
Cellulose Acetate Butyrate (CAB): Butyric Acid in Coatings and Inks
The "butyrate" in one of the coating industry's most versatile resins. Here is how butyric acid builds better flow, clarity and durability into CAB.
Ask most people what butyric acid (butanoic acid, CAS 107-92-6) is used for and few will mention coatings - yet this is one of its most technically important roles. Butyric acid is the source of the butyryl groups in cellulose acetate butyrate (CAB), a cellulose-ester resin prized across coatings, inks and plastics. 🎨 It is also the reason butyric acid sits within a coatings portfolio in the first place.
This article explains what CAB is, the specific role butyric acid plays, and where the resin earns its keep. It is part of our butyric acid series - for the flavor-and-fragrance ester story, see Butyric Acid Esters in Flavors & Fragrances, and for the full application map, the pillar guide Butyric Acid Uses and Applications.
⚗️ What Is Cellulose Acetate Butyrate?
CAB is a mixed cellulose ester. Cellulose - a natural polymer of glucose units, each carrying hydroxyl groups - is reacted with both acetic acid/anhydride and butyric acid/anhydride. This attaches a mix of acetyl and butyryl groups along the cellulose chain. 🔬
The ratio of acetyl to butyryl (and residual hydroxyl) is what makes CAB tunable: adjust it and you dial in solubility, hardness, flexibility and compatibility for a given coating system.
🧩 The Role Butyric Acid Plays
Why add butyryl groups at all, rather than just making cellulose acetate? Because the longer butyryl chain changes the resin's behavior in ways coatings formulators want: ✅
📊 CAB vs Cellulose Acetate
| Property | Cellulose Acetate (CA) | Cellulose Acetate Butyrate (CAB) |
|---|---|---|
| Moisture resistance | Lower | Higher |
| Solvent/resin compatibility | More limited | Broader |
| Flexibility | Stiffer | More flexible (tunable) |
| Typical coatings use | Narrower | Wide (auto, wood, inks) |
🚗 Where CAB Is Used
Automotive & Refinish Coatings
CAB's flagship application. It controls the orientation of metallic and pearlescent flakes for an even, brilliant finish, speeds solvent release to reduce sags and mottling, and improves flow. This is why CAB grades are a mainstay of automotive basecoats and refinish systems. 🚗
Wood & Industrial Finishes
In wood coatings, CAB contributes fast drying, good clarity, and a smooth, hard yet flexible film - useful for furniture and cabinetry finishes. 🪵
Printing Inks
CAB acts as a resin in certain printing inks, improving pigment wetting, film clarity and rub resistance, and helping control flow on press. 🖨️
Plastics, Films & Coatings for Optics
Beyond liquid coatings, CAB is molded and cast into clear, tough plastics and films, used historically in items from eyewear frames to tool handles, thanks to its clarity, dimensional stability and toughness. 🕶️
🧪 Sourcing Butyric Acid for Coatings
Coating and resin applications typically use technical-grade butyric acid, where reactivity and consistent assay matter more than food-safety limits. To match the right grade to your process, see How to Choose a Butyric Acid Grade. 💡
As a specialty chemical supplier to the coatings and inks sector - backed by the manufacturing strength of the Sinolook group - Sinolook Chemical can support both the butyric acid feedstock and related coating raw materials. Browse our N-Butyric Acid product page for specifications.
💬 Frequently Asked Questions
🔹 What is cellulose acetate butyrate used for?
CAB is used in automotive and refinish coatings, wood and industrial finishes, printing inks, and clear molded plastics and films. It improves flow, leveling, solvent release, clarity and weather resistance.
🔹 How does butyric acid relate to CAB?
Butyric acid (or its anhydride) supplies the butyryl groups that are attached to the cellulose backbone alongside acetyl groups. Those butyryl groups are what give CAB its improved compatibility, moisture resistance and flexibility versus plain cellulose acetate.
🔹 Why is CAB used in automotive coatings?
It controls metallic and pearlescent flake orientation for an even finish, promotes fast, uniform solvent release to prevent defects, and improves flow and leveling - all valuable in basecoats and refinish systems.
🔹 What is the difference between CAB and cellulose acetate?
CAB contains butyryl groups in addition to acetyl groups, giving it better moisture resistance, broader compatibility and more flexibility than cellulose acetate - which is why it is favored in a wider range of coatings.
🔹 What grade of butyric acid do coatings applications need?
Typically technical/industrial grade, since the acid is consumed in making the resin and food-safety impurity limits are not relevant. Confirm assay and specification with your supplier - see our grade-selection guide.
📚 Related Reading
🍍 Other Esters
Butyric Acid Esters in Flavors & Fragrances →The other side of butyrate esters - fruity aromas instead of coating resins.
🛒 Buyer's Guide
How to Choose a Butyric Acid Grade →Technical grade for coatings and resins - and the specs to confirm.
🗺️ Pillar Guide
Butyric Acid Uses and Applications →The complete map of butyric acid applications across every major industry.
Sourcing Butyric Acid for Coatings or Inks? 📩
We supply butyric acid (CAS 107-92-6) for coating, resin and ink applications, with technical documentation, CoA and SDS. Tell us your process and volume and our team will match specification and packaging. Sinolook Chemical, backed by the Sinolook group, serves customers in 50+ countries.
