Papermaking is a core area of strength for CMC/CMS:

● Internal addition: enhances the retention of fillers and fine fibers (retention aid and drainage aid), reduces fiber loss in white water, and improves paper machine operational efficiency.

● Surface sizing: Enhances the paper’s dry and wet strength, oil resistance, ink absorbency, and water resistance, while improving printability.

● Coating adhesives: Used in coatings as thickening and stabilizing agents to improve coating rheology and enhance paper gloss and printability.

● Filler stabilization: Acts as a thickening and binding agent in fillers, enhancing paper gloss, improving toughness, and increasing abrasion resistance. CMS offers outstanding cost-effectiveness in the papermaking industry and is the preferred alternative to CMC.

In oil and gas drilling operations, CMC is primarily used as a viscosity enhancer and fluid-loss reducer in drilling fluids (mud):

● Increases mud viscosity, enhancing its ability to carry cuttings;

● Forms a dense filter cake on the wellbore wall, reducing fluid loss and ensuring wellbore stability;

● Excellent salt and calcium resistance, suitable for complex formations;

● High-viscosity, salt-tolerant CMC is the core grade for drilling applications; CMS can serve as a cost‑effective alternative in certain scenarios.

Food-grade CMC (FH9/FH9, extra‑high grade) is a food additive approved for use in China (INS No. 466), and its primary functions in food are as a thickener, stabilizer, and emulsifier.

● Beverages: In fruit juices and plant‑protein drinks, it prevents pulp settling and layering, enhances mouthfeel, and is added at 0.1%–0.5%.

● Ice cream / frozen foods: Controls ice crystal growth, increases overrun, and delivers a smooth, creamy texture; use at 0.2%–0.5%.

● Dairy products: Stabilizes protein systems in yogurt and milk beverages, preventing whey separation.

● Seasonings: In soy sauce, ketchup, salad dressings, and jams, it provides thickening, stabilization, and improved adhesion to container walls.

● Flour-based products: In noodles and bread, it enhances gluten strength, reduces breakage, and improves texture.

● Meat products: In ham sausages and luncheon meats, it enhances water retention, improves elasticity, and facilitates slicing.

Viscosity selection depends on the application and formulation requirements:

● Low-viscosity type (<100 mPa·s): Suitable for applications requiring high‑concentration incorporation and low system viscosity, such as pharmaceutical tablet coating, paper surface sizing, and low‑viscosity coatings, among others.

● Medium-viscosity type (100–1000 mPa·s): Offers the broadest versatility and is suitable for food thickening, toothpaste, detergents, textile printing pastes, ceramic green bodies, and more.

● High-viscosity grade (1,000–5,000 mPa·s): Suitable for applications requiring strong thickening and excellent water retention, such as oilfield drilling muds, personal care products, coatings, construction putties/mortars, ice cream, latex paints, and more.

● Ultra-high viscosity grade (>5000 mPa·s): For specialized high-end applications, such as oilfield fracturing fluids and high‑water‑retention specialty construction materials.

The key metrics and their definitions are as follows:

● Appearance: White or slightly yellowish powder or granules, reflecting the product’s purity and processing quality.

● Viscosity (mPa·s): The rotational viscosity of a 1% or 2% aqueous solution at 25°C, which is the key parameter for classifying product grades and directly determines thickening performance. Common categories include low viscosity (<100), medium viscosity (100–1,000), high viscosity (1,000–5,000), and ultra‑high viscosity (>5,000).

● Degree of Substitution (DS): The average number of hydroxyl groups on each anhydroglucose unit that have been substituted by carboxymethyl groups, ranging from 0.2 to 1.5. A higher degree of substitution results in improved water solubility, greater transparency, and enhanced salt tolerance.

● Purity (Content): Percentage of active ingredients; food-grade ≥ 99.5%.

● pH: The pH of a 1% aqueous solution is typically between 6.0 and 8.5, reflecting the product’s acidity or alkalinity.

● Moisture (%): ≤10%; excessive moisture can lead to caking and compromise storage stability.

● Chloride (%): Reflects residual by-products; stricter control is applied to high-end products.

● Insoluble matter (%): Reflects solubility; the lower, the better.

Both belong to the class of carboxymethyl ether–based water-soluble polymers, but their key differences are as follows:

Comparison dimension	CMC (Sodium Carboxymethyl Cellulose)	CMS (Sodium Carboxymethyl Starch)
Source of raw materials	Natural cellulose (cotton linters / wood pulp)	Natural starches (corn / cassava / potato)
Molecular structure	Linear molecular chain	Branched molecular structure
Acid resistance / Heat resistance	Stronger, with a broader pH tolerance range.	Relatively weak; select a model suitable for high-acid, high-temperature environments.
Viscosity performance	Stable viscosity and excellent shear stability.	Slightly inferior long-term stability
Cost	Relatively high	Outstanding value for money, with low costs.
Typical areas of strength	Food, pharmaceuticals, oil drilling, high-end personal care products, papermaking, ceramics, coatings, textile printing and dyeing, cat litter, animal feed, fertilizers, desiccants, and more.	Papermaking, textile sizing agents, building‑material putties, and general daily‑use chemical products, among others.

Selection recommendation: For high-end formulations that demand excellent acid resistance, heat resistance, and long-term stability, CMC is the preferred choice; for applications with higher water‑retention requirements, cost sensitivity, and mid‑ to low‑end industrial uses, CMS offers better value. The two can also be blended to balance performance and cost.

Both CMC and CMS are environmentally friendly polymeric materials, and their safety has been widely recognized.

● Human Safety: Food-grade CMC/CMS is an internationally recognized safe food additive. The FAO/WHO Joint Expert Committee on Food Additives (JECFA) has set its ADI (Acceptable Daily Intake) at “not specified,” meaning it may be used in appropriate amounts as needed for production. The U.S. FDA classifies it as a GRAS (Generally Recognized As Safe) substance, and China’s GB 2760 permits its use in various foods at levels consistent with production requirements. Pharmaceutical‑grade products meet pharmacopoeial standards and can be directly incorporated into oral and topical formulations.

● Skin‑contact safety: This cosmetic‑grade product is non‑irritating and non‑sensitizing to the skin, making it widely suitable for use in toothpastes, cosmetics, and other products that come into direct contact with the human body.

● Environmental friendliness: CMC/CMS is derived from natural cellulose and starch, is biodegradable, and does not persist in the environment. Its production process generates no highly toxic or hazardous emissions, making it a green chemical product.

Sodium carboxymethyl starch (CMS) is a water-soluble polymeric starch ether obtained by carboxymethylation of natural starches such as corn and cassava. It appears as a white or slightly yellowish powder, exhibits excellent solubility in cold water, and possesses functions including thickening, stabilization, water retention, film formation, and suspension. CMS serves as an ideal substitute for CMC, offering distinct advantages in cost-effectiveness and rapid dissolution in cold water, and is widely used in papermaking, textiles, construction materials, daily chemicals, food, pharmaceuticals, and other industries.

Sodium carboxymethyl cellulose (CMC) is an anionic cellulose ether polymer derived from natural cellulose through alkalization and etherification. It appears as a white or slightly yellowish powder, readily soluble in water to form a transparent, viscous colloid. CMC exhibits excellent thickening, suspending, emulsifying, water-retaining, film-forming, and stabilizing properties, earning it the nickname “the MSG of industry.” It is widely used in the food, pharmaceutical, personal care, petroleum, textile, papermaking, construction materials, and ceramics industries.