What is the optimal pH for HPMC in detergents?

Hydroxypropyl methylcellulose (HPMC), a nonionic, water-soluble polymer, is widely used in detergent formulations, primarily as a thickener, stabilizer, suspending agent, and film-forming agent. Its performance is highly dependent on the pH environment.

HPMC is generally stable within the pH range of 3–11, but its solubility, viscosity, and long-term stability vary significantly under different pH conditions. Detergent systems typically adjust their pH based on their intended use: household laundry detergents are typically neutral to slightly alkaline (pH 7–9), industrial cleaners are more alkaline (pH 9–11), and detergents for sensitive fabrics or skin care are often controlled at a slightly acidic to neutral pH (pH 6–7).

Under acidic conditions (pH < 5), HPMC may undergo partial hydrolysis, resulting in a decrease in viscosity and a shortened shelf life. Strong alkaline conditions (pH > 10) accelerate its alkaline hydrolysis, causing substituent shedding and performance loss. Therefore, the optimal pH range for HPMC in detergents is 6–9. Within this range, HPMC exhibits significant thickening effects, stable rheological properties, and good compatibility with anionic and nonionic surfactants, while also meeting the safety and mildness requirements of most household detergents.

If the formulation requires exposure to high alkalinity, it is recommended to select a high-substitution, high-viscosity grade of HPMC, or to combine it with an alkali-resistant polymer (such as a polyacrylic thickener) to enhance system stability. During production, avoid adding HPMC directly to high-alkaline media. Instead, disperse it in water and then gradually adjust the pH to minimize the risk of localized degradation.

In summary, while HPMC has a wide pH tolerance, its optimal application range in detergents is pH 6–9, achieving both maximum performance and system stability.