Differences, types and uses of HPMC

Introduction

Hydroxypropyl methylcellulose (HPMC) is a multifunctional polymer compound widely used in construction, pharmaceuticals, food, cosmetics and other fields. HPMC has diverse structures and different properties, and its specific applications vary due to its different types and properties. This article will discuss in detail the differences, types and uses of HPMC in various fields, and explore its importance and value in practical applications.

### 1. Differences of HPMC

#### 1.1 Chemical structure

HPMC is a semi-synthetic polymer obtained by chemical modification of natural cellulose. Its basic structural unit is glucose, which is connected by β-1,4-glycosidic bonds to form long-chain molecules. The chemical structure of HPMC mainly includes two substituents: methoxy (-OCH3) and hydroxypropoxy (-OCH2CHOHCH3). The introduction of these substituents makes HPMC have diverse physical and chemical properties.

#### 1.2 Degree of substitution and molecular weight

The performance of HPMC is closely related to its degree of substitution and molecular weight. The degree of substitution refers to the number of hydroxyl groups in the cellulose molecule that are replaced by substituent groups. Depending on the substituent, the substitution degree of HPMC can be divided into methoxy substitution degree (DS) and hydroxypropyl substitution degree (MS). HPMC with a high substitution degree usually has better solubility and water retention. Molecular weight affects the viscosity and thickening effect of HPMC. The higher the molecular weight, the stronger the viscosity and thickening effect.

#### 1.3 Solubility

HPMC has good solubility in both cold and hot water, but the solubility is affected by the substitution degree and molecular weight. HPMC with a high substitution degree dissolves faster in cold water, while HPMC with a low substitution degree dissolves better in hot water. Different solubilities enable HPMC to meet various needs in different application fields.

### 2. Types of HPMC

#### 2.1 Classification by use

HPMC can be divided into three categories according to its main use: industrial grade, food grade and pharmaceutical grade.

##### 2.1.1 Industrial grade HPMC

Industrial grade HPMC is mainly used in building materials, coatings, paints, ceramics, daily chemicals and other fields. It has excellent thickening, water retention, film-forming, lubricating and other properties. It can be used in cement-based materials, gypsum products, tile adhesives, putty powder, etc. in building materials. In coatings and paints, HPMC can be used as a thickener and stabilizer to improve the fluidity and construction properties of coatings.

##### 2.1.2 Food-grade HPMC

Food-grade HPMC is mainly used in the food industry as a thickener, emulsifier, stabilizer, gelling agent, etc. It has good thickening, water retention, film-forming and other functions in food, and is widely used in the production of ice cream, jelly, noodles, condiments and other foods. Food-grade HPMC must meet strict food safety standards to ensure its safety and functionality in food.

##### 2.1.3 Pharmaceutical-grade HPMC

Pharmaceutical-grade HPMC is widely used in the pharmaceutical industry as a tablet binder, a capsule film-forming agent, and a matrix material for sustained-release preparations. Pharmaceutical grade HPMC has good biocompatibility and safety, and can be used in various pharmaceutical forms such as oral, topical, and injection. In pharmaceutical preparations, HPMC can improve the stability of drugs, control the release rate, and improve the bioavailability of drugs.

#### 2.2 Classification by function

According to the functions and application characteristics of HPMC, it can be divided into thickening type, water retention type, film-forming type, emulsifying type and other types.

##### 2.2.1 Thickening HPMC

Thickening HPMC is mainly used in application scenarios where viscosity needs to be increased, such as building materials, coatings, paints, etc. It provides good fluidity and construction properties by increasing the viscosity of the solution. Thickening HPMC has a high molecular weight and high degree of substitution, high viscosity, and significant thickening effect.

##### 2.2.2 Water-retaining HPMC

Water-retaining HPMC is mainly used in application scenarios where moisture needs to be retained, such as building materials, cosmetics, and food. It prolongs the working time of the material and prevents moisture loss and cracking through its excellent water retention performance. Water-retaining HPMC has a medium molecular weight and a moderate degree of substitution, and has a good water-retaining effect.

##### 2.2.3 Film-forming HPMC

Film-forming HPMC is mainly used in application scenarios where a protective film needs to be formed, such as drug coating, cosmetics, food coating, etc. It improves the stability and protective effect of the product by forming a uniform protective film on the surface. Film-forming HPMC has a moderate molecular weight and degree of substitution, and has an excellent film-forming effect.

##### 2.2.4 Emulsified HPMC

Emulsified HPMC is mainly used in application scenarios that require emulsification and stability, such as cosmetics, food, emulsions, etc. It maintains a stable state of oil-water mixture through good emulsification properties to prevent stratification and precipitation. Emulsified HPMC has a moderate molecular weight and degree of substitution, and has a significant emulsification effect.

### 3. Uses of HPMC

#### 3.1 Application in building materials

HPMC is widely used in cement-based materials, gypsum products, tile adhesives, putty powder, etc. in building materials.

##### 3.1.1 Cement-based materials

In cement-based materials, HPMC, as a thickener and water-retaining agent, can significantly improve the working performance of mortar and concrete. Its thickening effect makes the mortar have good viscosity and fluidity, which is convenient for construction; the water-retaining effect can extend the open time of the mortar, ensure the full hydration of the cement, and improve the strength and durability.

##### 3.1.2 Gypsum products

In gypsum products, HPMC, as a thickener and water-retaining agent, can improve the working performance and molding effect of gypsum slurry. Its thickening effect makes the gypsum slurry have good fluidity and operability; the water-retaining effect can extend the setting time of gypsum, reduce cracking and shrinkage, and improve the strength and stability of the product.

##### 3.1.3 Tile adhesives

In tile adhesives, HPMC, as a thickener and water-retaining agent, can improve the construction performance and bonding strength of the adhesive. Its thickening effect makes the adhesive have good viscosity and fluidity, which is easy to apply and adjust; its water retention effect can prolong the open time of the adhesive, ensuring sufficient adhesion and stability.

##### 3.1.4 Putty powder

In putty powder, HPMC, as a thickener and water retainer, can improve the construction performance and adhesion of putty powder. Its thickening effect makes putty powder have good viscosity and fluidity, which is convenient for construction and leveling; its water retention effect can prolong the open time of putty powder, prevent cracking and falling off, and improve construction quality.

#### 3.2 Application in pharmaceuticals

HPMC is widely used in tablets, capsules, sustained-release preparations, etc. in the pharmaceutical industry.

##### 3.2.1 Tablets

In tablets, HPMC, as a binder and disintegrant, can improve the tablet's formability and disintegration properties. Its adhesive effect allows the drug particles to form uniform tablets during tableting, improving the hardness and stability of the tablets; its disintegration effect allows the tablets to disintegrate rapidly in the gastrointestinal tract, releasing the drug and improving bioavailability.

##### 3.2.2 Capsules

In capsules, HPMC acts as a film-forming agent and adhesive to improve the formability and stability of the capsules. Its film-forming effect gives the capsule shell good strength and toughness, protecting the drug from external influences; its adhesive effect allows the capsule shell to be tightly combined with the drug, ensuring the stability and release effect of the drug.

##### 3.2.3 Sustained-release preparations

In sustained-release preparations, HPMC acts as a matrix material and controlled-release agent to control the release rate of the drug and improve the efficacy and stability of the drug. Its matrix effect allows the drug to be evenly distributed in the HPMC matrix.