Hydroxypropyl Methyl Cellulose(HPMC)

HPMC (Hydroxypropyl Methyl Cellulose) is a non-ionic cellulose ether derived from the chemical modification of natural cellulose. It is widely used in industries such as construction, pharmaceuticals, food, cosmetics, and coatings, primarily as a thickener, water retention agent, binder, and film-forming agent.

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Chemical Structure

HPMC is produced by reacting cellulose with methyl chloride (CH₃Cl) and propylene oxide (C₃H₆O) under alkaline conditions. Its chemical structure is as follows:

Cellulose-O-CH3andCellulose-O-CH2CH(OH)CH3Cellulose-O-CH3​andCellulose-O-CH2​CH(OH)CH3​

Here, methyl (-CH₃) and hydroxypropyl (-CH₂CH(OH)CH₃) groups replace the hydroxyl groups (-OH) in the cellulose molecule.

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Key Properties

1. Water Solubility:
   • Easily dissolves in cold water, forming a transparent or semi-transparent colloidal solution.
2. Thickening Ability:
   • Provides excellent thickening effects, significantly increasing the viscosity of the system.
3. Water Retention:
   • Effectively prevents rapid water evaporation in construction materials.
4. Film-Forming Ability:
   • Can form flexible and transparent films.
5. Stability:
   • Exhibits good stability in acidic, alkaline, and saline solutions.
6. Thermal Gelation:
   • Forms a gel when heated, which dissolves upon cooling.
7. Eco-Friendliness:
   • Biodegradable and environmentally friendly.

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Applications

1. Construction Materials:
   • Dry-Mix Mortars: Such as tile adhesives, plasters, and skim coats, to improve workability and water retention.
   • Self-Leveling Mortars: Enhances flowability and anti-settling properties.
   • Waterproofing Mortars: Improves waterproofing performance and bonding strength.
2. Pharmaceuticals:
   • Used as a drug release agent, capsule material, or tablet binder.
3. Food Industry:
   • Used as a thickener, stabilizer, or emulsifier in products such as ice cream, yogurt, and sauces.
4. Cosmetics:
   • Used in emulsions, creams, and other products as a thickener and stabilizer.
5. Coatings:
   • Used in water-based paints to improve viscosity, stability, and film formation.

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Role in Construction Materials

1. Improved Workability:
   • Enhances the lubricity and operability of mortars.
2. Enhanced Water Retention:
   • Prevents rapid water loss, improving the strength after hardening.
3. Reduced Cracking:
   • Minimizes shrinkage and cracking by improving water retention and cohesion.
4. Increased Bonding Strength:
   • Enhances the bonding performance between mortar and substrates.

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Technical Parameters

• Degree of Substitution (DS): Typically ranges from 1.2 to 2.0 for methyl groups and 0.1 to 0.3 for hydroxypropyl groups.
• Viscosity: Available in different viscosities based on application requirements.
• Appearance: White or light yellow powder.
• Solubility: Easily dissolves in cold water, forming a transparent or semi-transparent solution.

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Usage Methods

1. Direct Addition: Add HPMC directly to dry-mix mortars and mix thoroughly with other components.
2. Pre-Dissolution: Dissolve it in water first, then add it to the system.

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Storage and Handling

• Store in a cool, dry place to avoid moisture absorption.
• Keep the packaging sealed to prevent clumping.
• Avoid contact with strong acids, bases, or oxidizers.

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Summary

HPMC is a versatile polymer material widely used in construction, pharmaceuticals, food, cosmetics, and coatings due to its excellent thickening, water retention, film-forming, and eco-friendly properties. If you need more information about its applications or technical details, feel free to ask!