What is the equivalent of HPMC?

A cellulose ether serving as an emulsifier or thickening agent to disperse colloids in water.

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Hypromellose (also known as hydroxypropyl methylcellulose or HPMC) is a synthetic, inert polymer characterized by its viscoelastic properties. It is commonly utilized in various applications, such as in eye drops, as well as a crucial excipient in oral medications, being a component found in numerous commercial products.

In the food industry, hypromellose functions as an emulsifier, thickening agent, and a vegetarian alternative to animal gelatin, designated under the Codex Alimentarius code E464.

Chemical Properties

Hypromellose appears as a slightly off-white to beige powder, and it can also be processed into granules. When dissolved in water, it forms colloids. This non-toxic ingredient is combustible and can react with oxidizing agents.

Like methylcellulose, hypromellose solutions exhibit thermal gelation; they congeal into a semi-flexible mass when heated to a specific critical temperature. This temperature depends inversely on the concentration of HPMC solution and the methoxy group content. Higher concentrations of methoxy correlate with lower critical temperatures, while the viscosity or rigidity of the resultant mass positively correlates with methoxy concentration.

Applications of Hypromellose

Hypromellose has a wide range of applications across various industries, including:

• Tile adhesives
• Cement renders
• Gypsum products
• Pharmaceuticals
• Coatings and paints
• Food products
• Cosmetics
• Detergents and cleaners
• Eye drops
• Contact lenses
• Polyvinyl Chloride (PVC)

Utilization in Whole Grain Breads

Research is being conducted by Agricultural Research scientists to explore the potential of using hypromellose as a gluten substitute in the creation of all-oat and other grain breads. Similar to gluten, hypromellose can capture air bubbles produced by yeast, facilitating the rising process in bread dough.

Role in Construction Materials

Primarily found in construction materials such as tile adhesives and renders, HPMC serves as a rheology modifier and water retention agent. This polymer enhances the workability and performance of gypsum mixtures, showcasing functionality comparable to HEMC (hydroxy ethyl methyl cellulose).

Major manufacturers, such as DuPont, formerly produced under Dow Wolff Cellulosics GmbH, are among the leading producers of these materials.

Applications in Ophthalmology

Hypromellose solutions are recognized as a semisynthetic tear-film substitute, distinguished by high water solubility, which contributes to visual clarity. The application of hypromellose swells and absorbs water, thickening the tear film. This enhanced retention reduces eye irritation, especially in dry environments.

Moreover, its vegetarian nature offers an alternative to gelatin, which may inflate production costs due to its semisynthetic manufacturing process. Hypromellose 2% solutions are frequently utilized during surgeries for corneal protection.

As an Excipient in Tablets

In addition to ophthalmic uses, hypromellose acts as an excipient in oral tablet and capsule formulations. Depending on its grade, it can control the release of medicinal compounds into the digestive system, also serving as a binder and tablet coating agent.

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Testing Methods

A variety of benchmark tests are conducted to assess hypromellose, including:

• Viscosity
• Degree of substitution (DS)
• Molar substitution (MS)
• Salt content
• Moisture

Viscosity Testing

Hypromellose exhibits non-newtonian characteristics and thixotropic behavior. Various methodologies exist for viscosity testing, with results that may not consistently align across different viscosimeters. Typically, viscosity is presented as a mean within acceptable error ranges. Standard parameters for viscosity testing can include:

• Solution concentration
• Viscometer types
• Viscometer spindle number
• Solution temperature

Degree of Substitution

The degree of substitution reflects the average level of methoxy substitution on the cellulose chain, given simplified as a number between 0 and 3.

Molar Substitution

The molar substitution pertains to hydroxypropoxy levels on the cellulose, possibly exceeding three.

Moisture Content

As cellulose ethers are hygroscopic, moisture levels must be monitored, as exposure can affect their properties. Moisture content is determined by weighing a sample, evaporating it, and comparing weights pre and post drying.

Related Topics

References

Hydroxypropyl Methyl Cellulose (HPMC)

Introduction

SidleyCel® Hydroxypropyl Methyl Cellulose (HPMC) is a non-ionic cellulose ether derived from natural cotton fibers through extensive chemical processes. This odorless, tasteless, and non-toxic white powder dissolves in cold water to create a transparent, viscous solution that possesses properties such as thickening, binding, dispersing, emulsifying, film coating, suspending, absorbing, gelling, and water retention.

Application in Construction

Construction Grade HPMC

Features include:

• Excellent workability, providing appropriate viscosity, good plasticity, and ease of construction.
• Good water retention, ensuring full hydration of mixtures, extending open time, and preventing cracking.
• Good slip resistance, allowing slurry to strongly adhere to surfaces and preventing slippage.

Usage Guidelines: The product can be blended directly into dry mixes, with water added post-dispersion. Recommended dosage is between 0.2% to 0.4%.
Packaging is in 25kg paper bags with PE inner lining. Maximum capacity is 12 tons with pallets in 20' FCL.

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