Types of Methyl Cellulose
Methyl cellulose is a chemical compound that has widely different uses across different industries from construction, where it acts as a binding and workability agent, to food, where it is used as a thickener and emulsifier, and even in the pharmaceutical industry. Its versatile properties such as water solubility and gel-forming ability make it an ideal candidate for multiple applications. In turn, this has led to the compound being manufactured into types that have specific characteristics that make them suited to certain applications.
The various types of methyl cellulose differ from each other mainly in the type of viscosity they exhibit, that is, whether they are of the low, medium, or high viscosity type, as well as the grade of the methyl cellulose.
- Low viscosity methyl cellulose - grades of methyl cellulose that have low viscosity are primarily used in industries where they are needed as coating materials, as a release agent in moulds for mass concrete casts, and as a binder in paints, to mention a few uses.
- Medium viscosity methyl cellulose - medium viscosity methyl also has many applications. It is commonly used as a thickener, binder, and lubricant in the construction, food, and pharmaceutical industry. In construction, it is used in plaster and mortar as a water-retaining agent and improves workability in those applications.
- High viscosity methyl cellulose - high viscosity grades of methyl cellulose are commonly used in applications where they serve a temporary function, such as in eye drops, where their efficacy is based on their ability to thicken and gel; in food products, they may be used to mimic textures in low-calorie formulations, and in the oil industry, they may be used as viscosity modifiers in drilling fluids for more effective oil recovery.
Specifications and Maintenance of Methyl Cellulose
Methyl cellulose is manufactured in a wide variety of grades, which differ from each other in the degree of substitution of the cellulose backbone and also the viscosity arising from that degree of substitution. The diverse grades of methyl cellulose are suited to different industries due to their unique rheological profiles.
The major specifications of methyl cellulose that need to be considered include:
- Viscosity - the viscosity of methyl cellulose may be defined in several ways, but the most widely used are the Brookfield Viscosity and the Falling Ball Viscosity. The Brookfield Viscosity is determined using a viscometer that measures viscosity at constant shear rates during the measurement, while falling ball viscosity measures viscosity by measuring the time a ball takes to fall through a sample of the material. Methyl cellulose viscosity grades are specified by the manufacturers in ranges.
- Degree of substitution - the degree of substitution is a measure of the average number of hydroxyl groups on the cellulose chain that have been substituted with methyl ether groups. The degree of substitution is crucial in determining the solubility and gelling properties of the methyl cellulose. For example, low methoxyl cellulose has a lower degree of substitution than high methoxyl cellulose.
- Water solubility - methyl cellulose is available in grades that are readily soluble in cold or hot water.
- Gel point - the gelling properties of methyl cellulose make it ideal for its use in food formulation since it forms gels that are desirable for texture in low-fat foods. The gel point is the temperature at which a solution of methyl cellulose will start to form a gel. The gel point is directly related to the degree of substitution of methyl by ether group.
- Purity - the purity of methyl cellulose is important for specific applications, especially in the pharmaceutical industry, where the compound is used in drug formulation.
Maintenance of Methyl Cellulose
The unique characteristics of the various grades of methyl cellulose that make them suitable for a wide variety of applications also imply that the compound is often exposed to different environments and conditions that may affect it. Maintenance of methyl cellulose is, therefore, important to preserve its properties.
- Storage conditions - It is important to store methyl cellulose in a cool, dry place, away from direct sunlight. UV radiation can break the methyl cellulose polymer chains and reduce their viscosity. Exposure to heat can also increase the rate of hydrolysis of methyl cellulose, which will decrease the degree of polymerization, and consequently, the viscosity of that particular grade of methyl cellulose.
- Contamination - Methyl cellulose is very sensitive to contamination, especially by chemicals that can react with it and alter its chemical structure. Seemingly innocuous substances such as oils and grease can severely contaminate and damage methyl cellulose or render it ineffective. It is, therefore, important to store methyl cellulose in airtight containers that will prevent access by foreign materials.
- Mixing and formulation - Methyl cellulose comes in various viscosity grades that depend on the degree of polymerization of the cellulose backbone. Any mechanical action, including vigorous stirring, can increase the shear stress and, therefore, increase the temperature of the methyl cellulose grade mixture.
- Hygroscopic nature of methyl cellulose - There are various grades of methyl cellulose that are used for different applications in various industries, and they all have to be stored in dry and cool places because they are hygroscopic.
Applications of Methyl Cellulose
Methyl cellulose is a versatile compound with a plethora of applications across many industries due to its unique physicochemical properties. Depending on the viscosity grade, methyl cellulose finds diverse applications that range from providing texture, thermal stability, and emulsification in food to drug delivery systems in the pharmaceutical industry and increased workability, adhesiveness, water retention, and decreased segregation in the construction industry.
- Pharmaceutical Industry - Methyl cellulose's ability to form stable gels makes it an essential polymer in the formulation of controlled-release drug delivery systems. Methyl cellulose is an ophthalmic preparatory ingredient in eye drops where it acts as a moisturizing and lubricating agent with a longer residence time on the eyes.
- Cosmetics and Personal Care Products - Methyl cellulose is used in lotions and creams where it acts as a thickening agent. In cosmetics such as mascaras, methyl cellulose will provide smooth application and improve the product's overall texture and stability. It is also used in the formulation of hair creams where it provides combability and smoothness to the hair.
- Food Industry - Methyl cellulose is a prevalent food additive characterized by E number E461. Methyl cellulose has varied applications in the food industry, particularly in low-fat and reformulated foods, where it improves texture and mouthfeel, which is a desirable characteristic of most foods. Another important application of methyl cellulose in the food industry is where it is used as a temporary fat replacer in products such as sauces and creams.
- Construction Industry - In plaster and mortar, methyl cellulose improves workability, provides water retention that prevents the plaster from drying too quickly during installation, and improves adhesion between the mortar and the surface.
How to Choose Methyl Cellulose
Methyl cellulose is one of the most versatile organic compounds with a plethora of applications across different industries, from food to construction. Its versatility is a function of viscosity grade, degree of substitution, gel formation, and water retention capacity, to mention a few.
It becomes imperative then that questions of the choice and use of methyl cellulose for a particular application depend on the user's needs. The following should be considered when choosing methyl cellulose.
- Viscosity- There are low, medium, and high viscosity grades of methyl cellulose. Low-viscosity grades are used in applications where the user needs a low thicker concentration of methyl cellulose. They find applications in the construction industry, where they are used as water-retaining agents in mortars and plasters. Medium viscosity grades of methyl cellulose find applications in the food industry, particularly as a fat mimetic. The high-viscosity grades are more often than not used in pharmaceutical applications where they are prescribed as thickening agents in eye drops and other medicinal applications.
- Degree of substitution- The degree of substitution of methyl cellulose affects its chemical reactivity and, by extension, its solubility. Grades with a higher degree of substitution are more soluble in water than those with a lower degree of substitution. Pure and high-grade methyl cellulose is used in the pharmaceutical industry in drug formulations and as an eye drop.
- Solubility- Certain viscosity grades of methyl cellulose are soluble in either hot or cold water. Low-viscosity grades are soluble in cold water, while the high-viscosity grades are soluble in hot water.
- Purity - Methyl cellulose is a derivative of cellulose, a natural polysaccharide. The first priority is that naturally occurring cellulose, usually extracted from wood pulp or cotton, has to be of the highest purity to get the best quality of methyl cellulose. Also, chemical processes have to be employed to remove lignin, a complex organic polymer belonging to a class of phenolic compounds that is found in the cell wall of plants, particularly in wood and straw.
Q&A
Q1: Is methyl cellulose eco-friendly?
A1: Yes, methyl cellulose is eco-friendly because it is a derivative of cellulose, which is naturally extracted from wood pulp and cotton.
Q2: Is methyl cellulose vegan-friendly?
A2: Yes, methyl cellulose is vegan-friendly. It is a plant-derived compound that is a synthetic alternative to gelatin, which is animal-derived.
Q3: Does methyl cellulose make organic foods not organic?
A3: No, methyl cellulose does not make organic foods non-organic. It is naturally plant-derived.
Q4: Is methyl cellulose hypoallergenic?
A4: Yes, methyl cellulose is hypoallergenic. It may be used as a thickener, binder, and filler in pharmaceutical applications in drug formulations.
