**2.3 Colloid preparation**

For the production of colloids there are two groups with different production methods, they are: dispersion methods and condensation methods [3].

#### *2.3.1 Methods of dispersion*

*Mechanical spraying:* for the production of colloids a solid substance is used added to a liquid, using colodal mills, which is a method used in the industry for the production of colloidal pigments.

*Electric spraying:* produced using the Bredig method, in which two electrodes are immersed in water to generate an arc. Spraying results in a coarse suspension from the metal particles. In the suspension you get the hydrosol. Electric spraying is used in the production of metallic colloids. In the reaction of substances such as benzene and ethyl ether, alkaline and alkaline earth colloids are produced.

*Spraying by Ultrasound*: from mechanical vibrations, which can be produced under a piezoelectric quartz generator in an excitation process, the formation spray of colloidal solutions is generated.

*Peptization:* performed with peptizing agents that have the ability to disintegrate, with colloids as the final product. These materials are used, for example, in the food industry in the production of gelatins, gums, and agar from the use of hot water, which is a peptizing agent.

#### *2.3.2 Condensation methods*

The condensation method is a means of producing colloids carried out with the precipitation of an insoluble substance by means of a chemical transformation between solvent substances. During its chemical transformation, the insoluble product is in the molecular state, occurring after condensation.

#### **2.4 Stability of colloids**

The different interactions between the dispersed phase (particles) and the dispersion phase (continuous) constitute one of the critical points in the study of the behavior and stability of colloids. The interactions between the particles that make up a dispersion and the dispersing medium are fundamental to understand colloidal stability [9].

The stability of a dispersion can be thermodynamic or kinetic and one of the ways to understand the difference between them is in terms of the colloid stabilization time. While a thermodynamically stable colloid will remain unchanged for an infinite time, maintaining properties like temperature and concentration unchanged, kinetically stable colloids tend to aggregate over time. Therefore, the study of colloidal chemistry makes it possible to change the time in which the colloid remains kinetically stable [8].

When it comes to particles, the energy in van der Waals' interactions comes from integrating the potential of all the molecules that make it up [10]. Van der Waals interactions between two particles will always be attractive if the particles are made of the same material, no matter what medium they are in [11]. If the particles are different in nature, van der Waals interactions can be attractive or repulsive [12]. In the study of colloidal dispersions, the focus is mostly on the interaction of particles of the same nature, that is, they are attractive interactions [13].

To increase the stability of a colloidal dispersion the steric effect of macromolecules is used to prevent the particles from aggregating by adding a stabilizer that will adsorb on the surface of the particle [13]. If the adsorbed macromolecule is in a good solvent, its chains expand. When it encounters a chain from another particle, there is a restriction in the conformation of both chains in the volume between the two particles, causing a decrease in configurational entropy and an

**127**

**Figure 1.**

*Chemical structure of cellulose.*

*Colloidal Stability of Cellulose Suspensions DOI: http://dx.doi.org/10.5772/intechopen.94490*

ing aggregation.

mechanical agitation [15].

energy of the system [11].

approximately 40 to 45% of the wood mass [17].

**3. Cellulose**

increase in free energy [14]. To minimize this effect, the chains of the macromolecules repel each other, causing a repulsive effect between the particles, prevent-

Regarding the stability of aqueous colloidal dispersions, they are sensitive to the presence of electrolytes and polyelectrolytes (charged polymers of high molecular mass), since the colloidal particles can irreversibly aggregate in the presence of electrolytes and result in large and compact aggregates (clots) by a process called coagulation, while in the presence of polyelectrolytes there may be the formation of less dense aggregates (floccules), which can be easily broken and dispersed by

Understanding and controlling the stability of colloidal dispersions is essential for its satisfactory use. Some specific applications require that such dispersions be maintained over a wide range of temperatures and chemical conditions [8]. For both economic and environmental reasons, water is often required as a dispersing phase, even when the particles that need to be kept in suspension are hydrophobic. Water is a highly structured material, due to the hydrogen bonds that connect the molecules to each other. In the vicinity of a hydrophobic surface, ruptures of the hydrogen bonds between water molecules occur, increasing the free energy in relation to the solution. As a consequence, water is expelled to regions more favorable to hydrogen bonding. The migration of water molecules results in a mutual attraction between hydrophobic surfaces that implies a reduction in the free

Cellulose has stood out in the last 20 years as a study material for several applications, as it is the most abundant, renewable and natural polymer on the face of the Earth [15], and can be found mainly in woody plants (wood), annuals and in grasses [16]. Cellulose is located mainly in the secondary cell wall, corresponding to

Cellulose (C6H10O5) n is a polysaccharide, linear chain containing from hundreds

to thousands of chemical bonds involving carbon, hydrogen and oxygen atoms (**Figure 1**) [18]. The cellulose chain is of high molecular weight, which tends to form hydrogen bonds between the molecules [19, 20]. The hydroxyl groups of cellulose molecules form hydrogen bonds that can be intramolecular or intermolecular,

#### *Colloidal Stability of Cellulose Suspensions DOI: http://dx.doi.org/10.5772/intechopen.94490*

*Colloids - Types, Preparation and Applications*

*Mechanical spraying:* for the production of colloids a solid substance is used added to a liquid, using colodal mills, which is a method used in the industry for the

*Spraying by Ultrasound*: from mechanical vibrations, which can be produced under a piezoelectric quartz generator in an excitation process, the formation spray

The condensation method is a means of producing colloids carried out with the precipitation of an insoluble substance by means of a chemical transformation between solvent substances. During its chemical transformation, the insoluble

The different interactions between the dispersed phase (particles) and the dispersion phase (continuous) constitute one of the critical points in the study of the behavior and stability of colloids. The interactions between the particles that make up a dispersion and the dispersing medium are fundamental to understand

The stability of a dispersion can be thermodynamic or kinetic and one of the ways to understand the difference between them is in terms of the colloid stabilization time. While a thermodynamically stable colloid will remain unchanged for an infinite time, maintaining properties like temperature and concentration unchanged, kinetically stable colloids tend to aggregate over time. Therefore, the study of colloidal chemistry makes it possible to change the time in which the colloid

When it comes to particles, the energy in van der Waals' interactions comes from

integrating the potential of all the molecules that make it up [10]. Van der Waals interactions between two particles will always be attractive if the particles are made of the same material, no matter what medium they are in [11]. If the particles are different in nature, van der Waals interactions can be attractive or repulsive [12]. In the study of colloidal dispersions, the focus is mostly on the interaction of particles

To increase the stability of a colloidal dispersion the steric effect of macromolecules is used to prevent the particles from aggregating by adding a stabilizer that will adsorb on the surface of the particle [13]. If the adsorbed macromolecule is in a good solvent, its chains expand. When it encounters a chain from another particle, there is a restriction in the conformation of both chains in the volume between the two particles, causing a decrease in configurational entropy and an

of the same nature, that is, they are attractive interactions [13].

*Peptization:* performed with peptizing agents that have the ability to disintegrate, with colloids as the final product. These materials are used, for example, in the food industry in the production of gelatins, gums, and agar from the use of hot water,

and ethyl ether, alkaline and alkaline earth colloids are produced.

product is in the molecular state, occurring after condensation.

*Electric spraying:* produced using the Bredig method, in which two electrodes are immersed in water to generate an arc. Spraying results in a coarse suspension from the metal particles. In the suspension you get the hydrosol. Electric spraying is used in the production of metallic colloids. In the reaction of substances such as benzene

*2.3.1 Methods of dispersion*

production of colloidal pigments.

of colloidal solutions is generated.

which is a peptizing agent.

*2.3.2 Condensation methods*

**2.4 Stability of colloids**

colloidal stability [9].

remains kinetically stable [8].

**126**

increase in free energy [14]. To minimize this effect, the chains of the macromolecules repel each other, causing a repulsive effect between the particles, preventing aggregation.

Regarding the stability of aqueous colloidal dispersions, they are sensitive to the presence of electrolytes and polyelectrolytes (charged polymers of high molecular mass), since the colloidal particles can irreversibly aggregate in the presence of electrolytes and result in large and compact aggregates (clots) by a process called coagulation, while in the presence of polyelectrolytes there may be the formation of less dense aggregates (floccules), which can be easily broken and dispersed by mechanical agitation [15].

Understanding and controlling the stability of colloidal dispersions is essential for its satisfactory use. Some specific applications require that such dispersions be maintained over a wide range of temperatures and chemical conditions [8].

For both economic and environmental reasons, water is often required as a dispersing phase, even when the particles that need to be kept in suspension are hydrophobic. Water is a highly structured material, due to the hydrogen bonds that connect the molecules to each other. In the vicinity of a hydrophobic surface, ruptures of the hydrogen bonds between water molecules occur, increasing the free energy in relation to the solution. As a consequence, water is expelled to regions more favorable to hydrogen bonding. The migration of water molecules results in a mutual attraction between hydrophobic surfaces that implies a reduction in the free energy of the system [11].
