**5.1. Cation exchange property**

Cation exchange capacity is a property of soil introduced by clay and organic matters. It is the capacity of soil to hold cations (generally Al3+, Ca2+, Mg2+, Mn2+, Zn2+, Cu2+, Fe2+, Na+ , K<sup>+</sup> , H+ ) [20] and described as the quantity of positively charged ions held by the negatively charged surface of clay minerals. It may also be termed as cation exchange capacity (CEC) that may be measured as a centimol positive charge per kg of soil or milli-equivalent (meq) of positive charge per 100 g of soil.

The distribution of electrical ions around clay pores is called membrane polarization. In membrane polarization, the negative ions are oriented to one end of the pore under the influence of

In the study of soil, the clay content in soil can be determined using electrical conductivity

Montmorillonite is a good heat insulator, and heat-resistant effects are obtainable using it as an additive in any substance. This is an area of significant research to produce thermal barrier

Thermal barrier properties of clay minerals had been used in heat-resistant and flameretardant applications. Nanoclay is currently used extensively and investigated in polymer

The variation in the expansion, under heat effects, for metals, polymers, and ceramics had been noted. Generally, the order of thermal expansion magnitude in polymer, metal, and

This relative order is based on the values of linear thermal expansion coefficient which are in

Therefore, an increased thermal stability of montmorillonite introduces its use as a filler in producing polymers to impart a low thermal expansion. However, enhancement in polymer thermal stability requires an increasing aspect ratio, and an aspect ratio of greater than 100 is

Water sorption is an important characteristic of natural clay particles. Clay particles can absorb or lose water in response to changes in humidity content in the ambient environment;

Montmorillonite typically exhibits a gradual dehydration and phase change to a stronger nonexpendable clay. The specific gravity of any type of clay is variable resulting from loss or gain of water. Most of the known clay types are available in nature as a mixture containing

Several studies addressed the swelling behavior of montmorillonite. The interaction of montmorillonite with water introduces useful effects. Water molecules cause swelling in montmorillonite. This swelling is a result of complex montmorillonite-water interactions between

when water is absorbed, it fills the spaces between the stacked silicate layers [27].

several varieties including carbonates, feldspars, micas, and quartz.

C for polymers, metals, and ceramics, respectively [26].

Montmorillonite: An Introduction to Properties and Utilization

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DC potential across the clay pore, and this polarization resists the current flow.

composite to obtain an increased thermal stability and flame retardancy.

Polymer > metal > ceramic.

and membrane polarization as the function of clay content.

**5.3. Heat resistance**

effects in composite material structure.

ceramic may be indicated as follows:

the range of 20–100, 3–20, and 3–5 ppm/°

particles and within the particle itself.

useful.

**5.4. Water sorption**

Fine-grained particles of clay result in an increased surface area per unit mass. Smaller particle size (0.002–0.001 mm in diameter) results in a significantly higher surface area, where a large number of cations can be adsorbed. Theses adsorbed cations impart significant level of electrical conductivity in clay [21].

Ionic substitution in the sheet structure produces useful modifications. Ions like Fe3+ and Al3+ are small enough to enter the tetrahedral coordination with oxygen and substitute Si4+. Similarly, cations like Mg2+, Fe2+, Fe3+, Li1+, Ni2+, and Cu2+ can substitute Al3+ in the octahedral sheet [22]. Large-sized cations such as K<sup>+</sup> , Na+ , and Cs+ are located between the layers and referred as interlayer cations.
