**6.7. Montmorillonite in biopolymer**

Biopolymer modification using montmorillonite as nanofiller is found to improve the thermomechanical properties. Biopolymer produced from chitosan/montmorillonite nanocomposite through diluted acetic acid used as solvent for dissolving and dispersing chitosan and montmorillonite.

Pure chitosan was compared with chitosan-montmorillonite nanocomposite with and without acetic acid in terms of morphological structure and selected properties. Results obtained in XRD and TEM indicated an intercalated and exfoliated nanostructure at a reduced montmorillonite loading and an intercalated and flocculated nanostructure at an increased montmorillonite loading.

Thermal stability and mechanical properties were determined using TGA and nanoindentation. Thermal stability, hardness, and elastic modulus of nanocomposite matrix improve with the increasing loading of nano-dispersed montmorillonite. Crystallinity, thermal stability, and mechanical properties may be influenced by acetic acid residue in chitosan matrix [41].

The study of montmorillonite in potato starch showed the improvement in thermal and Young modulus properties. Nanocomposite films of glycerol-plasticized starch/ montmorillonite were produced. Three different loadings of montmorillonite aqueous suspension were applied to potato starch.

Dispersion of montmorillonite in starch was studied using X-ray diffraction (XRD). Results indicated that the nanomontmorillonite formed an intercalated structure and complete exfoliation was not observed under the experimental conditions used. Thermogravimetric analysis indicated the enhancement in the thermal resistance with the increased loading of montmorillonite; however, the water absorption by the starch-montmorillonite nanocomposite, at 75% constant relative humidity, was reduced. The result of micro-tensile test of nanocomposite film showed that Young modulus improved up to 500% at 5 wt.% of montmorillonite [42].

Multiple porosity model supports two different groups of water present in bentonite: one present in the interlamellar space and the other found in the volume between clay stacks.

Synthetic mica-montmorillonite (SMM) shows Bronsted acidity. SMM studied, for Bronsted

**i.** isomorphous substitution of Si4+ by Al3+ in the tetrahedral layer, and additional NiF doping,

The evaluation of SMM for adsorption energies using ammonia and pyridine showed the acid strength. The composition of SMM platelets influences the acidity [46]. Interesting results were obtained in the study explaining the Bronsted acidity in relation to the platelet structure.

Bronsted and Lewis acid catalytic sites in montmorillonite provided the useful applications [47]. The exchangeability of interlayer cations, through ion exchange, helps in altering the acidic nature. Modified montmorillonite types known as montmorillonite-K-10 (produced by the calcinations of montmorillonite) were found as efficient catalysts. Cation exchange produces

Sodium montmorillonite (NaMMT) is indicated to accelerate the curing of urea-formaldehyde resin. In acid-curing conditions, urea-formaldehyde resin was used as adhesive for plywood and wood particleboard. Cross-linking of urea-formaldehyde in the presence of NaMMT produces plywood with improved water resistance. An accelerating effect on urea-formaldehyde curing was observed in differential scanning calorimetry results. Dry internal bond strength

Organic reagents synthesized using montmorillonite types (cation substituted) used as catalyst include α- aryl β-hydroxycyclic amines, silanols, and methyl cinamates, and the production of multi-substituted imidazopyridines, imidazopyrazines, and imidazopyrimidines.

Green chemistry is a demanding approach in organic synthesis, where the release of hazardous gases and liquids is undesired. Environment damage and ecological balance are required to be least affected. Montmorillonite is a solid acid used in organic synthesis. It has the poten-

Natural and modified clays, including montmorillonite, received significant interest as catalyst (Section 7.8). The use of montmorillonite as a greener catalyst in organic synthesis is reviewed [49]. Several clay-based or montmorillonite-based catalysts are available in market

montmorillonite and clayfen.

Montmorillonite: An Introduction to Properties and Utilization

http://dx.doi.org/10.5772/intechopen.77987

was

17

The strongest acidity was demonstrated by SMM structure where octahedral [AlO]+

replaced adjacent to tetrahedral [Si-(OH)-Al] moieties in the tetrahedral layer.

of wood particleboard increases with small additions of NaMMT [48].

tial to replace liquid acid catalyst with greener effects (**Figure 2**).

including claycop TM, clayfen TM, clayzinc TM, envirocat TM, and so on.

**6.11. Bronsted acidity**

acidity, was based on

**ii.** the effects on platelets, and

**7. Environment concern**

**iii.** the edge termination of clay platelets.

more effective montmorillonite types including Fe<sup>+</sup>

## **6.8. Effects in fiber-forming polymer**

Important properties of fiber-forming polymers may be improved using montmorillonite as a filler [43]. In general, clay mineral (nm) showed flame–retardant effects as assessed by a reduction in the peak heat release rate for various thermoplastic polymers including polystyrene, polyamide-6, polypropylene, polyamide-12, poly(methyl methacrylate), polyethylene, and ethylene vinyl acetate (EVA).

Montmorillonite-nylon-6 (nm) composite was produced through melt bending or compounding technique followed by injection molding using percent loading of organo-montmorillonite (nm) composites ranging 0–5 wt.% content. The desired properties of tensile and flexural properties were indicated optimum at 5 wt.% loading. Other improvement observed includes storage modulus, stiffness, and heat distortion temperature, and the reduction in water absorption relative to virgin nylon-6.

Nanometer-sized particles of montmorillonite may be introduced in polymers/fibers, resulting in an increased resistance to electricity, chemicals, heat and flaming, and enhanced ability to block UV light.

Montmorillonite may be incorporated in fiber-forming polymer through electrospinning/melt spinning. Electrospinning is the technique successfully used for the production of a variety of polymer nanofibers.

The properties of polymer nanofiber produced through electrospinning are influenced by melt viscosity, surface tension, dielectric permeability, electric field strength, solvent properties to evaporate, polymer molecular weight, and concentration.

### **6.9. Flame-retardant finishing of cotton fiber**

Interest in using the clay was observed to obtain the flame-retardant properties in cotton fiber [44]. The two types of local clay samples study to evaluate the flame-retardant effects on bleached cotton fabric.

Aqueous water dispersion was applied to bleached cotton fabric. The finished fabric was assessed using vertical flame-retardant test BS EN ISO 6940 2004. Flame retardancy was improved as indicated by the ease of ignition and the char length of burnt cotton fabric.

#### **6.10. Geological repository for spent nuclear fuel**

The growing variety of montmorillonite utilization is perhaps indicated by the use of bentonite in the study to form a part of deep geological repository for spent nuclear fuel. Pure homo ionic Ca-montmorillonite may be considered bentonite-similar system to obtain information on natural bentonite behavior. Water-saturated structure and porosity of Ca-montmorillonite were studied using X-ray diffraction, small angle X-ray scattering, nuclear magnetic resonance, transmission electron microscopy, and ion exclusion. The obtained results indicate multiple porosity for the bentonite structure [45].

Multiple porosity model supports two different groups of water present in bentonite: one present in the interlamellar space and the other found in the volume between clay stacks.
