Clays and Clay Minerals as Layered Nanofillers for (Bio)Polymers

Abstract

This introductory chapter presents the most relevant structural, physical, and chemical properties of clay minerals for the formation of nanocomposites with polymers. The general principles of silicates classification are outlined in order to better understand the structures of the various types of clay minerals as phyllosilicates. Cation exchange capacity (CEC), surface area, porosity, and rheological properties of clay minerals are briefly discussed. The physico-chemical properties of clay mineral layers, including the reactivity at the edges surfaces, are introduced together with their consequences for the various mechanisms of clay-polymer interactions. The chapter closes on a brief presentation of synthetic clay minerals and a general introduction to clay polymer nanocomposites.

Advanced Nano-biocomposites Based on Starch

“…The layer is the result of the condensation of tetrahedral sheets (T) and octahedral sheets (O) (Bergaya et al 2012). Phyllosilicates are often referred to as 1:1 or 2:1.…”

“…In fact, the lath-like fragments of T-O-T structure extend along the c axis, being connected by siloxane bridges (Fig. 8) (Bergaya et al 2012;Duquesne et al 2007). Some isomorphic substitutions occur inside these central layers creating a negative charge naturally counterbalanced by the presence of inorganic cations (Na + , Ca 2+ , etc.).…”

“…Another example is halloysite, which has a structure similar to kaolinite but has a single layer of water molecules existing between the T-O sheets. It has structural constraints in the layers which cause them to curl and forms spheroidal aggregates (Bergaya et al 2012).…”

“…Thus, the potassium is trapped in these cavities, leading to the reduced hydration ability. Swelling is typical enough of smectites to have provided their alternative name of "swelling clays" (Bergaya et al 2012). In contrast, the other natural phyllosilicates lack the ability to swell in water, which greatly limits their application in the development of starch-based nano-biocomposites.…”

Synthesis of organoclays: A critical review and some unresolved issues

“…Among the smectite groups, montmorillonite (Mt) has held the limelight in the preparation of OC because of its moderate charge density and cation exchange capacity (CEC), interlayer swelling ability, and propensity for intercalating simple and polymeric organic compounds (Bergaya et al, 2011b(Bergaya et al, , 2012Murray, 2000;SwartzenAllen and Matijevic, 1974;Theng, 1974Theng, , 2012, not to mention its availability and low cost. At the same time, quaternary ammonium halides bearing long alkyl chains have been widely used for modifying clay minerals because of the ease with which the QAC can exchange the inorganic compensator exchangeable cation in the interlayer space of Mt.…”