Structural and Physical Properties of Polyurethane Nanocomposites and Foams

Abstract

Polyurethanes (PUs) are very versatile polymeric materials with a wide range of physical and chemical properties. PUs also have desirable properties, such as high abrasion resistance, tear strength, shock absorption, flexibility, and elasticity, and are widely used as elastomers and coatings. PUs have poor thermal stability, mechanical strength, prone to degradation, etc., and can be improved by using treated clay or by polymer-layered silicates. Basic structure of PU is composed of a linear segmented copolymer with a relatively flexible component derived from a macrodiol mainly of polyester, polyether, or polycarbonate chains, called the soft segment, and a relatively hard and stiff component derived from a diisocyanate and a chain extender, called the hard segment. Thermodynamic incompatibility of the so-called soft and hard segments leads to the formation of the microphase separated structure which determines the physical property of the PUs. In the preparation of PU/clay nanocomposites, modifications of clay nanofillers like montmorillonite by using organic modifiers such as alkylammonium improve the compatibility between hydrophilic organomontmorillonite and hydrophobic PUs. These organic modifiers having positively charged ends can be bonded to the surface of the negatively charged silicate layers resulting in an increase of the interlayer gap (exfoliation), is usually associated with large improvements in properties of PU/clay nanocomposites. This entry describes the present state of science and technology of polyurethane (PU) nanocomposites which include nanosilica and organically modified clay (organoclay) with recent trends like PU/clay nanocomposites and its foams.