Geopolymers - Inorganic polymeric new materials

Abstract

Spectacular technological progress has been made in the last few years through the development of new materials such as 'geopolymers', and new techniques, such as 'sol-gel'. New state-of-the-art materials designed with the help of geopolymerization reactions are opening up new applications and procedures and transforming ideas that have been taken for granted in inorganic chemistry. High temperature techniques are no longer necessary to obtain materials which are ceramic-like in their structures and properties. These materials can polycondense just like organic polymers, at temperatures lower than 100‡. Geopolymerization involves the chemical reaction of alumino-silicate oxides (Al3+ in IV-fold coordination) with alkali polysilicates yielding polymeric Si-O-Al bonds; the amorphous to semi-crystalline three dimensional silico-aluminate structures are of the Poly(sialate) type (-SiO-Al-O-), the Poly(sialate-siloxo) type (-Si-O-Al-O-Si-O-), the Poly(sialate-disiloxo) type (-Si-O-Al-O-Si-O-Si-O-). This new generation of materials, whether used pure, with fillers or reinforced, is already finding applications in all fields of industry. Some examples:pure: for storing toxic chemical or radioactive waste, etc. filled: for the manufacture of special concretes, molds for molding thermoplastics, etc. reinforced: for the manufacture of molds, tooling, in aluminum alloy foundries and metallurgy, etc. These applications are to be found in the automobile and aerospace industries, non-ferrous foundries and metallurgy, civil engineering, plastics industries, etc. © 1991 Wiley Heyden Ltd., Chichester and Akadémiai Kiadó, Budapest.