Polymerization Kinetics and Characterization of Dual Cured Polyurethane-Acrylate Nanocomposites for Laminates

In last years, many studies have been devoted to develop exfoliated polymer nanocomposite based on fillosilicates exhibiting novel properties, such as a decreased oxygen permeability a good optical transmittance (i.e. low haze) (21 and an enhanced thermal stability and flexural mechanical modulus The clay-polymer composites have been generally divided in three main types s) conventional composites, if the original fillosilicate aggregation is maintained and the polymer matrix does not intercalate the clay Iamellae; ii) intercalated composites, if few molecular layers of polymer are inserted into the clay structure (i.e. the composite properties are typically resembled to ceramic materials); and iii) exfoliated composites if the individual layers of the clay are continuously separated by the polymer matrix (see Scheme I). The dispersion of fillosilicates in thermoplastic polymers can be achieved by several methods, such as the use of intercalation compounding and in situ and melt polymerization already applied to polyamides polyimides 181 and polypropylene Two methods have been suggested to prepare disordered exfoliated thermosetting polymer nanocomposites: I) monomer impregnation, if the clay is firstly saturated with a monomer and subsequently the monomer/clay complexes are inserted into the reactive mixture before the curing or polymerization reaction 1101; and ii) cation exchange by a monomer which swells the clay generating organophilic layered-monomer intercalates containing polymerizable moieties bonded to the lamellar clay surfaces