Preparation of halloysite containing thermoset nanocomposites by free radical photopolymerization

UV curing is a process in which radiation is used to initiate, via ionic or free radical formation, the combination of monomers resulting in the formation of oligomers or high molecular weight polymers. This process utilizes light energy to form polymers and, therefore, may provide a simple method for in situ preparation of polymer nanocomposites from well-dispersed nanofiller–monomer formulations. Conventional methods of producing a composite involve direct mixing of polymer with inorganic fillers either melt-mixing or solvent-based processes and thus usually cause thermal degradation of the polymer or release large amounts of volatile organic compounds during the process. UV-curing process may overcome these drawbacks of conventional processes by producing polymer through irradiation at ambient temperature with 100% solid content. In addition to, UV-curing process has some advantages (fast, environment friendly, energy saving, spatial and temporal control, etc.), and can be used to prepare polymer nanocomposites. The main objective is to develop novel UV-curable nanocomposites containing halloysite (HNT) as nanofillers. This green nanofiller nanomaterial has a unique combination of tubular structure, large aspect ratio, natural availability, rich functionality, good biocompatibility, and high mechanical strength. HNTs offer also an inexpensive, low-tech alternative that is morphologically similar to carbon nanotubes (CNTs). These characteristics result in exceptional mechanical, thermal, and barrier properties at a low price for HNTs-polymer nanocomposites. In this study, a methacrylate-functional HNT was firstly prepared by the reaction of 3-(trimethoxysilyl) propylmethacrylate with inner and outer hydroxyl groups of HNT. Then, the functional halloysite was included in free radically polymerizable UV-curable systems with various concentration. These formulations was cured by UV-light irradiations at room temperature. The mechanical and thermal properties of obtained composites were investigated by tensile machine and TGA analyses. Moreover, the structural characterization as well as morphological distribution of halloysite in the matrix were monitored by FT-IR and SEM analysis.