Preparation and Mechanico-Optical Properties of Ultraviolet-Curable Transparent Polyurethane Elastomer Nanocomposites

Nanotechnology is presently seen as one of the most promising approaches in the field of materials science toward the development of advanced materials for future engineering applications. We report on the preparation of transparent elastomer based on polyurethane–PEG₄₀₀/PEG₂₀₀₀–acrylate copolymers. UV curing was pursued. In order to render the polymer hydrophilic, a poly(ethylene glycol) (PEG) chain is used as the polyol portion of the polyurethane. The molecular weight of the PEG chain was matrix from PEG₂₀₀₀ g/mol and PEG₄₀₀ at 1:3 ratio, respectively. An aliphatic di-isocyanate, namely, isophorone di-isocyanate (IPDI), was used to obtain transparent samples. A PEG-IPDI polymer was produced in the first step. 2-hydoxyethyl acrylate (HEA) was added to react with the excess of IPDI. Dibutyltin dilaureate (DBTL) was employed as the catalyst for formation of the urethane bond. Cross-linking occurred via free radical polymerization of the acrylate group. Nano dry silica powder (Aerosil R7200) is economical and widely used in the industry. The nanoparticles were dispersed in the polyurethane solution in the presence of photo-initaitor by using Ultra-Turrax homogenizer, and the resulting polyurethane nanocomposite solution was molded in the mold glass at room temperature. UV curing was achieved in few seconds. It is noticed that the inorganic filler can be used up to 5% (wt/wt) without affecting the transparency of the polyurethane elastomer sheets. Nanocomposites showed significantly enhanced mechanical properties at 3% (wt/wt). Optical absorption measurements show that the fundamental absorption edge obeys Tauc’s relation for the allowed nondirect transition. Optical band gap (E_g) of the polyurethane (PU)/Aerosil R7200 nanocomposites decreases with the increase of nanosilica content from 1% to 5%. Good mechanical and optical properties make the polyurethane nanocomposites good candidate for different applications such as thin film coating and photovoltaic.