Fast UV-Curable Elastic Composite Films With Good Thermal, Mechanical and Dielectric Performances for Flexible Electronics

Fast UV-cured Polybutadiene films were prepared in 10 s by using mercaptan pentaerythritol tetra(3-mercaptopropionate) (PETMP) as the cross-linker and PETMP-treated nano-SiO 2 as the filler, achieving significant improvements in overall performance, which may be applied as insulating materials for flexible printed circuits. The dispersion of SiO 2 in the polymer matrix was improved after treatment by PETMP and served as a “hard core” in enhancing their hardness greatly and improving the tensile strength about 50% from 7.5 to 15.2 MPa; they still retain excellent flexibility, maintaining shapes without cracking and peeling while folding in half under squeezing. The thermal expansion coefficient decreased from 2.22 × 10 −4 /°C to 2.02 × 10 −4 /°C and the glass transition temperature rose from 47.50°C to 58.62°C; meanwhile, they exhibited higher decomposing temperatures and higher residues, indicating the stabilizing effect of nano fillers. The incorporation of SiO 2 decreased their dielectric constant from 3.12 to 2.94 while maintaining stable dielectric loss of less than 0.02. Moreover, the addition of pretreated SiO 2 also improved their resistance to pure and salt water. Nevertheless, the excessive addition of SiO 2 led to local aggregations and thus adversely affected their overall properties if its addition was above 8% as seen from SEM pictures.