A series of simultaneously interpenetrating polymer networks of polyurethane and poly(methyl methacrylate)were synthesized.Dynamic mechanical analysis was carried out to determine the system damping performance.The effects of composition ratio

crosslinking density

nano-SiO2 content

content of octadecyl methacrylate with long and soft pendant group

and content of internetwork grafting agent

hydroxyethyl methylacrylate on the system damping performance were investigated.The morphology of the interpenetrating polymer networks system was studied with transmission electron microscope.The damping performance of interpenetrating polymer networks system could not be improved by changing the system crosslinking density

but could be improved in the range between the two glass transition phases by adding a moderate amount of nano-SiO2.With the addition of octadecyl methacrylate

the glass transition of poly(methyl methacrylate)phase shifted to a lower temperature to obtain a continuous and widened damping range.Hydroxyethyl methylacrylate was an efficient internetwork grafting agent.The system would be optically transparent and only one glass transition could be found

when 3% hydroxyethyl methylacrylate was added.