The urea formaldehyde polymerization controlled by using glyoxal was investigated.The sizes of the resin microspheres were in the range of 1.0~14 m

and the size range was 6.5~9.0 m in the presence of glyoxal.Sizes and morphology of the resin microspheres could be adjusted or improved with altering the aldehyde amount or glyoxal ratio in the reaction.Addition of glyoxal or increment of its ratio in the reaction significantly extend the induction time of precipitation (more than 25% longer).Infrared and XRD analyses show that the increment of both the aldehydes or the formaldehyde proportion can reduce the crystallization characteristics of polymers.Glyoxal is able to adjust the nucleation of urea formaldehyde resin or the growth of the primary particles

it was considered that the glyoxal covered the polymer surface or the active sites

limiting the diffusion of urea formaldehyde.The average size of silica microspheres prepared under the presence of glyoxal is only 20% of that of their precursor hybrids.A radial silica content gradient in the hybrid microspheres was suggested

which might result from the rate differences between silica hybridization and urea formaldehyde resin polymerization.