A new method was developed for preparation of phenolic hollow microspheres via in situ polymerization.Tetraethyl orthosilicate being the core and poly(acrylic acid) being the anionic surfactant were placed into flask

the mixture was stirred

and its pH value was adjusted to be acidic

then a s table oil-in-wa ter emulsion was formed.Tetraethyl orthosilicate was emulsified uniformly in the aqueous solution and dispersed into a large quantity of droplets with very smal l size covered by anionic surfactant of poly(acrylic acid).The pre-prepared res oles

being the shell

were dribbled into the flask slowly.The mixture was stir red at 60℃and hold for 3 h

and at 90℃ hold for 2 h

respectively.A large numb er of yellow microspheres were formed.The “core-shell" phenolic microspheres w e re then filtered and dried.Hollow phenolic microspheres were produced after the yellow solids dried at 170℃ for 4 h to eliminate tetraethyl orthosilicate from the microspheres in an oven.The hollow phenolic microspheres were characterized by scanning electron microscopy (SEM)

Fourier-transform infrared spectroscopy( FTIR) and th ermogravimetric analysis (TG).FTIR indicates that a significant number of the hy dr oxymethyl groups remain in the microspheres

which provide adherence force with t he matrix resin during application.TG analysis demonstrates that the resultant holl ow phenolic microspheres have good thermal stability.SEM results show that the average of diameter of the microspheres is about 600 μm.The hollow microspheres have good close cell and smaller pores formed in the wall when water vaporized

It is also observed that the morphology of microspheres is very tough

which ca n provide good bonding between microspheres and resin matrix.