Silica/phenol resin hybrid material was prepared by a sol-gel process.Resole

tetraethoxysilare (TEOS)

ethanol and water were mixed to form the precursor

the ratio being resole∶TEOS∶ethanol∶water = 4.1 g∶1.5 g∶20 mL∶2 mL.The precursor was hydrolysed for 24 h to obtain a hybrid material (organic/inorganic weight ratio 9∶1).Resole and the precursor was cured at 120℃

2 h concurrently

then

part of the hybrid material was postcured at 160℃

1 h.The three samples (phenol resole

hybrid material and post-cured hybrid material) were analysed by FTIR and evaluated in view of application as organic coatings.Because phenol resin is liable to change its color in service

the hybrid material is only applied as undercoat.The wavenumber shift of O—H stretch vibration

the ratio of peak width at half hight Δ1/2(O—H)/Δ1/2(C=C) and absorbance ratios were used to characterize the structure changes of the hibrid material.Under the same curing conditions (120℃

2 h)

the O—H peak of the hybrid material shifts 49 cm-1 downward from that of resole

Hbond of the hybrid material (half hight 4.25) is stronger than that of resole (half hight 7.76)

and there is more hydroxyl concentration in the hybrid material.As an undercoat

the hybrid material can have enough functional groups to react with those of the topcoat in order that the multiple coatings can cure without interface between undercoat and topcoat.Post cure (160℃

1 h) can greatly reduce the hydroxyl concentration of the hybrid material.Phenol resole has a weak absorbance peak at 1070 cm-1 (A1070/A1612=0.81)

the hybrid materials (A1067/A1612=1.87; postcured A1069/A1612=2.99) have two very strong absorbance peaks in the range of 1100～1065 cm-1

therefore

the hybrid materials have more ether bonds than resole

and post-cure can form more ether bonds.The absorbance ratio ［A］754/［A］1612 that expresses the substitution reaction of o-positions of the phenol rings increases from 4.25 of resole to 7.76 of the hybrid material

which means the substitution reaction of o-positions in the hybrid material is much more remarkabe than that in resole.The ［A］818/［A］1612 that expresses the substitution reaction of p-positions increases from 0.32 of the hybrid material to 0.51 of postcured hybrid material

but ［A］754/［A］1612 increases unremarkably

which means the substitution reaction of p-positions in the hybrid material during postcure is predominant

and the substitution reaction of o-positions is negligible.The ratio A1646/A1612 of phenol resin is 0.53

and that of the post-cured hybrid material is 0.54

which means the postcured hybrid material gets the same oxidation degree as the phenol resin.The post-cured hybrid material does not have free phenols

consequently

the post-cured hybrid material is more environment-friendly than resole.