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In this study , water-soluble sulfonated phenolic (SP)
resins were made from formaldehyde , phenol and sodium bisulfits
as reactants , and sodium hydroxide as catalyst , through four
reaction steps , namely addition , sulfonation , condensation
and rearrangment.The influence of reaction conditions (i.e.,
temperature , pH value , time) on the concentrations of
intermedia products were examined through HPLC analyses.The
effect of the formaldehyde/phenol (F/P) ratio was also
investigated. The molecularweight and distribution of
synthesized SP resins were determined through GPC measurements.
The adsorption behaviors of these SP molecules on the surfaces
of cement particles, as well as the fluidity of SP added cement
pastes and concrete, were also studied. The
experimental results indicate that the proper reaction
conditions to prepare water-soluble resins are more restricted
for F/P=3/1 are (T1=65~80℃, pH1=10~12.5 , t1=10~20min；T2=75~83
℃ , pH2=11~12 , t2=60~90min；T3=50℃, pH3=4~5 , t3=90min；T4=85
~95℃ , pH4=7~9 , t4=60min)；the reaction conditions for F/P=2/1
are [1] (T=50~100℃, pH1=10~12 , t1=20~80min；T2=70~100℃,
pH2=10~11.4, t2=30~120min；T3=50℃ , pH3=4~6 ,t3=90min；T4=80~90
℃ , pH4=7~9 , t4~60min). This is mainly because that more
trimthylolphenol(TMP) and condensates are formed in both
addition and sulfonation reactions , for F/P=3/1. SP resins were
found to be more stable in the acidic environment. The resins
with molecular weight ranging from 4000 to 40000 or their
weight-average molecular weight about 13500, are more effective
in adsorption on cement particles , and thus enhance the
fluidity of cement pastes and concretes.
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