Exploration On Synthesis And Application Of Novel Polycarboxylate Superplasticizers With Propylene Glycol Side Chains

Polycarboxylate ether superplasticizer( PCE) is usually synthesized from acrylic acid and allyl polyoxyethylene ether, which is a poly carboxylic polymer with PEG long side chains. PCE molecules are absorbed on cement particles and form steric hindrance, which can disperse cement particles better. That’s why the dispersion of PCE on cement is better than lignin sulfonate and naphthalene sulfonate. Because PCE possesses high water reducing rate and its molecular structure can be designed, we produce PCEs with different functions, such as standard type, retarded type PCE etc. This also promotes the application of PCE and makes PCE occupy more and more market share. The research direction of PCE currently turns to synthesize PCEs with specific functions. In this research, we synthesized a novle PCE possessing clay tolerance. In addition, we used polyol recycled from waste polyurethane to synthesize PCE.When synthesizing PCE from PPG400, PPG400 was needed to be esterified with maleic anhydride firstly. But the water solubility of esterification macromonomer was sensitive to pH, so it should be neutralized with aqueous NaOH before polymerization. Then copolymerization reaction occurred between macromonomer and sodium acrylate. Although the adsorption mode of this PCE on montmorillonite was surface adsorption and the adsorption was small, the dispersion and clay tolerance properties of PCE was not excellent. PPG400 can’t become side chains of novel PCE, but we can try to use smaller molecular weight PPG to synthesize a PCE possessing clay tolerance in future.It was another try after PPG400 that we used two kinds of triblock polyether, which consisted of 50 wt % PEG and 50 wt % PPG, to synthesize a PCE possessing clay tolerance. They were firstly esterified with maleic anhydride and then the product polymerized with acrylic acid and sodium methylallyl sulfonate. Comparing with conventional PCE, although the dispersion of novel PCE was a little weaker, but the reduction of cement paste fluidity with montmorillonite of novel PCE was less, which was consistent with their adsorption on montmorillonite. The reason was probably that the adsorption capacity of montmorillonite to conventional PCE was much higher than cement which was due to surface and interlayer adsorption, but the adsorption capacity of montmorillonite to novel PCE was a little higher than cement which was due to surface adsorption( main adsorption mode). Block polyether could be used to synthesize PCE which possessed some clay tolerance, and the clay tolerance was obtained by sacrificing some dispersion. Next it is still needed to be explored which kind of block polyether could be used to synthesize a PCE possessing both good dispersion and clay tolerance.Polyol was recycled from waste polyurethane by alcoholysis or glycolysis. After purification polyol was esterified with acrylic acid, which produced a macromonomer. Then PCE was synthesized from acrylic acid and macromonomer in butyl acetate. This way could not only make full use of waste polyurethane, but also reduced the cost of PCE. This PCE was insoluble in water. Next we can continue to study the degradation of polyol, and try to use low molecular weight polyol recycled from waste polyurethane to synthesize PCE.