Synthesis And Properties Of A Three-Arm Polycarboxylate Superplasticizer

As a new generation of water reducing agent,polycarboxylate superplasticizer has become the development direction of concrete water reducing agent because of its high water reducing rate,good collapse resistance,good adaptability and environmental friendliness.However,with the continuous improvement of the construction industry and the development of concrete technology,polycarboxylate superplasticizer gradually exposed some problems,such as the effect of clay on the dispersion of polycarboxylate superplasticizer.Therefore,the purpose of this paper is to develop a new kind of polycarboxylate superplasticizer to provide guidance for the practical synthesis and application of water-reducing agent in the future.According to the molecular structure,adsorption and water reduction mechanism of the comb polycarboxylate superplasticizer and the advantages of atom transfer radical polymerization(ATRP),A four-steps method was used to synthesize a Polycarboxylate Superplasticizer(TAPCE)with three arms structure.In the first step,trimethylolpropane(TMP)was used as a nuclear molecule to prepare a small molecule initiator with trifunctional(Br-TMP-Br);In the second step,the first block of three-arm polycarboxylate superplasticizer(PtBA)was synthesized by the extraction of tert-butyl acrylate(tBA)with small molecular initiator;In the third step,the first block synthesized in the second step is used to initiate the polymerization of the HPEG to obtain a second block(P(tBA-HPEG));In the fourth step,the polymer obtained in the third step is hydrolyzed in an aqueous solution of trifluoroacetic acid to obtain a three-arm polycarboxylate water reducing agent.The experimental results show that the synthetic three-arm polycarboxylate water-reducing agent has good dispersion and dispersion retention,when the macromonomer is selected HPEG3000,the optimum molar ratio of 2-bromoisobutyryl bromide to trimethylol propane is 3.2: 1.0,the ratio of the two monomers to the initiator for tBA: HPEG: Br-TMP-Br = 60.49: 8.93: 1.0.Compared with the conventional comb industrial sample comparison,the three arm polycarboxylate superplasticizer showed a more excellent effect in paste dispersion and dispersion performance retention,mortar dispersion and dispersion retention,mortar water reduction,mortar mechanical properties by testing according to relevant test standards.It is particularly noteworthy that TAPCE has an excellent anti-mud performance relative to the comb-type water reducing agent,and when the fluidity of the cement paste containing 1 % bentonite reaches 260 ± 5 mm,the amount of TAPCE is only 80 % of the conventional watereven less.