Synthesis Of Hyperbranched Polyesters With Retarding Groups And Its Retarding Performance In Cement Concrete

Concrete retarder is a kind of concrete admixture that can prolong the setting time of cement concrete and keep the plasticity of the concrete for a long time.It can enhance the performance of concrete and effectively increase the scope of use of concrete.Extensive research outside.Although there are many types of concrete,there are still many problems such as: poor retarding effect,adverse effect on concrete performance,and poor compatibility with other concrete admixtures,which greatly limits the development and use of retarder in China.Hyperbranched polymers have a three-dimensional network structure,large molecular weight,good stability,and a large number of reactive functional groups at the ends,making them widely used in material modification research.The purpose of this paper is to apply hyperbranched polymers to the field of retarders.By synthesizing hyperbranched polymers and performing terminal modification,two hyperbranched polymers with different terminal groups are used as retarders,and their properties are discussed.analysis.The main content of this paper:1.Synthesis and characterization of hydroxyl-terminated hyperbranched polyester(HTHP)With itaconic acid as the core molecule,succinic acid and triethanolamine as the monomers,p-toluenesulfonic acid as the catalyst,and N,N-dimethylacetamide(DMAC)as the solvent,it conducts a divergent reaction at a certain temperature.Control the ratio of core molecules to various monomers to generate first-generation hydroxyl-terminated hyperbranched polyester(HTHP-G1),second-generation hydroxyl-terminated hyperbranched polyester(HTHP-G2),and third-generation hydroxyl-terminated hyperbranched polyester(HTHP-G3),perform infrared spectrum analysis,nuclear magnetic resonance hydrogen spectrum/carbon spectrum and branching degree calculation,polyester polyol hydroxyl value determination and element analysis to verify whether the molecular structure of hydroxyl-terminated hyperbranched polyester complete.2.Synthesis and characterization of carboxyl terminal hyperbranched polyester(CTHP)The terminal modification of the synthesized HTHP-G1,G2,G3,using esterification reaction to obtain different generations of carboxyl terminal hyperbranched polymer(CTHP),through infrared spectroscopy,nuclear magnetic resonance hydrogen spectroscopy and elemental analysis,successfully synthesized the expected Carboxyl-terminated hyperbranched polyester structure;the modification conditions were discussed through the controlled variable method,which mainly includes: reaction time,reaction temperature,type of catalyst,amount of catalyst.3.Performance test of hyperbranched retarderThe HTHP and CTHP of different generations were added to the concrete.Through the performance test,it was found that the two types of hyperbranched retarders have a good influence on the fluidity of the cement paste,and the bleeding rate of the concrete has been improved.It can effectively prolong the setting time of concrete and improve the early compressive strength of concrete,and the performance of HTHP-G3 and CTHP-G3 is better than G1 and G2.4.Compatibility of hyperbranched retarder with different admixturesThe compatibility of retarders with other concrete admixtures has always been a problem.This article discusses the synthesis of two hyperbranched retarders and cement types,mineral admixtures,and polycarboxylic acid water reducers by testing the mortar spread.Compatibility,and through compounding with polycarboxylic acid water reducing agent,get an optimal ratio,and study the basic performance of concrete under the optimal ratio.5.Retarding mechanism of hyperbranched retarderThe retardation mechanism of the hyperbranched retarder was studied by various methods such as Zeta potential,X-ray diffraction analysis,hydration heat,and scanning electron microscopy.The retardation effect of the hyperbranched retarder obtained was related to its terminal polar groups.These groups can be adsorbed on the surface of cement particles,extend the setting time by means of electrostatic repulsion,inhibit nucleation sites,etc.,and can reduce the rate of hydration,reduce the amount of heat,promote the growth of ettringite(AFt),etc.The early strength of concrete.In summary,under the appropriate amount of blending,the synthetic HTHP and CTHP can effectively prolong the setting time of concrete,and at the same time improve the earlycompressive strength of concrete,compared with other concrete admixtures such as water reducer,mineral admixture,etc.The capacity is good,the effect is in line with the expectations,and it can be applied in the field of concrete.