连续管式反应器中降黏型聚羧酸减水剂的合成及性能

Synthesis and performance of viscosity-reducing polycarboxylate superplasticizer in continuous tubular reactor

摘要:

以异戊烯醇聚氧乙烯聚氧丙烯醚（IPEPPG）和马来酸酐（MA）为主要反应原料，通过连续管式反应器连续进料，利用热引发可逆加成-断裂链转移（RAFT）聚合，合成了一款窄相对分子质量分布的降黏型聚羧酸减水剂VR-PCE-TR。采用1H NMR、FTIR和GPC表征VR-PCE-TR分子的结构参数，采用表面张力、匀质性实验、混凝土拌合物性能实验、力学性能实验考察VR-PCE-TR对混凝土的工作性能和流变性能的影响，并与釜式反应器中采用常规水相自由基聚合制备的降黏型聚羧酸减水剂进行性能对比。结果表明，当减水剂溶液质量分数为10%时，VR-PCE-TR具有最低表面张力（30.65 mN/m）；当减水剂含量为8 mg/g时，掺加VR-PCE-TR后的水泥具有更高的吸附量（2.803 mg/g）；在减水剂掺加量0.13%时，掺加VR-PCE-TR后的水泥浆体具有更好的分散性和分散保持性能；在减水剂掺加量0.4%时，掺加VR-PCE-TR后的水泥净浆具有更小的屈服应力(1.3 Pa)和更低的塑性黏度(0.26 Pa·s)。此外，连续管式反应器避免了物料除氧步骤，同时能够保持聚合控制性和聚合反应速率，因此制备的VR-PCE-TR具有更窄的相对分子质量分布（多分散性指数为1.19），进而有更好降黏效果和应用性能。

Abstract:

A viscosity-reducing polycarboxylate superplasticizer (VR-PCE-TR) with narrow molecular distribution was synthesized by thermally initiated reversible addition-fragmentation chain transfer (RAFT) polymerization in continuous tubular reactor, using isoprenyl-PE-PPG and maleic anhydride as main raw materials. The molecular structure of VR-PCE-TR was determined by 1H NMR、FTIR and GPC. Then, the surface tension, uniformity, concrete experiment and mechanical strength have been measured to compare working performance and rheological properties with various viscosity-reducing polycarboxylate superplasticizers, which are synthesized by conventional free radical polymerization. The results show that when the mass fraction of polycarboxylate superplasticizer is 10%, VR-PCE-TR has a lower surface tension (30.65 mN/m); When polycarboxylate superplasticizers content are 8 mg/g, the cement slurry with VR-PCE-TR has a higher adsorption capacity (2.803 mg/g); When the dosage of polycarboxylate superplasticizers are 0.13%, the cement slurry with VR-PCE-TR has better dispersion and dispersion retention performance; When the dosage of polycarboxylate superplasticizers are 0.4%, the cement slurry with VR-PCE-TR has a lower yield stress (1.3 Pa) and lower plastic viscosity (0.26 Pa·s).Furthermore, the synthesis of VR-PCE-TR by thermally initiated RAFT polymerization in continuous tubular reactor without degassing process, are able to maintain the polymerization speed and control, achieving narrower molecular distribution (PDI=1.19), better viscosity reduction effect and application performance.