PB-g-PS胶乳改性水泥砂浆的微观结构及改性机理

Mechanism and Microstructure of PB-g-PS Latex-Modified Cement Mortars

利用氧化还原引发体系,采用半连续乳液接枝共聚的方法合成了聚丁二烯接枝聚苯乙烯(PB-g-PS)接枝共聚胶乳,其中聚丁二烯(PB)与聚苯乙烯(PS)的质量比为70/30,50/50和30/70。在固定流动度为(175±5)mm,在20℃、相对湿度(RH)为90%的标准养护箱中养护24 h后脱模,且在两种养护条件下(在20℃水中养护6 d,然后在20℃,RH为65%的空气中养护21 d的混合养护或在20℃水中养护27 d)。利用SEM考察了聚合物改性水泥砂浆(PMMs)的微观结构,微观结构分析表明:由于没有聚合物,未改性砂浆各组分彼此松散的结合在一起,相比之下,改性砂浆的结构更为致密,聚合物与水泥水化物形成了一个整体结构;在PMMs观察到了聚合物粒子的形态、不同的聚合物膜形态、不同的粒子结构、桥接结构、互穿网络结构、孔洞结构以及界面结构。综合上述微观结构得到了新的聚合物改性机理。

Polybutadiene - graft - polystyrene （PB - g - PS ） latexes were prepared via emulsion graft copolymerization method using a redox initiator, the weight ratios of polybutadiene to styrene were 70/30, 50/50 and 30/70, respectively, and then the PB - g - PS latex was used to modify cement mortar. In the constant water - cement ratio of 0. 5, and curing 24 h under the two conditions of 20 ℃, RH 90% air and 6 d immersed in 20 ℃ water followed by 21 d at 20 ℃, RH 65% air or 27 d at 20 ℃ water. The microstructure of PMMs was studied by SEM. The microstructure analysis showed that mortar constituents of unmodified mortar （UMM） were loosely joined with each other due to the absence of polymer. By contrast, the structure of the modified mortar was more compact, and forming a monolithic structure. The morphology of polymer particles, different shape of polymer film, particle shape, bridge structure, the interpenetrating network structure, pores structure and interface structure were observed in the PMMs. The new polymer modified mechanism was concluded on the basis of microscopic structure.