聚氨酯改性砂浆中的有机与无机反应(英文)

Organic and Inorganic Reactions in Polyacrylate Modified Cement Mortars

基于聚合物与水泥水化产物之间的有机与无机反应,研究了从开始搅拌到硬化过程中聚氯酯改性砂浆微观结构的形成过利。从有机聚合物乳液与无机水泥基材料的反应活性出发,提出了一个改进的水泥基材料聚合物改性机理的四阶段分析模型。通过分析孔结构和聚合物的分布情况,揭示了聚氨酯乳液对水泥砂浆微观结构的影响。由于各种有机与无机反应,聚氨酯有机物不会均匀的分布在砂浆内部,聚合物颗粒将聚集在水泥颗粒的表面并在砂浆的局部部位凝聚成较大的有机物团。因此聚氯酯有机物对水泥基材料的改性都存在于砂浆的局部部位,这个现象也称为聚合物物改性的局部化。由于表面活性剂与水泥水化产物的反应,添加聚氯酯乳液也会以砂浆中引入较大的孔隙。研究结论表明,在水泥基材料中添加少量精心配制的聚合物乳液可以有效的提高水泥基材料的物理与力学性能,这对降低聚合物改性水泥基材料的成本并提高其可应用性具有非常重要的意义。

The microstructure forming process of polyacrylate(PA) latex modified mortars was investigated from mixing to hardening,with specific emphasis on the organic and inorganic reactions between polymer and cement hydration products.An improved four-step model was proposed to clarify the mechanism of polymer modification in view of the reactivity of organic polymer latex in inorganic cement-based materials.And the influence of PA latex on the microstructure formation of mortars was revealed through an analysis of pore structure and polymer distribution.Owing to organic and inorganic reactions,polyacrylate polymer will not disperse uniformly in fresh mortar,and polymer particles will deposit on cement particles and flocculate into big groups at some local areas in mortars.The modification of polyacrylate polymer on cement-based materials is localized which can be stated as the localization of polymer modification.The addition of PA latex will also introduce some air voids into the mortars due to the chemical reaction between its surfactant and cement hydrates.This is important for the physical and mechanical properties improvement because a kind of purposefully designed polymer latex will effectively enhance the performance of cement-based materials in a relative small dosage,which means cutting the cost down and broadening its application.