School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, USA.
ACS Appl Mater Interfaces. 2010 Apr;2(4):1220-7. doi: 10.1021/am1000618.
Negatively charged colloidal poly(methyl methacrylate-co-butyl acrylate) (P(MMA-BA)) particles and positively charged dissolved poly(ethyleneimine) (PEI) were adsorbed onto a cement block using a layer-by-layer (LBL) assembly technique. The block was fashioned so as to have a cylindrical hole running from one face to another along the long axis of the rectangular block, and a fluid containing either of the two charged materials was pumped through the block. The result was a film tens of micrometers thick, and the pressure required to crack the cement block was measured after one end of the hole was sealed. Latex particles with a T(g) near the use temperature showed the maximum improvement in the cracking stress of the blocks. In a multilayer coating with identically sized particles, the cracking stress of the blocks increased to an improvement of 25% and then dropped off with increasing number of layers, even though the relationship between film thickness and the number of layers was linear. An improvement of about 30% in the cracking stress of the coated blocks was obtained when using multiple layers with different particle sizes. The effects of the number of layers and particle size on the cracking stress suggest that both the morphology and the thickness of the film play a role in performance. Tests done under confinement, e.g., with an external stress applied to the outside of the blocks, suggest that not only does a film-forming mechanism contribute to performance but that filling of microcracks in the rock may also play a role.
带负电荷的胶体聚（甲基丙烯酸甲酯-丙烯酸丁酯）（P（MMA-BA））颗粒和带正电荷的溶解聚（亚乙基亚胺）（PEI）通过层层（LBL）组装技术被吸附到水泥块上。将该块制成这样的形状，即有一个圆柱形孔，从一个面沿长方形块的长轴延伸到另一个面，并且含有两种带电荷材料之一的流体被泵通过该块。结果是形成了几十微米厚的薄膜，并且在孔的一端被密封之后测量了使水泥块破裂所需的压力。在使用温度附近具有 T(g)的乳胶颗粒显示出对块体破裂应力的最大改善。在具有相同尺寸颗粒的多层涂层中，块体的破裂应力增加到提高 25%，然后随着层数的增加而下降，尽管膜厚和层数之间的关系是线性的。当使用具有不同粒径的多层时，涂层块体的破裂应力提高了约 30%。层数和粒径对破裂应力的影响表明，膜的形态和厚度都对性能有影响。在受限条件下进行的测试，例如在块体外部施加外部应力，表明不仅成膜机制对性能有贡献，而且岩石中的微裂缝的填充也可能起作用。
