聚氨酯-丙烯酸酯柔性壁的减阻性能

采用种子乳液聚合法和物理共混交联法制备了以水为溶剂的聚氨酯-聚丙烯酸乙酯(PU/PEA)乳液和聚氨酯-聚丙烯酸丁酯(PU/PBA)乳液柔性壁。该乳液不仅环保,而且强度高,弹性好,粘接性优良。小型水洞平板阻力测试结果表明,PU/PEA复合乳液有一定的减阻作用,水流速度高时减阻率也高,流速为3.0 m/s时达到8.8,PU/PEA(40/60)复合乳液涂层在0.5~3 m/s的速度范围内平均减阻率达到5%;粒子图像速度测试给出了在相同雷诺数下柔性壁与铝板的平均摩擦阻力系数的比较以及计算得到的减阻率。结果表明,PBA/PU和P(BA-EA)/PU的减阻效果差不多,平均约5.3%,而PBA/PU-MMA低速减阻,高速不减阻。PU/PBA混合乳液涂层在0.5 m/s和1 m/s的流速下减阻率分别为7%和4%。

Drag Reduction Properties of Polyurethane-Poly(acrylate) Hybrid Emulsions

Polyurethane-poly(ethyl acrylate) (PU/PEA) hybrid emulsions and polyurethane-poly(butyl acrylate) (PU/PBA) mixed emulsion flexible were synthesized by seed emulsion polymerization and physical blending crosslinking.The emulsion is not only environmentally friendly,but also has high strength,good elasticity and excellent adhesion.The results of drag tests show that the PU/PEA (40/60) hybrid emulsion coating has certain drag reduction effect,the drag rate is high when the flow velocity is high,and the average drag reduction ratio reaches 5％ at the flow velocity of 0.5～3 m/s,especially the drag reduction rate is 8％ when the flow rate is 3.0 m/ s.The particle image velocity test gived the comparison of the average frictional resistance coefficient of the flexible wall with the aluminum plate under the same Reynolds number,and the calculated drag reduction rate.The results show that the effect of PBA /PU and P (BA-EA) /PU is about 5.3％,while the average reduction of PBA /PU-MMA is not drag reduction.The PBA/PU-MMA shows drag reduction at low-speed,and non-drag reduction at high-speed.The PU/PBA mixed emulsion coatings also have certain drag reduction effects and the drag reduction ratio is 7 ％ or 4 ％ at 0.5 m/s or 1 m/s of the flow velocity,respectively.