双级微结构上二氧化硅粒子对微注压成型PP表面润湿特性的影响

Effect of Silica Particles Adhered to Dual-level Microstructure on Wetting Characteristics of PP Surfaces Replicated by Microinjection Compression Molding

提出一种柔性复制法,采用微注射压缩(μ-ICM)成型具有微拓扑结构的仿生聚丙烯(PP)表面.通过复制模板上的双级微结构,所成型的PP材料表面上呈现具有锥形顶面的双级微结构,即微棱和高纵横比的微锥体.由于微锥体之间的间隙较大,水滴浸润其间隙的上方,这使该表面呈现中等黏附的超疏水特性.在μ-ICM过程中,涂覆在模板上的二氧化硅纳米粒子(SNPs)被转移到熔体中,并牢牢附着于微结构表层,赋予其表面亚微米或微米粗糙度,形成多层次微结构.在附着有亲水SNPs的微结构上,高表面自由能使水滴完全浸润微锥体之间的间隙,表面的水接触角为161.9°、滚动角大于90°,呈现极高黏附的超疏水特性(花瓣效应);在附着有疏水SNPs的微结构上,水滴受疏水SNPs的排斥而减弱与表面之间的黏附作用,表面的水接触角为163.5°、滚动角为3.5°,呈现极低黏附的超疏水特性(荷叶效应).

The present work proposes a flexible replication method for bio-inspired polypropylene（ PP） surfaces with microtopographies using microinjection compression molding（ μ-ICM）. A dual-level microstructure appears on the PP surfaces prepared via replicating the dual-level microstructure within a template. The microstructure on the PP surfaces exhibits micro ridges and high-aspect-ratio micropillars with conical top. When water is dropped onto the micropillars,the droplet penetrates into the upper part of the gap between the micropillars due to the relatively large gap,resulting in a mid-adhesive superhydrophobicity for the PP surfaces. The silica nanoparticles（ SNPs） coated on the template are transferred to the viscous state-dominated melt during its filling in μ-ICM,and firmly adhered to the skin of the dual-level microstructure,endowing the surface with submicron-scale or micron-scale roughness and so forming hierarchical microstructures. On the microstructures coated with hydrophilic SNPs,the droplet wets the intermicropillar areas on the surface completely due to high surface free energy,and the prepared surface has a water contact angle（ CA） of 161. 9° and a roll-off angle of above 90°,exhibiting extremely high adhesion with superhydrophobicity（ i. e.,petal effect）; on the microstructures coated with hydrophobic SNPs,the water is repelled by the hydrophobic SNPs and so the adhesion to the surface is weak,and the prepared surface has a CA of 163. 5° and a RA of 3. 5°,exhibiting extremely low adhesion with superhydrophobicity（ i. e.,lotus effect）.