Dissertation
Dissertation > Industrial Technology > General industrial technology > Materials science and engineering > General issues of engineering materials > Materials Corrosion and Protection

Fabricating Polymer Superhydrophobic Surfaces by Replica-Molding Method Using CaCO3 Particles as Template

Author ZhengJianYong
Tutor ZhongMingQiang;FengJie
School Zhejiang University of Technology
Course Materials Science
Keywords CaCO3 particles template method polymer superhydrophobic surface spontaneous loading
CLC TB304
Type Master's thesis
Year 2010
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With the continuous developments of micro/nano-technologies, people have learned much from state-of-the-art microstructure of natural materials, and are trying to find out approaches to mimic them. Superhydrophobic surface with lotus leaf effect has many practical and potential applications in different fields. Although attempts to produce artificial superhydrophobic films have always been intensively performed in recent years, however, a simple and economical procedure to mass-produce superhydrophobic surfaces still remains to be found.In this paper, a novel process, replica-molding method using CaCO3 particles as template, was developed to fabricate bionic superhydrophobic polymer films. Briefly, CaCO3 particle suspension was first cast onto a glass substrate and then was dried towards forming a thin layer of particles. Then linear low-density polyethylene (LLDPE) was thermally pressed onto such a CaCO3 particles template. After being cooled, peeled off from the substrate and rinsed with flowing water, the LLDPE film with superhydrophilic surface was obtained. Then this superhydrophilic LLDPE surface was further etched in 20 wt% HCl solution for 10 min. After washing and drying, the LLDPE film with superhydrophobic surface was created, with water contact angle (WCA) up to (152.7±0.8)o and sliding angle~3o. Moreover, such superhydrophobicity was confirmed stable under water rushing with high pressure and durable in hot water (less than 50oC).SEM imaging showed that the above superhydrophobicity of LLDPE was attributed to the typical micro- and nanometer scale porous surface structure. Other types of polymers such as LDPE, HDPE, polypropylene (PP) and polystyrene (PS) had also been replica molded using the similar process. All formed superhydrophobic and micro- and nano- porous surfaces. Because CaCO3 microparticle is low-cost and can be easily covered onto the surface of the rolling mold, which is generally used in flow-casting process in manufacturing plastic films, superhydrophobic plastic films could be thus produced cost-effectively in large scale.Calcium carbonate particles, because of their size and shape are not uniform, although the performance of the super-hydrophobic surface, which was fabricated by replica-molding method using CaCO3 particles as template, was stable, but the surface structure is disorderly.In order to obtain the orderly surface structure of super-hydrophobic surface, we used porous spherical CaCO3 particle layers as templates. After thermal replica-molding and acid etching, a stable superhydrophobic surface was created, with water contact angle up to (152.8±2.5)o and sliding angle~6o. SEM imaging showed that completely different with honeycomb structures that were generally formed by using soluble spherical particles as replica templates, conglutinated spherical particles structure were found on the LDPE surface. Element characterizations by EDS and XRF both demonstrated that no Ca element existed on or blow herein microstructured LDPE surface.To elucidate the formation mechanism of conglutinated spherical particles structure, the LDPE smooth surface was first covered with sparse porous spherical CaCO3 particles, then heated to melt state and held for 30 min. After being cooled and thoroughly etched with HCl solution, the LDPE surface presented lotus seedpod like structure, e.g., smaller spheres staying within larger holes. Such phenomena demonstrated that it was the spontaneous loading of hydrophobic melt LDPE macromolecules into PSS walled nano pores of CaCO3 microparticles that formed conglutinated spherical particles structure on LDPE surface. This find not only supplies a new method for fabricating polymer superhydrophobic films but also develops a novel strategy for expanding applications of porous spherical CaCO3 particles.

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