FABRICATING POLYMER SUPERHYDROPHILIC/SUPERHYDROPHOBIC SURFACES BY REPLICA-MOLDING METHOD USING CaCO3 PARTICLES AS TEMPLATE

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 is still in nead. In this paper, a novel 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 obtained, with water contact angle (WCA) up to (152. 7 +/- 0. 8)degrees and sliding angle less than 3 degrees. Moreover, such superhydrophobicity was confirmed stable under water jet at high pressure and durable in warm water (lower than 50 degrees C). SEM imaging showed that such superhydrophobicity was attributed to the typical micro- and nanometer scale porous surface structure. Other types of polymers such as LDPE, HDPE, polypropylene (PP), polystyrene (PS) and polyurethane (PU) had also been replica molded using the similar process. All formed superhydrophobic and micro-and nano-porous surfaces except for PU, which only formed normal hydrophobic and microporous surface. 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.