Ice Adhesion Tests on Pliable Polymer Sheets for Protection Against Sea-Water Spray Icing

摘要

Heavy sea-water spray icing is a major problem in the maintenance of lighthouses situated in northern harbors facing the Sea of Japan. Moreover, low ice adhesion materials or anti-icing coatings are ineffective over long periods. In this study, we have investigated the characteristics of saline ice adhesion on hydrophilic and hydrophobic pliable polymer sheets that can be used to envelop and thereby protect small lighthouses. We conducted experiments in cold room laboratories, and further, we verified the deicing conditions. Ice adhesion strength tests using fresh water indicated that a highly hydrophobic surface exhibited lower adhesion strength than other test materials. The results of saline ice adhesion tests at -20°C indicated that the adhesion strength decreases very rapidly as the salinity increases for all materials; this trend was particularly remarkable in case of superhydrophilic materials. The water spray icing tests were verified by experiments conducted using an ice model basin. Wet growth of ice occurred on all test specimens including the highly hydrophobic sheets. Furthermore, the initial icing depended significantly on the hydrophobic or hydrophilic surface properties. The icing on the hydrophobic surface was characterized by the formation of vertical streaks of ice; irregular projections could be observed on the ice surface. On the other hand, a thin fluid flow was formed on superhydrophilic surfaces. Exfoliation of pieces of the sheet ice was often observed during the initial growth. Deicing could be easily performed for both pliable polymer sheets. A combination of low ice adhesion property and rapid distortion was effective for the deicing of sea-water spray icing.