Hydrophobicity Tuning by the Fast Evolution of Mold Temperature during Injection Molding

Abstract

The surface topography of a molded part strongly affects its functional properties, such as hydrophobicity, cleaning capabilities, adhesion, biological defense and frictional resistance. In this paper, the possibility to tune and increase the hydrophobicity of a molded polymeric part was explored. An isotactic polypropylene was injection molded with fast cavity surface temperature evolutions, obtained adopting a specifically designed heating system layered below the cavity surface. The surface topology was characterized by atomic force microscopy (AFM) and, concerning of hydrophobicity, by measuring the water static contact angle. Results show that the hydrophobicity increases with both the temperature level and the time the cavity surface temperature was kept high. In particular, the contact angle of the molded sample was found to increase from 90°, with conventional molding conditions, up to 113° with 160 °C of cavity surface temperature kept for 18 s. This increase was found to be due to the presence of sub-micro and nano-structures characterized by high values of spatial frequencies which could be more accurately replicated by adopting high heating temperatures and times. The surface topography and the hydrophobicity resulted therefore tunable by selecting appropriate injection molding conditions.

Three-Dimensionally-Printed Polyether-Ether-Ketone Implant with a Cross-Linked Structure and Acid-Etched Microporous Surface Promotes Integration with Soft Tissue

“…At present, it is not possible to use CAD/CAM technology alone to manufacture objects with a fine internal structure [39,40]. Although injection molding can be used to manufacture peek implants with a definite shape, substitute models with a fine structure can be made by technicians, but the fine internal structure cannot be reconstituted [41,42]. Therefore, in the present study, we combined 3D printing and injection-molding technologies to fabricate peek specimens with an internal cross-linked structure, which completely reconstituted the structure designed with computer software.…”

Improvement in nano‐pattern replication of injection molding by polyamide/dendrimer blend

“…[ 5,14 ] In general, pattern structures, such as pattern size, shape, and aspect ratio, and molding conditions, such as melting temperature, mold temperature, injection pressure, and injection speed, affect the precision of replication. [ 15–19 ] Improved replication precision has been reported by adjusting molding methods such as rapid heating of mold surface, [ 20,21 ] vacuum molding, [ 22 ] and injection compression molding. [ 23,24 ]…”

“…[5,14] In general, pattern structures, such as pattern size, shape, and aspect ratio, and molding conditions, such as melting temperature, mold temperature, injection pressure, and injection speed, affect the precision of replication. [15][16][17][18][19] Improved replication precision has been reported by adjusting molding methods such as rapid heating of mold surface, [20,21] vacuum molding, [22] and injection compression molding. [23,24] Polymer resin, a material used in injection molding, is injected into the mold by an injection molding machine resulting in solidification of the resin followed by rapid decrease in its flowability, which makes it difficult for it to fill the nanostructure of the nano-pattern.…”

Atomistic Investigation on the Wetting Behavior and Interfacial Joining of Polymer-Metal Interface

“…Injection molding, or the direct joining method is one of the most commonly used technologies in the fabrication of polymer products [ 7 , 8 , 9 ]. With metallic part as an insert assembled in the cavity of injection mold, the polymer-metal hybrid structure can be easily fabricated in mass production.…”