Continuously extruded micro‐textured polypropylene films

Abstract

The continuous extrusion of micro‐textured isotactic polypropylene (i‐PP) film and its tribological properties are reported. As analyzed by scanning electron microscopy, a rectangular‐semicircular micro‐patterned die successfully produced extruded cast‐films with hill‐like micro‐texture. Such films displayed static and kinetic coefficients of friction (COFs and COFk) values of 0.247 ± 0.028 and 0.245 ± 0.003, respectively, for a steel fixture sliding along the micro‐texture of the film. The equivalent COFs and COFk values for non‐textured (NT) films were 0.369 ± 0.036 and 0.340 ± 0.024, respectively, confirming that textured films displayed a reduction in COF of about 30%. For textured and NT films sliding on textured films, the COFk values were even lower at 0.161 ± 0.013 and 0.113 ± 0.004, which represents about 20–40% reduction as compared with that for the NT‐NT counterparts. Films coated with a silicone lubricant displayed COFs and COFk values of 0.334 ± 0.042 and 0.099 ± 0.012, respectively, for NT films sliding over lubricated NT films, and 0.426 ± 0.031 and 0.063 ± 0.006, respectively, for textured films sliding over lubricated textured films. The COFk values for textured/non‐lubricated films approach those of NT/lubricated films, indicating that micro‐textured polypropylene films may be used in environmentally sensitive applications where lubricants and fluorinated additives may not be used for reducing friction. POLYM. ENG. SCI., 54:2147–2154, 2014. © 2013 Society of Plastics Engineers