Dr. Tiina Rasilainen
Tiina Rasilainen - Controlling water on polypropylene surfaces with micro- and micro/nanostructures
Classification
1. Nanosurfaces and coatings 7. Characterization 8. Fabrication 11. Something else
Abstract
During recent years, surface structuring has become a common method to modify the surface properties of materials. Especially fabrication of biomimetic micro-, nano- and hierarchical structures in polymers has gained attention when aiming to create water-repellent and self-cleansing surfaces. In this work, polypropylene surfaces were furnished with several types of micro- and hierarchical micro/nanostructures, and contact and sliding angles of water were measured. Protrusive structures comprised micropillars or micropillars covered with nanobumps. On some surfaces, the pillars were arranged isotropically, on the rest the patterns were anisotropic, with parallel stripe- or zone-like structures. Hollow structures were isotropic and consisted of micropits or of micropits covered with nanodepressions.
Wetting properties of surfaces were investigated with contact and sliding angle measurements. Pillar structures on polypropylene increased the hydrophobicity of the material. With hierarchical isotropic structures, the superhydrophobic region was reached, and even with isotropic microstructures a clear increase was achieved in contact angles and decrease in sliding angles. On stripe- and zone-like surfaces, behaviour was anisotropic with direction-dependent contact and sliding angles. With proper parameters and hierarchical micro/nanostructures, stripe-like surfaces also showed superhydrophobicity. Pitted structures increased the contact angles, and with hierarchical micropits/nanodepressions, contact angle values were near the superhydrophobic limit.
All structures were fabricated by injection moulding. Aluminium foils were microstructured with a micro-working robot and further processed to obtain appropriate mould inserts for different structure types. For hierarchical structures, the aluminium foils were anodized to aluminium oxide patterned with microdepressions and nano-pores. For pit structures, a novel fabrication method was developed where the pillar-structured mould inserts were fabricated by cold mounting of epoxy resin on structured aluminium or aluminium oxide foils. Dimensions and patterns of the polypropylene structures could be planned and controlled with the working parameters of the micro-working robot.
Linkki väitöskirjaan: http://urn.fi/URN:ISBN:978-952-61-0276-4:
Contact
Dr. Tiina Rasilainen, tiina.m.rasilainen@gmail.com, tel +358 40 7462 393