Browsing by Subject "polymer coatings"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    UV Curing and Micromolding of Polymer Coatings
    (2018-08) Du, Yuyang
    UV curable films and coatings have a wide range of applications in everyday life and various industrial sectors. With surface microstructures, patterned coatings can be used as a general way to provide surface textures or serve critical design purposes, such as providing engineered optical performances and altering the surface hydrophobicity. This thesis addresses key challenges in the UV curing process and their patterning applications, aiming to make UV curing faster, better, and cheaper. Firstly, the UV curing speed is the bottleneck of the process throughput for many applications. Traditionally, high-intensity light sources are used to achieve fast cure but bring with potential problems, e.g. significant heat accumulation. In this thesis, the intense pulsed light was investigated as an alternative curing method, where the UV energy is delivered in discrete pulses with a dark period between pulses. A systematic study was performed on a model acrylate system to understand the curing conversion as a function of various processing parameter, including illumination conditions, the photoinitiator concentration, and the curing temperature. It was revealed that sufficient curing of acrylates was achieved within seconds without significant heat built-up in the substrate. Second, this thesis investigates the fabrication of surface microstructures with UV curable materials. The UV micromolding process is used for pattern replication, where a liquid coating is brought into contact with a patterned mold and then UV cured to obtain surface microstructures. However, the wide application of this process is limited the stringent material requirements of the process: low viscosities, fast cure, low surface energy, and tunable mechanical properties. This thesis describes the design of thiol-ene based coating formulations for the UV micromolding process. The coating system allows for the preparation of microstructured coatings within seconds and significantly expands the achievable mechanical and surface properties of cured materials. Finally, continuous fabrication of microstructured coatings was explored to move the process a step further towards mass production. The roll-to-roll imprinting process with thiol-ene based formulations was discussed. In the process, a roller mold was used for pattern replication on large-area substrates. The coating formulations were optimized for a fast cure and high curing extents. In addition, the influences of processing variables on the curing extents were studied systematically.