X-ray photoelectron spectroscopy and atomic force microscopy of high-solid polyurethane resins

High-solid polyester polyol resins and high-solid acrylic polyol resins were synthesized, cured by isophorone diisocyanate trimer (IPDI) to obtain polyurethane films, and then characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS analysis showed that the top layers of these polymer films are dominated by the soft segments of the resins; the IPDI segments tend to remain inside the bulk. The polyester resins cured by IPDI at room temperature show more soft segments than these resins cured by IPDI at 120degreesC. The change in mole ratios of hydroxyl to carboxylic and/or anhydride groups during the synthesis of the resins does not give rise to distinct variation in surface composition in our experimental range. AFM topographic images demonstrate that high-solid resins cured by IPDI exhibit numerous grains or aggregates on the surfaces, while low-solid resins cured by IPDI produce surfaces with only a few aggregates. Curing temperature, such as room temperature or 120degreesC, does not cause distinct differences in topographic images. Higher hydroxyl content of the resins results in smaller grains or aggregates on the surfaces. High-solid acrylic polyol resins cured by IPDI give rise to separated aggregates surfaces, which is different from high-solid polyester polyol resins cured by IPDI.