Wen Shi

Date of Award


Degree Type


Degree Name

Master of Engineering Science


Chemical and Biochemical Engineering


Dr. Jesse Zhu

Second Advisor

Dr. Hiran Perinpanayagam

Third Advisor

Dr. Stephen Ferrier


Powder coating is a coating process that applies the coating materials to a target substrate in dry powder form. As an alternative coating technique to liquid coating technique, powder coating has many advantages, such as environmental friendly, low cost, high efficiency in materials usage. However, problems such as unable to handle ultrafine cohesive powders limit the application of powder coating technology in industry. With a new invention that can effectively fluidize ultrafine powders by enhancing their flowability, a novel electrostatic ultrafine powder coating technique has been developed by our group. Based on this novel technique, many functionalized powder coatings have been created.

In this study, electrostatic ultrafine powder coating technique has been utilized to fabricate a polymeric powder coating (PPC) on pure titanium substrates, which contains a bioactive agent, mineral trioxide aggregates (MTA). The study demonstrated that this technique could successfully create MTA enriched polyester powder coating surfaces, that not only have excellent adhesion on pure titanium substrate but also have nano­ topographies and nano-roughness that promote cells growth. Human embryonic palatal mesenchymal stem (HEPM) cells were cultured on PPC coated surfaces and pure titanium surfaces to test the biocompatibility of these surfaces. The results demonstrated that PPC coated surfaces could support the attachment, proliferation and differentiation of HEPM cells, and in some cases, better than pure titanium.

Another study was to utilize the same novel fluidization method of fine powders to modify the flowability of glass ionomer cements (GIC) (GC Fuji I®and Ketac-Cem®) for their application in dentinal tubules occlusion by the electrostatic ultrafine powder coating technique. High hydroscopicity was observed for both GIC powders, with Fuji I® taking up water to 2.43 wt% and saturated after 10 hours and with Ketac-Cem® taking up water to 7.37 wt% and saturated after 19 hours. The water absorption decreased the flowability of both Fuji I®and Ketac-Cem® powders. By blending in nano-Al203or nano-


Si02 or nano-Ti02 as flow additives, the flowability of those GIC powders can be improved. 3.0 wt% of nano A12C>3and 4.0 wt% of nano-Si02were found to be optimal in improving the flowability of dry Fuji I® and Ketac-Cem® powders, while 3.0 wt% of nano Al203 to be effective on improving the flowability of the water-saturated Fuji I ® and Ketac-Cem® powders. Nano Ti02 showed limited effect, with 1.0wt% giving slight improvement in powder flowability.

In conclusion, this study demonstrated the potential applications of the novel ultrafine powder flow enhancement technique for orthopaedic and dental implants as well as for dentine tubules occlusion.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.