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If old good approaches fail - Innovate your own theory 

January 2018

by Natalia Mukhina

Dr. Chaimongkol Saengow

Dr. Chaimongkol Saengow

Whether you are unfolding your non-slip mat before yoga class, packing your fragile items with bubble wrap, or touching your laptop keyboard, you likely encounter things made from polymers every day. Polymer, a word we hear about a lot, is found in almost every material used in our daily lives. Have you ever thought about how your swimsuit, pen, or plastic water bottle looked before becoming what they are now?

“In general, all plastic things once were a viscous fluid substance. Polymeric materials can be shaped depending on their intended purposes.  Polymer processing mainly consists of a series of operations when the polymer is heated to the molten state, and then this fluid is tailored using the model of the final object,” explained Dr. Chaimongkol Saengow.

Dr. Saengow is a post-doctoral researcher at Queen’s Polymer Research Group and has two doctoral degrees under his belt. He earned one in Mechanical and Aerospace Engineering at King Mongkut’s University of Technology North Bangkok, and the other in Chemical Engineering at Queen’s. His current focus is on rheology and its application in polymer processing.

As an academic discipline, rheology is a young one (it is not even a hundred years old) and has wide ranging, diverse applications. The term “rheology” comes from the Greek words ‘rheo’ translating as ‘flow’ and ‘logia’ meaning ‘the study of’. Dr. Saengow explains that rheology studies the flow and deformation of matter that pose a combination of viscous and elastic behaviours, mainly liquids, but also soft materials which exhibit some level of flow. 

“Rheology deals with substances that have complex molecular structures, such as polymers. We normally use oscillatory flow to induce deformation, which incites rheological properties. The purpose of rheology is thus to predict how a material will respond under the influence of certain circumstances,” Dr. Saengow says.

Recently, Dr. Saengow has received the 2017 Award for Best Graduate Student Paper Published in The Canadian Journal of Chemical Engineering. The article, titled “Bubble Growth from First Principles”, touches on the emergence and control of bubbles in viscous fluids like polymeric liquids. Dr. Saengow is the primary author, and one of the co-authors is his supervisor, Dr. Jeffrey Giacomin, who holds Queen’s Tier 1 Canada Research Chair in Rheology.

In this paper, Dr. Saengow along with the co-authors discusses how a solitary bubble grows from its own internal pressure in a sea of Newtonian fluid without interference from other bubbles. This is the simplest relevant problem in the foaming of molten plastics. They began their analysis from a detailed examination of the classical approaches and failed to fit the data with them. The “Old good theory” seemed not to work.

“In the second part of the paper, I suggested that we do a novel exploration of the essential decelerating role of viscous heating. We explored both isothermal and adiabatic expansions, and the decelerating role of surface tension. We also looked at the pressure profile, and the components of the extra stress tensor, in the surrounding fluid. I believe that the research will help manufacturers to precisely predict and control bubble formation. Specifically, plastic foaming might be the right application for the new theory. Engineers will be able to determine how big bubbles could be inside the foam.”  

Asked about the motivating interest in the paper, Dr. Saengow stresses that he could not find any theory that would be crafted from first principles - the fundamentals of physics, i.e. conservation of mass, momenta and heat - and be of help in pursuing his research goals. “I just finished my course work and wanted to do actual research. Plastic foaming caught my eyes, and I became interested in bubble growth, but found out that there was no actual theory for me. I talked to Professor Giacomin, and he said, ‘I think you should write a paper about that! That is a good opportunity to write a paper about something that hasn’t been done yet.”

Dr. Saengow underlines that much work still needs to be done to polish his theory. While the award article is from an application point of view, his post-doc research focuses on fundamental aspects of rheology. “Dr. Giacomin’s lab is equipped with the most sophisticated rheometer worldwide. We can do so many things in rheology at Queen’s! For example, there is a rheological test method called large-amplitude oscillatory shear (LAOS) flow. With LAOS we are capable of measuring various things, but we can’t associate their behaviors to their physical molecular structure.  My current interest therefore is about developing a fluid model to bridge these two together.” 

Chai’s innovative way of thinking directs his every endeavor, be it teaching, research or something more prosaic like… cooking. Yes, Chai likes cooking and having a lot of friends who are always happy to taste his cookery. “I am thinking of doing food video channel on YouTube with my friends at some point,” he says with laugh. “I never have a recipe when cooking. I just start cooking and mix what I have. I love the feeling when you start doing something new. It fuels creativity and is just exciting, isn’t it?”

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