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Everwide newsletter No.54


Experiment § Questions about the light source

The reason why the lamp source produces ultraviolet light:

The mercury vapor in the tube is excited and degraded to the excited state, and emits ultraviolet light when it returns to the ground state from the excited state.

Common types of lights are as follows:

1. Electrodeless lamp: (electrodeless) UV lamp developed by Fusion Company in the United States. Excited by microwaves generated by magnetrons. It contains mercury and a small number of other metals such as tin, iron, lead, etc., which are added to change the emission spectrum. The models are as follows: H-bulb, D-bulb, V-bulb, etc. Because there are no electrodes at both ends, no cooling time is required for restarting, as shown in Figure 1.

2. High-voltage gas discharge (with electrode quartz tube): use ultra-high voltage to start the igniter, the igniter jumps off instantly, the high voltage drops rapidly, and the current rises rapidly (within 1min). After 3-5min, the current is stable and the gas is excited, as shown in Figure 2. Restarting will give the light source a few minutes to cool down.

─Author: Ms. Lin Miao-Ling, R&D Engineer, Everwide Chemical

 

Product introduction § Composite material - sewer regeneration material

Everwide Chemical and Changtong Engineering Technology Co., Ltd. have jointly developed a series of engineering resins, which make the renewal of water pipes fast and convenient and the traditional construction method is to directly excavate the ground and replace it with new water pipes. This method will have a serious impact on the environment, traffic, and people's lives. The underground pipeline repair method without excavation has the advantages of superior leakage prevention, earthquake resistance, long service life, etc., and there is no need to close the road during construction, and there is no dust flying, so the impact on the public can be minimized.

This series of materials are suitable for making high-quality tap water, sewage, and gas regeneration pipes. We have sufficient practical experience and can provide high-quality and related products and related application technical services.

For related product information, please visit Everwide Chemical's official website: http://www.everwide.com.tw/manuals/dm/Pipeline-Rehabilitation.pdf

 

Knowledge § What is the inhibition reaction of the epoxy resin cationic polymerization system?

What are the possible inhibition reactions of epoxy resin cationic polymerization systems (including light-curing systems)? What are the sources? Cationic polymerization is carried out by a superacid, so any basic substance may inhibit the above reaction, resulting in poor curing or even failure to react. In addition to the raw materials of the glue itself, the source of alkaline substances often comes from the composition of the surface of the substrate or external pollution. In the former case, the cationic polymerization system is not suitable and the resin system must be changed. The latter case can be overcome by cleaning the substrate surface, possibly with solvent wiping alone to achieve complete improvement. Be very careful about contamination of the surface and always be vigilant. There have been cases where the UV glue of the acrylic system was used nearby, and the vapor was scattered in the air, causing the cationic polymerized epoxy resin to fail to react.

 

Living § Qualifying Exam (Part 1)

To graduate, all doctoral students need to pass two major hurdles, one is the qualification examination for the doctoral class, and the other is to publish papers in international journals. Now let's talk about the qualification test. Take the doctoral class I was in that year as an example. The class requires all doctoral students to pass the qualification exam within three years, and those who fail to pass will drop out. The qualification examination for the doctoral class is taken twice a year. The examination subjects are divided into two categories: the first category is basic subjects including chemical thermodynamics, chemical kinetics, and transport phenomena. The second category is professional disciplines including polymer science, unit operations, biomedical materials, etc. Each doctoral student is required to take one of the first and second types of examination subjects. Usually, the second category of professional subjects is easier to pass, because we can choose subjects that are more similar to our own thesis to take the test. For example, I am doing a dissertation on epoxy resin, so I choose the subject of "polymer science" to take the test. The vast majority of candidates will have a headache with the first category of basic subjects because they are almost irrelevant to our thesis. For example, I don't like chemical kinetics and transport phenomena, so I have to choose "chemical thermodynamics" because it is closer to "physical chemistry". Many students quickly passed the qualification test for the second category of professional disciplines, but they were unable to pass the first category of basic disciplines. Two of my fellow students and brothers passed the qualification test only in the second semester of the third year of the doctoral class. They were almost expelled, and two were expelled for failing the qualifying exam. There are probably no very stupid students in my doctoral class. There are so many people who have failed the qualification test, which shows how difficult it is. The difficulty in the qualification test lies in the scope of his propositions. Taking the subject of "Chemical Thermodynamics" as an example, five teachers each time a proposition, one for each person, and each question are 20 points Some of these five teachers will give problems on metallurgical phase diagrams, so you have to read some metallurgical thermodynamics in the Department of Materials to understand them. In addition, there is physical chemistry in the Department of Chemistry, and chemical thermodynamics in the Department of Chemical Engineering. Guess how many books you need to read to pass the exam? After the teacher who asked the question, he will directly note "He thinks that this question, the students in the doctoral class should get a few points to pass." The sum of the scores of the five teachers is the passing score. The exam papers of the qualification exam are sealed, so the teacher does not know who the exam papers belong to when they change them. In addition, each teacher who writes the question only corrects the question that he has issued, so it is very objective and fair. After completing the revision of the test papers and counting the scores, the teachers will hold a meeting to see how many students have passed the test. If the number of passing students is too small, the teachers will discuss whether to lower the passing standard to the original set of 80. % and after the passing standards and the number of passers is determined, the list is finally unpacked and released.

─Author: Dr. Ming-Xu Li Everwide Chemical




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