Experiment § How did the crack happen?
The material will cause cracks due to stress. Cracks have many forms and are not easy to be observed. Figure1 is a liquid resin with a soft formula sandwiched between two pieces of glass, the thickness is controlled at 100um. After the resin is cured, insert the blade between the two pieces of glass and slowly push it forward in the X-direction. Use a microscope to photograph the area marked by the red dot in Figure 1. Figure 2 shows the resin before the blade is inserted into the glass. Figure 3 shows that after the blade is inserted, the gap between the glass is enlarged and the resin is stretched on the z-axis. The reason why there are many voids inside is that the area of the resin does not change, the thickness increases, and the voids are created to expand the volume. The left side is close to the blade, and the gap is enlarged, so the voids are denser. Figure 4 illustrates the cause of void formation from the side of the test piece. The blade is pushed further forward, and the crack further advances in the X-direction. The more transparent part on the left of Figure 5 is that the resin has been split into upper and lower parts, just like the pillar in Figure 4 is broken from the middle under force. The right side of Figure 5 shows the situation where small holes are condensed into large holes, which are about to break. If the two pieces of glass are completely separated, you can find a rough cracked surface. This phenomenon can be clearly seen when the soft gel does not peel off from the substrate.
—Author: Dr. Ming-Xu, Li
Activity § Additional smoke extraction equipment
A fire can cause serious losses. According to statistics, most of the fire victims were not burned but choked. It can be seen that the harm of dense smoke is far more terrible than the flame itself. The smoke extraction equipment is set up to quickly exhaust the event of a fire so that personnel can quickly and completely escape. The equipment of the early Everwide’ plant was set up according to the fire protection regulations at that time, but with several renovations and amendments to the regulations, the old equipment no longer meets the design of fire safety. The fire brigade recommends that we add additional smoke exhaust equipment, these equipment, and the alarm system will automatically be online, if abnormal conditions occur, they will automatically start the smoke exhaust program. We hope we won’t use these devices in the future.
Knowledge § What is the method of polymer flame retardant
Macromolecule combustion has three elements: fuel, oxygen, and heat. If we want to make polymers have flame retardancy, we must consider these three elements. Fuel refers to the polymer itself and certain products when it burns. If you want to reduce the fuel supply, you must design from the structure of the polymer. Some plastic structures have a large proportion of aromatics, and the Char yield content after burning is high, and it is not easy to burn by itself. Many flame retardants will generate strong acids at high temperatures. These strong acids will help the polymer to quickly dehydrate and form an aromatic structure, which will also help flame retardant. Oxygen is the element of combustion. Many flame retardants will produce a large proportion of gas at high temperatures. Some are similar to ceramic structures covering the surface of the material to block the transmission of oxygen to the inside, and some are diluting the concentration of oxygen to achieve the purpose of flame retardancy. In addition, combustion requires sufficient heat supply, which exceeds the activation energy of the reaction to proceed. Some flame retardants will decompose and absorb heat when burned, causing the material to cool, such as aluminum hydroxide, melamine, etc. It will also decompose gas to reduce the oxygen concentration and hinder the combustion process.
Living § MOOC-online class
Franklin said that “If you think education is expensive, try ignorance!” and this shows the importance of lifelong learning. When we leave school, the most well-known way of learning is to read or take courses and lectures. But with the development of the Internet and the evolution of technology, we now live in an era where information is very easy to obtain. MOOC(Massive Open Oline) large-scale open online classroom is a new form of education in recent years. MOOC has the following characteristics: Its teaching method is to record the teaching content so that students can watch it anytime and anywhere without being restricted by space and time; the courses are shared, no qualifications and expensive tuition are required, and there is no limit to the number of courses; the MOOC uses assessment methods to give students learning certificates, and the assessments methods are diverse, including discussion reports between students and tests. It’s the same as we used to teach in school, except that the method is changed to online teaching. The famous MOOC is like Coursera. There are more than one million people in Khan Academy who have participated in online classes. If you are worried about bad English, you can also choose some Chinese websites such as National Taiwan University MOOC. Don’t underestimate these free courses. They come in various categories, such as management, cooking, criminal law, machinery, psychology, negotiation skills, etc. There are many famous lecturers, and more and more companies are beginning to accept MOOC learning vouchers. Do you want to go abroad without spending money to listen to Harvard courses, do you want to develop more interest in your leisure time and discover your expertise? MOOC is definitely worth a try. More reading
——Author: Mr. Zhi-Hong, Wei
