Experiment § Measure the possible change of Tg with DSC
DSC judges Tg based on the change in heat flow of the test piece, so it is affected by the thermal history of the test piece. If the Tg obtained by the second heating scan is higher than the first one, it means that the reaction of the original test piece is incomplete. The high temperature of the first heating scan increases the reaction rate. If the Tg obtained by the second heating scan is lower than the first one, it means that the temperature of the original test piece was cooled too fast during production, or it was hardened at room temperature for a long time, so that the phenomenon of relaxation enthalpy occurred. In this case, it seems that there is an endothermic melting near Tg, so Tg is overestimated. There is no relaxation enthalpy during the second heating scan, so the Tg is relatively low. Another common phenomenon is that the test piece is affected by moisture. Figure 1 shows the state of the resin after baking and curing, and directly measuring Tg is 167℃; After standing for 4 days under normal environment, Tg becomes 158℃; If placed in a high-humidity environment like Figure 2 does, Tg will be 153℃ after 4 days; Put the test piece in the aluminum foil bag of Figure 3 for 4 days, Tg will be 163℃; If the desiccant is placed in the aluminum foil bag, Tg becomes 165°C (Figure 4). It can be seen that the Tg obtained by using the DSC test piece is not unchangeable, and has a lot to do with the condition of the test piece.
─Author: Li-Ling, Liu
Activity § Smoke extraction equipment
In the fire protection regulations, the smoke extraction equipment includes natural smoke exhaustion and mechanical smoke exhaustion. Natural smoke exhaustion, such as installing a smoke exhaust window above the wall, is lower in cost but less effective; Mechanical exhaustion uses a smoke exhaust machine to forcibly exhaust indoor smoke, which has the best effect and relatively high cost. In March of this year, we installed exhaust fans and water-cooled fans for the production plants to improve the ventilation of the work environment and the comfort of employees. Based on employees' lives, equipment, properties, stable supply, and compliance with the latest regulatory requirements, Everwide has added 7 explosion-proof mechanical smoke exhaust fans for the fire-fighting equipment of the plant since the middle of last year. When a fire occurs, it can automatically and forcefully discharge the deadly thick smoke and toxic gas at high temperature in time, and play an important role in emergency rescue and escape. In addition, it is usually used as a ventilation device. Not only can the ventilation rate be increased in time, but also the on-site working environment can be more comfortable. Of course, if it is not used for emergency rescue, it is the best!
Knowledge § The reaction of epoxy resin is fast and then slow
The epoxy resin is liquid when it reacts at first. Resin and curing agent can move quickly in the liquid state and collide with each other, so the reaction speed is fast. As the reaction rate gradually increases, the unreacted monomers gradually decrease, resulting in less chance of collision with each other, so the reaction rate slowly decreases. The resin becomes solid after gelling, so the unreacted components must diffuse in the solid before they can collide each other. Diffusion in solids is much slower than in liquids. The gelled resin will further react from the soft rubber state to the glass state, so the molecular chain becomes more and more stiff, and the diffusion rate drops lower. At this time, if it can be heated and cured so that the unreacted components have relatively high energy to collide each other in an environment that is easy to diffuse, the reaction rate can be improved. If some formulas do not cure after increasing the temperature, they cannot show good strength because the diffusion reaction at room temperature is too slow and will never reach a high reaction rate.
Living § Experience of Shanghai Exhibition
When the first time I went to Shanghai to participate in the exhibition, everything was curious. The exhibition park is composed of nearly 25 exhibition halls. The huge hardware construction is breathtaking. However, the subway stations and factory hall entrances to the exhibition area needed to pass through security checks every day. It felt like people were packed like sardines. which was where I were relatively uncomfortable. When participating in the exhibition, I interacted with manufacturers and distributors from all walks of life, and then I realized that I were not familiar with many electronic parts. Fortunately, the leadership of a senior colleague gave me a fulfilling lesson. After the exhibition, everyone went to several famous scenic spots in Shanghai together. I was impressed by the trails along the Bund and Lujiazui River, which was very comfortable and clean. We sat in a coffee shop, looking at the Bund across the Huangpu River. The floors of each building were equipped with a variety of neon lights, which were especially brilliant at night. The lights of the whole city reflected with each other, forming a brightly lit Shanghai beach. During this five-day trip to Shanghai for the exhibition, I felt that the ambition of the local people was very high. Perhaps the population is huge and the competition is fierce, so everyone has an active spirit of seeking knowledge. In contrast, people in Taiwan are relatively more comfortable. Back to Taiwan, I want to share this experience with everyone, and we have to work harder.
─Author: Tung-Chiao, Yang
