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Everwide Newsletter No.295


Experiment § Strength of 5 minutes hardening adhesive

The epoxy resin is combined with a mercaptan hardener to select an appropriate catalyst, which can make a fast-reacting formula. Taking JA484 as an example, the gelation time is mostly set to 5 minutes, the response is too fast to operate, and too slow to lose the design intent. These systems developed the initial strength after 5 minutes, but in fact a large percentage remained unreacted. (Figure1) is a DSC temperature-raising scan after AB mixing for 30 minutes. The blue area shows JA484 has a large unreacted exothermic peak, and even some residual exotherm after 48 hours (Figure 2). There are some applications that hope to obtain a stable strength in a short time, so we developed JD883. The red curve in Figure 1 shows that the proportion of unreacted exotherm after 30 minutes is really small. (Figures 3 and 4) are the Tg and hardness of the hardened product, respectively, and Figure 5 is the adhesion strength of the adhesive on the aluminum sheet. The physical properties of JA484 will gradually increase at room temperature, which is relatively stable after about 48 hours; JD883 will have good strength after 30 minutes, and the properties will not change significantly with time, which is very good compared with general products.

─Author: Chih-Yu, Huang

 

Activity § Beach cleanup

In 2017, we first adopted a one-year coastline and had a series of beach activities. This year we applied for a three-year adoption activity. In order to ensure the traffic and safety issues of future activities, we first went to the site to investigate. Currently, abandoned bamboo rafts and garbage are scattered on the shore. As the saying goes: "The most beautiful people in Taiwan are people." Let's practice together and clean our home.

 

Knowledge § High temperature& high humidity lead to subsequent strength decline

Polymers absorb moisture in the air. The higher the temperature and the higher the humidity, the greater the amount of absorption. After the polymer absorbs moisture, it will be plasticized and softened by the moisture, so the strength decreases. This phenomenon is a reversible reaction. If the parts are placed in a low humidity environment, the water will diffuse out of the polymer and restore its original strength. Some polymer structures will undergo a hydrolysis reaction, which breaks the molecular chain, resulting in a substantial decline in strength. The influence of moisture on the adhesive force also occurs at the interface between the adhesive and the adherend. Originally, there was a chemical bond between the two. After the water enters, it will form a bond with the adhesive and the adherend separately, destroying the original relationship between the two. The latter two factors will cause the irreversible intensity to drop.

 

Living § Question behind question

Reading this book reminds me of the experience of high school leading a team to volunteer in Africa. I was appointed as the team leader. At that time, I often complained "Why can't others do it?" and "Why are there so few resources available". Not only does it affect the operation of the team, it also makes me very unhappy. Later, I changed to become the material leader. I have to think for myself how to pack materials with the most streamlined manpower? This position has given me different insights, not only activating my teammates to interact with me, but also allowing everyone to see my growth. QBQ's book is completely consistent with my personal experience: everyone's influence is enough to infect the surroundings of life. Learn not to complain and think about the greatest possible possibilities with limited resources. QBQ is a common language for people to cooperate. Every time I read this book, I feel a deeper step. I recommend this book here to better you.

─Author: Yu-Jen, Chang




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