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Everwide Newsletter No.271


Experiment § Precipitation of filler

Inorganic powders are often added as fillers in resin formulations to provide specific functions, such as heat conduction, flame retardancy, crack resistance, low shrinkage, etc. The specific gravity of these powders is usually between 2.5-4.5, and the specific gravity of the resin is around 1.0-1.2, so the filler is easy to precipitate in the resin. Figure 1 shows the initial appearance of a resin formulation (filler content is 70%), and precipitation can be clearly seen after standing for 24 hours (Figure 2). The precipitated powder is easy to squeeze and accumulate at the bottom to form hard lumps, which is the so-called hard precipitation (Figure 3). Some formulas can prevent the powder from forming hard lumps when it precipitates. A little stirring before use can easily re-disperse the precipitate. This is called soft precipitation (Figure 4). Some applications require completely non-flowing thixotropy, such as thermal paste (Figure 5, 6). This formula will not cause precipitation, and a small amount of resin will be precipitated after long-term storage, and it can be mixed evenly by simply stirring. However, for applications such as infusion of electronic parts, some are mixed with a glue mixer, and some need to be vacuum defoamed. Therefore, it is necessary to design a flowable formula to meet the processing conditions. This product has more or less precipitation during storage. In order to avoid hard precipitation, maintaining soft precipitation that is easy to stir is a requirement for formulation design.

─Author: Wei-Ting, Tu

 

Activity § Repair roof of sheet metal house

After being exposed to wind, sun and rain, the sheet metal outer wall on the site has gradually become mottled and leaking. In order to solve this problem, we repaired the roof of sheet metal house. we used a relatively simple covering and laying, without removing the original sheet metal roof. In addition to the simple construction method, there is no need to stop working on order to rebuild the sheet metal roof. What's more, we also set up transparent corrugated boards in the original ventilation equipment, which not only maintains the original lighting, but also looks more beautiful. Under the scorching sun, the workers stepped on the hot sheet metal roof and worked hard to repair. Silicone is carefully applied to the seams of the corrugated board, the sink and the water cut to prevent water leakage from happening again. Here, I pay the highest respect for their hard work!

 

Knowledge § Adhesion of plastic surface after corona treatment

There are many types of corona treatment, but the principle are all to bombard the plastic surface with ions produced by high-voltage electricity, so that the molecular chain generates free radicals, undergoes oxidation reactions, and obtains polar functional groups. The surface tension of the corona-treated plastic will increase, which will help the wetting and spreading of the paint and adhesive, thus improving the adhesive force. This improvement is sometimes obvious, sometimes not. Take printing as an example. The adhesion of the ink to the PP substrate only conducted adhesion test, and the required adhesion is actually not high, so the corona treatment can have a good effect. However, if epoxy resin is used to glue the corona-treated PP sheet, the adhesion force is still not enough to deform or break the material. The main reason is that the structure of epoxy resin and treated PP is still very different. Being able to wet the surface does not mean that it can swell into the material, so it may not be able to obtain high strength.


 

Living § Forget who she is

When I was a child, Mrs.Pao in the community were angels for the children. After school, as long as we recited a Tang poem, a text, or write a calligraphy to Mr. Pao, we could get handmade desserts made by Mrs. Pao. She was illiterate, but she could always make a sign when we were reciting Tang poems. A few years ago, Mrs. Pao disappeared and everyone could not find her. Two days later, the police found her in front of Changhua Station. It turned out that Mrs. Pao had Alzheimer’s disease. She would put the pots and pans in storage room, so when she was about to cook, she could not find them. She would also put fresh vegetables in the closet until rotten and smelly. She often forget to eat, and occasionally she was missing. Her family could only send her to a nursing center near her home. Thus, Mr. Pao's most important job every day was to accompany Mrs. Pao for dinner. He told me, "Mrs. Pao only recognizes my voice and cannot remember others. If I didn't go, she would not eat." I often see Mrs. Pao sitting in a wheelchair with empty eyes. I greeted her loudly, but she just smiled softly and did not respond. I thought maybe Mrs. Pao was living in another parallel time and space. In that time and space, she still smiled and made a lot of desserts for everyone. There is no cure for Alzheimer's disease. It can only delay the onset of symptoms. Brainstorming, exercise, and a healthy diet are all possible ways to prevent Alzheimer's disease.One day we will all be old.Maybe we should think of a way to avoid forgetting ourselves and living in a lonely world.More about Alzheimer's disease: http://www.tada2002.org.tw/

─Author: Heng-Jung, Li




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