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Everwide newsletter No.413

Updated: Nov 6, 2023


Experiment § Yellowing resistance test of PU

We have introduced a haze tester that can test chromatic aberration and use it to evaluate the yellowing of PU (polyurethane) under UV exposure. The three coordinates of chromatic aberration CIE L*a*b* represent the brightness, hue, and chromaticity of a color. L* data is black for 0 and white for 100, a* is green for negative values and red for positive values, and b* is blue for negative values and yellow for positive values. (Figure 1). In this experiment, the specimens were placed in a QUV weatherometer and exposed for 500 and 1,000 hours, and then the degree of yellowing was tested using a haze tester. PU is made from a combination of polyols and polyisocyanates, and the selection of different isocyanates affects the weathering properties. Figure 2 takes three isocyanates as an example, including MDI, H12MDI, and HDI. The MDI system is aromatic with a benzene ring structure, which resonates and discolors when exposed to UV light, thus leading to yellowing. Aliphatic HDI and H12MDI (hydrogenated MDI) have excellent weathering properties and are suitable for transparent, non-yellowing products. (Figure 2,3). MDIs that are not tolerant to yellowing have limited effect on adding antioxidants, and no difference after 1,000 hours (Figure 4, 5). The instrument can have the color data and clearly show the differences between recipes, which is an indispensable tool for research and development. ——Author: Miss, Yi-Ling, Xie

 

Activity § Exhibitions in the second half of this year

In the second half of the year, we participated in the following exhibitions: the China adhesives and sealants expo in Shanghai (Figure 1,2), NEPCON Vietnam (Figure 3,4), and Optoelectronics Exposition Taiwan, for more information, please visit Everwide official website . We hope to promote our products through exhibitions, as well as attracting more attention and obtaining the latest developments in the market and also going to Nuremberg Germany exhibitions as a spectator (Figure 5). Participating in exhibitions can learn about innovations and trends in different industries and is an important way to supplement knowledge.

 

Knowledge § What is a Blocked PU? (1)

PU is composed of isocyanate and polyol or polyamine. Isocyanates are highly reactive and can easily react with components containing reactive hydrogen, such as water, acids, alcohols, amines, etc., which is sometimes not easy to control. If an isocyanate is reacted with a Blocking agent, the resulting oligomer will be very stable, and this thing is called a Blocked PU. Blocked PUs are mostly high-viscosity liquids that can be mixed with components such as solvents or polyols, and will undergo a reverse reaction of de-blocking at specific temperatures, releasing isocyanates and Blocking agent. At this point, the isocyanate regains its original activity and then reacts with the components we need to form the final PU cure.

 

Living § Travel to northeastern Taiwan

I recently traveled to northeastern. The first stop was the "Alisai Cold Spring", where admission is free at certain times, and the spring water is a low-temperature white mineral spring that is good for the skin. There are shaded relaxation areas outdoors, perfect for a hot summer day. Next, go to "Dongsanhe Forest Park", The large garden is great for walking, and you can also explore the mysterious waterway, or take a green boat through the lakes of Dongsanhe to observe the wildlife. On the way back, drive in the direction of Keelung, and there are many beautiful mountain sceneries along the way, such as the most beautiful lonely road "Buyan Pavilion". On the way, you can go to the "Shifen Waterfall" in Pingxi Area, to see the magnificent waterfall and release sky lanterns. Local food recommendation: "Peng Ji’s Scallion pancake" in Yilan Dongmen Night Market, which is fragrant when bitten, and baked very crispy. There are many seafood restaurants in the harbor near Yilan, and this time I tried the "Happiness Hall 2 Seafood Restaurant". If you are also interested in visiting the Northeast, you can refer to my recommended attractions and food! There will be many people traveling on holiday, so it is recommended to plan your trip and leave early.—Author: Miss. Yu-Hui, Liao



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