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Everwide Newsletter-No.65

Experiment § Evolution of STPU

The last time I introduced the FS series moisture-curable STPU (silane terminated polyurethane), Everwide Chemical has developed an improved version that uses UV irradiation to achieve preliminary surface dryness. FS006WV-white UV pre-cured version; FS006V-colorless UV pre-cured version. These two are the original formula with 20% of UV reactive monomer added and continue to retain the characteristics of the original sealing elastic colloid. The applicable materials are ① Inorganic: glass, ceramics, iron, magnesium, zinc, aluminum, copper, and Silicon; ② Organic: PC, PVC, ABS, and PU. It has a good adhesion effect between dissimilar materials because the introduction of UV shortens the initial pre-fixing time, and the latter stage is fully cured by moisture reaction, which adds to the product features.

─Author: Mr. Hui-xu, Li, R&D Engineer, Everwide Chemical


Process § Grinding and degassing

Continuing the weighing and stirring in the previous issue will introduce the production process of grinding and defoaming. (5) Grinding: Many powders are easy to coagulate, and in mixing solid (powder) and liquid phase, they cannot be uniformly dispersed by simple stirring. Using a three-drum machine and grinding in a high shear environment is necessary to obtain the homodisperse product. (6) Deaeration: The stirring and grinding processes are easily involved in air bubbles, resulting in poor product quality. Therefore, the manufacturing barrel is placed on the vacuum device to remove air bubbles. In high-viscosity systems, the vacuum device can also be equipped with a stirring blade to allow the liquid to flow, help the bubbles float, and improve defoaming efficiency.


Knowledge § How to measure water vapor transmission rate?

According to the Japanese JIS Z 0208 standard, the experimental steps are as follows: 1. Lay the copper cup table flat. 2. Lay the aluminum dish flat in the center groove of the copper cup stand. 3. Put calcium chloride desiccant in the aluminum dish. 4. Put an appropriate size test piece (100um) on the inner edge of the aluminum dish. 5. Place the copper guide frame in the outer groove of the copper cup holder. 6. Put the aluminum ring into the hollow part of the copper guide frame. 7. Place the French code directly above the aluminum ring. 8. Remove the copper guide frame. 9. Pour the liquid PU resin into the groove of the aluminum dish. 10. Wait for the PU resin to cure. 11. Remove the French code above the aluminum pan, and the copper cup stand below. 12. Place the moisture permeability test piece set in a high temperature and humidity machine. 13. Measure the weight change of the test piece at 0hr, 24hr, 48hr, and 96hr. 14. Calculate the water vapor transmission rate according to the following formula: Water vapor transmission rate (unit: g/m2*24hr) = 240*m / t*s

*Remarks: s represents the area of the test piece penetrated by water vapor (cm2); t represents the time interval (hr) between changes in the weight of the test piece; m represents the change in the weight of the test piece (mg).


Living § How much do you know about temperature (4)

The endothermic reaction has already been conceptualized in the first unit, the "Making Popsicles" experiment. The process of melting salt is an endothermic reaction, as it absorbs the surrounding heat to lower the temperature so that the juice can freeze. In dissolving in water in the experiment, we recorded that the temperature would drop by two or three degrees. Does the sugar dissolve in water, fall or rise? Let the kids go home and experiment!

I remember my teacher taught us to make plaster casts in the fourth grade of elementary school. After the plaster hardened, we started sculpting the following week. At that time, I carved a beautiful shape of a fish. The teacher asked us to make rubbings, and I got a high score of 98. When I got back to my seat, my plaster cast was stolen by other little friends. Someone saw a male classmate taking it, but he said no when I went to ask him. It was because of the deep memory that the idea of ​​​​making a plaster cast came up.

This experiment asks children to observe the process of adding water to raw gypsum to become mature gypsum. It feels warm to the touch, so it is an exothermic reaction. Everyone prepares the small plastic boxes left after eating the jelly and the metal model boxes for making cakes, which are very suitable for making plaster models!

─Author: Ms. Miao-ling, Lin, R&D Engineer, Everwide Chemical


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