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Everwide Newsletter No.148

Updated: Sep 23, 2021

Experiment § The influence of resin content in composite materials

In addition to the different types of carbon fiber and resin affecting the strength of the composite. The Resin content (RC %) of the prepreg cloth also affects the physical performance of the materials after molding. The FAW (fiber weight per unit area) is controlled by the arrangement of carbon fibers and the resin film of different thicknesses can be used to make prepreg cloth with different RC values. In general, the lower RC value get the better measured strength of the finished product. However, the RC is too low, the fiber cannot be penetrated by the resin. It defects form in the prepreg cloth, resulting in poor strength. In this experiment. the prepreg cloth (FAW=160 g/m², RC=40%) was placed in a mold with 13 and 15 layers, respectively, and hot-pressed at 150℃. Finally, the flexural strength of the prepreg cloth was tested (Figure 1~3). Because the internal thickness and volume of the mold are fixed, more resin will be extruded in the case of hot pressing with more layers, and the sample with lower resin content will be formed. Through theoretical calculation, we found that the resin content of the sample formed by hot pressing with 13 layers of prepreg cloth was 35%, and the sample with 15 layers of prepreg cloth was 26%. The properties of the two specimens before and after hot pressing are compared with the bending strength as shown in the table above. Through the experiment, it is found that when the number of layers is more (15 layers), the overall resin content decreases, and the strength and rigidity are better. Theoretically, the number of layers can be used to control the resin content and physical properties of the finished product, but it still needs to be adjusted according to the overall properties of the prepreg cloth in the application. For example, resin loss, resin distribution uniformity, hot pressing conditions, etc. In fact, carbon fiber can also be squeezed out and affect overall performance, so many details need to be worked out continuously.

─Author:Ms. Zhen-Ru, Liao


Activity § Tabebuia rosea

In the garden of the second factory, there is an amazing Tabebuia rosea. In spring, the pink flowers are in full bloom and they are very beautiful. The Tabebuia rosea belongs to the Bignoniaceae and blooms in late spring to summer every year which is a common street tree. This tree has been planted since the beginning of the construction of the second plant in 2005. After a long wait, I saw the beautiful scenery full of flowers for the first time last year. When the Tabebuia rosea bells are in full bloom, the full stamens hang on the branches like strings of wind chimes, swaying in the wind and dancing. If you haven't seen such beautiful scenery before, don't forget to visit us in the spring to explore the beauty!


Knowledge § Is the reaction speed of PU must be faster than epoxy resin?

In the last issue, we talked about the advantages and disadvantages of two-component PU (Polyurethane) in the application. PU has a very fast reaction rate, which is its biggest advantage, but is the reaction rate of PU faster than that of epoxy resin? The answer is that the reaction speed of PU is not necessarily faster than that of epoxy resin. Because the reaction rate is related to the type of epoxy resin curing agent and the content of the reaction catalyst. Epoxy resin uses mercaptan as a curing agent and its gel time is about 5-10 minutes. There are some products with gel time as short as 40 seconds, so the reaction speed of PU is not necessarily faster than epoxy resin. In fact, there are many types of epoxy resin curing agents. If it is used as an amine curing agent, the shortest gel time is 10 minutes. If it is an acid anhydride curing agent, it must be heated to have a good reaction rate, because the reaction rate will not be very fast at low temperatures.


Living § Evolution of uniforms

We didn't have uniforms when we started. Our uniforms started had more employees. For early uniforms, we chose white t-shirts, which were cheap and the least heat-absorbing. The white t-shirts get dirty easily and don't feel very formal, so a few years later we switched to collared uniforms to make everyone full of life . The blue uniforms of the second generation were made of synthetic fibers, which were relatively hot. The third version was developed two years later. The colors of the uniforms were chosen by unanimous vote, and since red and blue were equally popular, we decided to use both colors. These two uniforms always have a shortcoming that is difficult to break through. These are not comfortable and breathable in the high temperature and sweaty environment in summer. Since last year, we have chosen the fabric of sweatshirts to make uniforms. In the case of airflow, this kind of cloth can really breathe and wick away sweat. In the case of static air, this kind of cloth will stick to the skin and feel uncomfortable. This year, we changed the fabric to a porous cotton design without changing the appearance, while taking into account the sweat absorption, perspiration, and comfortable touch. As for the color of the uniform, whether short sleeves in summer, long sleeves in winter, tank top or coat, in recent years we have fixed the choice of light grass green. Because this color has the feeling of environmental protection, clean, and fresh. On behalf of our farewell to the dirty chemical plant. Choosing a good uniform is also a stereotype that distinguishes traditional factories: no matter which department you are in, you must cultivate the consciousness of engineers and use a serious attitude to improve the quality of work.

─Author: Ms. Heng-Rong, Li


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