Everwide Newsletter No.245

The original form of epoxy resin is two-component, which are resin (agent A) and curing agent (agent B). The curing agent is originally liquid and can be miscible with epoxy resin. If this type of curing agent (mostly amines) is reacted or blended with other resins to increase their molecular weight and a solid with a softening point of 80~150°C can be obtained. This solid is crushed and ground into a powder with a small particle size, and dispersed in an epoxy resin in an appropriate proportion to make a one-component epoxy resin formulation. The picture on the left shows the curing agent modified by phenolic resin mixed with epoxy resin (JB634, 80℃/1hr), the initial appearance is light yellow and long-term storage is brown. This discoloration has nothing to do with the reactivity of the resin and the characteristics of the cured product, it is purely the nature of the unstable color of the phenolic resin. These powdered curing agents will not be dissolved by the resin at room temperature, so they have good storage stability. Usually, the shelf life is several days or several months. On the contrary, when the temperature rises, the curing agent will dissolve into the epoxy resin, and then produce a curing reaction to achieve the purpose of one component. In general, the curing reaction at around 80°C belongs to the low-temperature curing system; the curing system at 100-120°C belongs to the medium temperature curing system, and the curing system above 120°C belongs to the high-temperature curing system. The curing temperature is related to the temperature range in which the curing agent is dissolved by the resin. At present, the one component resin JD661 with the lowest reaction temperature is around 60℃/1hr, and the special formula JD652 can be reduced to 50℃/1hr. Customers with low-temperature curing requirements are welcome to contact us.

—Author: Miss. Zi-hui, Huang

We participated in a series of exhibitions this year, including the Shanghai Munich Electronics Show from March 14th to 16th (Picture 1, 2); the Taipei International Bicycle Show from March 22nd to 24th (Heng Sponsored by Yan); Japan Display Manufacturing Exhibition from April 5th to 7th (The 1st Adhesive Exhibition, Figures 3, 4); Istanbul International Auto Parts, Repair Tools and Inspection from April 6th to 9th Equipment exhibition (Figure 5, 6). Immediately following the show: the Taipei International Automotive Electronics Show from April 19th to 22nd; Shenzhen International Small Motor and Magnetic Materials Exhibition for Electrical Machinery Industry from May 18th to 20th (De Nordis Host); Shanghai International Electric Exhibition (Sponsored by De Nordis) from June 7th to 9th; Taipei International Optoelectronics Week from June 14th to 16th-Automotive Optoelectronics Zone; Shanghai International New Energy Vehicle Motor and Electronic Control Exhibition (sponsored by De Nordis) from July 18th to the 20th; August 23rd to 25th China International Adhesives and Sealants Exhibition (Shanghai); Vietnam International Electronic Process Equipment and Microelectronics Exhibition from March 13th to 15th. We hope that we will make some progress, and you are welcome to come and guide us.

Without the addition of inorganic powder, the one component epoxy resin will not have any flow marks on the surface after curing. Adding inorganic powder to the epoxy resin, especially in the application of infusion, often shows resin flow lines on the cured surface, which looks not uniform in color, and the greater the amount of inorganic powder added, the more obvious the trace of flow. This phenomenon is because the long axis of the powder and granular body will be parallel to the direction of the flow field when the liquid is flowing, reducing the flow resistance. When we infuse resin into parts, the flow behavior of resin is not always consistent and will be affected by the flow sequence. These different flow behaviors have different powder and granular arrangements, which show signs of flow. The larger the aspect ratio of the powder and granule, the more obvious this phenomenon, if the powder and granule are spherical, there will be no traces of flow because they have no directionality.

D230 is a commonly used curing agent raw material, its full name is Jeffamine D230. Speaking of D230, it reminds me of a past event. Around 1994, a visitor visited his uncle's factory, and I was also there to accompany him. At that time, the visitor asked his uncle, "What is the source of the technology developed?" Uncle told him that part of the research was done on his own and the other part was technically cooperating with an American consultant. I was at a loss when I heard it. When will we cooperate with American consultants on technology? Because the visitor was there, I had to be calm. As soon as the visitor left, I couldn't wait to ask my uncle what he mentioned about "technical cooperation with American consultants"? Uncle unhurriedly raised the product catalog of Jeffamine on the table and said, "This is our American consultant." I almost fell off the chair after hearing this. How can the catalog be called technical cooperation? Uncle is too deceiving. Uncle showed a strange smile and told me a little seriously that in this catalog, there are D230's viscosity, reaction speed, mechanical properties, heat resistance, chemical resistance, and structural formula... etc. The data is quite abundant, as long as We understand and digest its content, and the effect is the same as that of hiring a US consultant. Twenty-three years have passed. The copy of the catalog of "Technical Cooperation with American Consultants" that year was still lying quietly on the shelf in the library, witnessing the past. Having said that, now that network information is extremely developed, there is no way to find consultants if you are interested. Further reading and learning new things: http://tinyurl.com/lbrlfpn

—Author：Dr. Ming-Xu, Li