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Everwide Newsletter No.154

Updated: Aug 10, 2021

Experiment § Analysis of prohibited substances

Countries around the world have successively proposed regulations on Prohibited and Restricted Substances. The most famous is Substances of Very High Concern, SVHC's candidate list. The 144 substances have been declared restricted for use. Many epoxy raw materials are also on the list, such as NP (nonylphenol, catalyst), MDA (4,4'-diaminodiphenylmethane, amine curing agent), MEHHPA (methyl hexahydrophthalic anhydride, acid anhydride curing agent). If the resin in the goods we provide to customers contains NP, NP can be detected after the resin is cured. NP is a catalyst and it will not become a part of the network structure. If the resin that we ship to customers contains MDA or MEHHPA, the resin may not be tested after curing, because they are curing agents and will become part of the network structure and cannot be separated. However, there are two conditions that cannot be detected: 1. The ratio of resin to curing agent must be correct. If the curing agent is excessive, there will be a curing agent remaining no matter how it reacts. 2. The reaction rate of resin and curing agent should be high enough. When the reaction rate is not high enough, a lot of unreacted curing agent remains in the system. MEHHPA is currently an irreplaceable curing agent for epoxy resin encapsulated LEDs. The cured product obtained at low temperature will produce incomplete reaction monomers at 200°C. After curing at high temperatures, the signal of MEHHPA will disappear completely. In the face of prohibited substances, not using them is the first choice. When it is unavoidable, controlling the reaction rate is also a method.

─Author: Dr. Ming-Xu, Li


Activity § Autonomous maintenance equipment

The vacuum pumps are the important equipment in the process and we use it to remove air bubbles from the formulation. When vacuuming, a small amount of resin will always run into the pump and deposit near the axis, which is the main cause of failure. When there is a problem with the operation of the machine, we usually disassemble the pump to see if there are any problems that need to be cleaned up. The actions of dismantling, cleaning, and assembling seem to be simple, but that's not the case. How can I dismantle it without hurting the machine? Does the order of disassembly conform to the mechanical principle? Judgment of the cause of the failure after disassembly? The details need to be considered when assembling back. It is a common situation that the screw lock cannot be returned, the gasket is not properly positioned, and the leakage occurs after assembly. If the machine runs smoothly after assembly, the boss will buy a drink to celebrate! What should we do, the strategy is unsuccessful in some cases? You have to re-check all the steps to see if you have forgotten any details. In the past, when the machine was broken, we directly sent it to the manufacturer for repair, but now we are trying to fix by ourselves . This is called professionalism, right?


Knowledge § How to evaluate the rupture energy under slow rupture?

Common indicators for evaluating slow fracture behavior are GIC (Fracture energy) and KIC (Fracture toughness). The simplified relationship between them is as follows: GIC=KIC2/E, E is Young's modulus. The method of measuring KIC is briefly as follows: Use an extremely sharp blade to knock out a natural crack on the test piece, and then use a universal tensile machine to measure the force required for this crack to grow. Incorporating this force into the formula, considering the thickness, width, span of the force, the length of the crack, and other parameters of the test piece, we can calculate the energy consumed when the crack grows. For detailed test specifications, please refer to ASTM E399-90.

Since the universal tensile machine pulls the test piece apart very slowly, the energy obtained in this way represents the behavior of slow rupture. The behavior of rapid rupture can be represented by the Izod impact (ASTM D256). This method uses a fast-moving pendulum to knock the test piece, and the energy lost by the pendulum represents the energy consumed when the test piece ruptures.


Living § Explore the secrets: Pomegranate Station

Pomegranate Station is located in the northern part of Douliu City, Yunlin County, between Douliu Station and Linnie Station. At present, only the inter-area tram will stop and it is the closest super mini station to Everwide. The pomegranate station was set up as early as 1905 and has a history of more than a century. It was originally set up to transport local soil and rock. The existing station was built in 1950. Due to the lack of materials at the end of the war, it adopted a simple structure and became the only wooden Japanese station in Yunlin. Another thing to mention is that the name pomegranate refers to quarry rubbish, not the plant pomegranate. In 2012, Taiwan Railways carried out a restoration project on the old station. The dilapidated iron and wood station was renovated and restored to the original style of the simple station building. After the surrounding environment was improved and revitalized, the Japanese-style dormitory seemed to be a story hall in the deep green forest. On weekdays, there are many volunteers to keep it tidy. On holidays, there are occasional arts and cultural activities and bicycle outings. Pomegranate Station will be planned as a complete tourist route with neighboring scenic spots in the future. Everyone is welcome to visit when you have time.

─Author: Mr. Wen-Zheng, Zeng


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