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Everwide Newsletter-No.64

Experiment § STPU moisture hardening adhesive

Everwide Chemical has developed the FS series of moisture-curable STPU (silane terminated polyurethane), which are mainly used to bond plastics, metals, and glass. Different from traditional PU applications, isocyanate (NCO) contains toxicity. The reaction mechanism we use is the same as the release mechanism. Alcohol type Silicon does not have the odor of deacidification type but has the effect of fast surface drying, and the adhesion to plastic is far better than Silicon. The biggest disadvantage of Silicon is that it is polluting. Its internal components will slowly diffuse to the outside world. In civil applications, it will cause pollution to buildings, and in electronic applications, it will cause poor contact of contacts. Compared with Silicon, STPU does not have these disadvantages. STPU is widely used in the potting and encapsulation of the 3C industry. Initially, it mainly promoted the building materials market, cement exterior walls, and glass window packaging industries, but it could not be revitalized because Silicon prices destroyed the market. At present, Everwide Chemical focuses on developing STPU, which is quite a challenge in terms of technology, products, applications, etc. The future outlook is very worth looking forward to.

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


Process § Weighing and stirring

Continuing to prepare and calculate the previous issue. It will introduce the production process of weighing and stirring.

(3) Weighing: Two process engineers pour the raw materials into the production tank according to the instructions of the operation manual. There is also a quality assurance engineer who records the weight, batch number, and operation time of each step at the same time to prevent mistakes.

(4) Stirring is divided into liquid-liquid phase mixing and solid (powder)-liquid phase mixing. In the area where we stir and disperse, the air is maintained in a laminar flow mode at a wind speed of more than 0.8m/sec to avoid dust and odors that endanger colleagues' health. The extracted gas is also cleaned by the water gas tower, which has almost no impact on the surrounding environment.


Knowledge § How to evaluate the weatherability of plastics?

The focus of evaluating the weatherability of plastics is how to set the conditions for environmental testing. Exposure experiments in natural weather are irreplaceable and cannot be completely simulated, and the only downside is that it is time-consuming and inefficient. Commercially available accelerated testing machines can provide a reference for evaluation. They can simulate the natural conditions of moisture and dew, which are recommended alternatives but cannot predict the results under actual weather. Another essential point in evaluating the weatherability of plastics is the test method.

Some use the yellow index, and some use gloss meters from different angles to reflect the color and surface condition of the plastic. Some test the mechanical strength of plastics, such as tensile strength, tensile modulus, etc., to evaluate the usability of plastics. Different test methods cannot be interoperable in the application and have different meanings. Epoxy resins, for example, may not suffer much from mechanical strength when severely yellowed under UV light.


Living § How much do you know about temperature (3)

In the second half of the course, we mentioned examples of exothermic and endothermic reactions. The so-called exothermic reaction is that the reaction process feels hot and the temperature rises; the endothermic reaction is that the reaction process feels cold, and the temperature decreases. To put it simply: Combustion is an exothermic reaction; the warm pack used in winter is also an exothermic reaction. There are two principles of the warm pack: one is an irreversible reaction (iron powder composition), and the other is a reversible reaction (a small metal flake inside the transparent solution).

The irreversible principle is to use the iron powder to rust to carry out an exothermic reaction to increase the temperature, and then add activated carbon, salt, vermiculite, etc., to the iron powder; the purpose is to make the rusting process proceed slowly, which is a chemical change. After the experiment, we cut the paper bag open for the children to touch.

Touch the black iron oxide inside. The other kind of warming pack is reversible, which is a process of exothermic reaction in the crystallization process, which is a physical change. We can buy a pack of supersaturated solutions sealed with a thick plastic film at the pharmacy, with a metal sheet inside. When the metal sheet is refracted, the supersaturated solution begins to grow crystal nuclei, continuously and rapidly crystallizes. An exothermic phenomenon occurs during the crystallization process to achieve the temperature increase. Through these two different principles of warming pack experiments, I take this opportunity to introduce children to understand that temperature changes occur in daily life. This time, the children already have the concept of temperature. When the children are in their senior year, we will make the warm packs ourselves, so it will not be tough.

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

*Answer to the 61st issue of "The World Under the Microscope (Part 2)": (1) Figure 5: Human red blood cells; (2) Figure 6: Pig neuron cells.

(3) If I write the English letters "AB," what will be the difference between the dissecting microscope and the general microscope? The original on the paper will become


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