Experiment § Adhesion area and adhesion strength
Textbooks or test specifications all mention that the adhesion strength is equal to the strength measured by the tensile test piece divided by the adhesion area. This statement gives everyone an idea that when the adhesion area doubles, the strength of the test piece will also double, and the adhesion strength after dividing by the area will remain the same. This is true in theory, but in reality, there are many variables that will make the result not completely the case. Picture 1 is an adhesive test piece in shear mode, and then the measured adhesive area is designed to be 3mm in length and 25.4mm in width. The measured maximum strength of the test piece is 288kg, and the adhesion strength per unit area obtained by dividing by the adhesion area is 378kg/cm2 (Picture 2). Judging from the virtual centerline in Picture 3, the test piece roughly maintained the Shear mode during the test. Picture 4 The length of the tested adhesion area of the design is 12mm, and the width is 25.4mm. The measured maximum strength of the test piece is 771kg, and the adhesion strength per unit area obtained by dividing by the adhesion area is 253kg/cm2 (Picture 5). The virtual center line in picture 6 shows that the test piece is seriously distorted so that in addition to the shear model to be tested, the adhesion area also has the component of the tearing mode (picture 7). This phenomenon causes the adhesion area of the latter to be 4 times that of the former, but the adhesion strength per unit area is only 0.67 times that of the former. This phenomenon also implies that in addition to the adhesion area, the thickness, hardness, etc. of the test piece all affect the degree of deformation of the test piece. In other words, the adhesion strength of different sources can only be used as a reference and is not suitable for direct comparison with each other.
—Author: Miss. Li-Ling, Liu
Activity § The star charity baseball game for the elderly
The "Love the Elderly Star Charity Baseball Tournament" organized by the Huashan Foundation started on June 13th at the Yunlin Douliu Baseball Stadium. Originally, we were very worried that the tickets would not be sent out, but in the end, we only passed one day's efforts and all the tickets were issued. Everyone shouted excitedly to watch a baseball game together! There are also some of my colleagues' children because they participate in the baseball and softball club of the school, and they are also very interested in the ball game. I really hope that some teams will adopt Douliu Baseball Stadium so that there will be more and more baseball games in Yunlin! Of course, while everyone is watching the game, don’t forget to care about the elders around you and make them laugh often!
Knowledge § What is the reason for the decline of adhesion caused by moisture?
The application of adhesion will evaluate the influence of moisture, soak the test piece in water or put it in a high-temperature and high-humidity machine, and then test the change in strength after a certain period of time. Most experiments have shown that the adhesive strength will decrease due to the following reasons: (1) Moisture diffuses between the adhesive interface and replaces the original bond between the adhesive and the adherend. Take epoxy resin as an example: The hydroxyl group in the structure has a good force between glass and metal, but this force will be replaced by water molecules. (2) Moisture corrodes the adherend, and it is common in the metal to oxidize and rust. (3) The adhesive decomposes due to moisture, like the ester structure of some PUs, and will lose strength due to chain scission due to the hydrolysis reaction. (4) The adhesive swells and becomes soft due to water absorption, which reduces its strength. The factors (1) to (3) above are irreversible recessions, and only (4) is reversible. When the adhesive is in a low-humidity environment and moisture diffuses from the inside to the outside, the adhesive strength can be restored.
Living § Lessons in getting along with the new generation
In the modern information explosion, new things are produced and eliminated every day. It is much easier to obtain information now than in the past, so the new generation "knows" faster than any previous generation. However, it takes a lot of time and experience to process huge amounts of information, and new information will impact before it is processed, resulting in the result of only accepting information but not being able to process information. It has become the characteristics of the new generation: there is more "knowledge", but less "understanding" and "discrimination", and the thinking mode is dualistic, straightforward, and simple. Also because the amount of information is too large, there is too much to process and receive, thus creating an efficiency-oriented fast-food culture. Fast food culture not only refers to the "food" part, other things like the acquisition of knowledge and information (GOOGLE & Wikipedia) and the interaction of interpersonal relationships (FB & Twitter) all reflect another characteristic of the new generation: "real-time as long as there is a network, you can instantly connect with the world. Another difference from other generations is the concept of facing authority and obedience. The awe of the past generations in the face of parents, teachers, supervisors, and seniors, the ethics and potential rules in the workplace, and even the self-requirements of authorities are all related to the mastery and inheritance of key information. These things are really incomprehensible history for the new generation flooded with information. In any case, the information explosion has changed the tradition, and the past viable management models must be reviewed. We have to admit that the young people of the new generation are different from us, and we cannot stop the changes they bring. Only changing your thinking and learning to get along with them is the best way.
—Author: Mr. Jin-Lei, Chen
