Everwide Newsletter No.311
Experiment report § Room temperature hardening PP adhesive
Polypropylene (Polypropylene, PP) and thermoplastic olefin (Thermoplastic olefin, TPO) have the advantages of easy molding, chemical resistance and low cost. Its disadvantage is that the chemical structure is low in polarity, and many of them are crystalline polymers, which causes difficulties in connection. We are developing free radical polymerization acrylic adhesives to try to solve this bottleneck. Coat the glue on the PP test piece (Figure 1), and cure the two test pieces at room temperature (Figure 2). The test piece was subjected to a shear strength tensile test, and the adhesive showed a cohesive failure (Cohesive Failure). The transverse cracks on the cracked surface show the toughness of the glue: when the glue stretches with the test piece, it is caused by segmental fracture (Figure 3). Adjust the toughness and rigidity of the glue to obtain different strengths. In some formulations, the test piece has whitening during the stretching process (Figure 4). This is the result of PP crystallization in the direction of stress, which means that the adhesive strength of the resin is greater than the tensile strength of PP itself. At present, the shear strength of the PP adhesive in the experiment is about 35Kgf/cm2 under the condition of curing at room temperature and not applying Primer (Figure 5). In the future, there are still some problems that need to be broken through, such as: oxygen interference, further enhancement of strength, application to other non-polar materials... etc. We will continue to work hard.
─ author: Dr. Wu JiaxingAbout Everwide § Coastal beach cleaning
This is our fourth beach cleaning activity. The weather was very hot that day. After taking protective measures, everyone walked on the uneven rocks for the campsite and worked together to clean up the garbage. After several hardships, the coast was cleaned. a lot of. Caring for the environment requires perseverance. Looking forward to the next beach cleaning activity, you can participate with your enthusiasm. Let us work together for the earth!
Knowledge exchange § Is there any relationship between the initial curing time of MS resin and the bonding strength?
In terms of ordinary metal and plastic materials, most MS resins have initial bonding strength after 1 hour and can move the workpiece. For some resins, the reaction speed can be adjusted faster, and the bonding strength can be achieved within 30 minutes. The initial curing speed of MS resin has no certain relationship with the initial bonding strength. The initial curing will occur on the surface first, caused by the cross-linking reaction of the resin. Resins mixed with polyfunctional groups will reduce the reaction rate required for gelation to occur, making the initial solidification time seem shorter. The initial bonding strength needs to consider the wetting compatibility of the resin and the substrate, the number of resin reactive functional groups, and the polarity of different MS resins themselves. The concepts of the two are different and should not be confused.
Bi-weekly strike § My hometown
My hometown is Macau, a small land just 1/9 the size of Taipei City. Speaking of Macau, I believe that the first time you think of it is the magnificent casino. When I was studying in Taiwan, the most people asked me: "Are Macau people very good at gambling?" My answer is: "Most of us are No gambling.” In fact, besides casinos, there are many places worthy of appreciation. Macau was ruled by Portugal for 446 years, so no matter what you eat, drink, play, culture, buildings... etc., you can see the trace of "the integration of Chinese and Western".
September and December are the months I recommend everyone to travel to Macau, because every Saturday night in September, there will be a fireworks competition that lasts for 40 minutes. Many countries have participated in this grand event, which is dazzling. The fireworks bloomed in the night sky, and the scene was extremely shocking. There will be a light and shadow festival in December, which uses large-scale colorful lighting effects to be projected on many tourist attractions, making people feel like they are in a wonderful world. It only takes 90 minutes to fly from Taiwan to Macau, and it takes about four days to get to know Macau. However, although the sparrow is small, it has all kinds of internal organs. It is definitely a tourist attraction suitable for all ages and people. Welcome everyone. Come to my hometown and feel the difference of Macau.
─ Author: Miss Chen Shi Min