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Everwide Newsletter No.311


Experiment § PP adhesive cured at room temperature

Polypropylene (PP) and Thermoplastic olefin (TPO) have advantages of easy molding, chemical resistance and low cost. However, their shortcoming is low-polarity of chemical structure, and many of them are crystalline polymers, causing difficult bonding. Thus, we are developing acrylic adhesives polymerized by free radicals to solve this obstacle. Coat adhesive on PP test piece (Figure 1); adhere two test pieces together and cure at room temperature (Figure 2). The test piece was subjected to a shear strength tensile test, and it exhibited cohesive failure. The transverse cracks on cracked surface show toughness of the adhesive: When colloid is tensiled with the test piece, it is caused to break section by section (Figure 3). In addition, adjusting toughness and stiffness of the adhesive can obtain different strengths. Test pieces of some formulas have whitening phenomenon during tensiling (Figure 4). This is the result of PP forward crystallization in stress, which means that adhesive strength of the resin is greater than tensile strength of PP itself. At present, the shear strength of PP adhesive in the experiment is about 35Kgf/cm² when curing at room temperature without primer (Figure 5). In the future, there are still some problems that need to be broken through, such as oxygen interference, further improvement of strength, and application to other non-polar materials.

─Author: Chia-Hsiang, Wu

 

Activity § Beach cleanup

This is our fourth times of beach cleanup. The weather was very hot on that day, but everyone still worked hard to clean up the rubbish. After hard working, the coast was much cleaner. The environment needs constant care from everyone, looking forward to your enthusiastic participation

 

Knowledge § Is initial curing time related to adhesive strength?

In the case of general metal and plastic materials, most MS resins have initial adhesive strength after 1 hr and can move the workpiece. What’s more, Some resins can speed up the reaction, and within 30 minutes there will be adhesion strength. However, There is no certain relationship between the initial curing speed of MS resin and the initial adhesive strength. Initial curing will first occur on the surface, caused by the cross-linking reaction of resin. The resin mixed with multifunctional groups will reduce the reaction rate required when gelation occurs, and make the initial curing time seem shorter. The initial adhesive strength needs to consider the wetting compatibility of resin and substrate, the number of reactive functional groups of the resin, and the polarity of the different MS resins. The two concepts are different and should not be confused.

 

Living § My hometown

My hometown is Macau, which is only 1/9 of the size of Taipei City. When it comes to Macau, I believe everyone first thinks of magnificent casinos. When I was studying in Taiwan, most people asked me, "Are all Macanese good at gambling?" My answer was, "Most of us do not gamble." Besides casinos, there are many places worthy to be appreciated. Macau was once ruled by Portugal for 446 years, so in eating, drinking, playing, culture and buildings, you can see the trace of " Integration of Chinese and Western". September and December are my most recommended months for traveling to Macau, since every Saturday night in September has a 40-minute fireworks competition. There will be a Macao Light Festival in December, which uses large-scale colorful lighting effects to be projected on many tourist attractions. Macau is definitely a popular tourist destination for all ages. Thus, welcome everyone to visit my hometown.

─Author: Shih-Min, Chen


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