Everwide newsletter No.55

The curing of acrylic anoxic glue mainly depends on the initiation of metal oxides (for example, transition metal oxides such as Fe2O3 CuO ZnO), which cracks the peroxide in the glue to produce a polymerization reaction. Since the polymerized monomer is acrylic resin, a photoinitiator can also be added to make it have a dual curing mechanism. In addition, if there is no metal oxide on the surface of the substrate (such as plastic, glass, and ceramics), we can add copper ions (commonly known as green red glue) into the original components and divide them into A and B components. During the mixing process, the free radical reaction will still be triggered to complete the curing. Due to the instant initiation of free radicals, its performance is much faster than existing AB epoxy and can be cured in five minutes. In addition, there is also a brushing accelerator method (commonly known as Primer), that is, brushing a solution containing metal oxide ions on the non-metallic oxide surface to modify the surface, and then it can also achieve the effect when it is dipped in the oxygen-deficient glue.

The caulking of anoxic glue is a cover door due to free radicals, which are only on the contact surface and cannot be fully expanded, and oxygen inhibition makes the polymerization incomplete, so it cannot trigger the polymerization reaction of the internal photoinitiator with UV deep irradiation. Oxygen caulking can only be done by AB two-component or UV+ anoxic method. The acrylic oxygen-deficient adhesive makes up for the limitation of UV glue when it cannot be illuminated, greatly improving the scope of application and reliable heating and curing. It has more development potential in the design process of adhesive materials.

─Author: Mrs. Hui-Xu, Li R&D Engineer Everwide Chemical

As the name implies, composite materials are composed of two or more materials, and the composite effect is achieved through the characteristics of different materials. A general composite material is composed of a base material (Matrix) and a reinforcement material (reinforcement). Commonly used reinforcing materials are glass fiber, carbon fiber, Kevlar fiber, etc., which can be subdivided into the short fiber, continuous long fiber, woven fiber, and powdered fiber according to the fiber form. The substrates include unsaturated polyester resins, phenolic resins, and epoxy resins. Among them, epoxy resin is the most widely used in sports equipment, printed circuit boards, engineering reinforcement, automotive trim, and other industries. There are many processing methods for composite materials. Among them, the prepreg lamination method is to uniformly coat the resin on the unidirectional or bidirectional woven fibers to make a viscous prepreg, and then cut and paste according to the design. Finally, it is cured and formed.

*Epoxy resin for prepreg: The manufacture of prepreg can be divided into hot-melt adhesive process and solvent-based process. The former uses a solvent-free solid epoxy resin, which is melted at 70~75°C and coated on the fiber. The latter use methyl ethyl ketone to dissolve the epoxy resin, impregnate the fiber, and heat it to volatilize the solvent.

*High Tg epoxy resin: High Tg composite materials can be used in higher temperature environments, such as intake manifolds of automobile engines, exhaust pipes of heavy motorcycles, rims of bicycles, and electronic components. General high Tg resin systems often have shortcomings such as insufficient toughness, too short prepreg life, too high viscosity, etc., resulting in manufacturing difficulties. A new generation of epoxy resin systems addresses these shortcomings, offering good processability and physical properties.

*Auxiliary materials: The process of composite materials needs to be matched with many functional products, such as soil filling, gold oil, and foaming materials. These auxiliary materials have a very important impact on the process and the appearance of the product. Generally, the adhesive strength of polyfill soil is insufficient, and it is easy to peel off in a vibration environment, resulting in product defects. The filling soil using the epoxy system shows good adhesion, transparency, and has thixotropy, which is suitable for filling cavities of various shapes.

For related product information, please visit the official website of Everwide Chemical: http://www.everwide.com.tw/manuals/dm/Pipeline-Rehabilitation.pdf

To measure the filler content of the resin, the early method was to disperse the uncured resin in a solvent, and then pour out the upper layer liquid after the filler was precipitated. This was repeated several times to obtain the filler in the resin and calculate the content. Another method is to disperse the uncured resin in a solvent and filter it with filter paper. The above methods have some disadvantages: 1. Some curing agents are also in the state of powder and granules and will be calculated as fillers. 2. Nanoparticles are difficult to be precipitated or filtered out in solution and then separate. 3. It is not easy to accurately calculate the content. 4. Not suitable for cured resins. However, these practices can sometimes still provide irreplaceable information. At present, the use of TGA to determine the filler content is the simplest experimental method. During TGA experiments, the heating rate should not be too fast (below 10°C/min), and oxygen should be used to avoid incomplete combustion. Stepwise Isothermal model was used to avoid the interference of organic cracking products, and pay attention to whether the filler will decompose. (For example calcium carbonate will release carbon dioxide, residual calcium oxide. Aluminum hydroxide will release water, residual aluminum oxide, etc.). When there is a suspicion that the filler will decompose at high temperature, further comparison of the infrared spectrum, identifying the type of filler, and even separating the filler with a solvent are all possible experimental options.

The first qualifying test I took was the "Polymer Science" test, and at that time, nine people took the test and three passed. The second time I took the qualification test was the "Chemical Thermodynamics" test. That time, 27 people took the test and one passed, and I was not the one who passed. The third time I took the qualifying exam was to retake the "Chemical Thermodynamics" exam. That time, 28 people took the exam, and 6 passed. Judging from the proportion of these three passes, the difficulty of the qualification test can be imagined. Most people have to take the test many times before they can pass the test. At that time, some students reported to the professor: Why is the qualification test so difficult? Especially the first category of subjects are not related to our thesis, is it worth our time to spend a lot of time on it? Teachers have different opinions. They think that doctoral graduates may take up teaching positions. In addition to professional subjects (elective courses), they will also be assigned to general subjects (required courses), so each student must be very familiar with certain subjects. Only then is a qualified doctoral graduate. It's been 15 years since I took the qualifying exam. The exam questions have long been forgotten, but the spirit is still vivid in my mind. Our work, our life is the qualification test again and again. Our attitude to take the test determines our achievement: pass, retake, or pass.

─Author: Dr. Ming-Xu Li of Everwide Chemical