The role and relationship of the three major elements of FRP?
(a) Glass fiber
Glass fiber is the main bearing part of FRP. It can not only improve the strength and elastic modulus of FRP, but also reduce shrinkage deformation, increase heat distortion temperature and low temperature impact strength, etc. Listed as 306# polyester resin casting body, in After adding 50% glass cloth, the tensile strength can be increased from 50MPa to 200MPa, and the tensile modulus can be increased from 3.9GPa to 14GPa.
(2) Synthetic resin
Synthetic resin is the base of FRP, and the loose glass fiber is bonded to it as a whole.
The resin mainly acts as a transfer stress, so the resin plays an important role in the strength of the FRP, especially the compressive, bending, torsion, and shear strength.
Since the resin is a matrix material, it has an influence on the elastic modulus, heat resistance, electrical insulation, head electromagnetic wave, chemical corrosion resistance, weather resistance, and aging resistance of the glass fiber reinforced plastic. The resistance to chemical liquid erosion and water resistance of glass reinforced plastics depends mainly on the properties of the resin matrix. Usually unsaturated polyester resin 197# is better resistant to chemical corrosion, while 1289# is better resistant to water. Different types and different grades of resin have different properties.
The resin content also has an effect on the properties of FRP. Usually, the resin content is 20%-35%, which is related to the molding method and Zengqiang material variety. For example, winding and compression molding, the resin content is low, while the hand lay-up and resin content is slightly higher. The resin content of the strength layer is slightly lower, usually between 25% and 40%; the resin content of the corrosion-resistant and anti-seepage layer is generally higher than 50%, and the glass cloth is used as the reinforcing material, and the resin content is lower than that of the glass felt. When a glass fiber surface felt is used as the reinforcing material. Up to 85% or more of the resin content.
(three) interface
The so-called interface is the interface between any two-phase material.
The properties of FRP are not only related to the reinforcing materials and synthetic resins used, but also to a large extent to the quality and durability of the interfacial adhesion between the fibers and the resin.
As we all know, glass fiber is a kind of cylindrical glass, the surface is also as smooth as glass, and the surface is often firmly adhered to a thin water film, which of course affects the bonding properties of glass fiber and resin. Especially in the process of drawing and weaving of glass fiber, in order to achieve the purpose of bundling, lubrication, static elimination, etc., a layer of infiltrant is often applied. Most of the infiltrants are paraffin-like substances, which remain on the surface of the glass fiber. The synthetic resin acts as a barrier to the glass fibers, preventing the bonding of the two. The visible interface has a great influence on the performance of FRP.
If there is a problem with the interface, it needs to be processed. For example, a surface treatment agent is coated on the surface of the glass fiber so that the glass fiber and the resin can be firmly bonded together. This method is a very effective way to improve the basic performance of FRP, and it is being researched and adopted at home and abroad. Practice has proved that the glass fiber and its fabric, after being treated by the surface treatment agent, not only improve the wear resistance, water resistance and electrical insulation properties of the glass fiber, but also improve the strength of the glass fiber reinforced plastic, especially in the case of moisture.
In addition, there are also interface problems between FRP and other materials or FRP itself. If you want to make FRP anti-corrosion lining on the inner layer of the metal can, you need to clean the inner surface of the metal can, such as removing dirt, oil, moisture and rust layer, etc., often using sandblasting, pickling and other treatments. If the metal surface is not handled well, the FRP lining will fail. Sometimes, you will also encounter a cured FRP layer, and then bond the FRP, there will be interface problems. If the layered curing process or FRP damage repair is used, the surface of the FRP layer needs to be treated to remove dirt, oil, water, etc., and the sandpaper for the surface needs to be roughened to increase the bonding area. Otherwise, There is a stratification of rickets.
It can be seen that the factors affecting the quality of FRP and its products, in addition to the two major components of glass fiber and resin, the interface is also very important. These three elements are indispensable, and they are closely related and inseparable. We call them three major factors, which are summed up in the long-term practice.
Experience tells us that fiber, resin and interface are the three elements of the success or failure of FRP products. It can be said that when there is an accident in FRP products, people can find reasons from the three major factors. Listed as a reinforced concrete fermentation tank of a brewery, the original asphalt is lined, and it will fall off after short-term use. With FRP lining, since the surface of the original concrete pool is not cleaned, the paste is detached and the economic loss is huge. In addition, some FRP factories pursue high profits in order to reduce the cost. They use glass fiber produced by clay pottery. The glass fiber reinforced plastic tile produced will fall off in less than half a year. Because the surface of the fiber pulled out by the clay pot is untreated, there is a wax film on the surface of the glass fiber, so that the resin can not be adhered. The exposed glass filament is visible on the edge of the corrugated tile. The root is very clean and the glue is not sticky. . This kind of untreated glass cloth is absolutely impossible to use on the glass fiber reinforced plastic, if it is necessary to be dewaxed by high temperature.
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