Selection of Hand Lay-Up FRP Reinforced Fiber Materials

FRP lining is the most common and most important means of corrosion control in heavy-duty anti-corrosion construction. Among them, hand-laid-up FRP is widely used because of its simple operation, convenience and flexibility. It can be said that in FRP anti-corrosion construction, hand-laid-up method accounts for more than 80%. proportion. The "three major materials" in hand-laid FRP are resin, fiber, and fiber powder. The fiber is the skeleton of FRP, which supports the strength of the FRP system, and is an important part of realizing the long-term use of FRP anti-corrosion.

According to the difference of corrosive environment and medium, the components of FRP will also change. Conditional material selection during construction is the key factor to ensure that FRP products are suitable for corrosive environments and durable. Therefore, the selection of FRP reinforcement materials must be determined before construction. For example, reinforcement materials represented by glass fiber are the most common fiber materials, which can resist most acid corrosion; but they are not resistant to hydrofluoric acid and hot phosphoric acid corrosion. Use polyester, polypropylene and other organic fiber glass cloth and chopped strand mat, and you can also choose to use linen or degreasing gauze. There are also some fiberglass products that need corrosion resistance and conductivity, and you can choose carbon fiber materials. In short, the selection of hand-laid FRP reinforced fibers is a skill and knowledge point that anti-corrosion technology and designers must master.

In hand lay-up FRP products, most of the reinforcing fibers are made of glass fiber, whether it is cloth, felt or yarn, the main reason is that in addition to the price factor, it also has the following excellent features:

01 Chemical Resistance

Inorganic fiberglass textile fibers will not rot, mold or deteriorate. They are resistant to most acids except hydrofluoric and hot phosphoric acid.

02 Dimensionally stable

The fiberglass yarns used to make glass fabrics do not stretch or shrink due to changes in atmospheric conditions. The nominal elongation at break is 3-4%. The average linear thermal expansion coefficient of bulk E glass is 5.4×10-6 cm/cm/℃.

03 Good Thermal Performance

Fiberglass fabric has a low coefficient of thermal expansion and high thermal conductivity. Fiberglass dissipates heat faster than asbestos or organic fibers.

04 High Tensile Strength

Fiberglass yarns have a high strength-to-weight ratio. A pound of fiberglass yarn is twice as strong as steel wire. The ability to engineer unidirectional or bidirectional strength into fabrics greatly increases end-use product flexibility.

05 High heat resistance

Inorganic glass fibers do not burn and are largely immune to the high baking and curing temperatures often encountered in industrial processing. Fiberglass will retain about 50% of its strength at 700°F and 25% of its strength at 1000°F.

06 Low hygroscopicity

Fiberglass yarn is made from non-porous fibers and therefore has very low moisture absorption.

07 Very good electrical insulation

High dielectric strength and relatively low dielectric constant, along with low water absorption and high temperature resistance, make fiberglass fabrics excellent for electrical insulation.

08 Product Flexibility

The extremely fine filaments used in fiberglass yarns, the variety of yarn sizes and configurations, different weave types, and many special finishes enable fiberglass fabrics to be used in a wide range of industrial end uses.

09 Low cost cheap

Fiberglass fabrics can do the job and are comparable in cost to synthetic and natural fiber fabrics.

Therefore, glass fiber is an ideal hand-lay-up FRP reinforcement material, which is economical, inexpensive, and easy to operate. It is one of the most widely used materials among many reinforcement materials.

The glass fiber cloth used in anti-corrosion engineering includes alkali-free untwisted glass fiber cloth, medium-alkali untwisted glass fiber cloth, and alkali-resistant glass fiber cloth. Of course, it must be a wax-free glass fiber cloth, which is what we often call " Three no" products. The grade of alkali-free glass fiber is E, the grade of medium-alkali glass fiber is C, and the grade of high-alkali glass fiber is A (this kind of material is hardly used in hand-laid glass fiber reinforced plastics). The glass fiber produced by clay crucible not only has safety hazards in the production process, In terms of product performance, there are many shortcomings such as low mechanical mechanics, poor water resistance, and poor performance stability, which have been banned by the state. Now most of the glass fiber materials used in anti-corrosion FRP construction on the market are glass fiber cloth, felt and yarn produced by platinum crucibles. .

The glass fiber cloth used for hand lay-up FRP usually uses glass fiber cloth with a thickness of 0.2mm and 0.4mm, and the density is 10*10 or 12*12. The chopped strand mat used is preferably 300-450g/㎡, and the glue content reaches about 70%. , and as a resin-rich layer, surface felt is generally used as a reinforcing material, which has a certain beautiful, smooth and smooth effect. The resin content reaches between 80% and 90%, and the thickness is 0.3mm-0.4mm.

Carbon fiber cloth is also called carbon fiber cloth, carbon fiber cloth, carbon fiber woven cloth, carbon fiber prepreg cloth, carbon fiber reinforced cloth, carbon cloth, carbon fiber fabric, carbon fiber tape, carbon fiber sheet (prepreg cloth), etc. Carbon fiber reinforced cloth is a unidirectional carbon fiber reinforced product, usually woven with 12K carbon fiber filaments, which is very suitable for use in high acid, alkali, salt and atmospheric corrosion environments. Carbon fiber cloth can withstand high temperatures of about 1000 degrees, fully meeting the high temperature environment of FRP lining Carbon fiber has conductive properties, so it can be used in FRP anti-corrosion equipment that needs to conduct static electricity. The disadvantage is that its price is relatively high.

By understanding the characteristics of hand-laid FRP reinforced fibers, anti-corrosion technicians can conditionally select fiber reinforced materials according to the corrosive environment or medium conditions during construction. At the same time, they also need to refer to relevant standards and requirements for the quality and Construction is identified and controlled.

With the development and progress of fiber technology, many new nanofibers have entered the application field of FRP one after another. On the basis of the original reinforced bearing and corrosion resistance, its more excellent physical and chemical properties have been presented, and have been widely used in not only It is the automobile, aircraft, wind power, civil and other fields within the anti-corrosion range, and it is developing towards a safer and lighter direction. Among them, the three major high-performance fibers in the world today are: aramid fiber, carbon fiber, and ultra-high molecular weight polyethylene fiber. Leading the frontier market of composite materials is also the vane of the empowerment of anti-corrosion FRP fiber reinforced materials.

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