Since the pultrusion FRP production process came out in the United States, it has experienced decades of development. Raw materials such as synthetic resins, glass fibers and fabrics suitable for pultrusion process applications have come out one after another, making the pultrusion process develop rapidly. In the 1980s, American pultruded FRP products increased at an annual rate of 12.5%. The main raw materials used for profiles were glass fiber untwisted roving, glass fiber continuous mat and various glass fiber fabrics, synthetic resins and corresponding additives and fillers. , Paint, etc. The technological process is roving, fabric pre-forming-impregnated resin continuous solidification molding-cooling-fixed length cutting-product packaging. The entire production process is automated and continuous; the production speed is 0.3m-0.8m/min; the maximum cutting profile size of the profile or hollow profile is 1000mm×300mm.
In the section of the profile, the center is a radially arranged glass fiber, whose tensile strength (3500-3600MPa) is much higher than the tensile strength (450-1500MPa) of the usual prestressed steel bars. Synthetic resin acts as a binder and resistance The corroded layer, continuous felt and glass fiber fabric are laid as designed to provide weft strength. Through the analysis of its stress-strain curve, it can be known that the failure of this material is caused by sudden brittle fracture rather than ductile yield. The study of its long-term mechanical properties shows that the ratio of its creep failure strength is linear with the logarithmic value of the action time. The so-called creep strength refers to the material's tensile strength when the fiber-reinforced plastic keeps the stress constant under long-term load, and its plastic deformation will continue to increase with the prolongation of the load, and finally become stable. Although under the action of alkali and chloride ions, the durability of fiber-reinforced plastic materials is much better than that of conventional steel.
Compared with ordinary structural steel, pultruded FRP profile has the advantages of high strength, light weight, toughness, corrosion resistance, insulation and heat insulation, and it does not require fire during installation and will not generate sparks due to collision during use. This is for chemical production. especially important. Listed below are examples of the application of pultruded FRP profiles as structural load-bearing parts in chemical corrosion protection. 1. Operation platform of purification section of cobalt electrolysis workshop; 2. Operation platform of purification section of nickel electrolysis workshop; trestle; skylight and electrolytic tank internal support; 3. Operation platform and walkway platform of zinc leaching workshop; 4. Anode precipitation tank support of aluminum electrolysis workshop, etc. .
The above environments are all mixed acid mist and acid corrosion conditions, and the pH value is between 1.7-5.0; the maximum load-bearing capacity is 6t/㎡ and the earliest application time was October 1994. Appraisal by the user and our on-site observation, there is no damage, no bending deformation, no obvious corrosion. Compared with the original steel structure, not only does it need to be painted with anti-corrosion paint every year, but it also reduces one major repair and replacement. The pultruded FRP profile structural parts only need to be washed with water to show bright colors, which greatly beautifies the production environment of the workshop.
Regarding the connection, the biggest inconvenience of pultruded FRP profile as a load-bearing structure is that it cannot be welded. The currently used connection methods are mainly card sleeve inserting, sleeve inserting, gasket butt and bonding, and the main load-bearing structure is also Common bolts or stainless steel bolts or even titanium bolts coated with epoxy resin are used to connect and fix the bolts. FRP bolts developed by some companies are used in application experiments.
The volume price of pultruded FRP profiles is about twice that of ordinary steel and one-half of that of stainless steel. When it was used as a building or structure, it was difficult for enterprises to accept it at the time, but pultruded FRP profiles do not need to be painted with anti-corrosion coatings every year, and the cost saved can be equal to the steel structure and engineering cost in 3 years. It is important that the service life of the pultruded FRP profile structure is not less than 10 years, while the service life of the ordinary steel structure in the above-mentioned corrosive environment is only two to three years. From this point of view, our application practice proves that the economic benefits of pultruded FRP profiles as buildings and structures in a corrosive environment are extremely considerable.
In the practice of industrial application, we also discovered two major benefits of pultruded FRP profiles as structural parts for industrial production. First, in the electrolysis process of non-ferrous metallurgy, due to the corrosion of steel structural parts, especially the inner support of the electrolysis cell, a large amount of iron ions enter the electrolyte, which seriously affects the purity of the electrolysis product. The company has to spend a lot of manpower and material resources to remove the electrolysis every year. Iron ions in the liquid, and the use of pultruded FRP profiles solves this problem, and its efficacy is not only a question of economic benefits. On the other hand, domestic enterprises are expanding and increasing the capacity, adding many equipment and structures, which often exceed the designed carrying capacity of all plant foundations. The use of pultruded FRP profiles as structural parts is very conducive to the expansion and transformation of the plant. Through the production and industrial application of pultruded FRP profiles, it is an economical and effective way to replace ordinary structural steel and stainless steel with pultruded FRP for buildings and structures in corrosive environments. The designability of the pultrusion FRP profile formula makes it have a broad promotion and application prospect and makes it play a greater role in the anti-corrosion industry.
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