Method for improving quality of glass fiber reinforced plastic rectangular pipeline lining

Abstract

The invention belongs to the technical field of glass fiber reinforced plastic preparation, and discloses a method for improving the quality of a glass fiber reinforced plastic rectangular pipeline lining, which comprises the following steps: 1) cleaning the surface of a mold; (2) uniformly paving impregnated glass cloth on a mold, and scraping out redundant glue liquid; (3) putting the mold coated with the impregnated glass cloth into a curing oven for low-temperature pre-curing, cooling and taking out the mold; and (4) the winding tension is controlled to be 2-5 kgf / yarn, the impregnated glass fiber yarn is wound on the mold, after winding is completed, post-curing is conducted, and demolding is conducted. According to the preparation method, a pre-curing-interface enhancement synergistic process is adopted, the surface defects caused by winding tension of glass fiber yarns are remarkably reduced by accurately controlling the pre-curing degree of epoxy resin and constructing a high-rigidity lining layer, meanwhile, the interlayer bonding strength is guaranteed, and finally the lining which is smooth in surface, high in interlayer shearing force and high in rigidity is prepared. And the FRP rectangular pipeline product is long in service time.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of glass steel preparation and relates to a method for improving the quality of glass steel rectangular pipeline lining. BACKGROUND

[0002] Fiberglass-reinforced plastics (FRP), also known as glass steel, is widely used in load-bearing structural parts due to its high specific strength and corrosion resistance. The production methods of FRP include hand lay-up molding, compression molding, filament winding and pultrusion. The filament winding method winds the fiber yarn impregnated with epoxy resin on the surface of the core mold through a winding machine. However, the epoxy resin matrix is in a viscoelastic state before curing, and the fiber yarn will be embedded in the uncured resin layer due to the tension, resulting in defects such as "lines" and "grooves" on the lining surface of the glass steel rectangular pipeline (as shown in Figure 1 The existing technology generally polishes the mold or adjusts the winding tension to solve this problem, but it cannot fundamentally solve the interfacial stress mismatch between the resin matrix and the fiber, and the quality of the lining surface of the glass steel rectangular pipeline cannot be improved, which seriously affects the mechanical properties and service life of the pipe. SUMMARY

[0003] The application provides a method for improving the quality of the lining surface of the glass steel rectangular pipeline, which can improve the tensile strength and service life of the product.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0005] The application provides a method for improving the quality of the lining surface of the glass steel rectangular pipeline, which includes the following steps:

[0006] 1) cleaning the mold surface;

[0007] 2) uniformly coating the glass cloth impregnated with glue on the mold and scraping off the excess glue;

[0008] 3) placing the mold coated with the glass cloth impregnated with glue in a curing oven for low-temperature pre-curing, cooling, and taking out the mold;

[0009] 4) controlling the winding tension to be 3.5 kgf / strand, winding the glass fiber yarn impregnated with glue on the mold, and performing post-curing and demolding after winding is completed.

[0010] In the above technical solution, the thickness of the glass cloth is 0.06 mm, and the areal density is 200 g / m 2 .

[0011] In the above technical solution, the low-temperature pre-curing condition is as follows: heating to 90-100℃ at a rate of 2℃ / min and keeping for 30-60min, and then cooling to 60℃ at a rate of 1℃ / min.

[0012] In the above technical solution, the post-curing condition is as follows: heating to 120℃ at a rate of 2℃ / min and keeping for 60min, and then heating to 150℃ at a rate of 2℃ / min and keeping for 180min.

[0013] Since the curing process of the epoxy resin follows a segmented reaction kinetics model: 1) Stage I (pre-gel region): the resin is in a liquid state, the crosslinking degree is low (hardness <10 Shore D), and the shear resistance is weak; 2) Stage II (gel-glass region): the crosslinking density increases sharply (hardness 20-50 Shore D), and the modulus rises; 3) Stage III (post-curing region): the residual groups react, and the hardness tends to be stable (>60 Shore D). In the traditional process, the glass fiber yarn is directly wound when the epoxy resin is in Stage I, and the yarn pressure causes the resin to flow-rebound effect, forming grooves. Based on this, the inventors found that if the resin hardness can be regulated to the critical point of Stage II (≥40 Shore D) through pre-curing, the interfacial adhesion and deformation resistance can be balanced, thereby effectively improving the quality of the rectangular pipeline lining.

[0014] Compared with the prior art, the present application has the following beneficial effects:

[0015] The present application adopts a pre-curing process, accurately controls the pre-curing degree of the epoxy resin (hardness 40-45 Shore D), constructs a high-rigidity lining layer, significantly reduces the surface defects caused by the winding tension of the glass fiber yarn, ensures the interlayer bonding strength, and finally prepares a FRP rectangular pipeline product with a smooth lining surface, high interlayer shear force and long service life.

[0016] Compared with the traditional winding-curing-demolding process, the present application adds a pre-curing process before winding, and is different from the traditional internal heating curing, greatly improves the product quality (the line defects are reduced by ≥90%, and the groove depth is reduced from 0.5-1.2mm to <0.1mm), and does not increase the equipment investment, has high process reliability, and is easy to mass produce. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The surface morphology of the glass steel rectangular pipeline lining produced by the traditional winding process.

[0018] Figure 2 The surface morphology of the glass steel rectangular pipeline lining produced by the embodiment 1 of the present application. DETAILED DESCRIPTION

[0019] The following examples are intended to illustrate the present application and are not intended to limit the scope of the application. Unless otherwise indicated, the techniques utilized in the examples are standard techniques commonly used in the art. The test methods used in the following examples are standard methods unless otherwise indicated.

[0020] Example 1

[0021] A method for improving the quality of a glass fiber reinforced plastic rectangular pipe lining, specifically comprising the following steps:

[0022] 1) Clean the surface of a mold (section: 380 mm x 380 mm, total length 2 m) and apply a mold release agent (Chemlease 41-90EZ) with a thickness of 5 μm.

[0023] 2) Uniformly lay a glass cloth impregnated with a resin on the mold and scrape off the excess resin. The thickness of the glass cloth is 0.06 mm and the areal density is 200 g / m 2 ; the resin is a mixture of 60 wt% epoxy resin, 39 wt% curing agent (70# anhydride curing agent) and 1 wt% accelerator (N,N dimethyl benzyl amine). A plastic scraper (blade angle 30°) is used to remove the excess resin, and the glass cloth is smoothly laid on the mold during the process of removing the excess resin, with no bubbles or wrinkles observed.

[0024] 3) Place the mold with the glass cloth impregnated with the resin in a curing oven for low-temperature pre-curing, heat to 90°C at a rate of 2°C / min and maintain for 60 min, so that the resin enters the end of stage II (hardness 42±2 Shore D), then cool to 60°C at a rate of 1°C / min, and take out the mold.

[0025] 4) Control the winding tension of the fiber winding machine to be 3.5 kgf / strand, and wind the glass fiber yarn impregnated with the resin on the mold. After winding is completed, post-curing is performed, the mold is removed, and the post-curing conditions are as follows: heat to 120°C at a rate of 2°C / min and maintain for 60 min, then heat to 150°C at a rate of 2°C / min and maintain for 180 min.

[0026] The surface morphology of the glass fiber reinforced plastic rectangular pipe lining produced in this example is shown in Figure 2 . It can be seen that the surface of the glass fiber reinforced plastic rectangular pipe lining produced by the method of the present application is smooth, and the defects such as lines and grooves are significantly reduced.

[0027] Example 2

[0028] This comparative example is substantially the same as Example 1, except that in step 3) the prepreg glass cloth laid-up mold is placed in a curing oven for low temperature pre-curing, and is heated at a rate of 2°C / min to 100°C and held for 30 min to make the resin enter the end of stage II (hardness 42 ± 2 Shore D), and then is cooled at a rate of 1°C / min to 60°C, and the mold is removed.

[0029] Example 3

[0030] This comparative example is substantially the same as Example 1, except that in step 4) the winding tension of the fiber winding machine is controlled to be 2 kgf / strand, and the prepreg glass fiber yarn is wound on the mold, and after winding is completed, post-curing is performed, the mold is removed, and the post-curing conditions are as follows: heating at a rate of 2°C / min to 120°C and holding for 60 min, and then heating at a rate of 2°C / min to 150°C and holding for 180 min.

[0031] Example 4

[0032] This comparative example is substantially the same as Example 1, except that in step 4) the winding tension of the fiber winding machine is controlled to be 5 kgf / strand, and the prepreg glass fiber yarn is wound on the mold, and after winding is completed, post-curing is performed, the mold is removed, and the post-curing conditions are as follows: heating at a rate of 2°C / min to 120°C and holding for 60 min, and then heating at a rate of 2°C / min to 150°C and holding for 180 min.

[0033] Comparative Example 1

[0034] This comparative example is substantially the same as Example 1, except that step 3) is omitted.

[0035] Comparative Example 2

[0036] This comparative example is substantially the same as Example 1, except that in step 3) the prepreg glass cloth laid-up mold is placed in a curing oven, and is heated at a rate of 2°C / min to 60°C and held for 120 min to make the resin enter the transition period of stage I→II, and then is cooled at a rate of 1°C / min to 60°C, and the mold is removed.

[0037] Comparative Example 3

[0038] This comparative example is substantially the same as Example 1, except that in step 4) the winding tension of the fiber winding machine is controlled to be 8 kgf / strand, and the prepreg glass fiber yarn is wound on the mold, and after winding is completed, post-curing is performed, the mold is removed, and the post-curing conditions are as follows: heating at a rate of 2°C / min to 120°C and holding for 60 min, and then heating at a rate of 2°C / min to 150°C and holding for 180 min.

[0039] The test data of the glass steel rectangular pipe obtained in Examples 1-4 and Comparative Examples 1-3 are shown in Table 1.

[0040] Table 1 Test data of the glass steel rectangular pipe obtained in Examples 1-4 and Comparative Examples 1-3

[0041] Examples Tensile strength, MPa Inner appearance quality Example 1 253 Inner appearance smooth Example 2 240 Inner appearance smooth Example 3 232 Inner appearance smooth Example 4 238 Inner appearance smooth Comparative Example 1 220 Many lines, many grooves Comparative Example 2 225 Many lines, many grooves Comparative Example 3 230 Many lines, many grooves

[0042] As shown in Table 1, the present application significantly improves the tensile strength and internal quality of the FRP rectangular pipe product by adding the pre-curing process, thereby prolonging the service life of the product.

[0043] The above-described examples are only preferred embodiments of the present application, and are used to explain the present application, but not to limit the scope of the present application. For those skilled in the art, other embodiments can be easily obtained by substitution or change based on the technical content disclosed in the present specification. Therefore, any changes and improvements made on the principle of the present application shall be included in the scope of the present application.

Claims

1. A method of improving the quality of glass steel rectangular pipe lining, characterized by, The method comprises the following steps: 1) cleaning the mold surface; 2) uniformly laying the impregnated glass cloth on the mold and scraping off the excess glue; 3) placing the mold with the laid impregnated glass cloth in a curing oven for low-temperature pre-curing, cooling, and taking out the mold; 4) controlling the winding tension to be 2-5 kgf / strand, winding the impregnated glass fiber yarn on the mold, and performing post-curing and demolding after winding is completed.

2. The method of claim 1, wherein, The glass cloth has a thickness of 0.06 mm and a areal density of 200 g / m 2 .

3. The method of claim 1, wherein, The low-temperature pre-curing conditions are as follows: increasing the temperature to 90-100 DEG C at a rate of 2 DEG C / min and maintaining for 30-60 min, and then decreasing the temperature to 60 DEG C at a rate of 1 DEG C / min.

4. The method of claim 1, wherein, The post-curing conditions are as follows: increasing the temperature to 120 DEG C at a rate of 2 DEG C / min and maintaining for 60 min, and then increasing the temperature to 150 DEG C at a rate of 2 DEG C / min and maintaining for 180 min.

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