Nano-modified glass reinforced plastic pipe

Abstract

The invention provides a nano-modified glass reinforced plastic pipe, and belongs to the technical field of glass reinforced plastic pipes. The invention relates to a sand-filled composite material which comprises an inner layer, an outer layer and a sand-filled layer, the inner layer comprises a lining layer, an inner circumferential winding layer and an inner axial fiber layer, the outer layer comprises an outer axial fiber layer, an outer circumferential winding layer and an outer protective layer, and the sand-filled layer is filled with modified resin and quartz sand compounds. The modified resin and quartz sand compound is prepared by adding hyperbranched modified silicon dioxide into epoxy resin, stirring and mixing, adding a cross-linking agent and a hindered urea curing agent, adding quartz sand, and heating and curing; the hyperbranched modified silicon dioxide is prepared by sequentially reacting phytic acid and hyperbranched polyester on the surface of nano silicon dioxide with amino on the surface. The nano-modified glass reinforced plastic pipe sand inclusion layer prepared by the invention is filled with the modified resin and quartz sand compound, has high strength and toughness, stable thermal performance and good flame retardance, has self-repairing performance, is not easy to brittle and break, and is easy to realize industrial application.

Description

Technical Field

[0001] The invention relates to the technical field of glass fiber reinforced plastic pipes, and in particular to a nano-modified glass fiber reinforced plastic pipe. Background Art

[0002] At present, the sand layer of FRP sand-filled pipes is a resin mortar layer (a mixture of quartz sand and resin). The function of this layer is to transfer the force between the inner and outer layers of the FRP pipe, improve the rigidity of the pipe, ensure a certain shear strength of the pipe, and avoid stratification during the product flexural performance test. Existing FRP sand-filled pipes usually use a method of directly mixing quartz sand and resin to make the sand layer. Although it improves the performance of the pipe to a certain extent, the existing sand-filled pipes still cannot meet the requirements in situations where high compressive strength and compressive toughness are required. Therefore, it is necessary to design a sand-filled pipe that can meet the requirements of high compressive strength and compressive toughness.

[0003] Chinese invention patent CN102705592B discloses a nano-modified glass fiber reinforced plastic pipe, which includes an inner layer, a sand layer and an outer layer from the inside to the outside, wherein the sand layer is prepared by the following steps: (1) dispersing and mixing nano-silicon dioxide and / or nano-active calcium carbonate with resin to obtain a modified resin matrix, wherein the weight ratio of the nano-silicon dioxide and / or nano-active calcium carbonate is 1-8%; stirring and mixing the modified resin matrix with quartz sand, wherein the weight of the resin accounts for 15-18% of the total weight. However, the nano-silicon dioxide and / or nano-active calcium carbonate used in the patent have poor compatibility in the resin, thereby limiting its performance.

[0004] Chinese invention patent CN102691829B discloses a nano-modified glass fiber reinforced plastic sand-filled pipe, which includes an inner layer, a sand-filled layer and an outer layer from the inside to the outside. The invention uses an independently designed nano-material mixing and dispersion process to evenly mix 1-8% by weight of a two-component nano-material (a mixture of surface-treated nano-silicon dioxide and nano-active calcium carbonate) into a resin to obtain a mixed nano-material modified resin matrix, and then fully mix the resin matrix and quartz sand to form a sand-filled layer. Although the patent uses surface-treated nano-materials to reduce the agglomeration of nano-materials to a certain extent, its mechanical enhancement effect needs to be further improved. Summary of the invention

[0005] The purpose of the present invention is to provide a nano-modified glass fiber reinforced plastic pipe, in which the sand-interlayer is filled with a modified resin and quartz sand composite prepared from self-repairing epoxy resin and hyperbranched modified silica, and has high strength and toughness, stable thermal properties, good flame retardancy, and self-repairing properties, is not easy to be brittle or broken, and is easy to realize industrial application.

[0006] The technical solution of the present invention is achieved in this way: The invention provides a nano-modified glass fiber reinforced plastic pipe, which comprises an inner layer, an outer layer and a sand-interlayer, wherein the sand-interlayer is filled with a modified resin and a quartz sand composite, wherein the modified resin and the quartz sand composite is prepared by adding hyperbranched modified silica to epoxy resin, stirring and mixing, adding a cross-linking agent and a hindered urea curing agent, adding quartz sand, and heating and curing, wherein the mass ratio of the epoxy resin, the hyperbranched modified silica, the cross-linking agent, the hindered urea curing agent and the quartz sand is 100:7-12:2-4:15-20:20-40; the hyperbranched modified silica is prepared by sequentially reacting nano-silicon dioxide with amino groups on the surface with phytic acid and a hyperbranched polyester; and the structure of the hindered urea curing agent is shown in Formula I: Formula I; The structural formula of the hyperbranched polyester is shown in Formula II: Formula II.

[0007] As a further improvement of the present invention, the structural formula of the hyperbranched polyester is shown in Formula II: Formula II; The preparation method of the hyperbranched polyester is as follows: pentaerythritol, trimellitic anhydride, a catalyst and a solvent are mixed for reaction, heated for reaction until the acid value remains unchanged, and the solvent is removed under reduced pressure.

[0008] As a further improvement of the present invention, the molar ratio of pentaerythritol to trimellitic anhydride is 1:4, the added amount of the catalyst is 0.1-0.15wt% of the total mass of the reactants, the catalyst is p-toluenesulfonic acid or triphenylphosphine, the temperature of the heating reaction is 130-140°C, and the solvent is DMF.

[0009] As a further improvement of the present invention, the preparation method of the hyperbranched modified silica is as follows: S1. Preparation of silica with amino groups on the surface: dropping aminosilane into water, stirring the reaction, centrifuging, washing, and spray drying to obtain silica nanospheres with amino groups on the surface; S2. Phytic acid modification: adding silica with amino groups on the surface to water, adding phytic acid and dipotassium hydrogen phosphate, hydrothermally reacting, centrifuging, washing, and drying to obtain modified silica nanospheres; S3. Preparation of hyperbranched modified silica: hyperbranched polyester is added to DMF solvent, NHS and EDC are added, stirred for activation, modified silica nanospheres are added, stirred for reaction, centrifuged, washed, and dried to obtain hyperbranched modified silica.

[0010] Preferably, the aminosilane is selected from at least one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl)-γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropyltriethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldiethoxysilane, and diethylenetriaminopropyltrimethoxysilane.

[0011] As a further improvement of the present invention, the rotation speed of the stirring reaction in step S1 is 1000-1500r / min, the time is 6-10h, and the reaction temperature is 50-60°C; the mass ratio of the silicon dioxide with amino groups on the surface, phytic acid and dipotassium hydrogen phosphate in step S2 is 10-15:3-5:0.2-0.3, the temperature of the hydrothermal reaction is 130-140°C, and the time is 5-7h; the mass ratio of the hyperbranched polyester, modified silicon dioxide nanospheres, NHS and EDC in step S3 is 5-8:12-15:1-2:1-2, the stirring activation time is 20-30min, and the stirring reaction time is 8-10h.

[0012] As a further improvement of the present invention, the preparation method of the hindered urea curing agent is as follows: under the protection of inert gas, diphenylmethane diisocyanate and triethylenediamine are dissolved in a solvent, N,N'-di-tert-butylethylenediamine is added, heated to reflux reaction, and impurities and solvent are removed under reduced pressure to obtain the hindered urea curing agent.

[0013] As a further improvement of the present invention, the solvent is dichloromethane, the molar ratio of diphenylmethane diisocyanate and N,N'-di-tert-butylethylenediamine is 1:2, the added amount of triethylenediamine is 0.2-0.5wt% of the total mass of the reactants, and the heating reflux reaction time is 6-8h.

[0014] As a further improvement of the present invention, the epoxy resin is E-51, and the cross-linking agent is 4,4'-diaminodiphenylmethane.

[0015] As a further improvement of the present invention, the heating curing conditions are heating at a temperature of 55-65°C for 2-3h, heating at a temperature of 95-100°C for 2-4h, heating at a temperature of 130-140°C for 2-4h, and heating at a temperature of 150-160°C for 0.5-1.5h.

[0016] The present invention has the following beneficial effects: The sand-interlayer of the nano-modified glass fiber reinforced plastic pipe of the present invention is filled with a modified resin and quartz sand composite, wherein the modified resin and quartz sand composite is prepared by adding hyperbranched modified silica to an epoxy resin, stirring and mixing, adding a cross-linking agent and a hindered urea curing agent, adding quartz sand, and heating and curing, wherein the epoxy resin is cured by a hindered urea curing agent, and the stable conjugated system of the urea bond can be disturbed by adding a bulky substituent to the nitrogen atom, although this may hinder the strong interaction between amines and isocyanates, resulting in the dissociation of the bond, but because the isocyanate can easily react with the amine, a new urea bond can also be quickly formed, so that the bond is dynamically reversible, and therefore, the post-treatment behavior of the large sterically hindered urea-based material at room temperature enables the material to have an adaptive dynamic covalent network, so that the epoxy resin obtained by curing and cross-linking can achieve its self-repairing performance under mild conditions, and also improves the toughness of the epoxy resin, reduces its brittleness, and ensures that the material has good mechanical properties.

[0017] In addition, hyperbranched modified silica is added to the modified resin and quartz sand composite. First, aminosilane is added dropwise into water, which is insoluble in water. It is dispersed into tiny droplets during stirring, and the amino group is protonated. While stabilizing the silane droplets, an alkaline environment is provided to catalyze the sol-gel reaction of the silane, thereby preparing silica nanospheres with amino groups on the surface. The surface of the nanosphere is further reacted with phytic acid, and then the amino group can react with the polyester of the hyperbranched polyester, thereby realizing the simultaneous modification of the phytic acid and the hyperbranched polyester. On the one hand, the phytic acid and hyperbranching modification improve the toughness of the resin, improve the dispersibility of the nanoparticles in the epoxy resin material, and avoid the agglomeration of the nanomaterial itself. At the same time, the remaining amino groups on the surface of the nanomaterial can also participate in the curing reaction of the epoxy resin, further improving the dispersibility of the nanomaterial. At the same time, the introduction of hyperbranched structure into epoxy resin can form a good network structure with epoxy resin. Inorganic nanoparticles as central core points can significantly improve the impact strength of epoxy resin, and also improve the tensile and bending strength, thereby improving the thermal properties of epoxy resin and further improving its flame retardancy.

[0018] The sand-interlayer of the nano-modified glass fiber reinforced plastic pipe prepared by the invention is filled with a modified resin and a quartz sand composite, has high strength and toughness, stable thermal properties, good flame retardancy, and self-repairing properties, is not prone to brittleness and breakage, and is easy to realize industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0020] Figure 1 This is a schematic structural diagram of a nano-modified glass fiber reinforced plastic pipe according to the present invention; Among them, 1 is the inner lining layer; 2 is the inner annular winding layer; 3 is the inner axial fiber layer; 4 is the sand-interlayer layer; 5 is the outer axial fiber layer; 6 is the outer annular winding layer; and 7 is the outer protective layer.

[0021] Figure 2 This is a comparison chart of the self-healing experiment of the modified resin and quartz sand composite prepared in Example 3 at different temperatures. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] NHS, N-hydroxysuccinimide; EDC, 1-ethyl-(3-dimethylaminopropyl)carbodiimide; particle size range of quartz sand: 10-20 mesh, 40wt%, 30-60 mesh, 20wt%, 70-100 mesh, 25wt%, >100 mesh, 15wt%.

[0024] Preparation Example 1 Preparation of hyperbranched polyester Synthesis route: ; Here’s how: 10mmol of pentaerythritol, 40mmol of trimellitic anhydride, triphenylphosphine and 50mL of DMF solvent were mixed for reaction. The amount of the catalyst added was 0.12wt% of the total mass of the reactants. The mixture was heated to 135°C and stirred until the acid value remained unchanged. The solvent was removed under reduced pressure. ESI-MS calculated value: C 41 H 29 O 24 (M+H) + 905.10, found value: 905.1, yield: 95%.

[0025] NMR results: 1H NMR (300MHz, CDCl3) δ11.2 (br, 8H), 9.12 (s, 4H), 8.62 (d, J =6.4Hz, 4H), 8.37(d, J =6.3Hz, 4H), 4.22 (s, 8H).

[0026] Preparation Example 2 Preparation of Hindered Urea Curing Agent Synthesis route: ; The method is as follows: under nitrogen protection, 10 mmol of diphenylmethane diisocyanate and triethylenediamine are dissolved in 50 mL of dichloromethane, wherein the amount of triethylenediamine added is 0.3 wt% of the total mass of the reactants, 20 mmol of N,N'-di-tert-butylethylenediamine is added, and the mixture is heated under reflux for 8 h, and impurities and solvents are removed under reduced pressure to obtain a hindered urea curing agent. ESI-MS calculated value: C 35 H 59 N6O2(M+H) + 595.46, found value: 595.5, yield is 87%.

[0027] NMR results: 1 H NMR (300MHz, CDCl3) δ7.65 (d, J =6.1Hz, 4H), 7.12(d, J =6.2Hz, 4H), 6.0 (br, 2H), 3.82 (s, 2H), 3.32 (t, 4H), 2.93 (t, 4H), 3.0 (br, 2H), 1.42 (s, 18H), 1.22 (s, 18H).

[0028] Preparation Example 3 Preparation of hyperbranched modified silica Here’s how: S1. Preparation of silica with amino groups on the surface: 2 g of N-β (aminoethyl) -γ-aminopropyltrimethoxysilane was dropped into 200 mL of water, stirred at 1000 r / min and 50°C for 6 h, centrifuged, washed, and spray-dried to obtain silica nanospheres with amino groups on the surface; S2. Phytic acid modification: 10 g of silica with amino groups on the surface was added to 200 mL of water, 3 g of phytic acid and 0.2 g of potassium dihydrogen phosphate were added, and the reaction was hydrothermally reacted at 130 ° C for 5 h, centrifuged, washed, and dried to obtain modified silica nanospheres; S3. Preparation of hyperbranched modified silica: 5 g of the hyperbranched polyester prepared in Preparation Example 1 was added to 200 mL of DMF solvent, 1 g of NHS and 1 g of EDC were added, and the mixture was stirred for activation for 20 min. 12 g of modified silica nanospheres were added, and the mixture was stirred for reaction for 8 h. The mixture was centrifuged, washed, and dried to obtain hyperbranched modified silica.

[0029] Preparation Example 4 Preparation of hyperbranched modified silica Here’s how: S1. Preparation of silica with amino groups on the surface: 2 g of γ-aminopropyltriethoxysilane was dropped into 200 mL of water, stirred at 1500 r / min and 60° C. for 10 h, centrifuged, washed, and spray-dried to obtain silica nanospheres with amino groups on the surface; S2. Phytic acid modification: 12 g of silica with amino groups on the surface was added to 200 mL of water, 5 g of phytic acid and 0.3 g of potassium dihydrogen phosphate were added, and the reaction was hydrothermally reacted at 140 ° C for 7 h, centrifuged, washed, and dried to obtain modified silica nanospheres; S3. Preparation of hyperbranched modified silica: 8 g of the hyperbranched polyester prepared in Preparation Example 1 was added to 200 mL of DMF solvent, 2 g of NHS and 2 g of EDC were added, and the mixture was stirred for activation for 30 min. 15 g of modified silica nanospheres were added, and the mixture was stirred for reaction for 10 h. The mixture was centrifuged, washed, and dried to obtain hyperbranched modified silica.

[0030] Preparation Example 5 Preparation of hyperbranched modified silica Here’s how: S1. Preparation of silica with amino groups on the surface: 2 g of γ-aminopropyltrimethoxysilane was dropped into 200 mL of water, stirred at 1200 r / min and 55° C. for 8 h, centrifuged, washed, and spray-dried to obtain silica nanospheres with amino groups on the surface; S2. Phytic acid modification: 12 g of silica with amino groups on the surface was added to 200 mL of water, 4 g of phytic acid and 0.25 g of potassium dihydrogen phosphate were added, and the reaction was hydrothermally reacted at 135 ° C for 6 h, centrifuged, washed, and dried to obtain modified silica nanospheres; S3. Preparation of hyperbranched modified silica: 6.5 g of the hyperbranched polyester prepared in Preparation Example 1 was added to 200 mL of DMF solvent, 1.5 g of NHS and 1.5 g of EDC were added, and the mixture was stirred for activation for 25 min. 13.5 g of modified silica nanospheres were added, and the mixture was stirred for reaction for 9 h. The mixture was centrifuged, washed, and dried to obtain hyperbranched modified silica.

[0031] Comparative Preparation Example 1 Compared with Preparation Example 5, the difference is that step S2 is not performed.

[0032] The details are as follows: S1. Preparation of silica with amino groups on the surface: 2 g of γ-aminopropyltrimethoxysilane was dropped into 200 mL of water, stirred at 1200 r / min and 55° C. for 8 h, centrifuged, washed, and spray-dried to obtain silica nanospheres with amino groups on the surface; S2. Preparation of hyperbranched modified silica: 6.5 g of the hyperbranched polyester prepared in Preparation Example 1 was added to 200 mL of DMF solvent, 1.5 g of NHS and 1.5 g of EDC were added, and the mixture was stirred for activation for 25 min. 13.5 g of silica nanospheres with amino groups on the surface were added, and the mixture was stirred for reaction for 9 h. The mixture was centrifuged, washed, and dried to obtain hyperbranched modified silica.

[0033] Comparative Preparation Example 2 Compared with Preparation Example 5, the difference is that step S3 is not performed.

[0034] The details are as follows: S1. Preparation of silica with amino groups on the surface: 2 g of γ-aminopropyltrimethoxysilane was dropped into 200 mL of water, stirred at 1200 r / min and 55° C. for 8 h, centrifuged, washed, and spray-dried to obtain silica nanospheres with amino groups on the surface; S2. Phytic acid modification: 12 g of silica with amino groups on the surface was added to 200 mL of water, 4 g of phytic acid and 0.25 g of potassium dihydrogen phosphate were added, and the reaction was hydrothermally reacted at 135° C. for 6 h. The reaction was centrifuged, washed, and dried to obtain modified silica nanospheres.

[0035] Comparative Preparation Example 3 Compared with Preparation Example 5, the difference is that steps S2 and S3 are not performed.

[0036] Preparation of silica with amino groups on the surface: 2 g of γ-aminopropyltrimethoxysilane was dropped into 200 mL of water, stirred at 1200 r / min and 55° C. for 8 h, centrifuged, washed, and spray-dried to obtain silica nanospheres with amino groups on the surface.

[0037] Example 1: Figure 1 The nano-modified glass fiber reinforced plastic pipe of the present invention comprises an inner layer, an outer layer and a sand-interlayer, wherein the inner layer comprises an inner lining layer 1, an inner annular winding layer 2, and an inner axial fiber layer 3, and the outer layer comprises an outer axial fiber layer 5, an outer annular winding layer 6, and an outer protective layer 7, and the sand-interlayer 4 is filled with a modified resin and quartz sand composite. The preparation method of the modified resin and quartz sand composite is as follows: 7 g of the hyperbranched modified silica prepared in Preparation Example 3 was added to 100 g of epoxy resin E-51, and the mixture was stirred and mixed for 20 min. 2 g of 4,4'-diaminodiphenylmethane and 15 g of the hindered urea curing agent prepared in Preparation Example 2 were added. 20 g of quartz sand was added, and the mixture was heated and cured to prepare a composite of modified resin and quartz sand. The conditions for heat curing are heating at a temperature of 55° C. for 2 h, heating at a temperature of 95° C. for 2 h, heating at a temperature of 130° C. for 2 h, and heating at a temperature of 150° C. for 0.5 h.

[0038] Example 2: Figure 1 The nano-modified glass fiber reinforced plastic pipe of the present invention comprises an inner layer, an outer layer and a sand-interlayer, wherein the inner layer comprises an inner lining layer 1, an inner annular winding layer 2, and an inner axial fiber layer 3, and the outer layer comprises an outer axial fiber layer 5, an outer annular winding layer 6, and an outer protective layer 7, and the sand-interlayer 4 is filled with a modified resin and quartz sand composite. The preparation method of the modified resin and quartz sand composite is as follows: 12 g of the hyperbranched modified silica prepared in Preparation Example 4 was added to 100 g of epoxy resin E-51, and the mixture was stirred and mixed for 20 min. 4 g of 4,4'-diaminodiphenylmethane and 20 g of the hindered urea curing agent prepared in Preparation Example 2 were added. 40 g of quartz sand was added, and the mixture was heated and cured to prepare a composite of modified resin and quartz sand. The conditions for heat curing are heating at 65° C. for 3 h, heating at 100° C. for 4 h, heating at 140° C. for 4 h, and heating at 160° C. for 1.5 h.

[0039] Example 3: Figure 1 The nano-modified glass fiber reinforced plastic pipe of the present invention comprises an inner layer, an outer layer and a sand-interlayer, wherein the inner layer comprises an inner lining layer 1, an inner annular winding layer 2, and an inner axial fiber layer 3, and the outer layer comprises an outer axial fiber layer 5, an outer annular winding layer 6, and an outer protective layer 7, and the sand-interlayer 4 is filled with a modified resin and quartz sand composite. The preparation method of the modified resin and quartz sand composite is as follows: Add 10 g of the hyperbranched modified silica prepared in Preparation Example 5 to 100 g of epoxy resin E-51, stir and mix for 20 min, add 3 g of 4,4'-diaminodiphenylmethane and 17 g of the hindered urea curing agent prepared in Preparation Example 2, add 30 g of quartz sand, heat and cure, and prepare a modified resin and quartz sand composite; The conditions for heat curing are heating at 60° C. for 2.5 h, heating at 98° C. for 3 h, heating at 135° C. for 3 h, and heating at 155° C. for 1 h.

[0040] Self-healing performance test: Scratch the sample surface with a knife, the scratch width is about 25μm, keep it at 100, 110, 120℃ for 10min, and observe the morphology of the damaged coating during the self-healing process with an optical microscope. Figure 2 As can be seen from the figure, after the sample prepared by the present invention is heated to above 110°C for 10 minutes, almost no scratches can be seen, indicating that it has good self-healing ability.

[0041] Comparative Example 1 Compared with Example 3, the difference is that the hyperbranched modified silica is replaced by the product prepared in Comparative Preparation Example 1.

[0042] Comparative Example 2 Compared with Example 3, the difference is that the hyperbranched modified silica is replaced by the product prepared in Comparative Preparation Example 2.

[0043] Comparative Example 3 Compared with Example 3, the difference is that the hyperbranched modified silica is replaced by the product prepared in Comparative Preparation Example 3.

[0044] Comparative Example 4 Compared with Example 3, the difference is that no hyperbranched modified silica is added.

[0045] Test Example 1 The modified resin and quartz sand composites prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to mechanical property tests. The results are shown in Table 1.

[0046] The tensile properties test refers to GB / T 2567-2021, measured at 25°C, and the test speed is 10mm / min.

[0047] The impact performance test refers to GB / T 2567-2021, selects the notchless impact method, and uses a plastic pendulum impact testing machine for the test. The sample size is 120mm×15mm×10mm.

[0048] The tensile shear strength test refers to GB / T7124-2008, and a 100mm×25mm×1.6mm SUS 321 stainless steel sheet is selected. The bonding surface length is 12.5±0.25mm, the width is 25±0.25mm, the adhesive layer thickness is about 0.2mm, and the overflow is cleaned up in time. After curing for 2 days, the test is carried out at 25℃ using a universal tensile testing machine with a test speed of 2mm / min.

[0049] Table 1 ; It can be seen from the above table that the modified resin and quartz sand composites prepared in Examples 1-3 of the present invention have good mechanical properties.

[0050] Test Example 2 The modified resin and quartz sand composites prepared in Examples 1-3 and Comparative Examples 1-4 were tested for flame retardancy, with reference to standard GB / T 2406.2-2009. The results are shown in Table 2.

[0051] Table 2 ; It can be seen from the above table that the modified resin and quartz sand composites prepared in Examples 1-3 of the present invention have good flame retardant properties.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A nano-modified glass fiber reinforced plastic pipe, comprising an inner layer, an outer layer and a sand layer, wherein the inner layer comprises an inner lining layer, an inner annular winding layer and an inner axial fiber layer, and the outer layer comprises an outer axial fiber layer, an outer annular winding layer and an outer protective layer, characterized in that: The sand-interlayer is filled with a modified resin and quartz sand composite, which is prepared by adding hyperbranched modified silica to epoxy resin, stirring and mixing, adding a crosslinking agent and a hindered urea curing agent, adding quartz sand, and heating and curing. The mass ratio of the epoxy resin, hyperbranched modified silica, crosslinking agent, hindered urea curing agent and quartz sand is 100:7-12:2-4:15-20:20-40; the hyperbranched modified silica is prepared by reacting nano-silica with amino groups on the surface with phytic acid and hyperbranched polyester in sequence; the structure of the hindered urea curing agent is shown in Formula I: Formula I; The structural formula of the hyperbranched polyester is shown in Formula II: Formula II.

2. The nano-modified glass fiber reinforced plastic pipe according to claim 1, characterized in that: The preparation method of the hyperbranched polyester is as follows: pentaerythritol, trimellitic anhydride, a catalyst and a solvent are mixed for reaction, heated for reaction until the acid value remains unchanged, and the solvent is removed under reduced pressure.

3. The nano-modified glass fiber reinforced plastic pipe according to claim 2, characterized in that: The molar ratio of pentaerythritol to trimellitic anhydride is 1:4, the added amount of the catalyst is 0.1-0.15wt% of the total mass of the reactants, the catalyst is p-toluenesulfonic acid or triphenylphosphine, the temperature of the heating reaction is 130-140°C, and the solvent is ‌N,N-dimethylformamide.

4. The nano-modified glass fiber reinforced plastic pipe according to claim 1, characterized in that: The preparation method of the hyperbranched modified silica is as follows: S1. Preparation of silica with amino groups on the surface: dropping aminosilane into water, stirring the reaction, centrifuging, washing, and spray drying to obtain silica nanospheres with amino groups on the surface; S2. Phytic acid modification: adding silica with amino groups on the surface to water, adding phytic acid and dipotassium hydrogen phosphate, hydrothermally reacting, centrifuging, washing, and drying to obtain modified silica nanospheres; S3. Preparation of hyperbranched modified silica: add hyperbranched polyester to ‌N,N-dimethylformamide solvent, add N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir to activate, add modified silica nanospheres, stir to react, centrifuge, wash, and dry to obtain hyperbranched modified silica.

5. The nano-modified glass fiber reinforced plastic pipe according to claim 4, characterized in that: The rotation speed of the stirring reaction in step S1 is 1000-1500r / min, the time is 6-10h, and the reaction temperature is 50-60°C; the mass ratio of the silicon dioxide with amino groups on the surface, phytic acid and dipotassium hydrogen phosphate in step S2 is 10-15:3-5:0.2-0.3, the temperature of the hydrothermal reaction is 130-140°C, and the time is 5-7h; the mass ratio of the hyperbranched polyester, modified silicon dioxide nanospheres, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in step S3 is 5-8:12-15:1-2:1-2, the stirring activation time is 20-30min, and the stirring reaction time is 8-10h.

6. The nano-modified glass fiber reinforced plastic pipe according to claim 1, characterized in that: The preparation method of the hindered urea curing agent is as follows: under the protection of inert gas, diphenylmethane diisocyanate and triethylenediamine are dissolved in a solvent, N,N'-di-tert-butylethylenediamine is added, heated under reflux reaction, and impurities and solvent are removed under reduced pressure to obtain the hindered urea curing agent.

7. The nano-modified glass fiber reinforced plastic pipe according to claim 6, characterized in that: The solvent is dichloromethane, the molar ratio of diphenylmethane diisocyanate and N,N'-di-tert-butylethylenediamine is 1:2, the addition amount of triethylenediamine is 0.2-0.5wt% of the total mass of the reactants, and the heating reflux reaction time is 6-8h.

8. The nano-modified glass fiber reinforced plastic pipe according to claim 1, characterized in that: The epoxy resin is E-51, and the cross-linking agent is 4,4'-diaminodiphenylmethane.

9. The nano-modified glass fiber reinforced plastic pipe according to claim 1, characterized in that: The conditions for the heating curing are heating at a temperature of 55-65° C. for 2-3 hours, heating at a temperature of 95-100° C. for 2-4 hours, heating at a temperature of 130-140° C. for 2-4 hours, and heating at a temperature of 150-160° C. for 0.5-1.5 hours.

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