Glycine bridged polyamine silane coupling agent as well as preparation method and application thereof

Abstract

The invention discloses synthesis of a glycine bridged polyamine silane coupling agent and application of the glycine bridged polyamine silane coupling agent in surface treatment of a glass fiber reinforced polymer engineering material. The silane coupling agent is a novel compound formed by bonding isocyanate propyl trialkoxysilane and polyamine through an amido bond. The silane coupling agent is mild in synthesis condition and simple to operate, and the hydrogen-bond interaction between the glass fiber and a resin material molecular chain can be improved by utilizing an active N-H bond of a polyamine linking group, so that the wettability of resin molecules to the glass fiber is improved, the acting force between the glass fiber and a resin matrix material is improved, and the service life of the resin matrix material is prolonged. Finally, the mechanical property of the glass fiber polymer composite material is obviously improved.

Description

Technical Field

[0001] The invention belongs to the field of materials and chemical engineering, and particularly relates to a glycine-bridged polyamine silane coupling agent and a preparation method and application thereof. Background Art

[0002] The emergence of composite materials with excellent performance since the 1940s can be considered a milestone in the history of the development of materials science. As the largest category of composite materials, fiber reinforced polymers (FRP) have made great progress in modern civilization due to their easy processing, corrosion resistance, light weight, high strength and cost-effectiveness. Reinforcing fibers, including glass fibers, carbon fibers, renewable fibers, etc., are used as load-bearing elements, and polymers are used as continuous phases or matrices, which can not only protect and disperse the fibers but also transfer the load. Commonly used matrix materials are divided into two categories, namely thermosetting materials, such as unsaturated resins, epoxy resins and polyurethane resins, and thermoplastic materials, such as polyamides, polycarbonates, polystyrene, PVC, PP, etc. Although fiber reinforced polymer composites have been used in engineering for 80 years, they can still be seen in fast-growing fields such as lightweight electric vehicles, composite insulators in ultra-high voltage transmission, wind turbine blades, liquid hydrogen storage, high-speed rail, and drones.

[0003] The macroscopic properties of fiber-reinforced polymers depend not only on the chemical composition and physical structure of the fiber and polymer, but also on the interface state between the matrix resin and the reinforcing fiber, including the interface composition, bonding mode and bonding strength. Taking glass fiber as an example, the surface of glass fiber is a hydrophilic inorganic silicon oxide structure, and the surface energy difference between it and the hydrophobic polymer material is very large. Therefore, if the surface of glass fiber is not treated, the matrix polymer material will not wet the surface of glass fiber, resulting in poor macroscopic mechanical properties. The interface between fiber and matrix is ​​crucial to the performance of composite materials. It plays a role in smoothly transferring the stress borne by the matrix material to the reinforcing fiber structure. Therefore, improving the interface bonding strength is an important consideration in designing high-performance composite materials. In order to improve the interface bonding, researchers have optimized the interface performance from different angles. More research is on depositing nanomaterials such as graphene, graphene oxide and carbon nanotubes on the fiber surface to improve the interface bonding strength through the size effect of nanomaterials. Although the layered interface formed by depositing nanomaterials on the reinforcing fiber can improve its mechanical properties to a certain extent, this may be mainly due to the mechanical bonding between the fiber and the matrix at the mesoscopic scale. The additional interface may increase the possibility of interlayer delamination failure and ultimately lead to material failure.

[0004] The above literature results indicate that in order to construct the critical interfacial phase, not only the graded surface roughness should be considered, but also chemical bonding, electrostatic interactions, hydrogen bonding, etc. Interestingly, in natural composites such as teeth and bones, there are extensive hydrogen bonding interactions between nanofibers and nanoscale hydroxyapatite, which may contribute to the toughening mechanism, including intrinsic plasticity, extrinsic crack bridging, and flexure to achieve strength and toughness simultaneously. However, in synthetic composites, the construction of hydrogen bonding has not received much attention, and there are no reports on whether the use of hydrogen bonding can improve the mechanical properties of materials.

[0005] In long-term practice, silane coupling agents are used to physically or chemically treat the surface of reinforcing fibers, which can not only protect the fibers from wear, but also improve the bonding force between glass fibers and polymer matrix, thereby achieving the purpose of improving the performance of composite materials. Silane coupling agents have two different reactive groups in their molecular structure, so they can form a bonding transition layer between reinforcing fibers and resins, thereby obtaining better bonding strength. Currently, the most widely studied are commercially available silane coupling agents such as KH550 (amino), KH560 (epoxy), KH570 (methacryloyloxy), KH151 (vinyl), KH590 (thiol), KH1160 (urea propyl), etc., and the development of new surface treatment agents to further improve the performance of composite materials is of great significance both in theoretical research and practical applications. Summary of the invention

[0006] The invention aims to solve the problems that glass fiber reinforced polymer materials treated with silane coupling agents in the past have poor mechanical properties and are prone to interface failure after long-term use. A silane coupling agent with a novel structure is formed by coupling polyamine with glycine, and the hydrogen bonding between the glass fiber surface and the polymer matrix material is improved, thereby improving the mechanical properties of the composite material. The invention is expected to be widely used in various fields such as glass fiber reinforced nylon automotive materials, glass fiber reinforced unsaturated resin corrosion-resistant high-strength pipeline materials, and glass fiber reinforced epoxy resin electrical materials.

[0007] The technical purpose of the present invention is to provide a glycine-bridged polyamine silane coupling agent and a preparation method and application thereof. The glass fiber modified by the glycine-bridged polyamine silane coupling agent can meet the reinforcement and filling requirements of different polymer matrix materials, greatly improve the mechanical properties of the fiber-reinforced polymer material, and at the same time improve the durability of the composite material, so as to solve the technical defects of the prior art such as the insufficient mechanical properties of the glass fiber reinforced polymer composite material treated with the surface treatment agent.

[0008] In order to achieve the technical purpose of the present invention, the technical solution of the present invention is:

[0009] A glycine-bridged polyamine silane coupling agent is obtained by bridging trialkoxysilane and a polyamine compound through an amide bond.

[0010] The polyamine compound includes a single component or a mixture of amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and hexaethyleneheptamine.

[0011] Trialkoxysilane is isocyanatepropyltriethoxysilane or isocyanatepropyltrimethoxysilane

[0012] The preparation method of the glycine-bridged polyamine silane coupling agent comprises the following steps:

[0013] (1) Synthesis of glycine methyl ester hydrochloride:

[0014] Take glycine and add it into a flask, add methanol to dissolve it, add SOCl2 dropwise at 0°C, react at 25°C for 12-24h, and after the reaction is completed, distill under reduced pressure, and then rotary evaporate to obtain a white solid product, glycine methyl ester hydrochloride;

[0015] (2) Synthesis of glycine methyl ester:

[0016] The crude product of glycine methyl ester hydrochloride was dispersed in dichloromethane, and triethylamine was added for neutralization. The reaction was carried out at 25°C for 12-24 hours. After the reaction was completed, the product was collected by filtration, extracted with ether, and distilled under pressure to obtain a yellow liquid product, glycine methyl ester;

[0017] (3) Synthesis of glycine formamide:

[0018] Under Ar protection, glycine methyl ester was dissolved in methanol, and then a polyamine compound was added to react overnight. After the reaction was completed, the product was purified by vacuum distillation, rotary evaporation and silica gel column chromatography, and finally an oily liquid product glycine carboxamide was obtained;

[0019] (4) Synthesis of glycine-bridged polyamine silane coupling agent:

[0020] Under Ar protection, glycine formamide was dissolved in tetrahydrofuran, isocyanate propyl trialkoxy silane was added, reacted at room temperature, stirred overnight, and after the reaction was completed, the solvent was distilled off under reduced pressure, filtered, and dried to obtain a white solid product, glycine bridged polyamine silane coupling agent.

[0021] The present invention also provides the use of the glycine-bridged polyamine-silane coupling agent in the preparation of modified glass fibers, comprising: immersing the glass fibers in a solution of the glycine-bridged polyamine-silane coupling agent for hydrolysis, filtering and drying.

[0022] The immersion hydrolysis method is: passing the solution of glycine-bridged polyamine-silane coupling agent and the impregnating agent in turn through the glass fiber drawing tower, or mixing the solution of glycine-bridged polyamine-silane coupling agent into the impregnating agent tank.

[0023] The mass ratio of the silicylic acid-bridged polyamine coupling agent to the glass fiber is 0.5% to 3%.

[0024] The present invention also provides the use of the modified glass fiber in preparing a fiber-reinforced polymer, wherein the polymer is a thermosetting material or a thermoplastic polymer material.

[0025] The thermosetting material is polyurethane, unsaturated resin or epoxy resin, and the thermoplastic polymer material is polycarbonate, polyester, nylon 6, nylon 66 or nylon 1212.

[0026] Compared with other technologies, the present invention has the following beneficial technical effects:

[0027] (1) Compared with previous commercial silane coupling agents, the new glycine-bridged polyamine silane coupling agent has more reaction sites and can establish more chemical bonds on the surface of glass fibers, thereby improving the bonding strength between the silane coupling agent and the glass fibers.

[0028] (2) By connecting the silane coupling agent with the glycine-bridging polyamine compound, on the one hand, the coverage of the polyamine on the glass fiber surface is improved; on the other hand, the amide bonds produced by the reaction of glycine with polyamine, the reaction of isocyanate with polyamine, and the active NH bonds in the structure of the polyamine compound form more hydrogen bonds with the oxygen-containing polymer matrix material, thereby increasing the interaction force between the reinforced glass fiber and the resin matrix material, and exhibiting better mechanical properties on a macro scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the Fourier transform infrared spectrum of glycine-bridged diethylenetriamine silane coupling agent DETA-GBSilane in Example 1.

[0030] Figure 2 Example 1 Glycine bridged diethylenetriamine silane coupling agent DETA-GBSilane H NMR spectrum 1 HNMR.

[0031] Figure 3 This is the mass spectrum of glycine-bridged diethylenetriamine silane coupling agent DETA-GBSilane in Example 1.

[0032] Figure 4 This is the thermogravimetric diagram of the modified glass fiber of Example 4.

[0033] Figure 5 This is a graph showing the tensile strength test of the glass fiber-nylon 6 composite material of Example 5.

[0034] Figure 6 This is a graph showing the impact strength test of the glass fiber-nylon 6 composite material of Example 5. DETAILED DESCRIPTION

[0035] The following is a further detailed description of the preparation method of the glycine-bridged polyamine silane coupling agent of the present invention, which is used to treat the surface of glass fiber and the treated glass fiber for preparing polymer composite materials in conjunction with specific examples, but this embodiment is not intended to limit the scope of protection of the present invention.

[0036] The content of silane coupling agent on the surface of glass fiber was determined by thermogravimetric analysis, and the specific method was as follows: thermogravimetric-differential thermal analysis was tested on a NETZSCH STA 409PC synchronous thermal analyzer. The heating rate was 10°C / min, the atmosphere was air, and the air flow rate was 50 mL / min.

[0037] Composite material specimen preparation method and mechanical property testing method

[0038] The composite materials with different compositions were dried at 80 °C for 6 h and injection molded into standard specimens according to ASTM D256-2010 and ASTM D638-2010, with the injection temperature at 240 °C and the mold temperature at 60 °C. Before the test operation, the specimens were placed in standard laboratory conditions of (25 ± 2) °C and relative humidity at (50 ± 5)% for 24 h, and then the tensile strength, flexural strength and impact strength were tested respectively. The tensile strength was in accordance with ISO527 "Fiber Reinforced Plastic Tensile Properties Test Standard", and the cantilever beam notched impact strength was in accordance with ISO179 "Fiber Reinforced Plastic Impact Properties Test Standard".

[0039] Comparative Example 1: Aminopropyltriethoxysilane KH550 treated glass fiber

[0040] KH550 and water were mixed into a silane treatment solution of a certain concentration, and the pH was adjusted to 4.0 with acetic acid. 100 g of glass fiber and 1000 mL of silane treatment solution (mass ratio of glass fiber to treatment solution = 1:10) were added to a 2000 mL three-necked flask in sequence. Nitrogen was introduced for protection, and the stirring paddle was turned on at a stirring speed of 200 r / min. The temperature was raised to 70 °C and maintained at 70 °C for 2 h. After the reaction was completed, the treatment solution was removed by filtration. The obtained glass fiber was repeatedly washed with anhydrous ethanol for 3 times, and then the treated glass fiber was placed in a vacuum drying oven at 40 °C for drying, bagged, sealed, and set aside.

[0041] Example 1 Synthesis of Glycine-bridged Ethylenediamine Silane Coupling Agent EDA-GBSilane

[0042] The reaction proceeds according to the following formula:

[0043] .

[0044] (1) Synthesis of glycine methyl ester hydrochloride:

[0045] 5.00 g of glycine was added to a flask, and 100 mL of methanol was added. Under ice bath conditions, the system was maintained at 0 °C, and 8.40 g of SOCl2 was added dropwise. After the addition was complete, the reaction was allowed to react at room temperature and stirred overnight. After the reaction was completed, vacuum distillation was performed. After the reaction liquid was reduced, an appropriate amount of dichloromethane was added and rotary distillation was continued. The operation was repeated twice, and the mixture was rotary dried to obtain a white solid (6.53 g).

[0046] (2) Synthesis of glycine methyl ester:

[0047] 6.53 g of crude glycine methyl ester hydrochloride was dissolved in 60 mL of dichloromethane to form a white suspension, and then a slightly excess amount of triethylamine was added to react at room temperature overnight. After the reaction was completed, the mixture was filtered and the filter cake was rinsed with dichloromethane several times. After a period of vacuum distillation, a small amount of white solid was precipitated, which was extracted with ether and vacuum distilled to obtain glycine methyl ester (2.36 g).

[0048] (3) Synthesis of glycine formamide:

[0049] Under Ar protection, 2.36 g of glycine methyl ester was dissolved in methanol, and then a slightly excess of ethylenediamine was added to react overnight. After the reaction was completed, it was first distilled under reduced pressure at 50 °C to spin out some methanol and ethylenediamine, and then silica gel was added for rotary evaporation, and purified by silica gel column chromatography. The ratio of column chromatography developing solvent was MeOH: DCM: Et3N = 10:10:1. After purification, the product glycine formamide (2.32 g) was obtained.

[0050] (4) Synthesis of glycine-bridged ethylenediamine silane coupling agent:

[0051] Under Ar protection, the above 2.32 g of glycine amide was dissolved in 50 mL of tetrahydrofuran, and 5.56 g of isocyanate propyl triethoxysilane was added to the solution, reacted at room temperature, and stirred overnight. After the reaction was completed, the solvent was removed by vacuum distillation, and the residue was washed with dehydrated n-hexane. Filtered and dried to obtain glycine-bridged ethylenediamine silane coupling agent EDA-GBSilane (8.04 g).

[0052] The structural test is attached. Figure 1-3 .

[0053] Example 2 Synthesis of Glycine-bridged Diethylenetriamine Silane Coupling Agent DETA-GBSilane

[0054] (1) Synthesis of glycine methyl ester hydrochloride:

[0055] 50.0 g of glycine was added to a flask, and 500 mL of methanol was added. The system was maintained at 0 °C under ice bath conditions, and 84.0 g of SOCl2 was added dropwise. After the addition was complete, the reaction was carried out at 30 °C for 12 hours. After the reaction was completed, the reaction was distilled under reduced pressure. After the reaction liquid was reduced, an appropriate amount of dichloromethane was added and the rotary evaporation was continued. The operation was repeated twice, and the reaction was dried by rotary evaporation to obtain a white solid (63.5 g).

[0056] (2) Synthesis of glycine methyl ester:

[0057] 63.5 g of crude glycine methyl ester hydrochloride was dissolved in 500 mL of dichloromethane to form a white suspension, and then a slightly excess amount of triethylamine was added to react at room temperature overnight. After the reaction was completed, the mixture was filtered and the filter cake was rinsed with dichloromethane several times. After a period of vacuum distillation, a small amount of white solid was precipitated, which was extracted with ether and vacuum distilled to obtain glycine methyl ester (25.4 g).

[0058] (3) Synthesis of glycine formamide:

[0059] Under Ar protection, 25.4 g of glycine methyl ester was dissolved in methanol, and then a slightly excess of diethylenetriamine was added to react overnight. After the reaction was completed, it was first distilled under reduced pressure at 60 °C, and some methanol and diethylenetriamine were spun out. Then silica gel was added for rotary evaporation, and purified by silica gel column chromatography. The ratio of column chromatography developing solvent was MeOH: DCM: Et3N = 10:10:1. After purification, an oily product glycine formamide (24.8 g) was obtained.

[0060] (4) Synthesis of glycine-bridged diethylenetriamine silane coupling agent DETA-GBSilane:

[0061] Under Ar protection, the above 24.8 g of glycine amide was dissolved in 300 mL of tetrahydrofuran, and 56.0 g of isocyanate propyl triethoxysilane was added to the solution, reacted at room temperature, and stirred overnight. After the reaction was completed, the solvent was removed by vacuum distillation, and the residue was washed with dehydrated n-hexane. Filtered and dried to obtain glycine-bridged diethylenetriamine silane coupling agent DETA-GBSilane (82.5 g).

[0062] Example 3 Synthesis of Glycine-bridged Triethylenetetramine Silane Coupling Agent TETA-GBSilane

[0063] (1) Synthesis of glycine methyl ester hydrochloride:

[0064] 25.0 g of glycine was added to a flask, and 200 mL of methanol was added. The system was maintained at 0 °C under ice bath conditions, and 42.0 g of SOCl2 was added dropwise. After the addition was complete, the reaction was carried out at 40 °C for 8 hours. After the reaction was completed, the reaction was distilled under reduced pressure. After the reaction liquid was reduced, an appropriate amount of dichloromethane was added and the rotary evaporation was continued. The operation was repeated twice, and the mixture was dried by rotary evaporation to obtain white solid glycine methyl ester hydrochloride (32.8 g).

[0065] (2) Synthesis of glycine methyl ester:

[0066] 32.8 g of crude glycine methyl ester hydrochloride was dissolved in 200 mL of dichloromethane to form a white suspension, and then a slightly excess amount of triethylamine was added to react at room temperature overnight. After the reaction was completed, the mixture was filtered and the filter cake was rinsed with dichloromethane several times. After a period of vacuum distillation, a small amount of white solid was precipitated, which was extracted with ether and vacuum distilled to obtain glycine methyl ester (12.5 g).

[0067] (3) Synthesis of glycine formamide:

[0068] Under Ar protection, 12.5 g of glycine methyl ester was dissolved in methanol, and then a slightly excessive amount of triethylenetetramine was added to react at 50 ° C for 12 hours. After the reaction was completed, it was first distilled under reduced pressure at 60 ° C, and some methanol and triethylenetetramine were spun out. Then silica gel was added for rotary evaporation and purified by silica gel column chromatography. The ratio of column chromatography developing solvent was MeOH: DCM: Et3N = 10:10:1. After purification, an oily product glycine formamide (13.2 g) was obtained.

[0069] (4) Synthesis of glycine-bridged triethylenetetramine silane coupling agent TETA-GBSilane:

[0070] Under Ar protection, the above 13.2 g of glycine amide was dissolved in 200 mL of tetrahydrofuran, and 28.0 g of isocyanate propyl triethoxysilane was added to the solution, reacted at room temperature, and stirred overnight. After the reaction was completed, the solvent was removed by vacuum distillation, and the residue was washed with dehydrated n-hexane. Filtered and dried to obtain glycine-bridged triethylenetetramine silane coupling agent TETA-GBSilane (43.5 g).

[0071] Example 4 Treatment of glass fiber surface with glycine-bridged ethylenediamine silane coupling agent EDA-GBSilane

[0072] Glycine-bridged ethylenediamine silane coupling agent EDA-GBSilane was mixed with water to prepare a silane treatment solution of a certain concentration. The pH was adjusted to 4.0 with acetic acid. 100 g of glass fiber and 1000 mL of silane treatment solution (mass ratio of glass fiber to treatment solution = 1:10) were added to a 2000 mL three-necked flask in sequence. Nitrogen was introduced for protection. The stirring paddle was turned on with a stirring speed of 200 r / min. The temperature was raised to 70 °C and maintained at 70 °C for 2 h. After the reaction was completed, the treatment solution was removed by filtration. The obtained glass fiber was repeatedly washed with anhydrous ethanol for 3 times. Then the treated glass fiber was dried in a vacuum drying oven at 40 °C, bagged, sealed and set aside. The mass ratios of silane coupling agent to glass fiber were 0.5%, 1.0%, 1.5% and 2.0%, respectively. The glass fibers modified with different concentrations of silane coupling agent were recorded as GF-GBSilane-0.5, GF-GBSilane-1.0, GF-GBSilane-1.5 and GF-GBSilane-2.0 (the numbers represent the amount of silane coupling agent used).

[0073] Determination of silane coupling agent content on glass fiber surface Figure 4 .

[0074] Example 5 Preparation of EDA-GBSilane treated glass fiber-nylon 6 composite material

[0075] Nylon 6 is first dehydrated and dried at 105 °C for 24 hours. Weigh the glass fiber surface treated with EDA-GBSilane and mix it with nylon 6 in a twin-screw extruder, with a glass fiber mass fraction of 40%. The extrusion temperature is 200-250 °C, the main engine speed is 120 r / min, the feed speed is 25 r / min, pelletizing, and vacuum drying. After the sample is dried, take it out, bag it, and set it aside.

[0076] The mechanical properties of the composite materials are shown in the attached Figure 5-6 .

[0077] Example 6 Preparation of DETA-GBSilane treated glass fiber-epoxy resin composite material

[0078] The raw materials used are bisphenol A epoxy resin model LY3572; curing agent model HY918; benzylamine accelerator DY602 produced by Huntsman Advanced Chemical Materials Co., Ltd. The weight of each component is calculated according to resin: glass fiber: curing agent: accelerator = 100: 30: 85: 0.5. First, weigh the resin and pour it into the mixing tank of the vacuum casting equipment. Then weigh the curing agent and accelerator in turn and mix them evenly. Pour them into the mixing tank. The temperature of the mixing tank is controlled at (45 ± 2) ° C. Vacuum is used to remove bubbles inside the material. Finally, pouring begins at 60 ° C and curing is carried out at 120 ° C for 12 h. After curing, take out the sample.

[0079] Compared with the epoxy composite reinforced with GF-KH550-1.0, the tensile strength of the epoxy composite reinforced with GF-DETA-GBSilane was increased by 75% and the fracture impact strength was increased by 118%.

[0080] Example 7 Preparation of TETA-GBSilane treated glass fiber-polyurethane composite material

[0081] Polyether polyol 330N and polycarbonate diol PCDL (PCDL / 330N mass ratio is 33:67) were vacuum dehydrated at 110~120℃ for 2h, and when the temperature dropped to 50~60℃, silane coupling agent modified glass fiber was added in batches in equal amounts, and stirred for 5min after each addition. After the last addition, the stirring time was 25min, and then the measured 4,4′-diphenylmethane diisocyanate MDI was added, and the temperature was raised to 75℃ for reaction for 3h. The measured mixed chain extender 1,4-butanediol BDO / ethylene glycol EG (BDO / EG mass ratio is 70:30) was added to the prepolymer and fully mixed (chain extension coefficient 1.0), poured into a mold at room temperature (23±2℃) and 8% humidity, and tested after curing at room temperature for 7d.

[0082] When the glass fiber content is 5%, the comprehensive performance of the composite material is the best. Compared with the polyurethane elastomer with 5% GF-KH550-1.0 modified glass fiber, the tensile strength of the composite material increased from 10.5MPa to 15.6MPa, and the elongation increased from 694.0% to 932.8% by adding 5% GF-TETA-GBSilane; the initial decomposition temperature increased from 259℃ to 280℃.

Claims

1. A glycine-bridged polyamine silane coupling agent, characterized in that: The glycine-bridged polyamine silane coupling agent is obtained by combining trialkoxysilane and a polyamine compound through amide bond bridging.

2. The glycine-bridged polyamine silane coupling agent according to claim 1, characterized in that: The polyamine compound includes a single component or a mixture of amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and hexaethyleneheptamine.

3. The glycine-bridged polyamine silane coupling agent according to claim 1, characterized in that: The trialkoxysilane is isocyanatepropyltriethoxysilane or isocyanatepropyltrimethoxysilane.

4. The method for preparing the glycine-bridged polyamine silane coupling agent according to claim 1, characterized in that: The steps include: Synthesis of Glycine Methyl Ester Hydrochloride: Take glycine and add it into a flask, add methanol to dissolve it, add SOCl2 dropwise at 0°C, react at 25°C for 12-24h, and after the reaction is completed, distill under reduced pressure, and then rotary evaporate to obtain a white solid product, glycine methyl ester hydrochloride; Synthesis of Glycine Methyl Ester: The crude product of glycine methyl ester hydrochloride was dispersed in dichloromethane, and triethylamine was added for neutralization. The reaction was carried out at 25°C for 12-24 hours. After the reaction was completed, the product was collected by filtration, extracted with ether, and distilled under pressure to obtain a yellow liquid product, glycine methyl ester; Synthesis of Glycine Carboxamide: Under Ar protection, glycine methyl ester was dissolved in methanol, and then a polyamine compound was added to react overnight. After the reaction was completed, the product was purified by vacuum distillation, rotary evaporation and silica gel column chromatography, and finally an oily liquid product glycine carboxamide was obtained; Synthesis of Glycine-bridged Polyamine Silane Coupling Agent: Under Ar protection, glycine formamide was dissolved in tetrahydrofuran, isocyanate propyl trialkoxy silane was added, reacted at room temperature, stirred overnight, and after the reaction was completed, the solvent was distilled off under reduced pressure, filtered, and dried to obtain a white solid product, glycine bridged polyamine silane coupling agent.

5. Use of the glycine-bridged polyamine silane coupling agent according to claim 1 in the preparation of modified glass fiber, characterized in that: include: The glass fiber is immersed in the solution of the glycine-bridged polyamine silane coupling agent for hydrolysis, filtered and dried.

6. The use according to claim 5, characterized in that: The immersion hydrolysis method is: passing the solution of glycine-bridged polyamine-silane coupling agent and the impregnating agent in turn through the glass fiber drawing tower, or mixing the solution of glycine-bridged polyamine-silane coupling agent into the impregnating agent tank.

7. The use according to claim 5, characterized in that: The mass ratio of the silicyl glycine-bridged polyamine coupling agent to the glass fiber is 0.5% to 3%.

8. Use of the modified glass fiber according to claim 5 in the preparation of fiber-reinforced polymers, characterized in that: The polymer is a thermosetting material or a thermoplastic polymer material.

9. The use according to claim 8, characterized in that: The thermosetting material is polyurethane, unsaturated resin or epoxy resin, and the thermoplastic polymer material is polycarbonate, polyester, nylon 6, nylon 66 or nylon 1212.

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