A preparation method of light / heat synergistically cured epoxy resin-based composite material

Abstract

The present invention relates to a method for preparing a light / heat synergistically cured epoxy resin-based composite material, which solves the technical problems that the resin fiber ratio is difficult to accurately control, the uniform distribution is difficult to achieve, and the composite material performance is not ideal in the preparation of existing materials. The method comprises the following steps: (1) raw material proportioning: the epoxy resin matrix, the active diluent, the photoinitiator, and the thermal initiator are uniformly stirred at high speed under light-proof conditions to obtain a resin system; (2) prepreg preparation: the resin system obtained in step (1) is irradiated under visible light, coated into a resin film after viscosity enhancement, and then the resin film and the reinforcing material are compounded by a prepreg machine to obtain a prepreg; (3) composite material preparation: the prepreg obtained in step (2) is cut and laid, and a free radical thermal curing reaction is initiated to obtain a light / heat synergistically cured epoxy resin-based composite material. The present invention can be used in the field of preparation of epoxy resin-based composite materials.

Description

Technical Field

[0001] The invention relates to a method for preparing a composite material, in particular to a method for preparing a light / heat synergistically cured epoxy resin-based composite material. Background Art

[0002] At present, as the intermediate with the largest consumption of composite materials, prepreg has gradually become the preferred material for corrosion protection and repair of metal pipes. However, the commonly used medium and high temperature thermal curing process often has problems such as long molding cycle and low efficiency of composite materials, which makes outdoor construction difficult. Photocuring technology has the characteristics of rapid light initiation and rapid curing, which has enabled it to develop rapidly in the field of repair technology, but there are also some technical problems: the photocuring resin has a low molecular weight and low viscosity, which cannot meet the process requirements of hot melt two-step prepreg, and can only be prepared by wet impregnation process; at the same time, the attenuation of the light source by the resin and fiber will also lead to insufficient curing in the shadow area.

[0003] The Chinese invention patent application with publication number CN104312192A discloses a method for preparing prepreg by impregnating glass fiber with vinyl ester resin, designs a "light-heat composite initiation system", realizes the free radical curing reaction of vinyl ester through dual light / heat initiation, and solves the problem of poor curing uniformity of prepreg caused by single light curing.

[0004] However, the above-mentioned wet process usually makes it difficult to accurately control the resin-fiber ratio and achieve uniform distribution, which in turn affects the performance of the composite material. Summary of the invention

[0005] The present invention is to solve the technical problems existing in the existing material preparation methods that the resin fiber ratio is difficult to accurately control, the uniform distribution is not easy to achieve, and the composite material performance is not ideal. It provides a preparation method of light / heat synergistically cured epoxy resin-based composite materials that can accurately control the resin fiber ratio, achieve uniform distribution, and have good composite material performance.

[0006] To this end, the present invention provides a method for preparing a light / heat synergistically cured epoxy resin-based composite material, which comprises the following steps: (1) raw material ratio: an epoxy resin matrix, an active diluent, a photoinitiator, and a thermal initiator having a mass fraction ratio of (77-94.8):(5-20):(0.1-2):(0.1-1) are uniformly stirred at high speed under light-proof conditions to obtain a resin system; (2) prepreg preparation: the resin system obtained in the step (1) is exposed to visible light for 1-5 minutes, and after viscosity enhancement, it is coated into a resin film, wherein the resin light curing reaction degree is 20%-30%, and the viscosity at room temperature reaches 7-10 Pa.s, and then the resin film and a reinforcing material are compounded by a prepreg machine to obtain a prepreg; (3) composite material preparation: the prepreg obtained in the step (2) is cut and laid, and a free radical thermal curing reaction is initiated at 50-80°C to obtain a light / heat synergistically cured epoxy resin-based composite material.

[0007] Preferably, the resin matrix contains epoxy groups that can undergo cationic ring-opening reaction, preferably one of alicyclic epoxy resin, aliphatic epoxy resin, bisphenol A glycidyl ether, bisphenol F glycidyl ether or a combination thereof.

[0008] Preferably, the reactive diluent contains an unsaturated double bond that can undergo free radical polymerization, and is preferably one or a combination of ethylene glycol diacrylate, propylene glycol diacrylate, hexanediol diacrylate, trimethylolpropane triacrylate (TMPTA), and vinyl monomers.

[0009] Preferably, the photoinitiator is a cationic one, preferably one of 4,4-dimethyl-diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluorophosphate (IOPF), (4-octyloxyphenyl)phenyliodonium hexafluoroantimonate (OPIA) or a combination thereof.

[0010] Preferably, the thermal initiator is a free radical type, preferably one of benzoyl peroxide (BPO), didecanoyl peroxide (LDEP), dodecanoyl peroxide (LPO), tetraphenylethylene glycol (TPED) or a combination thereof.

[0011] Preferably, the reinforcing material is one or more of glass fiber, quartz fiber, polyester fiber or fabric.

[0012] The present invention has the following beneficial effects:

[0013] (1) The present invention designs a "light / heat dual-initiator epoxy resin system" and adopts a reasonable amount of photoinitiator. The epoxy resin cationic curing reaction can be quickly initiated by irradiating light for a few minutes, thereby increasing the viscosity of the resin system and meeting the coating process of the hot-melt two-step prepreg preparation process;

[0014] (2) The prepreg of the present invention can complete the curing and crosslinking at a low temperature of 50-80°C by initiating the double bond reaction of the active diluent through free radicals, and at the same time realize the final curing of the temperature-sensitive epoxy resin cation, so as to achieve the complete curing of the prepreg by light / heat synergy;

[0015] (3) The prepreg obtained by the present invention is paved on the surface of the metal pipe. According to the time-temperature equivalence principle, it can be completely cured even if placed outdoors for a long time without additional heating, which greatly improves the convenience of outdoor on-site construction such as pipeline corrosion protection and structural damage. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with embodiments.

[0017] Example 1

[0018] Design of light / heat synergistic curing epoxy resin system: 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexylcarboxylate (ECC), tripropylene glycol diacrylate (TPGDA), (4-octyloxyphenyl)benzidonium hexafluoroantimonate (OPIA), and benzoyl peroxide (BPO) are stirred at high speed to obtain a light / heat curing resin mixture, in which the mass fraction ratio of each component is 78:20:1:1.

[0019] Preparation of prepreg: The prepared resin liquid is exposed to visible light for 1 minute to carry out cationic polymerization of epoxy groups, and the resin prepolymer is thickened to obtain a room temperature viscosity of 10Pa.s; the resin prepolymer is coated on release paper to prepare a film, and is compounded with E-glass fiber fabric through a prepreg machine to prepare prepreg.

[0020] Preparation of composite materials: The prepreg was cut and laid, and placed in a hot press to apply a temperature of 50°C and a pressure of 8MPa for curing to obtain a light / heat synergistically cured epoxy resin-based composite material.

[0021] Example 2

[0022] Design of light / heat synergistic curing epoxy resin system: Bisphenol F diglycidyl ether (DGEBF), 1,6-hexanediol diacrylate (HDDA), (4-octyloxyphenyl)benzidonium hexafluoroantimonate (OPIA), and tetraphenylethylene glycol (TPED) are stirred at high speed to obtain a light / heat curing resin mixture, in which the mass fraction ratio of each component is 89.3:10:0.5:0.2.

[0023] Preparation of prepreg: The prepared resin liquid is exposed to visible light for 2 minutes to carry out cationic polymerization of epoxy groups, and the resin prepolymer is thickened to obtain a room temperature viscosity of 9 Pa.s; the resin prepolymer is coated on release paper to prepare a film, and is compounded with E-glass fiber fabric through a prepreg machine to prepare a prepreg.

[0024] Preparation of composite materials: The prepreg was cut and laid, and placed in a hot press to apply a temperature of 70°C and a pressure of 9MPa for curing to obtain a light / heat synergistically cured epoxy resin-based composite material.

[0025] Example 3

[0026] Design of light / heat synergistic curing epoxy resin system: The resin system in Example 1 was used and stirred at high speed to obtain a light / heat curing resin mixture, in which the mass fraction ratio of each component was 94.8:5:0.1:0.1.

[0027] Preparation of prepreg: The prepared resin liquid is exposed to visible light for 5 minutes to carry out cationic polymerization of epoxy groups, and the resin prepolymer is thickened to obtain a room temperature viscosity of 7Pa.s; the resin prepolymer is coated on release paper to prepare a film, and is compounded with E-glass fiber fabric through a prepreg machine to prepare a prepreg.

[0028] Preparation of composite materials: The prepreg was cut and laid, and placed in a hot press to apply a temperature of 80°C and a pressure of 10 MPa for curing to obtain a light / heat synergistically cured epoxy resin-based composite material.

[0029] Example 4

[0030] Design of light / heat synergistic curing epoxy resin system: The resin system formula and mass fraction ratio in Example 1 are used, and the light / heat curing resin mixture is obtained by high-speed stirring.

[0031] Preparation of prepreg: The prepared resin liquid is exposed to visible light for 1 minute to carry out cationic polymerization of epoxy groups, and the resin prepolymer is thickened to obtain a room temperature viscosity of 10Pa.s; the resin prepolymer is coated on release paper to prepare a film, and is compounded with E-glass fiber fabric through a prepreg machine to prepare prepreg.

[0032] Preparation of composite materials: The prepreg was cut and laid, and placed in a hot press to apply a temperature of 80°C and a pressure of 8MPa for curing to obtain a light / heat synergistically cured epoxy resin-based composite material.

[0033] Comparative Example 1

[0034] Design of light-curing epoxy resin system: The resin formula was designed with reference to Example 3, but no thermal initiator was added in Comparative Example 1. A light / thermal curing resin mixture was obtained by high-speed stirring, and the mass fraction ratio of each component was 94.9:5:0.1.

[0035] Preparation of prepreg: The prepared resin liquid is exposed to visible light for 5 minutes to carry out cationic polymerization of epoxy groups, and the resin prepolymer is thickened to obtain a room temperature viscosity of 7Pa.s; the prepolymer is coated on release paper to prepare a film, and is compounded with E-glass fiber fabric through a prepreg machine to prepare prepreg.

[0036] Preparation of composite materials: The prepreg was cut and laid, and placed in a hot press to apply a temperature of 80°C and a pressure of 10 MPa for curing. The curing time of the prepreg in comparative example 1 was prolonged and could not be completely cured. The inner layer of the obtained composite material was sticky and had low mechanical strength.

[0037] Table 1: Mechanical properties of Examples 1-4 and Comparative Example 1

[0038] Tensile strength / MPa Tensile modulus / GPa Bending strength / MPa Flexural modulus / GPa Example 1 365 12.1 402 13.5 Example 2 514 20.4 608 22.3 Example 3 380 14.4 427 16.0 Example 4 428 19.2 506 21.8 Comparative Example 1 234 6.05 258 7.44

[0039] It can be seen from Table 1 that the epoxy resin type, thermal curing temperature, and the addition of thermal initiator all have an impact on the properties of the composite materials.

[0040] However, what is described above is only a specific embodiment of the present invention and should not be used to limit the scope of implementation of the present invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the scope of protection of the present invention should still fall within the scope covered by the claims of the present invention.

Claims

1. A method for preparing a light / heat synergistically cured epoxy resin-based composite material, characterized in that: The steps include: (1) Raw material ratio: an epoxy resin matrix, a reactive diluent, a photoinitiator and a thermal initiator in a mass ratio of (78-94.8): (5-20): (0.1-1): (0.1-1) are uniformly stirred at high speed under light-proof conditions to obtain a resin system; The epoxy resin matrix contains epoxy groups that can undergo cationic ring-opening reactions; the epoxy resin matrix is ​​one of alicyclic epoxy resins, bisphenol A glycidyl ether, bisphenol F glycidyl ether, or a combination thereof; The reactive diluent contains an unsaturated double bond that can undergo free radical polymerization reaction; the reactive diluent is one or a combination of ethylene glycol diacrylate, propylene glycol diacrylate, hexanediol diacrylate, trimethylolpropane triacrylate; The photoinitiator is a cationic type; the photoinitiator is one of 4,4-dimethyl-diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluorophosphate, (4-octyloxyphenyl)phenyliodonium hexafluoroantimonate or a combination thereof; The thermal initiator is a free radical type; the thermal initiator is one of benzoyl peroxide, didecanoyl peroxide, dodecanoyl peroxide, tetraphenyl glycol or a combination thereof; (2) Preparation of prepreg: The resin system obtained in step (1) is exposed to visible light for 1 to 5 minutes, and after viscosity enhancement, it is coated into a resin film, wherein the degree of light curing reaction of the resin is 20% to 30%, and the viscosity at room temperature reaches 7 to 10 Pa.s, and then the resin film and the reinforcing material are compounded by a prepreg machine to obtain a prepreg; (3) Preparation of composite materials: The prepreg obtained in step (2) is cut and laid, and a free radical thermal curing reaction is initiated at 50-80° C. to obtain a light / heat synergistically cured epoxy resin-based composite material.

2. The method for preparing the light / heat synergistically cured epoxy resin-based composite material according to claim 1, characterized in that: The reinforcing material is one or more of glass fiber, quartz fiber and polyester fiber.