Photocuring modified epoxy resin as well as preparation method and application thereof

Abstract

The invention belongs to the field of resin synthesis, and particularly relates to light-cured modified epoxy resin as well as a preparation method and application thereof. The preparation raw materials of the light-cured modified epoxy resin provided by the invention comprise a phase A and a phase B, wherein the phase A comprises DEM resin, and preparation raw materials of the DEM resin comprise DGEBA resin, an acrylic monomer, a reactive diluent, a polymerization inhibitor and a catalyst; and the phase B comprises a free radical photoinitiator and a polyether amine epoxy thermal curing agent. The light-cured modified epoxy resin can be rapidly cured under the illumination condition, and due to the special polyether amine epoxy thermal curing agent, the cured product has certain mechanical properties and higher stability, and is particularly suitable for being used in the field of casting.

Description

Technical Field

[0001] The invention relates to the field of resin synthesis, and in particular to a photocurable modified epoxy resin and a preparation method and application thereof. Background Art

[0002] Bisphenol A epoxy resin (DGEBA) is a widely used epoxy resin. Its unique molecular structure enables it to have excellent chemical corrosion resistance, strong adhesion, and high strength and high modulus mechanical properties. In terms of curing technology, DGEBA mainly relies on two methods: thermal curing and photocuring. For example, Chinese patent CN118834604A discloses a high temperature resistant photocuring transfer adhesive containing DGEBA, and its curing process includes two stages: UV pre-curing and thermal curing.

[0003] The thermal curing process can give epoxy resin products excellent mechanical properties and bonding properties, ensuring a high degree of curing, but this method has a long curing cycle and high energy consumption, and is difficult to adapt to application scenarios that require rapid curing. Relatively speaking, UV light curing technology is a greener industrial technology. With its advantages of fast curing speed, high production efficiency, and no volatile emissions during the curing process, light curing has been widely used in coatings, inks, adhesives and other fields. However, UV light curing technology has high requirements on the light transmittance of materials and limited curing depth. It is currently mainly used in the film field. Therefore, the development of new epoxy resins that can cure quickly and maintain good mechanical properties has become a hot topic in current research.

[0004] The existing DGEBA has a slow rate of cationic photocuring and limited curing depth, which makes it difficult to meet the requirements of high-performance materials. Therefore, it is particularly important to explore the theory of photocuring systems and optimize molecular structures. Considering that the thermal curing of epoxy resins is significantly affected by temperature, a feasible solution is to introduce unsaturated groups that can quickly change the temperature of the system into the epoxy resin structure, use the large number of hot-activated epoxy groups generated by the photocuring reaction of the unsaturated groups to polymerize, and use the heat cycle of the reaction itself to achieve the purpose of rapid curing, thereby improving the curing rate and curing depth while maintaining the mechanical properties of the material to meet the needs of more application scenarios. Summary of the invention

[0005] In order to solve the above technical problems, the first aspect of the present invention provides a photocurable modified epoxy resin, the preparation raw materials of which include phase A and phase B; wherein phase A includes DEM resin, and phase B includes a free radical photoinitiator and a polyetheramine epoxy thermosetting agent.

[0006] As an implementable case, the raw materials for preparing the DEM resin include: DGEBA resin, acrylic acid monomer, active diluent, inhibitor, and catalyst.

[0007] As an implementable example, the acrylic monomer includes: acrylic acid and / or methacrylic acid.

[0008] Furthermore, the acrylic acid monomer is methacrylic acid.

[0009] Furthermore, the molar ratio of the DGEBA resin to the acrylic acid monomer is (2-3):1.

[0010] Furthermore, the molar ratio of the DGEBA resin to the acrylic acid monomer is 2:1.

[0011] As an implementable case, the active diluent includes: one or more of 1,4-butanediol diglycidyl ether, 1,6-hexanediol diacrylate, and glycidyl methacrylate.

[0012] Furthermore, the active diluent is glycidyl methacrylate (GMA).

[0013] As an implementable case, the amount of the active diluent is 30-70% of the mass of the DEM resin.

[0014] Furthermore, the amount of the active diluent is 50% of the mass of the DEM resin.

[0015] As an implementable example, the catalyst includes benzyltriethylammonium chloride.

[0016] As an implementable case, the amount of the catalyst used is 0.1-1% of the mass of the DGEBA resin.

[0017] Furthermore, the amount of the catalyst used is 0.2% of the mass of the DGEBA resin.

[0018] As an implementable case, the inhibitor includes: p-hydroxyanisole and / or hydroquinone.

[0019] Furthermore, the polymerization inhibitor is p-hydroxyanisole.

[0020] As an implementable case, the dosage of the polymerization inhibitor is 0.1-1% of the mass of the DGEBA resin.

[0021] Furthermore, the dosage of the polymerization inhibitor is 0.1% of the mass of the DGEBA resin.

[0022] As an practicable case, the preparation method of the DEM resin comprises:

[0023] In a four-necked flask, first add DGEBA resin and polymerization inhibitor, wherein the polymerization inhibitor is used to inhibit the polymerization side reaction of carbon-carbon double bonds in acrylic acid monomer; then introduce nitrogen and heat to 50-60°C, stir evenly; then pour the acrylic acid monomer into a constant pressure funnel and drop it into the four-necked flask, while slowly heating to 110-125°C, add a catalyst and react for 2-3h, during which the acid value of the system is measured every 30min until the acid value of the system drops below 3mgKOH / g, and the reaction is terminated; cool to 30-40°C, add an active diluent, stir fully for 5-10min, and then discharge the material to obtain the product; the reaction formula is as follows:

[0024]

[0025] The present invention adopts DGEBA resin as a base resin for modification. In its molecular structure, each molecule has two epoxy functional groups. After being modified with methacrylic acid, the molecule still retains part of the epoxy functional groups and introduces unsaturated double bond functional groups. The modified product DEM resin has a double functional group reaction characteristic and can form a dense three-dimensional network space macromolecule through photocuring and cross-linking polymerization in a short time, which greatly shortens the curing molding process time of the epoxy resin.

[0026] As an implementable case, the free radical photoinitiator includes: one or more of 1173 initiator, 184 initiator, 2959 initiator, 907 initiator, 651 initiator, and TPO.

[0027] Furthermore, the free radical photoinitiator is 184 initiator (1-hydroxycyclohexyl phenyl ketone) and TPO.

[0028] Furthermore, the mass ratio of the 184 initiator to the DEM resin is (0.3-1):100.

[0029] Furthermore, the mass ratio of the 184 initiator to the DEM resin is 0.5:100.

[0030] Furthermore, the mass ratio of the TPO and DEM resins is (0.3-1):100.

[0031] Furthermore, the mass ratio of the TPO and DEM resins is 0.5:100.

[0032] As an implementable case, the brands of the polyetheramine epoxy thermal curing agent include: one of H-D230, H-D400, and H-T403.

[0033] Furthermore, the mass ratio of the polyetheramine epoxy thermal curing agent to the DEM resin is (20-40):100.

[0034] Furthermore, the mass ratio of the polyetheramine epoxy thermosetting agent with the brand name H-D230 to the DEM resin is (20-40):100.

[0035] Furthermore, the mass ratio of the polyetheramine epoxy thermosetting agent with the brand name H-D230 to the DEM resin is 22:100.

[0036] Furthermore, the mass ratio of the polyetheramine epoxy thermosetting agent with the brand name H-D400 to the DEM resin is (20-40):100.

[0037] Furthermore, the mass ratio of the polyetheramine epoxy thermal curing agent with the brand name H-D400 to the DEM resin is 39:100.

[0038] Furthermore, the mass ratio of the polyetheramine epoxy thermal curing agent with the brand name H-T403 to the DEM resin is (20-40):100.

[0039] Furthermore, the mass ratio of the polyetheramine epoxy thermal curing agent with the brand name H-T403 to the DEM resin is 24:100.

[0040] The amount of curing agent used needs to be calculated according to the type of polyetheramine epoxy thermosetting agent. Different polyetheramine epoxy thermosetting agents have different active hydrogen equivalents. In the present invention, based on the active hydrogen equivalent of the polyetheramine epoxy thermosetting agent and the epoxy equivalent of the DEM resin, the mass ratio of the polyetheramine epoxy thermosetting agent with the brand H-D230 and the DEM resin is further limited to 22:100, the mass ratio of the polyetheramine epoxy thermosetting agent with the brand H-D400 and the DEM resin is 39:100, and the mass ratio of the polyetheramine epoxy thermosetting agent with the brand H-T403 and the DEM resin is 24:100; this can ensure that the product has a shorter light curing time and certain mechanical properties.

[0041] The second aspect of the present invention provides a method for preparing a photocurable modified epoxy resin, comprising: mixing the raw materials of phase B, adding the raw materials to phase A, and stirring to mix the raw materials under light-proof conditions.

[0042] The third aspect of the present invention provides an application of a photocurable modified epoxy resin in the preparation of a casting, comprising: placing the photocurable modified epoxy resin in a vacuum oven for degassing for 5-10 minutes, and then irradiating it under a high-pressure mercury lamp for 10-20 minutes.

[0043] Beneficial Effects

[0044] (i) In the present invention, by introducing unsaturated double bond functional groups into the DEM resin, the modified product can form a dense three-dimensional network structure through photocuring in a short time, which greatly shortens the curing molding process time of the epoxy resin and improves production efficiency.

[0045] (ii) The modified product DEM resin in the present invention has a bifunctional reaction characteristic, which not only retains the advantages of epoxy resin, such as chemical resistance, bonding performance and high strength and high modulus mechanical properties, but also introduces unsaturated double bonds to enhance the reactivity of the material and the performance after curing.

[0046] (III) The present invention adopts a synergistic curing method of free radical photoinitiator and epoxy thermal curing agent, which can realize self-circulation of heat, so that the system can quickly heat up and cure under light conditions, forming a highly interpenetrating cross-linked structure, further improving the mechanical properties and thermal stability of the material.

[0047] (IV) The present invention provides a variety of polyetheramine epoxy thermosetting agents for selection, such as polyetheramine epoxy thermosetting agents with grades H-D230, H-D400 and H-T403. Since the curing agents have different active hydrogen equivalents and molecular weights, the dosage can be adjusted according to specific needs to meet the performance requirements of different application scenarios.

[0048] (V) Compared with the traditional thermal curing method, the light curing technology adopted in the present invention has the advantages of fast curing speed, high productivity, and no volatile matter generated during the curing process. It is in line with the development trend of green industrial technology and is conducive to reducing energy consumption and environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is the infrared spectra of DGEBA resin and DEM resin in Example 1.

[0050] Figure 2 This is the infrared spectra of the castings prepared in Examples 1-3 and Comparative Example 1.

[0051] Figure 3 Schematic diagram of the Barcol hardness of the castings prepared in Examples 1-3 and Comparative Example 1.

[0052] Figure 4 Schematic diagram of the mechanical properties of the castings prepared in Examples 1-3 and Comparative Example 1, wherein (a) represents a schematic diagram of tensile strength, (b) represents a schematic diagram of bending strength, (c) represents a schematic diagram of impact strength, and (d) represents a schematic diagram of elongation at break.

[0053] Figure 5 This is a SEM schematic diagram of the casting body prepared in Example 3 and Comparative Example 1.

[0054] Figure 6 Schematic diagram of the volume shrinkage of the castings prepared in Examples 1-3 and Comparative Example 1.

[0055] Figure 7 Schematic diagram of dynamic thermomechanical properties of the castings prepared in Examples 1-3 and Comparative Example 1, wherein (a) represents the relationship between storage modulus and temperature, and (b) represents the relationship between tanδ and temperature.

[0056] Figure 8 Schematic diagram of thermal stability performance of the castings prepared in Examples 1-3 and Comparative Example 1, wherein (a) represents a schematic diagram of residual carbon rate, and (b) represents a schematic diagram of DTG curve.

[0057] Fig. 9 This is a schematic diagram of the temperature-time variation relationship in the reaction of Example 3 and Comparative Example 1.

[0058] Fig.10 This is a schematic diagram of the DSC scanning results in the reaction of Example 3 and Comparative Example 1. DETAILED DESCRIPTION

[0059] Example 1

[0060] In the first aspect of this example, a photocurable modified epoxy resin is provided, and the raw materials for its preparation are phase A and phase B; wherein phase A is DEM resin, and phase B is a free radical photoinitiator and a polyetheramine epoxy thermosetting agent.

[0061] The raw materials for preparing the DEM resin are specifically: DGEBA resin, methacrylic acid, glycidyl methacrylate, p-hydroxyanisole, and benzyltriethylammonium chloride.

[0062] The molar ratio of the DGEBA resin to methacrylic acid is 2:1; the amount of glycidyl methacrylate is 50% of the mass of the DEM resin; the amount of p-hydroxyanisole is 0.2% of the mass of the DGEBA resin; and the amount of benzyltriethylammonium chloride is 0.1% of the mass of the DGEBA resin.

[0063] The preparation method of the DEM resin comprises: firstly adding DGEBA resin and p-hydroxyanisole into a four-necked flask, then introducing nitrogen and heating to 60°C, pouring methacrylic acid into a constant pressure funnel, adding dropwise into the four-necked flask, and heating to 115°C at the same time, adding benzyltriethylammonium chloride and reacting for 2h, measuring the acid value of the system every 30min during the reaction, until the acid value of the system drops below 3mgKOH / g, and the reaction is terminated; cooling to 40°C, adding glycidyl methacrylate, fully stirring for 5min, and then discharging to obtain the DEM resin.

[0064] The free radical photoinitiator is 184 initiator and TPO; the mass ratio of 184 initiator to DEM resin is 0.5:100; the mass ratio of TPO to DEM resin is 0.5:100.

[0065] The grade of the polyetheramine epoxy thermal curing agent is H-D230, and the mass ratio of the polyetheramine epoxy thermal curing agent with the grade of H-D230 to the DEM resin is 22:100.

[0066] The second aspect of this example provides a method for preparing a photocurable modified epoxy resin, which is specifically: under light-proof conditions, mix the raw materials of phase B, add them to phase A, and stir to mix.

[0067] The third aspect of this example provides an application of a photocurable modified epoxy resin, which is used in the preparation of a casting body. Specifically, the photocurable modified epoxy resin is placed in a vacuum oven for degassing for 5 minutes, and then placed under a high-pressure mercury lamp for irradiation for 15 minutes to obtain the product; the product is recorded as DEM / (184+TPO) / H-D230.

[0068] Example 2

[0069] In the first aspect of this example, a photocurable modified epoxy resin is provided, and the raw materials for its preparation are phase A and phase B; wherein phase A is DEM resin, and phase B is a free radical photoinitiator and a polyetheramine epoxy thermosetting agent.

[0070] The raw materials for preparing the DEM resin are specifically: DGEBA resin, methacrylic acid, glycidyl methacrylate, p-hydroxyanisole, and benzyltriethylammonium chloride.

[0071] The molar ratio of the DGEBA resin to methacrylic acid is 2:1; the amount of glycidyl methacrylate is 50% of the mass of the DEM resin; the amount of p-hydroxyanisole is 0.2% of the mass of the DGEBA resin; and the amount of benzyltriethylammonium chloride is 0.1% of the mass of the DGEBA resin.

[0072] The preparation method of the DEM resin comprises: firstly adding DGEBA resin and p-hydroxyanisole into a four-necked flask, then introducing nitrogen and heating to 60°C, pouring methacrylic acid into a constant pressure funnel, adding dropwise into the four-necked flask, and heating to 115°C at the same time, adding benzyltriethylammonium chloride and reacting for 2h, measuring the acid value of the system every 30min during the reaction, until the acid value of the system drops below 3mgKOH / g, and the reaction is terminated; cooling to 40°C, adding glycidyl methacrylate, fully stirring for 5min, and then discharging to obtain the DEM resin.

[0073] The free radical photoinitiator is 184 initiator and TPO; the mass ratio of 184 initiator to DEM resin is 0.5:100; the mass ratio of TPO to DEM resin is 0.5:100.

[0074] The grade of the polyetheramine epoxy thermal curing agent is H-D400, and the mass ratio of the polyetheramine epoxy thermal curing agent with the grade of H-D400 to the DEM resin is 39:100.

[0075] The second aspect of this example provides a method for preparing a photocurable modified epoxy resin, which is specifically: under light-proof conditions, mix the raw materials of phase B, add them to phase A, and stir to mix.

[0076] The third aspect of this example provides an application of a photocurable modified epoxy resin, which is used in the preparation of a casting body. Specifically, the photocurable modified epoxy resin is placed in a vacuum oven for degassing for 5 minutes, and then placed under a high-pressure mercury lamp for irradiation for 15 minutes. The product is recorded as DEM / (184+TPO) / H-D400.

[0077] Example 3

[0078] In the first aspect of this example, a photocurable modified epoxy resin is provided, and the raw materials for its preparation are phase A and phase B; wherein phase A is DEM resin, and phase B is a free radical photoinitiator and a polyetheramine epoxy thermosetting agent.

[0079] The raw materials for preparing the DEM resin are specifically: DGEBA resin, methacrylic acid, glycidyl methacrylate, p-hydroxyanisole, and benzyltriethylammonium chloride.

[0080] The molar ratio of the DGEBA resin to methacrylic acid is 2:1; the amount of glycidyl methacrylate is 50% of the mass of the DEM resin; the amount of p-hydroxyanisole is 0.2% of the mass of the DGEBA resin; and the amount of benzyltriethylammonium chloride is 0.1% of the mass of the DGEBA resin.

[0081] The preparation method of the DEM resin comprises: firstly adding DGEBA resin and p-hydroxyanisole into a four-necked flask, then introducing nitrogen and heating to 60°C, pouring methacrylic acid into a constant pressure funnel, and dripping it into the four-necked flask, while slowly heating to 115°C, adding benzyltriethylammonium chloride to react for 2h, measuring the acid value of the system every 30min during the reaction, until the acid value of the system drops below 3mgKOH / g, and the reaction is terminated; cooling to 40°C, adding glycidyl methacrylate, fully stirring for 5min, and then discharging to obtain the DEM resin.

[0082] The free radical photoinitiator is 184 initiator and TPO; the mass ratio of 184 initiator to DEM resin is 0.5:100; the mass ratio of TPO to DEM resin is 0.5:100.

[0083] The grade of the polyetheramine epoxy thermal curing agent is H-T403, and the mass ratio of the polyetheramine epoxy thermal curing agent with the grade of H-T403 to the DEM resin is 24:100.

[0084] The second aspect of this example provides a method for preparing a photocurable modified epoxy resin, which is specifically: under light-proof conditions, mix the raw materials of phase B, add them to phase A, and stir to mix.

[0085] The third aspect of this example provides an application of a photocurable modified epoxy resin, which is used in the preparation of a casting body. Specifically, the photocurable modified epoxy resin is placed in a vacuum oven for degassing for 5 minutes, and then placed under a high-pressure mercury lamp for irradiation for 15 minutes to obtain the product; the product is recorded as DEM / (184+TPO) / H-T403.

[0086] Comparative Example 1

[0087] In the first aspect of this example, a photocurable modified epoxy resin is provided, and the raw materials for its preparation are phase A and phase B; wherein phase A is DEM resin, and phase B is a free radical photoinitiator.

[0088] The raw materials for preparing the DEM resin are specifically: DGEBA resin, methacrylic acid, glycidyl methacrylate, p-hydroxyanisole, and benzyltriethylammonium chloride.

[0089] The molar ratio of the DGEBA resin to methacrylic acid is 2:1; the amount of glycidyl methacrylate is 50% of the mass of the DEM resin; the amount of p-hydroxyanisole is 0.2% of the mass of the DGEBA resin; and the amount of benzyltriethylammonium chloride is 0.1% of the mass of the DGEBA resin.

[0090] The preparation method of the DEM resin comprises: firstly adding DGEBA resin and p-hydroxyanisole into a four-necked flask, then introducing nitrogen and heating to 60°C, pouring methacrylic acid into a constant pressure funnel, adding dropwise into the four-necked flask, and heating to 115°C at the same time, adding benzyltriethylammonium chloride and reacting for 2h, measuring the acid value of the system every 30min during the reaction, until the acid value of the system drops below 3mgKOH / g, and the reaction is terminated; cooling to 40°C, adding glycidyl methacrylate, fully stirring for 5min, and then discharging to obtain the DEM resin.

[0091] The free radical photoinitiator is 184 initiator and TPO; the mass ratio of 184 initiator to DEM resin is 0.5:100; the mass ratio of TPO to DEM resin is 0.5:100.

[0092] The second aspect of this example provides a method for preparing a photocurable modified epoxy resin, which is specifically: under light-proof conditions, mix the raw materials of phase B, add them to phase A, and stir to mix.

[0093] The third aspect of this example provides an application of a photocurable modified epoxy resin, which is used in the preparation of a casting body. Specifically, the photocurable modified epoxy resin is placed in a vacuum oven for degassing for 5 minutes, and then placed under a high-pressure mercury lamp for irradiation for 15 minutes to obtain the product; the product is recorded as DEM / (184+TPO).

[0094] In the above Examples 1-3 and Comparative Example 1, the information of the raw materials is as shown in Table 1, and other components are common commercially available products unless otherwise specified.

[0095] Table 1

[0096]

[0097]

[0098] Performance Testing

[0099] 1. DEM resin infrared spectrum characterization test

[0100] In Examples 1-3, one epoxy group of the DGEBA resin reacts with the carboxyl group of MAA (methacrylic acid) to form an ester group and a hydroxyl group and introduce a carbon-carbon double bond, while the other epoxy group remains. Therefore, the number of epoxy groups is reduced, and an ester bond and a double bond are introduced into the molecule.

[0101] Figure 1 The infrared spectra of DGEBA resin before reaction and DEM resin after reaction are shown in Figure 2. -1 The stretching vibration peak attributed to the epoxy group appeared at 913 cm -1 The vibration peak of the epoxy group at 1721cm -1 The stretching vibration peak of the ester group appeared at 1640 cm -1 The stretching vibration peak at 3486 cm-1 is attributed to the carbon-carbon double bond. -1 The stretching vibration peak at 40° is attributed to the hydroxyl group, which further proves that MAA was successfully grafted onto DGEBA resin.

[0102] 2. Analysis of the solidification of the casting

[0103] 2.1) Infrared spectrum analysis of castings

[0104] The casting samples of Examples 1-3 and Comparative Example 1 were scanned by infrared spectroscopy potassium bromide tablet method.

[0105] Figure 2 The infrared spectra of the systems using three different polyetheramine epoxy thermal curing agents after light curing. It can be seen from the FT-IR that after adding the polyetheramine epoxy thermal curing agent, the 913cm -1 The stretching vibration peak of the epoxy group at 1640 cm -1 The stretching vibration peak of the double bond disappears, indicating that the double bonds and epoxy groups in the system have been fully cross-linked and cured, which is closely related to the medium and low temperature curing characteristics of polyether amine epoxy thermal curing agents.

[0106] After exposure to light, the free radical photoinitiator decomposes to produce primary free radicals that initiate a chain reaction of double bonds. The reaction system releases a large amount of heat, and the system temperature begins to rise, which then triggers a condensation polymerization reaction between the amino group and the epoxy group in the polyetheramine epoxy thermal curing agent, further increasing the heat released by the reaction, thereby achieving self-circulation of heat.

[0107] The results of infrared spectroscopy analysis show that the synergistic effect between the photoinitiated free radical polymerization reaction of the double bond and the condensation polymerization reaction of epoxy and amino groups makes the system produce a good curing effect.

[0108] 2.2) Barcol hardness analysis of casting

[0109] Hardness is an important indicator for evaluating the strength and durability of a casting.

[0110] Figure 3 The Barcol hardness analysis diagram of the casting samples of Examples 1-3 and Comparative Example 1 shows that the hardness of DEM / (184+TPO) without adding the polyetheramine epoxy thermal curing agent is 16HBa, and the casting is not fully cured; after adding the polyetheramine epoxy thermal curing agent, the hardness of the three systems of Examples 1-3 all reached more than 30HBa. Among them, the Barcol hardness of the DEM / (184+TPO) / H-T403 Example 3 system is the highest, reaching 42Hba.

[0111] 3. Characterization of casting performance

[0112] 3.1) Mechanical properties characterization

[0113] Figure 3 (a) and 3(b) are schematic diagrams of the tensile strength and bending strength of the castings of Examples 1-3 and Comparative Example 1.

[0114] As can be seen from the figure, the tensile strength of DEM / (184+TPO) corresponding to Comparative Example 1 is 44.5MPa; after adding epoxy thermosetting agents H-D230, H-D400 and H-T403 respectively, the tensile strength of the casting reached 92.7MPa, 89.2MPa and 85.4MPa respectively, which were increased by 108.3%, 100.4% and 91.9% respectively compared with DEM / (184+TPO), and the tensile strength was significantly improved. The low-temperature epoxy thermosetting agent of the polyetheramine type can initiate the ring-opening reaction with the epoxy group under free radical polymerization, realize the self-circulation of heat, so that the matrix resin DEM and the diluent GMA are fully cured, forming a highly interpenetrating cross-linked structure.

[0115] The cross-linked structure means that when the system is stretched by external force, the stress generated will be transmitted between the interpenetrating networks, which plays a role in dispersing stress. It takes a greater stress to destroy this network structure, which is manifested in an increase in the tensile strength of the sample.

[0116] Specifically, the tensile strength of DEM / (184+TPO) / H-D230 is higher than that of DEM / (184+TPO) / H-D400. This is because the molecular chain of H-D230 is smaller than that of H-D400. The shorter the chain, the greater the cross-linking density of the product after photocuring, and the greater the tensile strength. As for the DEM / (184+TPO) / H-T403 system, its strength is slightly lower than that of Example 1-2, which may be due to the different chemical structure and molecular weight of H-T403.

[0117] In addition, after adding the polyetheramine epoxy thermosetting agent, the flexural strength of the three castings corresponding to Examples 1-3 were all increased to above 140 MPa, indicating that the epoxy groups in the raw material DGEBA resin were fully ring-opened and polymerized to form a highly interpenetrating bulk cross-linked structure.

[0118] Figure 3 (c) and 3(d) are schematic diagrams of the impact strength and elongation at break of the castings of Examples 1-3 and Comparative Example 1.

[0119] When polyetheramine epoxy thermosetting agent was added to DEM / (184+TPO), the impact strength and elongation at break of the casting were significantly improved, indicating that the toughness of the system using free radical photoinitiator and polyetheramine epoxy thermosetting agent for synergistic curing was better. Among them, the impact strength and elongation at break of the DEM / (184+TPO) / H-T403 casting were the highest among all systems, reaching 18.3KJ / m 2The inventors analyzed that the excellent trifunctional H-T403 curing agent has higher reactivity and can form a highly interpenetrating system network structure in a short time. In addition, the molecular chain of H-T403 contains long-chain fatty amines with ether bonds, which has greater flexibility. Therefore, the casting has both certain flexibility and rigidity.

[0120] 3.2) Scanning electron microscopy analysis

[0121] In order to further analyze the internal structure of the casting, the tensile section of the DEM / (184+TPO) / H-T403 sample with the best toughness and the casting corresponding to Comparative Example 1 were observed by scanning electron microscopy. Figure 5 shown.

[0122] As can be seen from the figure, when the system is only subjected to free radical photocuring, such as Comparative Example 1, the casting sample shows obvious brittle fracture characteristics, the tensile fracture surface is smooth, and the crack does not extend. In addition, the fracture direction is single and concentrated, and there is no obvious stress dispersion phenomenon. This is because only the polymerization of carbon-carbon double bonds occurs in the system, and no flexible chain segments are formed in the cross-linked structure, resulting in high brittleness of the system.

[0123] With the addition of the flexible curing agent H-T403, the system underwent a synergistic curing reaction of free radical polymerization and epoxyamino condensation, and the cross-sectional morphology changed significantly, the fracture surface became rough, and the cracks had more branches. Therefore, from the perspective of microstructure, the toughness of the casting was significantly increased, and this result was consistent with the impact strength test results.

[0124] 3.3) Casting volume shrinkage analysis

[0125] Volume shrinkage has a great influence on the physical properties of thermosetting resins. Reducing or even eliminating the volume shrinkage phenomenon is an important indicator for improving the comprehensive performance of thermosetting resins.

[0126] The volume shrinkage of the free radical photoinitiator-polyetheramine epoxy thermal curing agent combination system after light curing was measured by density method. Figure 6 shown.

[0127] Depend on Figure 6 The experimental test results show that after adding the polyetheramine epoxy thermal curing agent, the volume shrinkage of the samples of Examples 1-3 increased relative to that of the control group, Comparative Example 1. This is because after adding the polyetheramine epoxy thermal curing agent, the epoxy groups undergo condensation polymerization, the original van der Waals forces between the epoxy groups become covalent bonds, and the distance between the molecular chains becomes smaller, thereby increasing the volume shrinkage of the cast solid on a macro scale.

[0128] Among the three different polyetheramine epoxy thermal curing agents, DEM / (184+TPO) / H-T403 has the smallest volume shrinkage of 8.7%. The inventors speculate that on the one hand, it may be because H-T403 has a larger structural unit, and the segment skeleton structure formed after curing is larger, and on the other hand, it is because the trifunctional H-T403 curing agent increases the cross-linking points of the resin network structure, so that the epoxy group ring-opening polymerization forms a larger size of the structural unit, which reduces the volume shrinkage of the casting body to a certain extent.

[0129] 3.4) Analysis of dynamic thermomechanical properties of castings

[0130] Figure 7 (a) and (b) are the curves of E' (storage modulus) and tanδ of the free radical photoinitiator-polyetheramine epoxy thermal curing agent combination system with temperature. Figure 7 (a), 7(b) and Table 2 show that after adding the polyetheramine epoxy thermosetting agent, the initial E′ of the casting at 40 °C is significantly improved, mainly due to the complete spatial three-dimensional cross-linked network formed by the system.

[0131] When the epoxy groups in the casting are fully ring-opened and polymerized, the cross-linked network formed by the system becomes more difficult to move and has greater rigidity, so the initial storage modulus increases. As the temperature rises, the storage modulus gradually decreases. This is because after the temperature rises, the solidified material gradually enters the rubber state, the molecular chain mobility increases, and the storage modulus decreases.

[0132] Table 2

[0133] project E′(MPa) <![CDATA[T g (℃)]]> DEM / (184+TPO) 3587.4 82 DEM / (184+TPO) / H-D230 3997.7 104 DEM / (184+TPO) / H-D400 3925.9 99 DEM / (184+TPO) / H-T403 3883.4 109

[0134] 3.5) Analysis of thermal stability of casting

[0135] The results of thermal stability analysis were Figure 8 It can be seen from (a) and Table 3 that the initial decomposition temperature T5% of DEM / (184+TPO) is 293.8°C. After adding polyetheramine epoxy thermosetting agents H-D230, H-D400 and H-T403 respectively, the initial decomposition temperatures of the castings are 323.6°C, 335°C and 325.6°C, all above 320°C. The initial decomposition temperature of the system is significantly improved.

[0136] The experimental results show that the initial decomposition temperature has a certain correlation with the high cross-linking density network structure formed by the system. In addition, the residual carbon rate of the DEM / (184+TPO) / H-T403 sample reached 10.86%, the highest value among the three groups of systems.

[0137] Table 3

[0138]

[0139] from Figure 8 (b) It can be seen from the DTG curve that the decomposition of the casting sample is mainly divided into two stages. The maximum decomposition temperature of the first stage is between 340-360℃, and this stage is mainly the thermal decomposition of the fat chain segments in the sample molecular chain; the maximum decomposition temperature of the second stage is between 415-425℃, and this stage is mainly the thermal decomposition of rigid structures such as benzene rings in the molecular skeleton. The addition of polyetheramine epoxy thermosetting agent delays the thermal decomposition temperature of the resin in the first stage and improves the thermal stability of the system.

[0140] 3.6) Curing mechanism analysis

[0141] In order to further analyze the synergistic relationship between the free radical polymerization of double bonds and the condensation polymerization of epoxyamino groups, based on the fact that both free radical polymerization and condensation polymerization of epoxyamino groups are exothermic reactions, a thermocouple was used to monitor the temperature changes of the DEM / (184+TPO) / H-T403 sample and its comparative example 1 during the illumination process in real time. The results are as follows: Fig. 9 shown.

[0142] As can be seen from the figure, the maximum temperature reached by DEM / (184+TPO) in comparative example 1 during the illumination process is 136.1°C, while the maximum temperature reached by DEM / (184+TPO) / H-T403 during the illumination process is 243.5°C, which is significantly higher than that of comparative example 1 without adding polyetheramine epoxy thermosetting agent. In addition, the result that the stretching vibration peak of the epoxy group in the infrared spectrum after curing has basically disappeared fully proves the previous conjecture: the large amount of heat released by the free radical polymerization after illumination can drive the ring-opening polycondensation reaction of the epoxy group and the epoxy thermosetting agent, and the reaction heat of the polycondensation reaction further increases the temperature, thereby accelerating the polymerization reaction of the epoxy group, and then realizing the self-circulation of heat.

[0143] At the same time, DSC was used to scan the curing heat release of DEM / (184+TPO) / H-T403 and Comparative Example 1. Fig.10 As shown. The results show that DEM / (184+TPO) / H-T403 starts to release heat from 40°C, with the maximum exothermic peak at 120°C, while DEM / (184+TPO) has no exothermic peak during the heating process. This is because H-T403 is a medium-low temperature curing agent, and its amino group can react with the epoxy group at low temperatures. As the temperature rises, the reaction speed accelerates. The free radical photoinitiator added to the control group will not decompose and produce free radicals when heated at low temperatures, so no free radical polymerization reaction will occur, and no exothermic peak will appear.

[0144] Therefore, the curing mechanism of the DEM / (184+TPO) / H-T403 system during the illumination process is as follows: after illumination, the free radical photoinitiator in the system decomposes to produce primary free radicals, which initiate free radical polymerization of the carbon-carbon double bonds in the matrix resin DEM and the diluent GMA, and then the system temperature rises. When the temperature is higher than 40°C, the ring-opening reaction of the epoxy group and the amino group is accelerated, and the reaction heat further increases the temperature, thereby continuing to accelerate the polymerization reaction of the epoxy group, thereby realizing the self-circulation of heat. In addition, the high-pressure mercury lamp will also release some heat during the illumination process. The heat released by the reaction itself combined with the heat released by the high-pressure mercury lamp enables the resin to cure rapidly at high temperature and in a short time. After the illumination ends, the system temperature is still high, and the molecular chains above the glass transition temperature can continue to move. The curing continues until the system is completely cooled to form a complete cross-linked network structure.

Claims

1. A photocurable modified epoxy resin, characterized in that: The preparation raw materials include phase A and phase B; phase A includes DEM resin, and phase B includes free radical photoinitiator and polyetheramine epoxy thermal curing agent.

2. The photocurable modified epoxy resin according to claim 1, characterized in that: The raw materials for preparing the DEM resin include: DGEBA resin, acrylic acid monomer, active diluent, inhibitor and catalyst.

3. The photocurable modified epoxy resin according to claim 2, characterized in that: The acrylic acid monomers include: acrylic acid and / or methacrylic acid.

4. The photocurable modified epoxy resin according to claim 3, characterized in that: The molar ratio of the DGEBA resin to the acrylic acid monomer is (2-3):

1.

5. The photocurable modified epoxy resin according to claim 4, characterized in that: The active diluent includes one or more of 1,4-butanediol diglycidyl ether, 1,6-hexanediol diacrylate, and glycidyl methacrylate.

6. The photocurable modified epoxy resin according to claim 2, characterized in that: The preparation method of the DEM resin comprises: In a four-necked flask, first add DGEBA resin and polymerization inhibitor, then introduce nitrogen and heat to 50-60°C and stir evenly; then pour acrylic acid monomer into a constant pressure funnel and drop it into the four-necked flask, while slowly heating to 110-125°C, add catalyst and react for 2-3h, during which the acid value of the system is measured every 30min until the acid value of the system drops below 3mgKOH / g, and the reaction is terminated; cool to 30-40°C, add active diluent, stir fully for 5-10min and then discharge to obtain the product.

7. The photocurable modified epoxy resin according to claim 1, characterized in that: The free radical photoinitiator includes one or more of 1173 initiator, 184 initiator, 2959 initiator, 907 initiator, 651 initiator and TPO.

8. The photocurable modified epoxy resin according to claim 1, characterized in that: The brands of the polyetheramine epoxy thermal curing agent include: one of H-D230, H-D400 and H-T403.

9. A method for preparing a photocurable modified epoxy resin according to any one of claims 1 to 8, characterized in that: include: Under light-proof conditions, mix the raw materials for phase B, add them to phase A, and stir to obtain the product.

10. An application of the photocurable modified epoxy resin according to any one of claims 1 to 8, characterized in that: The method is applied in the preparation of a casting body, comprising: placing the light-curing modified epoxy resin in a vacuum oven for degassing for 5-10 minutes, and then irradiating it under a high-pressure mercury lamp for 10-20 minutes to obtain the obtained product.

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