A self-healing flame-retardant soybean oil-based thermosetting resin and its preparation method

Abstract

The present invention discloses a self-healing flame-retardant soybean oil-based thermosetting resin and a preparation method thereof. It uses epoxidized soybean oil (ESO), 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl 2-methyl-2-propenoate phosphate (HEMAP), tannic acid (TA) and initiator tert-butyl peroxybenzoate (TBPB) to copolymerize to prepare a bio-based flame-retardant resin. The resin prepared by the present invention can be formed by one-pot stirring and then heating. It has a high bio-based content, is environmentally friendly, and the resin has good flame retardancy, thermal stability, tensile strength, bonding strength and self-healing effect.

Description

Technical Field

[0001] The present invention belongs to the field of flame-retardant polymer materials, and particularly relates to a self-healing flame-retardant soybean oil-based thermosetting resin and a preparation method thereof. Background Art

[0002] In recent years, epoxy resins have been widely used in various fields due to their excellent mechanical properties, thermal stability and chemical corrosion resistance. However, bisphenol A, the raw material of epoxy resin, is a petroleum-based product, which is non-renewable and has a negative impact on the environment, and is not conducive to promoting sustainable development and low-carbon life. As a commonly used edible oil, soybean oil is the vegetable oil with the highest production in the world at present. Different soybean oil derivatives can be prepared by simple processing of soybean oil, such as epoxidized soybean oil, soybean oil polyol, vinyl fatty acid, etc. At present, it is widely used in fields such as biodiesel, plasticizer, coating, ink, etc. Soybean oil is mainly composed of triglycerides, and after modification, it can form a three-dimensional cross-linked network structure, so as to prepare bio-based thermosetting resins to replace epoxy resins. However, the rich alkyl long chains on soybean oil lead to poor mechanical properties and flammability of soybean oil-based thermosetting resins, which limits the application of soybean oil in fields with fire protection grade requirements. Therefore, the preparation of a flame-retardant soybean oil-based thermosetting resin has a positive effect on broadening the application fields of soybean oil industrial products.

[0003] The traditional preparation method of flame-retardant thermosetting resins is to add additive flame retardants or reactive flame retardants to the resin matrix. Additive flame retardants are added to the resin matrix by physical filling, which often reduces the mechanical properties of the resin. Reactive flame retardants graft the flame retardants onto the resin matrix through chemical reactions, which have good durability and do not have a significant impact on the mechanical properties of the resin. Halogen-based flame retardants are widely used because of their high limiting oxygen index and charring property, but the gases generated by the combustion of halogen-based flame retardants are harmful to the human body and have been prohibited by major industries in recent years. Phosphorus-based flame retardants will release water to dilute combustible gases during combustion and form a layer of pyrophosphoric acid on the resin surface to isolate the spread of flames. Phosphorus-based flame retardants are considered to be an environmentally friendly flame retardant because of their non-toxicity and good flame retardant performance, and have been widely studied and used in recent years.

[0004] The present invention uses epoxidized soybean oil (ESO), 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl 2-methyl-2-propenoate phosphate (HEMAP), tannic acid (TA) and initiator tert-butyl peroxybenzoate (TBPB) as raw materials to prepare a self-healing flame-retardant soybean oil-based thermosetting resin, and studies its mechanical properties, flame retardant properties, bonding properties, etc., so as to explore efficient utilization ways and application fields of biomass resources, and at the same time reduce the use of petroleum-based products, which is conducive to the development of a low-carbon economy. Summary of the Invention

[0005] The object of the present invention is to solve the problems of poor mechanical properties of vegetable oil-based resins, non-recyclability and flammability of thermosetting resins, and to provide a preparation method of a flame-retardant soybean oil-based thermosetting resin. The prepared resin is derived from bio-based raw materials, environmentally friendly, and at the same time has good flame retardancy, thermal stability, mechanical properties and self-healing effect.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A self-healing flame-retardant soybean oil-based thermosetting resin is obtained by copolymerizing epoxy soybean oil (ESO), hydroxyethyl acrylate (HEA), 2-hydroxyethyl 2-methyl-2-acrylate phosphate (HEMAP) and tannic acid (TA) under the action of an initiator tert-butyl peroxybenzoate (TBPB).

[0008] The composition of the raw materials is as follows by mass fraction: 15 parts of ESO, 10 parts of HEA, 7-10 parts of HEMAP and 0-7 parts of TA; the mass fraction of TBPB in HEA and HEMAP is 1-3%.

[0009] A preparation method of a self-healing flame-retardant soybean oil-based thermosetting resin, the specific steps are: mixing ESO, HEA, HEMAP and TA in sequence according to the mass ratio and stirring for 30 min, then cooling to room temperature, adding tert-butyl peroxybenzoate and continuing to stir evenly, and then standing for defoaming to obtain a soybean oil-based prepolymer; pouring the prepolymer into a polytetrafluoroethylene mold, and hot pressing at 140 °C and a pressure of 0.5 MPa for 5 h to obtain a self-healing flame-retardant soybean oil-based thermosetting resin.

[0010] The beneficial effects of the present invention are as follows:

[0011] 1) The self-healing flame-retardant soybean oil-based thermosetting resin prepared by the present invention has the characteristics of high bio-based content and environmental friendliness, and at the same time has good flame retardancy, thermal stability, mechanical properties and self-healing effect.

[0012] 2) The present invention adopts an optimized combination of process parameters, and the mass fraction of the raw materials is: 15 parts of epoxy soybean oil, 10 parts of hydroxyethyl acrylate, 7 parts of 2-hydroxyethyl 2-methyl-2-acrylate phosphate and 7 parts of tannic acid; the mass fraction of tert-butyl peroxybenzoate in hydroxyethyl acrylate and 2-hydroxyethyl 2-methyl-2-acrylate phosphate is 2%; the curing process is: hot pressing at 140 °C and a pressure of 0.5 MPa for 5 h. Description of the Drawings

[0013] Figure 1 It is the reaction mechanism of the self-healing flame-retardant soybean oil-based thermosetting resin;

[0014] Figure 2DSC curve of self - healable flame - retardant soybean oil - based thermosetting resin;

[0015] Figure 3 TGA curve of self - healable flame - retardant soybean oil - based thermosetting resin;

[0016] Figure 4 Limiting oxygen index and vertical burning test of self - healable flame - retardant soybean oil - based thermosetting resin;

[0017] Figure 5 Surface self - healing effect of self - healable flame - retardant soybean oil - based thermosetting resin;

[0018] Figure 6 Lap shear strength of self - healable flame - retardant soybean oil - based thermosetting resin as an adhesive for different materials;

[0019] In the figure, ESO - HEMAP represents the resin made from ESO, HEA and HEMAP as raw materials, ESO - TA represents the resin made from ESO and TA as raw materials, and ESO - HEMAP - TA represents the resin made from ESO, HEMAP, HEA and TA; EHP 0.7 T0 represents the resin prepared from 15 parts of ESO, 10 parts of HEA, 7 parts of HEMAP and 0 part of TA (Example 1), EHP 0.7 T 0.7 represents the resin prepared from 15 parts of ESO, 10 parts of HEA, 7 parts of HEMAP and 7 parts of TA (Example 2), EHP1T 0.7 represents the resin prepared from 15 parts of ESO, 10 parts of HEA, 10 parts of HEMAP and 7 parts of TA (Example 3). Detailed implementation mode

[0020] To further disclose rather than limit the present invention, the following examples are used to further illustrate the present invention in detail.

[0021] Raw materials: Epoxidized soybean oil (ESO, with an average of 4.1 epoxy groups and an acid value ≤ 0.6 mg KOH / g), tannic acid (TA, AR), 2 - hydroxyethyl acrylate (HEA, 99%), 2 - hydroxyethyl 2 - methyl - 2 - acrylate phosphate (HEMAP, 99%) and tert - butyl peroxybenzoate (TBPB, 98%) were purchased from Shanghai Macklin Biochemical Technology Co., Ltd.

[0022] Example 1

[0023] Self - healable flame - retardant soybean oil - based thermosetting resin

[0024] Preparation process: Sequentially mix 15 g of epoxidized soybean oil, 10 g of hydroxyethyl acrylate, and 7 g of 2-hydroxyethyl 2-methyl-2-propenoate phosphate and stir for 30 min. After cooling to room temperature, add 0.34 g of tert-butyl peroxybenzoate and continue to stir evenly, then let it stand to defoam to obtain a prepolymer; pour the prepolymer into a polytetrafluoroethylene mold and hot press at 140 °C and a pressure of 0.5 MPa for 30 min to obtain a self-healing flame-retardant soybean oil-based thermosetting resin.

[0025] In the described preparation process, the dosage ratio of epoxidized soybean oil, hydroxyethyl acrylate, and 2-hydroxyethyl 2-methyl-2-propenoate phosphate is 1.5:1:0.7 by mass; the dosage of the initiator tert-butyl peroxybenzoate is 2% of the total mass of hydroxyethyl acrylate and 2-hydroxyethyl 2-methyl-2-propenoate phosphate.

[0026] Example 2

[0027] Self-healing flame-retardant soybean oil-based thermosetting resin

[0028] Preparation process: Sequentially mix 15 g of epoxidized soybean oil, 10 g of hydroxyethyl acrylate, 7 g of 2-hydroxyethyl 2-methyl-2-propenoate phosphate, and 7 g of tannic acid and stir for 30 min. After cooling to room temperature, add 0.34 g of tert-butyl peroxybenzoate and continue to stir evenly, then let it stand to defoam to obtain a prepolymer; pour the prepolymer into a polytetrafluoroethylene mold and hot press at 140 °C and a pressure of 0.5 MPa for 30 min to obtain a self-healing flame-retardant soybean oil-based thermosetting resin.

[0029] In the described preparation process, the dosage ratio of epoxidized soybean oil, hydroxyethyl acrylate, 2-hydroxyethyl 2-methyl-2-propenoate phosphate, and tannic acid is 1.5:1:0.7:0.7 by mass; the dosage of the initiator tert-butyl peroxybenzoate is 2% of the total mass of hydroxyethyl acrylate and 2-hydroxyethyl 2-methyl-2-propenoate phosphate.

[0030] Example 3

[0031] Self-healing flame-retardant soybean oil-based thermosetting resin

[0032] Preparation process: Sequentially mix 15 g of epoxidized soybean oil, 10 g of hydroxyethyl acrylate, 10 g of 2-hydroxyethyl 2-methyl-2-propenoate phosphate, and 7 g of tannic acid and stir for 30 min. After cooling to room temperature, add 0.34 g of tert-butyl peroxybenzoate and continue to stir evenly, then let it stand to defoam to obtain a prepolymer; pour the prepolymer into a polytetrafluoroethylene mold and hot press at 140 °C and a pressure of 0.5 MPa for 30 min to obtain a self-healing flame-retardant soybean oil-based thermosetting resin.

[0033] During the preparation process, the mass ratio of epoxidized soybean oil, 2-hydroxyethyl acrylate, 2-hydroxyethyl 2-methyl-2-propenoate phosphate, and tannic acid is 1.5:1:1:0.7; the amount of initiator tert-butyl peroxybenzoate is 2% of the total mass of 2-hydroxyethyl acrylate and 2-hydroxyethyl 2-methyl-2-propenoate phosphate.

[0034] Flame retardancy test of self-healing flame-retardant soybean oil-based thermosetting resin:

[0035] According to ASTM D 2863-97 standard, the limiting oxygen index (LOI) of the resin was tested on a British FTT 0077 type limiting oxygen index instrument, and rectangular specimens (specification: 100 mm in length, 12.5 mm in width, and 3 mm in thickness) were used for the test; according to UL-94 method, the vertical burning performance of the sample was tested on a British FTT 0082 type vertical burning tester, and rectangular specimens (specification: 125 mm in length, 10 mm in width, and 3 mm in thickness) were used for the test; according to ASTM E1354 standard, the cone calorimeter test was carried out on a British FTT0242 type horizontal and vertical burning tester, with a heat flux of 35 kW / m 2 , and rectangular specimens (specification: 100 mm in length, 100 mm in width, and 3 mm in thickness) were used for the test.

[0036] Mechanical properties and bond strength test of self-healing flame-retardant soybean oil-based thermosetting resin:

[0037] The tensile and flexural properties of the soybean oil-based thermosetting resin were tested on an American Instron 3365 type microcomputer-controlled electronic universal testing machine with a loading rate of 10 mm / min. The tensile strength samples were dumbbell-shaped (specification: 50 mm in length, 15 mm in standard width, 4 mm in narrow section width, and 3 mm in thickness), and the flexural strength test samples were rectangular (specification: 80 mm in length, 10 mm in width, and 3 mm in thickness); according to ASTM D 1002-01 standard, the lap shear strength of the thermosetting resin against different materials was tested on an American SANS C45 type universal mechanical testing machine with a loading rate of 10 mm / min.

[0038] Curing behavior test of the resin:

[0039] The curing behavior of the resin was characterized by a German Netzsch STA 449C non-isothermal differential scanning calorimeter. The test process was as follows: about 10 mg of the sample was placed in a ceramic crucible, placed in the sample cell for testing, and N2 with a flow rate of 30 mL / min was introduced as the protective gas. The temperature was gradually increased from 25 °C to 250 °C at a heating rate of 10 °C / min.

[0040] Thermal stability test of the resin:

[0041] The thermal stability of the resin was characterized using a Netzsch TG 209 F3 thermogravimetric analyzer from Germany. The testing process was as follows: Approximately 20 mg of the sample was placed in the sample cell for testing, and N2 was introduced for protection. The temperature was gradually increased from 30 °C to 800 °C at a heating rate of 10 °C / min.

[0042] Self-healing behavior of the resin:

[0043] A scratch approximately 35 μm deep was made on the surface of the resin (specifications: 50 mm long, 50 mm wide, and 3 mm thick) using a cutter, and it was repaired in an oven at 140 °C for 1 h. The surface morphology before and after repair was observed using a Chinese Optec SZ680 optical microscope.

[0044]

[0045]

[0046] Crosslinking mechanism of the self-healing flame-retardant soybean oil-based thermosetting resin:

[0047] As Figure 1 shown, there are three reactions in the system: 1) The reaction between the phosphoric hydroxyl group of HEMAP and the epoxy group of ESO introduces a dynamic phosphate structure; 2) The free radical polymerization reaction of the double bonds of HEMAP and HEA can significantly increase the crosslinking density of the resin; 3) The ring-opening reaction of TA and ESO stabilizes the charring agent TA.

[0048] Curing behavior of the self-healing flame-retardant soybean oil-based thermosetting resin:

[0049] As Figure 2 known, the peak that appears in the ESO-HEMAP-TA curve at 131 °C is mainly caused by the free radical polymerization reaction of the double bonds on HEMAP and HEA, and the exothermic peak at 235 °C mainly comes from the ring-opening reaction of the epoxy group on ESO and the phenolic hydroxyl group on TA.

[0050] Thermal stability of the self-healing flame-retardant soybean oil-based thermosetting resin:

[0051] As Figure 3 known, compared with the mass residue rate of EHP 0.7 T0 resin (15.41%), the mass residue rates of EHP 0.7 T 0.7 and EHP1T 0.7 resin (22.13% and 27.81%) with the addition of TA are significantly improved, indicating that the addition of TA significantly increases the charring rate of the flame-retardant soybean oil-based thermosetting resin.

[0052] Flame retardancy of the self-healing flame-retardant soybean oil-based thermosetting resin:

[0053] AsFigure 4 It is known that the addition of TA can significantly increase the limiting oxygen index of the resin, and the maximum limiting oxygen index of the resin reaches 26.88%; in the vertical burning test, EHP 0.7 T 0.7 and EHP1T 0.7 The resin showed self-extinguishing after two ignitions and no dripping phenomenon, reaching V-0 level in the UL-94 vertical burning test. As shown in Table 2, for the resin with TA added, its peak heat release rate (456 kW / m 2 ) and peak smoke release rate (0.06 m 2 ) both decreased significantly compared with the thermosetting resin without TA added, indicating that the prepared resin can reduce the harm caused by heat and smoke to people in a fire.

[0054] Self-healing effect of the self-healing flame-retardant soybean oil-based thermosetting resin:

[0055] As Figure 5 is known, due to the rapid transesterification of β-hydroxy phosphate esters in the soybean oil-based thermosetting resin, the scratches on its surface almost completely disappeared after 1 h at 140 °C, indicating that the prepared flame-retardant soybean oil-based resin has good repair effect at high temperature.

[0056] Mechanical properties and bonding properties of the self-healing flame-retardant soybean oil-based thermosetting resin:

[0057] As Figure 6 is known, the surface of polyethylene plastic lacks the action of polar groups and its shear strength is low; while the surface of wood board has the action of hydroxyl groups and its shear strength is significantly improved; because tannic acid will produce metal complexes with iron ions, the shear strength of the flame-retardant soybean oil-based resin for steel reaches 16.7 MPa. As shown in Table 1, the maximum tensile strength and tensile modulus of the resin with TA added are 19.97 MPa and 461.82 MPa, and the maximum flexural strength and flexural modulus are 36.7 MPa and 974.19 MPa.

[0058] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A self-healing flame-retardant soybean oil-based thermosetting resin, characterized in that: The self-healing flame-retardant soybean oil-based thermosetting resin is obtained by copolymerization of epoxy soybean oil, tannic acid, hydroxyethyl acrylate, and 2-hydroxyethyl 2-methyl-2-propenoate phosphate under the action of initiator tert-butyl perbenzoate.

2. The self-healing flame-retardant soybean oil-based thermosetting resin according to claim 1, characterized in that: The raw material composition is as follows by mass fraction: 15 parts of epoxy soybean oil, 10 parts of hydroxyethyl acrylate, 7-10 parts of 2-hydroxyethyl 2-methyl-2-propenoate phosphate, and 7 parts of tannic acid; the mass fraction of tert-butyl perbenzoate in hydroxyethyl acrylate and 2-hydroxyethyl 2-methyl-2-propenoate phosphate is 1-3%.

3. A preparation method of a self-healing flame-retardant soybean oil-based thermosetting resin as described in any one of claims 1-2, characterized in that: Epoxy soybean oil, hydroxyethyl acrylate, 2-hydroxyethyl 2-methyl-2-propenoate phosphate, and tannic acid are added in sequence according to the mass ratio, mixed and stirred for 30 min, then cooled to room temperature. Tert-butyl perbenzoate is added continuously, and after stirring evenly at room temperature, it is left to stand for defoaming to obtain a soybean oil-based resin prepolymer; the prepolymer is poured into a polytetrafluoroethylene mold and hot-pressed at 140 °C and a pressure of 0.5 MPa for 5 h to obtain the self-healing flame-retardant soybean oil-based thermosetting resin.

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