Thermosetting resin system with nanophase structure as well as cured product and preparation method thereof

Abstract

The invention discloses a thermosetting resin system with a nanophase structure as well as a cured product and a preparation method thereof, and particularly relates to a novel block copolymer derivative (BCPy) which contains reactive end groups and multiple hydrogen bond end groups and is good in heat resistance, and the novel block copolymer derivative (BCPy) is added into a typical thermosetting epoxy / bismaleimide (EBMI) resin system, so that the thermosetting resin system with the nanophase structure is obtained. Not only can a nanophase structure be formed in a resin matrix to toughen and modify thermosetting resin, but also the inherent heat resistance and strength of the thermosetting resin can be maintained. Compared with the prior art, the system not only has good manufacturability, but also has excellent mechanical properties and heat resistance, and can be applied to the fields of electronic circuits, aerospace and the like.

Description

Technical Field

[0001] The invention relates to a high-strength and high-toughness thermosetting epoxy / bismaleimide resin system with a nano-phase structure and a preparation method thereof, belonging to the technical field of functional high-performance resin-based materials. Background Art

[0002] Thermosetting epoxy / bismaleimide (EBMI) resin systems combine the excellent processability of epoxy with the superior heat resistance of bismaleimide resins, making them widely used in aviation, aerospace, automotive, electronics, and construction. However, like traditional high-performance thermosetting resin systems, these systems suffer from poor impact resistance, a major bottleneck that has hindered their engineering applications. While toughening thermosetting resins can be achieved by adding thermoplastic components and inorganic nanofillers, the introduction of thermoplastic components significantly reduces the material's processability and makes uniform phase structure difficult to control. The introduction of inorganic nanofillers, due to their dispersibility and agglomeration, can seriously destabilize the resin system structure and properties. Therefore, how to obtain high-strength, high-toughness thermosetting resin systems with uniform phase structure and excellent processability has been a hot research topic in this field.

[0003] Block copolymers offer flexible molecular structure design, making them easy to form nanostructures in thermosetting resins and also capable of toughening them. Therefore, using block copolymers to construct nanostructures and achieve material toughening in thermosetting resin systems is a simple and effective method. However, the low heat resistance of block copolymers and their weak interface with the resin matrix significantly reduce the heat resistance and strength of thermosetting resins. Summary of the Invention

[0004] The present invention addresses the bottleneck problem in the application of thermosetting epoxy / bismaleimide (EBMI) resin materials. The present invention discloses a block copolymer derivative (BCPy) containing reactive end groups and multiple hydrogen bond end groups and good heat resistance to modify the EBMI resin system, thereby obtaining a high-strength and high-toughness thermosetting epoxy / bismaleimide system with a nanophase structure.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A thermosetting resin system with a nanophase structure is prepared from raw materials including epoxy (EP) resin, bismaleimide (BMI), polylactic acid-b-polycaprolactone (BCPy) containing reactive end groups and multiple hydrogen bond end groups, and a curing agent.

[0006] A thermosetting resin cured product with a nano-phase structure is obtained by curing the above-mentioned thermosetting resin system with a nano-phase structure.

[0007] The present invention melt-mixes epoxy resin and bismaleimide, then adds a curing agent, and after prepolymerization, adds polylactic acid-b-polycaprolactone (BCPy) containing reactive end groups and multiple hydrogen bond end groups to obtain a thermosetting resin system with a nanophase structure.

[0008] The thermosetting resin system with a nanophase structure of the present invention is cured at 100-200° C. for 8-12 hours to obtain the thermosetting resin cured product with a nanophase structure.

[0009] In the present invention, the epoxy resin includes one of bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated epoxy resin, novolac epoxy resin, flame retardant epoxy resin or any combination thereof; the bismaleimide includes 4,4'-bismaleimidodiphenylmethane and bismaleimidodiphenyl ether; and the curing agent includes an amine curing agent.

[0010] In the present invention, PLA-b-PCL (polylactic acid-b-polycaprolactone) block copolymer and 2-amino-6-methylpyrimidin-4(3H)-one (UPy) are used as raw materials to react to prepare BCP-UPy; then BCP-UPy is reacted with a coupling agent to prepare a PLA-b-PCL derivative (BCPy) containing reactive end groups and multiple hydrogen bond end groups.

[0011] In the present invention, lactic acid (LA) is reacted with stannous octoate (Sn(Oct)2) to obtain a PLA oligomer, and then ε-caprolactone (ε-CL) is added to react to obtain a PLA-b-PCL block copolymer; PLA-b-PCL is reacted with 2-amino-6-methylpyrimidin-4(3H)-one (UPy) to obtain a yellow viscous product (BCP-UPy); and then reacted with γ-aminopropyltriethoxysilane (KH550) to obtain a block copolymer derivative containing reactive end groups and multiple hydrogen bond end groups of PLA-PCL derivatives, denoted as BCPy.

[0012] In the present invention, the weight of the epoxy resin (EP) and bismaleimide (BMI) is 100%, the weight of the PLA-b-PCL derivative (BCPy) with reactive end groups and multiple hydrogen bond end groups is 3%-30%, preferably 5%-15%, and the weight of the curing agent is 0%-40% (excluding 0), preferably 5%-20%, and more preferably 10%-17.5%; wherein the weight ratio of the epoxy resin to the bismaleimide is 1:(0.5-2).

[0013] In the present invention, the temperature of melt mixing is 120 to 170° C.; the temperature of prepolymerization is 120 to 170° C., and the time is 0 to 2 hours (excluding 0).

[0014] The present invention discloses the use of the above-mentioned thermosetting resin system with a nanophase structure, a derivative (BCPy) of PLA-b-PCL containing reactive end groups and multiple hydrogen bond end groups, or a thermosetting resin cured product with a nanophase structure in the preparation of resin-based materials.

[0015] The present invention prepares a thermosetting resin system with a nanophase structure from epoxy resin, bismaleimide, a PLA-b-PCL derivative (BCPy) containing reactive end groups and multiple hydrogen-bonding end groups, and an aromatic amine curing agent. Epoxy resin and BMI are melt-mixed, then DDS is added. After prepolymerization, the PLA-b-PCL derivative (BCPy) containing reactive end groups and multiple hydrogen-bonding end groups is added, followed by stirring to obtain a thermosetting resin system with a nanophase structure. The system is then poured into a conventional mold, degassed, and subsequently cured in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, 180°C for 2 hours, and 200°C for 2 hours to obtain a cured thermosetting resin with a nanophase structure.

[0016] Preferably, the epoxy resin comprises bisphenol A epoxy resin.

[0017] Preferably, the mass ratio of epoxy resin to bismaleimide (BMI) is 1:1, the epoxy resin is bisphenol A epoxy resin, and the bismaleimide (BMI) is 4,4'-bismaleimidodiphenylmethane.

[0018] In the above technical solution, the aromatic amine curing agent is: 4,4'-diaminodiphenyl sulfone (DDS), 4,4'-diaminodiphenylmethane (DDM) or 4,4'-diaminodiphenyl ether.

[0019] In the above technical solution, EP and BMI are put into a reaction vessel, heated at 140-160°C to melt into a transparent solution, and then DDS is added and prepolymerized for 0.5-1h. Then, BCPy is added and stirred. The mixture is poured into a preheated mold and degassed in a vacuum oven at 80°C. The mixture is then cured in a blast oven at 100°C / 4h+120°C / 2h+150°C / 2h+180°C / 2h to obtain a cured resin system.

[0020] In the above technical solution, the cured resin system has a nanophase structure, and its bending strength can reach 120MPa and its impact strength can reach 16KJ / m 2 , the tensile strength can reach 59MPa, the initial thermal decomposition temperature is 402℃, and the system has good processability.

[0021] The thermosetting resin system with nanophase structure prepared by the present invention is cured to obtain a thermosetting resin cured product with nanophase structure. The cured product has a nanophase structure and a bending strength of 120 MPa and an impact strength of 16 KJ / m2 , the tensile strength can reach 59MPa, the initial thermal decomposition temperature is 402°C; and the system has good processability.

[0022] Compared with the prior art, the present invention has the beneficial effects of: the thermosetting resin system of the present invention has excellent processability, outstanding mechanical strength and toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the GPC curve of PLA-b-PCL diblock copolymer.

[0024] Figure 2 FTIR spectra of LA, ε-CL and PLA-b-PCL.

[0025] Figure 3 For PLA-b-PCL 1 H NMR spectrum.

[0026] Figure 4 FTIR spectra of BCPy, UPy and KH550.

[0027] Figure 5 This is the DSC curve of BCPy.

[0028] Figure 6 TGA and DTG curves of BCPy.

[0029] Figure 7 DSC curves of (a) EP, BMI, DDS, BCPy, EBMI, EP / DDS, BMI / DDS, EBMI / DDS and (b) EP / BCPy, BMI / BCPy, EP / DDS / BCPy, BMI / DDS / BCPy, EBMI / DDS / BCPy.

[0030] Figure 8 These are SEM photos of the brittle fracture surfaces of Example 1(a) and Comparative Example 1-1(b) and SEM photos of the impact fracture surfaces of Example 1(a) and Comparative Example 1-1(b).

[0031] Figure 9 Optical microscope photos of the cured sample films of Example 1(a) and Comparative Example 1-1(b). DETAILED DESCRIPTION

[0032] To address the problem of low heat resistance of block copolymers and their weak interface with the resin matrix, which leads to a significant decrease in the heat resistance and strength of thermosetting resins, the present invention synthesizes a new block copolymer derivative (BCPy) containing reactive end groups and multiple hydrogen-bonding end groups and excellent heat resistance. This block copolymer derivative can not only form a nanophase structure in the resin matrix to toughen and modify the thermosetting resin, but also maintain the inherent heat resistance and strength of the thermosetting resin.

[0033] The invention discloses a thermosetting resin system with a nanophase structure and a preparation method thereof. The system comprises the following steps: an epoxy / bismaleimide resin, a block copolymer derivative BCPy containing reactive end groups and multiple hydrogen bond end groups, and an aromatic amine curing agent in a mass ratio of 100:(5-15):(5-20); and the preparation method comprises the following steps: adding EP and BMI into a reaction vessel, heating and melting them at 150°C to form a transparent solution, then adding the aromatic amine curing agent, prepolymerizing for 0.5-1h, then adding BCPy, stirring, pouring the solution into a preheated mold, degassing in a vacuum oven at 80°C, and then curing in a blast oven at 100°C / 4h+120°C / 2h+150°C / 2h+180°C / 2h to obtain a cured product of the resin system.

[0034] In the present invention, the preparation method of the PLA-PCL copolymer containing reactive end groups comprises the following steps: (1) Lactic acid (LA) and stannous octoate (Sn(Oct)2) were reacted under nitrogen at 120°C / 24h+170°C / 3h, and then naturally cooled to room temperature to obtain polylactic acid (PLA) oligomer. ε-caprolactone (ε-CL) was then added and treated at 130°C / 24h+170°C / 3h. The product was dissolved in acetone and precipitated in deionized water to obtain an off-white sticky solid, which was the PLA-b-PCL block copolymer. (2) PLA-b-PCL and 2-amino-6-methylpyrimidin-4(3H)-one (UPy) were condensed and refluxed at 90°C. The resulting product was dissolved in acetone and precipitated in deionized water to obtain a yellow viscous product (BCP-UPy). (3) γ-Aminopropyltriethoxysilane (KH550) was mixed with anhydrous ethanol and deionized water to form a solution, and then BCP-UPy was added. After the reaction, the unreacted monomer was removed by washing with deionized water. After filtration and drying, a derivative of the block copolymer PLA-b-PCL containing reactive end groups and multiple hydrogen bond end groups was obtained, which was recorded as BCPy.

[0035] In the present invention, the mass ratio of epoxy to bismaleimide is 1: (0.5-2), the epoxy resin is bisphenol A epoxy resin, and the bismaleimide is 4,4'-bismaleimidodiphenylmethane.

[0036] In the present invention, the amine curing agent includes any combination of one or more of aliphatic polyamines, alicyclic polyamines, polyetheramines, and aromatic amines; the aliphatic polyamine includes ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, or diethoxypropylamine; the alicyclic polyamine includes menthanediamine, N-aminoethylpiperazine, bis(4-aminocyclohexyl)methane, or isophoronediamine; the aromatic amine includes m-phenylenediamine, diaminodiphenylmethane, diaminodiphenyl sulfone, diaminodiphenyl ether, or m-phenylenediamine; and the tertiary amine compound includes pyridine, triethylamine, triethanolamine, or N-dimethylbenzylamine. Preferably, the aromatic amine curing agent is 4,4'-diaminodiphenyl sulfone (DDS), 4,4'-diaminodiphenyl ether, or 4,4'-diaminodiphenylmethane (DDM).

[0037] The technical solution of the present invention is further described below with reference to the accompanying drawings and examples. The raw materials used in the present invention are all existing products, and the specific preparation operations and performance tests are all conventional techniques.

[0038] The structure and performance test methods are briefly described as follows: The cross-sectional morphology of the samples was characterized by cold field emission scanning electron microscopy (SEM) and ultra-depth of field microscopy (VK-6000).

[0039] The thermal decomposition temperature of the samples was analyzed by thermogravimetric analyzer (TGA) under the conditions of N2 atmosphere (10 ml / min) and heating rate of 10 °C / min.

[0040] Differential scanning calorimetry (DSC) was used to analyze the thermal behavior of the samples. The test conditions were N2 atmosphere (50 ml / min) and the heating rate or cooling rate was 10 °C / min.

[0041] The glass transition temperature (Tg) of the sample was analyzed using a dynamic mechanical analyzer (DMA). The test mode was single cantilever mode with a single frequency of 1 Hz. The sample dimensions were 35 mm × 13 mm × 4 mm.

[0042] The mechanical properties of the materials were tested using an electronic universal testing machine according to the standard GB / T 2567-2008.

[0043] Synthesis Example Synthesis of a Block Copolymer PLA-b-PCL Derivative (BCPy) Containing Reactive End Groups and Multiple Hydrogen Bonding End Groups 45.4 g (0.5 mol) of lactic acid (LA) and 0.225 g of stannous octoate (Sn(Oct)2) (0.5 wt%) were reacted under a nitrogen atmosphere at 120°C / 24 h+170°C / 3 h. After the reaction was terminated, the mixture was naturally cooled to room temperature to obtain a polylactic acid (PLA) oligomer. 57.07 g (0.5 mol) of ε-caprolactone (ε-CL) was then added and reacted under a nitrogen atmosphere at 130°C / 24 h+170°C / 3 h. The product was dissolved in acetone and precipitated in deionized water to obtain an off-white sticky solid, which is polylactic acid-b-polyε-caprolactone block copolymer (PLA-b-PCL). 27.4 g of PLA-b-PCL and 0.88 g of 2-amino-6-methylpyrimidin-4(3H)-one (UPy) were condensed and refluxed at 90 °C for 12 h. The resulting product was then dissolved in acetone and precipitated in deionized water to obtain a yellow viscous product (BCP-UPy). 3.28 g of γ-aminopropyltriethoxysilane (KH550) was mixed with anhydrous ethanol and deionized water to form a solution with a volume ratio of 2:7:1. Subsequently, 16.23 g of BCP-UPy was added and stirred at 80°C for 1 hour. Unreacted monomers were then removed by washing with deionized water. After filtration and drying, a derivative of the block copolymer PLA-b-PCL containing reactive end groups and multiple hydrogen-bonding end groups was obtained, designated as BCPy, which was used in the following experiments.

[0044] The above reaction process is shown as follows:

[0045] The molecular weight of the synthesized PLA-b-PCL was characterized by GPC. Figure 1 As shown. It can be seen that the molecular weight M of PLA-b-PCL n =3907,M w =7102, molecular weight distribution (PDI) =1.81, and the curve shows a unimodal distribution. The performance parameters of PLA-b-PCL are listed in Table 1. Figure 2 The infrared (FTIR) spectra of LA, ε-CL, and PLA-b-PCL are shown. In the FTIR spectrum of LA, 3380 cm -1 is the absorption peak of -OH, 1720 cm -1 The peak at 2860 cm is the stretching vibration peak of C=O. -1 and 2920cm -1 is the stretching vibration peak of CH, 1720 cm -1 The peak at 3380cm is the stretching vibration peak of C=O. -1The characteristic peak intensity of -OH at the position is significantly weakened, as shown in the FTIR spectrum of PLA-b-PCL.

[0046] PLA-b-PCL 1 H-NMR spectrum Figure 3 shown. Figure 3 The chemical shifts of all H atoms in the block copolymer are presented, including the H atoms of the methine -CH connected to the PLA block (5.1ppm-5.3ppm), the H atoms of the methyl -CH3 (1.5ppm), the hydrogen atoms of the saturated chain -CH2 in the PLC block (1.4ppm-1.6ppm), the H atoms of O-CH2 (4.1ppm), the H atoms of -CH2 connected to the carbonyl group (2.4ppm). The H atoms of the methylene -CH2 connected to the terminal carboxyl group (3.5ppm) and the H atoms of the methine -CH connected to the terminal hydroxyl group (4.3ppm) are shown in Figure 2. Figure 3 It also appeared in the results that the synthesized PLA-b-PCL has both terminal carboxyl and terminal hydroxyl groups, which is consistent with the designed molecular structure.

[0047] Figure 4 The FTIR spectra of BCPy, UPy and KH550 are shown in Figure 2. In the FTIR spectrum of KH550, 1070 cm -1 is the stretching vibration peak of Si-O-Si, 780cm -1 It is the stretching vibration peak of Si-C. In the spectrum of UPy, 1680cm -1 is the stretching vibration peak of C=C and C=N double bonds. When PLA-b-PCL is modified with UPy and KH550, 3350cm -1 The NH vibration peak of the amine appeared near 1680 cm -1 The stretching vibration peaks of C=C and C=N double bonds appeared near 3080cm -1 There is also a vibration peak of C=CH near the PLA-b-PCL, which indicates that the hydroxyl group at the end of PLA-b-PCL and the amino group on UPy undergo a condensation reaction, and UPy is grafted onto the block copolymer molecular chain; at 1150cm -1 The Si-O-Si stretching vibration peak appeared near 780 cm -1 The Si-C stretching vibration peak appeared, indicating that KH550 had been successfully introduced into the chain end of PLA-b-PCL.

[0048] Figure 5 This is the DSC curve of BCPy. Figure 5 It can be seen that BCPy has an obvious crystalline melting peak and its melting temperature (T m ) at around 50 °C, which is mainly caused by the PCL chain segment. Figure 6The thermogravimetric (TG) and differential thermogravimetric (DTG) curves of BCPy. The onset thermal decomposition temperature of BCPy (T di , the temperature when weight loss is 5wt%) is 219℃, and the maximum thermal decomposition rate corresponds to the decomposition temperature (T max ) is 435℃.

[0049] Example 1 Epoxy resin EP (E51) and 4,4'-bismaleimidodiphenylmethane (BMI) were placed in a reaction vessel and heated at 150°C for 5 minutes to melt into a transparent solution. 4,4'-diaminodiphenyl sulfone (DDS) was then added and prepolymerized for 45 minutes. BCPy was then added and stirred conventionally. The mixture was poured into a mold preheated at 80°C and degassed in a vacuum oven at 80°C. The mixture was then cured in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours to obtain a cured resin system. The mass ratio of EP:BMI:DDS:BCPy was 70:70:24.5:10.5.

[0050] Comparative Example 1-1 Epoxy EP (E-51) and 4,4'-bismaleimidodiphenylmethane (BMI) were placed in a reaction vessel and heated at 150°C for 5 minutes to melt into a transparent solution. 4,4'-diaminodiphenyl sulfone (DDS) was then added and prepolymerized for 45 minutes. After stirring, the mixture was poured into a preheated mold and degassed in a vacuum oven at 80°C. The mixture was then cured in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours to obtain a cured resin system. The mass ratio of EP:BMI:DDS was 70:70:24.5.

[0051] Comparative Example 1-2 EP (E-51) and 4,4'-bismaleimidodiphenylmethane (BMI) were placed in a reaction vessel and heated at 150°C for 5 minutes to melt into a transparent solution. BCPy was then added and stirred, poured into a preheated mold, and degassed in a vacuum oven at 80°C. The mixture was then cured in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours to obtain a cured resin system. The mass ratio of EP:BMI:BCPy was 70:70:10.5.

[0052] Examples 1-3 Epoxy EP (E-51) was heated to 150°C, and then 4,4'-diaminodiphenyl sulfone (DDS) was added and prepolymerized for 45 minutes. BCPy was then added and stirred, poured into a preheated mold, and degassed in a vacuum oven at 80°C. Subsequently, the mixture was cured in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours to obtain a cured resin system. The mass ratio of EP:DDS:BCPy was 70:24.5:10.5.

[0053] Comparative Examples 1-4 Heat epoxy EP (E-51) to 150°C, then add 4,4'-diaminodiphenyl sulfone (DDS), prepolymerize for 45 minutes, pour into a preheated mold, and degas in a vacuum oven at 80°C. Subsequently, cure in a forced air oven at 100°C / 4h+120°C / 2h+150°C / 2h+180°C / 2h to obtain a resin system cured product; the mass ratio of EP:DDS: is 70:24.5.

[0054] Comparative Examples 1-5 Heat epoxy EP (E-51) to 150°C, then add BCPy and stir. Pour the mixture into a preheated mold and degas in a vacuum oven at 80°C. Then, cure the mixture in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours to obtain a cured resin system. The mass ratio of EP:BCPy is 70:10.5.

[0055] Comparative Examples 1-6 4,4'-bismaleimidodiphenylmethane (BMI), 4,4'-diaminodiphenyl sulfone (DDS) and BCPy were stirred and mixed, heated at 180°C to melt into a transparent solution, degassed, and then cured in an oven at 100°C / 4h+120°C / 2h+150°C / 2h+180°C / 2h to obtain a resin system cured product; the mass ratio of BMI:DDS:BCPy was 70:24.5:10.5.

[0056] Comparative Examples 1-7 4,4'-Bismaleimidodiphenylmethane (BMI) and 4,4'-diaminodiphenyl sulfone (DDS) were stirred and mixed, heated at 180°C to melt into a transparent solution, degassed, and then cured in an oven at 100°C / 4h+120°C / 2h+150°C / 2h+180°C / 2h to obtain a resin system cured product; the mass ratio of BMI:DDS was 70:24.5.

[0057] Comparative Examples 1-8 4,4'-Bismaleimidodiphenylmethane (BMI) and BCPy were mixed and prepolymerized at 150°C for 45 minutes, poured into a preheated mold, and degassed in a vacuum oven at 80°C. Subsequently, the mixture was cured in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours to obtain a cured resin system. The mass ratio of BMI:BCPy was 70:10.5.

[0058] Comparative Examples 1-9 After mixing epoxy EP (E-51) and 4,4'-bismaleimidodiphenylmethane (BMI), heat and prepolymerize at 180°C for 45 minutes, pour into the preheated mold and degas, then cure in a forced air oven at 100°C / 4h+120°C / 2h+150°C / 2h+180°C / 2h; the mass ratio of EP:BMI is 70:70.

[0059] Comparative Examples 1-10 Heat epoxy EP (E-51) at 150°C for prepolymerization for 45 minutes, pour into a preheated mold, and degas in a vacuum oven at 80°C. Then, cure in a forced air oven at 100°C / 4h+120°C / 2h+150°C / 2h+180°C / 2h.

[0060] Comparative Examples 1-11 4,4'-Bismaleimidodiphenylmethane (BMI) was prepolymerized at 180°C for 45 minutes, poured into a preheated mold, and degassed in a vacuum oven at 80°C. It was then cured in a forced air oven at 100°C / 4h+120°C / 2h+150°C / 2h+180°C / 2h.

[0061] Figure 7 The DSC curves of the raw materials and the raw material mixture show that EP is difficult to self-polymerize and undergoes self-etherification at a high temperature of around 258°C. The melting point of BMI monomer is 158°C, and self-polymerization occurs at around 234°C. The melting point of DDS is 177°C. The DSC curve of EBMI does not show a BMI melting peak. The exothermic peak of the self-polymerization reaction of the BMI double bond shifts to the low temperature region, with a peak temperature of 205°C. This shows that the introduction of EP effectively lowers the BMI polymerization reaction temperature and improves the processability of BMI. The addition of DDS can promote the reaction between EP and BMI. The DSC curves of BMI / BCPy and EP / BCPy show a clear exothermic peak near 105°C, which is due to the reaction of the amino functional group carried on BCPy with the epoxy functional group of EP and the double bond of BMI, respectively.

[0062] The DSC curve of BMI / DDS / BCPy exhibits both low-temperature and high-temperature reactions, with peak temperatures of 105°C and 223°C, respectively, driven by the BMI / BCPy and BMI / DDS reactions. The DSC curve of EP / DDS / BCPy also exhibits both low-temperature and high-temperature reactions, with peak temperatures of approximately 111°C and 210°C, respectively, driven by the EP / BCPy and EP / DDS reactions. The DSC curve of EBMI / DDS / BCPy also exhibits both low-temperature and high-temperature reactions, with peak temperatures of 106°C and 205°C, respectively. The DSC curves of BMI / DDS / BCPy and EP / BCPy / DDS indicate that the EBMI / DDS / BCPy system still exhibits reactions involving BMI / BCPy, BMI / DDS, EP / BCPy, and EP / DDS. Furthermore, due to the presence of amino groups, BMI and EP derivatives can undergo cross-linking reactions.

[0063] Figure 8 The fracture morphologies of the samples of Example 1 and Comparative Example 1-1 subjected to liquid nitrogen brittle fracture and impact fracture can be seen. It can be found that the fracture morphology of the sample of Example 1 clearly has a fibrous phase separation structure and fiber drawing, and the fracture morphology is rough, while the fracture of Comparative Example 1-1 is smooth, indicating that the system of the present invention can improve the mechanical properties of the resin matrix. Figure 9 These are optical microscope photos of the sample films of Example 1 and Comparative Example 1-1. Compared with Comparative Example 1-1, the sample of Example 1 clearly has a fibrous phase separation structure inside.

[0064] Table 1 shows the performance data of Example 1 and its comparative examples. As can be seen from Table 1, Example 1 exhibits the highest mechanical strength and impact resistance, as well as excellent thermal stability. This demonstrates the high degree of reactivity among the BCPy, EP, and BMI of the present invention, and the presence of the UPy structure, which allows for hydrogen bond formation, thereby dissipating energy during material loading through hydrogen bond dissociation. In particular, BCPy exhibits strong interfacial interactions with the resin matrix. Driven by the polymerization reaction dynamics, the linear BCPy structure is easily extruded into a linear structure during resin crosslinking, thereby forming a nanofiber structure within the resin matrix. This nanofiber structure further enhances the mechanical properties of the resin system and effectively maintains the thermal stability of the resin matrix.

[0065] Table 1 Performance data of Example 1 and Comparative Example

[0066] *: The system is not cured or the degree of cure is too low to form a shape, so mechanical properties cannot be obtained or other properties do not need to be tested. Example

[0067] Epoxy EP (E-51) and 4,4'-bismaleimidodiphenylmethane (BMI) were placed in a reaction vessel and heated at 150°C for 5 minutes to melt into a transparent solution. 4,4'-Diaminodiphenylsulfone (DDS) was then added and prepolymerized for 45 minutes. BCPy was then added and stirred, and the mixture was poured into a preheated mold. The mixture was degassed in an 80°C vacuum oven and subsequently cured in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours to obtain a cured resin system. The mass ratio of EP:BMI:DDS:BCPy was 70:70:24.5:7.

[0068] Table 2 shows the performance data of Example 2 and Comparative Example 1-1. As can be seen from Table 2, Example 2 has the best mechanical strength and impact resistance, as well as excellent thermal stability, indicating that the resin system constructed in the present invention is conducive to improving the overall performance of the material. This is mainly attributed to the low-temperature reaction behavior of BCPy with EP and BMI, the strong interface between BCPy and the resin matrix, and the unique nanofiber structure and hydrogen bonding in the resin matrix.

[0069] Table 2 Mechanical and thermal properties data of Example 2 and Comparative Example 2

[0070] Example 3 Epoxy EP (E-51) and 4,4'-bismaleimidodiphenylmethane (BMI) were placed in a reaction vessel and heated at 150°C for 5 minutes to melt into a transparent solution. 4,4'-Diaminodiphenylsulfone (DDS) was then added and prepolymerized for 45 minutes. BCPy was then added and stirred, and the mixture was poured into a preheated mold. The mixture was degassed in an 80°C vacuum oven and subsequently cured in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours to obtain a cured resin system. The mass ratio of EP:BMI:DDS:BCPy was 70:70:14:21.

[0071] Comparative Example 3 Epoxy EP (E-51) and 4,4'-bismaleimidodiphenylmethane (BMI) were placed in a reaction vessel and heated at 150°C for 5 minutes to melt into a transparent solution. 4,4'-Diaminodiphenylsulfone (DDS) was then added and prepolymerized for 45 minutes. After stirring, the mixture was poured into a preheated mold and degassed in an 80°C vacuum oven. The mixture was then cured in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours to obtain a cured resin system. The mass ratio of EP:BMI:DDS was 70:70:14.

[0072] Table 3 shows the performance data of Example 3 and its comparative examples. As can be seen from Table 3, Example 3 has the best mechanical strength and impact resistance, as well as excellent thermal stability, indicating that the resin system constructed in the present invention is conducive to improving the overall performance of the material. This is mainly attributed to the low-temperature reaction behavior of BCPy with EP and BMI, the strong interface between BCPy and the resin matrix, and the unique nanofiber structure and hydrogen bonding in the resin matrix.

[0073] Table 3 Mechanical and thermal properties data of Example 3 and Comparative Example 3

[0074] Example 4 Epoxy resin EP (E-44) and 4,4'-bismaleimidodiphenylmethane (BMI) were placed in a reaction vessel and heated at 150°C for 5 minutes to melt into a transparent solution. Diaminodiphenylmethane (DDM) was then added and prepolymerized for 45 minutes. BCPy was then added and stirred, and the mixture was poured into a preheated mold. The mixture was degassed in an 80°C vacuum oven and subsequently cured in a forced air oven at 100°C for 4 hours, 120°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours to obtain a cured resin system. The mass ratio of E-44:BMI:DDM:BCPy was 70:70:21:21.

[0075] Comparative Example 4-1 Epoxy resin EP (E-44) and 4,4'-bismaleimidodiphenylmethane (BMI) were placed in a reaction vessel, heated at 150°C for 5 minutes to melt into a transparent solution, and then diaminodiphenylmethane (DDM) was added and prepolymerized for 45 minutes. After stirring, the mixture was poured into a preheated mold and degassed in a vacuum oven at 80°C. Subsequently, the mixture was cured in a blast oven at 100°C / 4h+120°C / 2h+150°C / 2h+180°C / 2h to obtain a cured resin system.

[0076] Table 4 shows the performance data of Example 4 and its comparative examples. As can be seen from Table 4, Example 4 has the best mechanical strength and impact resistance, as well as excellent thermal stability, indicating that the resin system constructed in the present invention is conducive to improving the overall performance of the material. This is mainly attributed to the low-temperature reaction behavior of BCPy with EP and BMI, the strong interface between BCPy and the resin matrix, and the unique nanofiber structure and hydrogen bonding in the resin matrix.

[0077] Table 4 Mechanical and thermal properties data of Example 4 and Comparative Example 4

[0078] To address the problem of low heat resistance of block copolymers and their weak interface with the resin matrix, which leads to a significant decrease in the heat resistance and strength of thermosetting resins, the present invention synthesizes a new block copolymer derivative (BCPy) containing reactive end groups and multiple hydrogen-bonding end groups and excellent heat resistance. This block copolymer derivative can not only form a nanophase structure in the resin matrix to toughen and modify the thermosetting resin, but also maintain the inherent heat resistance and strength of the thermosetting resin.

Claims

1. A thermosetting resin system with a nanophase structure, characterized in that: The raw materials for preparing the thermosetting resin system with nanophase structure include epoxy resin, bismaleimide, polylactic acid-b-polycaprolactone containing reactive end groups and multiple hydrogen bond end groups, and a curing agent.

2. The thermosetting resin system having a nanophase structure according to claim 1, characterized in that: The epoxy resin includes one of bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated epoxy resin, novolac epoxy resin, flame retardant epoxy resin or any combination thereof; the bismaleimide includes bismaleimidodiphenylmethane and bismaleimidodiphenyl ether; and the curing agent includes an amine curing agent.

3. The thermosetting resin system with a nanophase structure according to claim 1, characterized in that: BCP-UPy was prepared by reaction of polylactic acid-b-polycaprolactone block copolymer and 2-amino-6-methylpyrimidin-4(3H)-one as raw materials; BCP-UPy was then reacted with a coupling agent to prepare polylactic acid-b-polycaprolactone containing reactive end groups and multiple hydrogen bond end groups.

4. The thermosetting resin system having a nanophase structure according to claim 1, characterized in that: The total weight of the epoxy resin and the bismaleimide is 100%, the weight of the polylactic acid-b-polycaprolactone containing reactive end groups and multiple hydrogen bond end groups is 3% to 30%, and the weight of the curing agent is 0% to 40% (excluding 0).

5. The method for preparing the thermosetting resin system having a nanophase structure according to claim 1, characterized in that: The method comprises the following steps: melting and mixing epoxy resin and bismaleimide, adding a curing agent, and adding polylactic acid-b-polycaprolactone containing reactive end groups and multiple hydrogen bond end groups after prepolymerization to obtain a thermosetting resin system with a nanophase structure.

6. The method for preparing a thermosetting resin system having a nanophase structure according to claim 5, characterized in that: The temperature of the melt mixing is 120 to 170° C.; the temperature of the prepolymerization is 120 to 170° C., and the time is 0 to 2 hours, excluding 0.

7. A polylactic acid-b-polycaprolactone containing reactive end groups and multiple hydrogen bond end groups, characterized in that: BCP-UPy was prepared by reaction of polylactic acid-b-polycaprolactone block copolymer and 2-amino-6-methylpyrimidin-4(3H)-one as raw materials; BCP-UPy was then reacted with a coupling agent to prepare polylactic acid-b-polycaprolactone containing reactive end groups and multiple hydrogen bond end groups.

8. A cured thermosetting resin having a nanostructure, characterized in that: The thermosetting resin cured product with a nanophase structure is obtained by curing the thermosetting resin system with a nanophase structure according to claim 1.

9. The method for preparing a cured thermosetting resin having a nanostructure according to claim 8, wherein: The thermosetting resin system with a nanophase structure according to claim 1 is cured at 100 to 200° C. for 8 to 12 hours to obtain the thermosetting resin cured product with a nanophase structure.

10. Use of the thermosetting resin system with a nanophase structure according to claim 1, the polylactic acid-b-polycaprolactone containing reactive end groups and multiple hydrogen bond end groups according to claim 7, or the thermosetting resin cured product with a nanophase structure according to claim 8 in the preparation of resin-based materials.

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