A modified POSS interpenetrating network-based epoxy resin with synergistic reinforcement and toughening and a preparation method thereof

Abstract

The present invention relates to the technical field of epoxy resin toughening, and in particular to an epoxy resin based on modified POSS interpenetrating network synergistically enhanced toughening and a preparation method thereof. It comprises an epoxy resin, a vinyl ester resin, a modified POSS, a curing agent, an initiator and a accelerator; the modified POSS is obtained by reacting OVPOSS with a 3-mercaptopropionic acid derivative. The modified POSS is used as a toughening core, and in the resin system, a phase-separated IPN structure is formed by introducing a VER component to improve the overall strength and plastic deformation capacity. Nano-scale dispersion is achieved in the resin matrix through chemical reaction, and plastic shear deformation is caused by particle debonding as a trigger point to achieve efficient toughening. Under the optimal state, the tensile strength can be increased by 17.92%, the Young's modulus can be increased by 9.0%, and the impact toughness can be increased by 139.6%. The simple and efficient synergistic toughening scheme provides ideas and methods for preparing a high-toughness and high-strength advanced composite material matrix.

Description

Technical Field

[0001] The invention relates to the technical field of epoxy resins, and in particular to an epoxy resin based on modified POSS interpenetrating network synergistically enhanced and toughened epoxy resin and a preparation method thereof. Background Art

[0002] Epoxy resin is widely used as a matrix for high-performance fiber-reinforced composites due to its excellent mechanical and thermal properties. In addition, it is the most versatile commercial thermosetting resin used in various scenarios, such as adhesives, coatings, and structural component matrices. However, since pure epoxy resin forms a three-dimensional cross-linked network structure after curing, it has disadvantages such as high brittleness and poor impact resistance. Therefore, the toughening of epoxy resin has always been one of the key research topics in related fields.

[0003] At present, the basic toughening modification methods for epoxy resins include: 1) introducing a second phase through physical blending; 2) chemically modifying epoxy resins by adding flexible main chains, etc.; 3) constructing an interpenetrating network structure (IPN). However, a single improvement in toughness is often accompanied by a decrease in other properties.

[0004] For example, CN106146857A discloses a method for preparing a carboxyl-terminated liquid fluororubber toughened modified epoxy resin system. The elongation at break of the obtained rubber toughening system can be increased by up to 45%, but the use of rubber toughening agents will also lead to a significant decrease in the glass transition temperature and modulus of the system. In summary, the toughening method for constructing an IPN structure can integrate the advantages of each component and is expected to comprehensively improve the performance of the system. CN114085491A discloses a method for preparing a polyetheretherketone modified epoxy resin composition. By modifying ordinary epoxy resin by mixing each group of raw materials according to the formula ratio, its flexibility is significantly improved. However, due to the difficulty in controlling the phase morphology and limited processing flexibility, there are certain challenges in further application.

[0005] Considering the limitations of a single toughening method, researchers have tried to combine two or more single toughening agents to seek comprehensive improvements in the performance of epoxy resins. However, a simple combination of single toughening agents is usually difficult to improve the performance of epoxy resins, and sometimes even leads to reduced mechanical properties. For example, Marouf (Marouf, BT; Pearson, RA; Bagheri, R. Anomalous fracture behavior in an epoxy-based hybrid composite [J]. Mat. Sci. Eng. A-Struct. 2009, 515 (1-2): 49-58.) added nanoclay and core-shell rubber particles to the epoxy resin matrix and found that the fracture toughness of the composite toughening system was significantly reduced compared with the single-component toughening method. They believe that this is due to the competitive effect of the mechanisms between different toughening components.

[0006] Polyhedral oligomeric silsesquioxane (POSS) has a diameter of 1-3nm and is the smallest existing form of silica. It has a special structure of an internal silicon / oxygen core and an external organic substituent. The former can significantly enhance the thermomechanical and physical properties of the modified resin matrix, while the latter makes it extremely designable. The above advantages make it one of the most promising candidate materials for achieving synergistic toughening. However, like other nanofillers, POSS is also plagued by agglomeration problems. Therefore, the improvement of the mechanical properties of unmodified POSS is largely limited. There have been many studies on the modification of POSS to obtain better dispersibility and higher toughness, but at the same time increase the complexity of the process. Therefore, a simple and effective modification preparation method that can simultaneously improve the strength and toughness of epoxy resin is an urgent problem to be solved in the current research field of high-performance resins and their composite materials. Summary of the invention

[0007] The invention aims to solve the problem that toughening and strength of epoxy resin cannot be achieved at the same time, and provides an epoxy resin with synergistically enhanced toughening based on a modified POSS interpenetrating network. A fully interpenetrating network structure toughening system is formed by utilizing an addition polymerization network formed by the modified POSS and a vinyl ester resin (VER) and an epoxy resin curing network, so that efficient toughening and strengthening are achieved at the same time, and an epoxy resin with high impact performance and strength is obtained.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] An epoxy resin based on modified POSS interpenetrating network synergistically enhanced and toughened comprises the following components: epoxy resin, vinyl ester resin, modified POSS, curing agent, initiator and accelerator;

[0010] The modified POSS is obtained by reacting octavinylsilsesquioxane (OVPOSS) with a 3-mercaptopropionic acid derivative.

[0011] The present invention realizes reactivity and compatibility simultaneously by designing a modified POSS with a special structure, wherein the unreacted vinyl bond can be subjected to free radical polymerization with a vinyl ester matrix, and the modified heteroatom group has structural similarity with the matrix on the one hand, and can be compatible with the surrounding matrix through physical entanglement on the other hand, and finally realizes nano-scale dispersion. In addition, the present invention establishes a full interpenetrating network structure by introducing a vinyl ester resin highly similar to the epoxy resin molecular structure, and realizes the comprehensive improvement (including the plastic deformation ability before failure) of the comprehensive performance under the non-phase separation. On the basis of this "preliminary" strengthening and toughening, the modified POSS is firstly strengthened by chemical crosslinking and physical entanglement integration into the interpenetrating network, and the plastic shear yield of the surrounding matrix is ​​triggered by particle debonding when subjected to external force, thereby absorbing energy significantly to realize the significant improvement of toughness.

[0012] The synthesis process of the modified POSS comprises the steps of: mixing OVPOSS (vinyl POSS) and 3-mercaptopropionic acid derivatives in a solvent, reacting under the action of a free radical initiator, and removing the solvent to obtain the modified POSS. In the present invention, 3-mercaptopropionic acid derivatives react with vinyl POSS, and through a mercapto-ene click reaction, a part of the vinyl groups on the OVPOSS octagonal cage is replaced with a flexible chain compound having a mercapto group, so that the prepared modified POSS has both polymerization reactivity and matrix compatibility, and can give full play to the performance advantages brought by its special structure on the basis of being integrated into an interpenetrating network structure.

[0013] The structure of the obtained EPOSS is as follows:

[0014]

[0015] Preferably, the 3-mercaptopropionic acid derivative includes any one of ethyl 3-mercaptopropionate (EMP), isooctyl 3-mercaptopropionate (IMP), octadecyl 3-mercaptopropionate (OMP), and 3-mercaptopropionic acid (AMP). Further preferably, the 3-mercaptopropionic acid derivative is ethyl 3-mercaptopropionate (EMP). As the chain length increases, the physical entanglement effect increases, and the cross-linking density of the matrix decreases. The physical entanglement can limit the increase of the free volume through the physical topological effect, thereby ensuring the mechanical properties (Young's modulus, tensile strength, hardness, etc.) at room temperature.

[0016] The molar ratio of OVPOSS to the 3-mercaptopropionic acid derivative is 1:3-5; preferably, the molar ratio of OVPOSS to the 3-mercaptopropionic acid derivative is 1:4; wherein the 3-mercaptopropionic acid derivative replaces the vinyl group at any position on OVPOSS, and its molecular structure is any one of the following formulas;

[0017]

[0018] The reaction temperature is 70-90°C and the reaction time is 4-8h;

[0019] The solvent includes one or more of toluene, xylene, and tetrahydrofuran; the free radical initiator includes AIBN and / or BPO; the amount of the free radical initiator used is 1-3wt% of the 3-mercaptopropionic acid derivative; the reaction is carried out under the protection of an inert gas; and the inert gas includes any one of nitrogen and argon.

[0020] The epoxy resin is a bisphenol A epoxy resin; preferably one or more of E54, E51, E44, and E42; the volume content of styrene solvent in the vinyl ester resin is 30-45%; if the styrene solvent is too little, the viscosity of the vinyl ester resin and even the toughening resin system will be too high. On the one hand, this will make it difficult to discharge bubbles during resin pouring, and on the other hand, it will also make it difficult to fully disperse the system through mechanical stirring, thereby affecting the subsequent sample performance; if the styrene solvent is too much, the cross-linking density of the prepared toughening system will be too high, and the brittleness will increase, which will have the opposite effect to the toughening purpose. Preferably, the volume content of styrene solvent in the vinyl ester resin is 30-40%, and more preferably 35-40%.

[0021] The curing agent includes one or more of methyltetrahydrophthalic anhydride (MeTHPA), tetrahydrophthalic anhydride (THPA), and hexahydrophthalic anhydride (HHPA); the free radical polymerization initiator includes BPO and / or TBPO; the accelerator includes DMP-30 and / or DMP-10;

[0022] The mass ratio of the epoxy resin to the vinyl ester resin is 0.8-1.2:0.8-1.2; when the ratio of the epoxy resin to the vinyl ester is too high or too low, the mixing free energy in the Flory-Huggins equation will be too large, resulting in phase separation. On the one hand, this will cause the island phase to be distributed along the fiber during the subsequent preparation of the carbon fiber composite material, thereby limiting the performance improvement. On the other hand, the inevitably introduced complex phase control process will increase the production cost. Preferably, the mass ratio of the epoxy resin to the vinyl ester resin is 1:1;

[0023] The mass ratio of EPOSS to vinyl ester resin is 1-10:100; with the addition of EPOSS, the tensile strength and Young's modulus show an upward trend, and the impact strength shows a trend of first increasing and then decreasing.

[0024] Preferably, the mass ratio of the EPOSS to the vinyl ester resin is 2-8:100, under which the comprehensive performance of the epoxy resin is more excellent.

[0025] The mass ratio of the curing agent to the epoxy resin is 80-90:100; the mass ratio of the initiator to the vinyl ester resin is 1-3:100, which is used to initiate vinyl ester polymerization, and the mass ratio of the accelerator to the epoxy resin is 0.5-2:100, which promotes epoxy curing.

[0026] The present invention also provides a method for preparing the modified POSS interpenetrating network-based synergistically enhanced and toughened epoxy resin, comprising the steps of: heating the epoxy resin in a water bath, adding vinyl ester resin and EPOSS, stirring and mixing, then adding a curing agent, stirring and mixing, adding an initiator and an accelerator after ultrasonic treatment, stirring and mixing, and curing to obtain the epoxy resin.

[0027] The water bath heating temperature is 40-70°C; within this temperature range, a low viscosity can be ensured, allowing mechanical stirring to proceed smoothly, and there will be no premature reaction between monomers.

[0028] The temperature during ultrasound is 40-70°C, and the ultrasound time is 15-60min; after ultrasound, the modified POSS has a better dispersion effect in the system, further reducing the agglomeration phenomenon.

[0029] The stirring and mixing time for each time is more than 10 minutes; preferably 10-60 minutes, or 10-30 minutes;

[0030] The curing procedure is 85-105℃ / 4h, 130-150℃ / 3h, 170-190℃ / 2h.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The EPOSS synthesized in the present invention has good reactivity and compatibility, wherein the unreacted vinyl bonds can undergo free radical polymerization with the vinyl ester matrix, while the modified heteroatom groups have structural similarities with the matrix on the one hand, and can be compatible with the surrounding matrix through physical entanglement on the other hand, ultimately achieving nanoscale dispersion.

[0033] (2) The present invention uses non-phase separation in-situ toughening technology to prepare a fully interpenetrating network structure toughening system constructed with a VER / EPOSS polymerization network and an EP curing network, wherein no phase separation occurs in the entire system, thereby avoiding the complex process of regulating the phase morphology.

[0034] (3) Compared with the unmodified epoxy resin, the toughened epoxy resin prepared by the present invention has an improved tensile strength of 17.92%, an improved Young's modulus of 9.0%, and an improved impact toughness of 139.6% under the preferred ratio (the amount of EPOSS is only about 2wt% of the total mass of the system).

[0035] (4) Efficient reinforcement and toughening are achieved through cheap raw materials and simple methods, which has great practical feasibility and industrial potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the H-NMR spectrum of EPOSS synthesized in Example 1.

[0037] Figure 2 The NMR silicon spectrum of EPOSS synthesized in Example 1

[0038] Figure 3 This is the TEM high-resolution morphology image of the E / V / EPOSS-6 sample.

[0039] Figure 4 This is the TEM morphology of the E / V / OVPOSS-6 sample.

[0040] Figure 5 This is the SEM agglomeration morphology of the E / V / OVPOSS-6 sample.

[0041] Figure 6 For E / V / OVPOSS-6 samples Figure 8 Energy spectrum mapping of silicon element under agglomerated morphology.

[0042] Figure 7 This is the SEM tensile fracture morphology of pure EP, the left side is 1k times, and the right side is 20k times.

[0043] Figure 8 This is the SEM tensile fracture morphology of the E / V sample, the left side is 1k times, and the right side is 20k times.

[0044] Fig. 9 This is the SEM tensile fracture morphology of the E / V / EPOSS-6 sample, the left side is 1k times, and the right side is 20k times. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art can make modifications or equivalent substitutions based on the understanding of the technical scheme of the present invention without departing from the spirit and scope of the technical scheme of the present invention, and all should be included in the protection scope of the present invention.

[0046] The present invention designs a modified POSS with a special structure, and the particularity of its structure can realize reactivity and compatibility at the same time; on the other hand, the present invention establishes a full interpenetrating network structure by introducing a vinyl ester resin highly similar to the epoxy resin molecular structure, and realizes the comprehensive improvement of comprehensive performance (including deformation capacity before failure) under the condition of non-phase separation. On the basis of this "preliminary" strengthening and toughening, the modified POSS is first integrated into the interpenetrating network by chemical crosslinking and physical entanglement for strengthening, and the strong bonding force makes the stress uniformly distributed, and the physical entanglement effect can limit the increase of the free volume caused by the decrease of the crosslinking density, thereby ensuring the improvement of the mechanical strength of the sample at room temperature. In addition, when subjected to a large load, the system can trigger the plastic shear yield of the surrounding matrix through particle debonding, thereby absorbing energy significantly to realize a significant improvement in toughness. The physical entanglement of the modified POSS side chain is an effective strengthening mechanism at room temperature, and the plastic shear yield of the matrix caused by the POSS debonding is the main reason for toughening, and the advantages of the two can be fully utilized in the VER / EP / POSS interpenetrating network structure.

[0047] The invention first synthesizes a modified POSS that can simultaneously achieve good reactivity and compatibility with resins, and the synthesis steps include: adding OVPOSS and 3-mercaptopropionic acid derivatives in a molar ratio of 1:3-5 into a solvent, stirring at room temperature until fully dissolved and dispersed; after nitrogen bubbling purification, adding an initiator into a flask and stirring, and heating the reaction system to continue the reaction. The solvent is removed by rotary distillation, and after vacuum drying, a light yellow or milky white viscous liquid is obtained as the modified POSS.

[0048] Then, the fully interpenetrating IPN composite system with modified POSS as the core is constructed to achieve full interpenetrating reinforcement and toughening of epoxy resin. The construction steps include: mixing VER with epoxy resin and adding curing agent. The system is uniformly distributed through mechanical stirring and ultrasonic dispersion, initiator and accelerator are added, the system is degassed and debubbled under vacuum, and heated and cured in a mold to obtain high-toughness and high-strength epoxy resin.

[0049] The raw materials used in the following specific embodiments are all purchased from the existing market; the "parts" referred to are all parts by weight.

[0050] Example 1

[0051] 2 g (3.159 mmol) of vinyl POSS and 1.696 g (12.638 mmol) of EMP were added to a 250 mL three-necked flask containing 50 mL of toluene. The three-necked flask was placed in a constant temperature water bath with a magnetic stirrer and stirred thoroughly. After bubbling purification for 30 min, 17.0 mg of AIBN was added and bubbling and stirring were continued for 10 min. The reaction system was then heated to 80 ° C for 5 h. After the reaction, toluene was removed by rotary distillation, and a light yellow viscous liquid was obtained after vacuum drying for 24 h, which was expressed as EPOSS.

[0052] Example 2

[0053] Mix 100 parts of VER with 100 parts of epoxy resin system, in which the curing agent MeTHPA is 85 parts. After the two are mixed, add 1 part of EPOSS prepared in Example 1, mechanically mix at 55°C for 30 minutes, and then disperse in ultrasound for 30 minutes, and then add initiator BPO and accelerator DMP-30 in a mass ratio of 0.5:1. Stir for 3 minutes, degas the system under vacuum to remove bubbles, then pour it into a stainless steel mold, heat and cure under the set program, and the curing system is 85°C / 4h, 140°C / 3h, 180°C / 2h. The sample is named E / V / EPOSS-1.

[0054] Example 3

[0055] Mix 100 parts of VER with 100 parts of epoxy resin system, in which the curing agent MeTHPA is 85 parts. After the two are mixed, add 3 parts of EPOSS prepared in Example 1, mechanically mix at 55°C for 30 minutes, and then disperse in ultrasound for 30 minutes, and then add initiator BPO and accelerator DMP-30 in a mass ratio of 0.5:1. Stir for 3 minutes, degas the system under vacuum to remove bubbles, then pour it into a stainless steel mold, heat and cure under the set program, and the curing system is 85°C / 4h, 140°C / 3h, 180°C / 2h. The sample is named E / V / EPOSS-3.

[0056] Example 4

[0057] Mix 100 parts of VER with 100 parts of epoxy resin system, in which the curing agent MeTHPA is 85 parts. After the two are mixed, add 6 parts of EPOSS prepared in Example 1, mechanically mix at 55°C for 30 minutes, and then disperse in ultrasound for 30 minutes, and then add initiator BPO and accelerator DMP-30 in a mass ratio of 0.5:1. Stir for 3 minutes, degas the system under vacuum to remove bubbles, then pour it into a stainless steel mold, heat and cure under the set program, and the curing system is 85°C / 4h, 140°C / 3h, 180°C / 2h. The sample is named E / V / EPOSS-6.

[0058] Example 5

[0059] 100 parts of VER were mixed with 100 parts of epoxy resin system, in which the curing agent MeTHPA was 85 parts. After the two were mixed, 10 parts of EPOSS prepared in Example 1 were added, mechanically mixed at 55°C for 30 minutes, and then dispersed in ultrasound for 30 minutes, and then initiator BPO and accelerator DMP-30 were added in a mass ratio of 0.5:1. Stir for 3 minutes, degas the system under vacuum to remove bubbles, and then pour it into a stainless steel mold and heat cure under the set program. The curing system is 85°C / 4h, 140°C / 3h, and 180°C / 2h. The sample is named E / V / EPOSS-10.

[0060] Comparative Example 1

[0061] 100 parts of VER were mixed with 100 parts of epoxy resin system, in which the curing agent MeTHPA was 85 parts. After the two were mixed, they were mechanically mixed at 55°C for 30 minutes, and then dispersed in ultrasound for 30 minutes, and then initiator BPO and accelerator DMP-30 were added in a mass ratio of 0.5:1. After stirring for 3 minutes, the system was degassed and debubbled under vacuum, and then poured into a stainless steel mold and heated and cured under the set program. The curing system was 85°C / 4h, 140°C / 3h, and 180°C / 2h. The sample was named E / V.

[0062] Comparative Example 2

[0063] Mix 100 parts of VER with 100 parts of epoxy resin system, in which the curing agent MeTHPA is 85 parts. After the two are mixed, add 1 part of unmodified OVPOSS, mechanically mix at 55°C for 30 minutes, and then disperse in ultrasound for 60 minutes, and then add initiator BPO and accelerator DMP-30 in a mass ratio of 0.5:1. Stir for 3 minutes, degas the system under vacuum to remove bubbles, then pour it into a stainless steel mold, heat and cure under the set program, and the curing system is 85°C / 4h, 140°C / 3h, 180°C / 2h. The sample is named E / V / OVPOSS-1.

[0064] Comparative Examples 3-5

[0065] According to the process of Comparative Example 2, the addition amount of unmodified OVPOSS was adjusted to 3 parts, 6 parts and 10 parts, respectively, to obtain E / V / OVPOSS-3, E / V / OVPOSS-6 and E / V / OVPOSS-10, respectively.

[0066] Example 6

[0067] 2g (3.159mmol) of vinyl POSS and 2.759g (12.638mmol) of 3-isooctyl mercaptopropionate (IMP) were added to a 250mL three-necked flask containing 50mL of toluene. The three-necked flask was placed in a constant temperature water bath with a magnetic stirrer and stirred thoroughly. After bubbling purification for 30min, 27.59mg of AIBN was added and bubbling and stirring were continued for 10min. The reaction system was then heated to 70°C for 6h. After the reaction, toluene was removed by rotary distillation, and a milky white viscous liquid was obtained after vacuum drying for 24h, which was expressed as IPOSS.

[0068] Mix 100 parts of VER with 100 parts of epoxy resin system, in which the curing agent MeTHPA is 80 parts. After the two are mixed, add 6 parts of IPOSS, mechanically mix at 70℃ for 30 minutes, and then disperse in ultrasound for 15 minutes, then add initiator BPO and accelerator DMP-10, with a mass ratio of 0.5:1. Stir for 3 minutes, degas the system under vacuum to remove bubbles, then pour it into a stainless steel mold, heat and cure under the set program, and the curing system is 100℃ / 4h, 150℃ / 3h, 190℃ / 2h. The sample is named E / V / IPOSS-6.

[0069] Example 7

[0070] 2g (3.159mmol) of vinyl POSS and 4.532g (12.638mmol) of octadecyl 3-mercaptopropionate (OMP) were added to a 250mL three-necked flask containing 50mL of xylene. The three-necked flask was placed in a constant temperature water bath with a magnetic stirrer and stirred thoroughly. After bubbling and purification for 30min, 45.32mg of AIBN was added, and bubbling and stirring were continued for 10min. The reaction system was then heated to 90°C for 4h. After the reaction, toluene was removed by rotary distillation, and a milky white viscous liquid was obtained after vacuum drying for 24h, which was represented by OPOSS.

[0071] Mix 100 parts of VER with 100 parts of epoxy resin system, in which the curing agent THPA is 80 parts. After the two are mixed, add 1 part of OPOSS, mechanically mix at 55℃ for 30 minutes, and then disperse in ultrasound for 40 minutes, then add initiator BPO and accelerator DMP-30, with a mass ratio of 0.5:1. Stir for 3 minutes, degas the system under vacuum to remove bubbles, then pour it into a stainless steel mold, heat and cure under the set program, and the curing system is 90℃ / 4h, 150℃ / 3h, 190℃ / 2h. The sample is named E / V / OPOSS-3.

[0072] Example 8

[0073] 2 g (3.159 mmol) of vinyl POSS and 1.341 g (12.638 mmol) of 3-mercaptopropionic acid (AMP) were added to a 250 mL three-necked flask containing 50 mL of tetrahydrofuran. The three-necked flask was placed in a constant temperature water bath with a magnetic stirrer and stirred thoroughly. After bubbling purification for 30 min, 13.41 mg of BPO was added and bubbling and stirring were continued for 10 min. The reaction system was then heated to 80 ° C for 5 h. After the reaction, toluene was removed by rotary distillation, and a milky white viscous liquid was obtained after vacuum drying for 24 h, which was expressed as APOSS.

[0074] Mix 100 parts of VER with 100 parts of epoxy resin system, in which the curing agent HHPA is 90 parts. After the two are mixed, add 1 part of APOSS, mechanically mix at 55℃ for 30 minutes, and then disperse in ultrasound for 30 minutes, then add initiator BPO and accelerator DMP-10, with a mass ratio of 0.5:1. Stir for 3 minutes, degas the system under vacuum to remove bubbles, then pour it into a stainless steel mold, heat and cure under the set program, and the curing system is 90℃ / 4h, 130℃ / 3h, 170℃ / 2h. The sample is named E / V / AMPOSS-1.

[0075] Example 9

[0076] Take a vinyl ester resin (VER-1) with a styrene solvent volume fraction of 30%, mix 100 parts of VER with 100 parts of epoxy resin system, in which the curing agent MeTHPA is 85 parts. After the two are mixed, add 3 parts of EPOSS prepared in Example 1, mechanically mix at 70°C for 30 minutes, and then disperse in ultrasound for 30 minutes, and then add initiator BPO and accelerator DMP-30, with a mass ratio of 0.5:1. Stir for 3 minutes, degas the system under vacuum to remove bubbles, then pour it into a stainless steel mold, heat and cure under the set program, and the curing system is 85°C / 4h, 130°C / 3h, 170°C / 2h. The sample is named E / V-1 / EPOSS-6.

[0077] Example 10

[0078] Take a vinyl ester resin (VER-2) with a styrene solvent volume fraction of 45%, mix 100 parts of VER with 100 parts of epoxy resin system, in which the curing agent MeTHPA is 85 parts. After the two are mixed, add 3 parts of EPOSS prepared in Example 1, mechanically mix at 55°C for 30 minutes, and then disperse in ultrasound for 30 minutes, and then add initiator BPO and accelerator DMP-30, with a mass ratio of 0.5:1. Stir for 3 minutes, degas the system under vacuum to remove bubbles, then pour it into a stainless steel mold, heat and cure under the set program, and the curing system is 100°C / 4h, 150°C / 3h, 190°C / 2h. The sample is named E / V-2 / EPOSS-6.

[0079] Performance Testing

[0080] 1. Data representation

[0081] The EPOSS prepared in Example 1 was subjected to nuclear magnetic resonance scanning.

[0082] like Figure 1 As shown, each 1 The assignment marks of H NMR signals are as follows: 6.27-5.68 ppm (m, 3H, 8 and 7), 4.14 ppm (q, 2H, 5), 3.01-2.70 ppm (m, 2H, 4), 2.70-2.40 ppm (m, 4H, 2 and 3), 1.25 ppm (t, 3H, 6), 1.04 ppm (m, 2H, 1). The above quantitative results indicate that when the stoichiometric ratio of OVPOSS:EMP is equal to 1:4, half of the vinyl groups on OVPOSS react with EMP.

[0083] like Figure 2 The measured 29 As shown in the Si NMR spectrum, OVPOSS only shows one chemical shift peak at -79.67ppm due to the single chemical environment of silicon atoms in the silicon-oxygen octagonal cage, while another peak of EPOSS at -68.76ppm proves that the EMP group has successfully reacted with the OVPOSS molecule. In addition, there are four sub-peaks in the enlarged view of each signal peak in the EPOSS silicon spectrum (enlarged and shown on the left and right respectively). For the R1-Si peak of about -80.49ppm, it includes four consecutive sub-peaks, located at -80.68ppm, -80.56ppm, -80.42ppm and -80.30ppm, respectively, corresponding to (R1-Si)(R1-Si)3, (R1-Si)(R1-Si)2(R2-Si), (R1-Si)(R1-Si)(R2-Si)2, (R1-Si)(R2-Si)3, as shown in FIG. Figure 2Similarly, for the R2-Si peak, there are four peaks around -68.75ppm, corresponding to the four chemical situations of R2-Si: (R2-Si)(R2-Si)3(-68.68ppm), (R2-Si)(R2-Si)2(R1-Si)(-68.77ppm), (R2-Si)(R2-Si)(R1-Si)2(-68.84ppm), (R2-Si)(R1-Si)3(-68.94ppm).

[0084] In summary, EPOSS with four vinyl groups and four EMP groups was successfully synthesized.

[0085] 2. Dispersion effect of EPOSS

[0086] Since the dispersibility of nanoparticles is an important factor in determining whether they can exert mechanical performance advantages, the dispersion of nanoparticles in the samples before and after modification was characterized.

[0087] The E / V / EPOSS-6 prepared in Example 4 and the E / V / OVPOSS-6 prepared in Comparative Example 4 were subjected to TEM scanning to observe their dispersion in the matrix. The results are as follows: Figure 3 and Figure 4 It can be seen that the modified EPOSS is evenly dispersed in the system, presenting a nanoscale dispersion morphology without agglomeration. Figure 4 The unmodified OVPOSS showed obvious agglomeration morphology in the system, and the size of the agglomeration domain was about several microns.

[0088] exist Figure 5 SEM images and Figure 6 In the silicon element energy spectrum mapping scan, the unmodified OVPOSS showed obvious agglomeration morphology in the matrix, which also greatly affected the mechanical properties of the sample (see Table 1).

[0089] 3. Mechanical properties

[0090] Mechanical properties of pure epoxy resin (EP) and epoxy resins prepared in Examples 2-10 and Comparative Examples 1-5 were tested. Pure epoxy resin (EP) refers to samples containing only epoxy, no VER and initiator, and the same curing agent and accelerator. The tensile test was conducted according to GB T2567-2008 standard, and the impact test was conducted according to GBT 1043.1-2008 standard. The results are shown in Table 1.

[0091] Table 1 Mechanical properties of epoxy resins in Examples and Comparative Examples

[0092]

[0093]

[0094] As can be seen from Table 1, with the addition of EPOSS, the mechanical properties show a significant enhancement. Among them, the tensile strength continues to increase, reaching a maximum value of 103.37MPa at E / V / EPOSS-6, which is 17.92% higher than pure EP. The Young's modulus first decreases slightly and then increases, and finally reaches 2110MPa, which is 9.0% higher than pure EP. The elongation at break increases when VER is added. This is because the construction of the interpenetrating network structure improves the local migration ability of the chain segments, while the addition of EPOSS slightly decreases it. For impact strength, the addition of EPOSS greatly improves it, among which the E / V / EPOSS-6 sample has a maximum value of 37.88KJ / m 2 , which is an increase of 139.6% compared to pure EP, but then shows a downward trend due to the aggregation of EPOSS.

[0095] The overall improvement of mechanical properties is attributed to the fully interpenetrating network structure with modified POSS as the triggering site of the toughening mechanism. When loaded, the modified POSS is first chemically cross-linked through the unmodified vinyl and physically entangled with the modified side chains and the surrounding matrix segments to integrate into the interpenetrating network for reinforcement. Good bonding makes the stress uniformly distributed, and the physical entanglement will limit the increase in free volume caused by the decrease in cross-linking density, thus ensuring the improvement of the mechanical strength of the sample at room temperature. In addition, when subjected to large loads, the system can trigger the plastic shear yield of the surrounding matrix through particle debonding, thereby absorbing a large amount of energy to achieve a significant improvement in toughness. The physical entanglement of the modified POSS side chains is an effective reinforcement mechanism at room temperature, and the plastic shear yield of the matrix triggered by POSS debonding is the main reason for toughening, and the advantages of both can be fully utilized in the VER / EP / POSS interpenetrating network structure.

[0096] For other modified samples (E / V / IPOSS, E / V / OPOSS, E / V / AMPOSS), it can be seen that the addition also makes the mechanical properties show an enhancing trend, but the mechanical properties are not ideal. The EPOSS modified samples have better comprehensive mechanical properties than other samples with the same proportion.

[0097] For the toughening systems of resins with different styrene contents, the toughening effects of E / V-1 / EPOSS-6 and E / V-2 / EPOSS-6 of Examples 9 and 10 are weaker than those of Example 5 (E / V / EPOSS-6). In fact, if the styrene solvent is reduced, the viscosity of the vinyl ester resin and even the toughening resin system will be too high, which may make it difficult to discharge bubbles during resin pouring, or make it difficult to fully disperse the system through mechanical stirring, thereby affecting the subsequent performance of the sample. If the styrene solvent is too much, the crosslinking density of the prepared toughening system will be too high, and the brittleness will increase, which will have the opposite effect to the toughening purpose. If the styrene solvent in VER is further reduced or increased, it will be unfavorable to the result.

[0098] The tensile fracture samples of pure EP, E / V of comparative example 1 and E / V / EPOSS-6 of example 4 were observed for fracture morphology. The results are as follows: Figure 7-9 . Figure 7 It can be seen that the pure sample EP exhibits obvious brittle fracture characteristics, while the comparative example 1 ( Figure 8 ) shows an obvious matrix shear yield toughening mechanism morphology, indicating that the interpenetrating network structure formed by the introduction of VER not only toughens and strengthens the resin system as a whole, but also increases the ductility of the matrix, which enables the matrix to dissipate energy through plastic shear deformation when subjected to external stress loads; Fig. 9 It can be seen that for the system with EPOSS introduced, the E / V / EPOSS-6 sample not only shows the plastic shear deformation morphology, but also shows the debonding of nanoparticles at a smaller scale, and the holes formed after the debonding of POSS provide sites and space for the plastic shear deformation of the matrix. Under the action of the former, the latter is widely triggered as the main toughening mechanism, thereby greatly improving the toughness of the matrix. Fig. 9 The circled part is the morphology of the “particle debonding-matrix shear yielding” toughening mechanism, which can be seen to be widely distributed in the sample.

Claims

1. An epoxy resin based on modified POSS interpenetrating network synergistically enhanced and toughened, characterized in that: The invention comprises the following raw material components: epoxy resin, vinyl ester resin, modified POSS, curing agent, initiator and accelerator; The modified POSS is obtained by reacting OVPOSS with substance A; The volume content of styrene solvent in the vinyl ester resin is 30-45%; the substance A is any one of ethyl 3-mercaptopropionate, isooctyl 3-mercaptopropionate, octadecyl 3-mercaptopropionate, and 3-mercaptopropionic acid.

2. The epoxy resin based on the synergistically enhanced toughening of modified POSS interpenetrating network according to claim 1, characterized in that, The synthesis process of the modified POSS comprises the steps of: mixing OVPOSS and substance A in a solvent, reacting under the action of a free radical initiator, and removing the solvent to obtain the modified POSS.

3. The epoxy resin based on the modified POSS interpenetrating network synergistically enhanced toughening according to claim 2, characterized in that, The molar ratio of OVPOSS to substance A is 1:3-5; the reaction temperature is 70-90°C, and the reaction time is 4-8h; The solvent includes one or more of toluene, xylene, and tetrahydrofuran; the free radical initiator includes AIBN and / or BPO; the amount of the free radical initiator used is 1-3wt% of substance A; and the reaction is carried out under the protection of an inert gas.

4. The epoxy resin based on modified POSS interpenetrating network synergistically enhanced toughening according to claim 1, characterized in that, The epoxy resin is bisphenol A epoxy resin; The curing agent includes one or more of methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and tetrahydrophthalic anhydride; the initiator includes BPO and / or TBPO; and the accelerator includes DMP-30 and / or DMP-10.

5. The epoxy resin based on modified POSS interpenetrating network synergistically enhanced toughening according to claim 1, characterized in that, The mass ratio of the epoxy resin to the vinyl ester resin is 0.8-1.2:0.8-1.2; the mass ratio of the modified POSS to the vinyl ester resin is 1-10:

100.

6. The epoxy resin based on modified POSS interpenetrating network synergistically enhanced toughening according to claim 1, characterized in that, The mass ratio of the curing agent to the epoxy resin is 80-90:100; the mass ratio of the initiator to the vinyl ester resin is 1-3:100; and the mass ratio of the accelerator to the epoxy resin is 0.5-2:

100.

7. according to the preparation method of the epoxy resin based on the synergistically enhanced toughening of modified POSS interpenetrating network described in any one of claims 1-6, it is characterized in that, The method comprises the following steps: heating the epoxy resin in a water bath, adding vinyl ester resin and modified POSS, stirring and mixing, adding a curing agent, stirring and mixing, adding an initiator and an accelerator after ultrasonic treatment, stirring and mixing, and curing to obtain the epoxy resin.

8. The preparation method of the epoxy resin based on the modified POSS interpenetrating network synergistically enhanced toughening according to claim 7, characterized in that, The water bath heating temperature is 40-70°C; the ultrasonic temperature is 40-70°C, and the ultrasonic time is 15-60min; and the stirring and mixing time is more than 10min each time.

9. The preparation method of the epoxy resin based on the modified POSS interpenetrating network synergistically enhanced toughening according to claim 7, characterized in that, The curing procedure is 85-105 ℃ / 4 h, 130-150 ℃ / 3 h, 170-190 ℃ / 2 h.

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