CN113698575B

CN113698575B - Siloxane Schiff base structure-based high-impact-resistance remodelable flame-retardant epoxy resin and preparation method thereof

Info

Publication number: CN113698575B
Application number: CN202111027406.5A
Authority: CN
Inventors: 王玉忠; 丁晓敏; 陈力; 郭德明; 刘博文; 罗曦; 何凤鸣; 肖艳芳
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2021-09-02
Filing date: 2021-09-02
Publication date: 2022-04-26
Anticipated expiration: 2041-09-02
Also published as: CN113698575A

Abstract

The invention discloses a high-impact-resistance remodelable flame-retardant epoxy resin based on a siloxane Schiff base structure and a preparation method thereof, wherein the preparation method comprises the following steps of 1: adding aromatic aldehyde compounds and a phase transfer catalyst into excessive epoxy chloropropane for reaction; dropping sodium hydroxide solution under the ice bath condition for reaction, diluting and washing the solution, taking an organic phase, drying and carrying out rotary evaporation to obtain an epoxidized aromatic aldehyde compound; step 2: adding an epoxy aromatic aldehyde compound, a catalyst and siloxane diamine into a solvent, fully reacting, and then performing rotary evaporation to obtain a liquid epoxy monomer; and step 3: and fully mixing the liquid epoxy monomer and the curing agent, and forming and curing to obtain the required high-impact-resistance remodelable flame-retardant epoxy resin based on the siloxane Schiff base structure. The epoxy resin obtained by the invention has excellent impact resistance, solves the inherent contradiction between high mechanical property and easy plasticity of the aromatic Schiff base epoxy resin, and shows higher fire safety.

Description

Siloxane Schiff base structure-based high-impact-resistance remodelable flame-retardant epoxy resin and preparation method thereof

Technical Field

The invention relates to the technical field of epoxy resin, in particular to high-impact-resistance remodelable flame-retardant epoxy resin based on a siloxane Schiff base structure and a preparation method thereof.

Background

Because of its excellent dimensional stability, adhesion property, electrical insulation property, mechanical property and corrosion resistance, epoxy resin is widely used in various fields of national defense and national economy, and especially becomes an indispensable important material in the fields of composite materials and structural materials, electronics and electrical, coatings, adhesives and the like. However, the three-dimensional network structure formed after the epoxy resin is cured limits the mobility of the molecular chain segment, so that the cured product shows obvious brittleness and poor resistance to crack propagation and external force impact. Meanwhile, the limited oxygen index of the epoxy resin is only about 20 percent, the epoxy resin belongs to a flammable material, and once the epoxy resin is ignited, the fire rapidly spreads and a large amount of dense smoke and toxic gas are generated, so that the epoxy resin has great fire safety hidden danger in practical application. Once fully cured, the permanently cross-linked structure of the epoxy resins makes them difficult to reprocess and recycle, thus producing a significant amount of damaged, aged, and discarded epoxy resins. Particularly, the accumulation of epoxy composite wastes not only occupies agricultural and industrial fields but also pollutes the environment, and the above-mentioned characteristics become a bottleneck restricting the application and further development of epoxy resin in high-tech fields.

At present, Schiff base structure epoxy resin reports, for example 2006101189196, disclose a Schiff base type liquid crystal epoxy resin and a preparation method and application thereof. Aromatic groups or aromatic groups with flexible intervals are arranged between double conjugated imine bonds of the epoxy prepolymer. The liquid crystal epoxy resin has wide liquid crystal interval, and is easy to control the curing reaction with the curing agent to obtain the cured product with frozen liquid crystal structure. Although the epoxy resin has good thermal property and shape memory capability, the mechanical property or impact resistance and flame retardant property which restrict the development of the traditional bisphenol A epoxy resin are not taken into consideration. For example, 2006101189209 discloses a method for modifying an epoxy resin with a Schiff base type liquid crystal epoxy resin. The modified epoxy resin is obtained by blending the Schiff base epoxy prepolymer with a commercial epoxy formula and curing. The modified epoxy resin has higher tensile strength and elongation at break because the liquid crystal Schiff base can induce phase separation to form a fibril structure. But is far from the mechanical properties of the traditional bisphenol A epoxy resin, and greatly limits the application potential of the traditional epoxy resin in the application field.

The aromatic Schiff base bond has the characteristic of thermal excitation dynamic reversibility, and the aromatic Schiff base epoxy resin developed by the structure can realize self-repairing and cyclic utilization of the matrix thermosetting material. For example, 2020101023237 discloses a self-healing epoxy resin material and a preparation method thereof. The epoxy resin is prepared by curing commercial epoxy resin by amine curing agent containing Schiff base, has high-efficiency scratch self-repairing capability, but does not concern the remolding capability of matrix resin. For example, 2017108451915 discloses an intrinsic self-repairing hyperbranched epoxy resin, a preparation method and an application thereof, wherein the epoxy resin is obtained by epoxidizing and curing a polyol and a phenolic compound monomer containing an aromatic Schiff base bond. The epoxy resin has the capability of multiple fracture-repair and crushing-repair, the repair efficiency is about 90 percent, and the cyclic utilization of matrix resin is realized. However, the introduction of the hyperbranched flexible polyol epoxy monomer destroys the mechanical properties of the epoxy resin, and greatly limits the applicable field range of the epoxy resin.

Therefore, the novel epoxy resin with high impact resistance, flame retardance and substrate plasticity is developed to meet the application in the high-end technical field, so that the service life of the epoxy resin material can be prolonged, resources can be saved, the environment can be protected, and the practical significance is important.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a high-impact-resistance remodelable flame-retardant epoxy resin with a siloxane Schiff base structure and a preparation method thereof.

The technical scheme adopted by the invention is as follows:

a high impact resistant remodelable flame-retardant epoxy resin based on a siloxane Schiff base structure has the following structure:

in the formula, R₁Is composed of

Any one, two or more of them are formed in an arbitrary proportion; n and

the number of the groups is consistent; r₂Is composed of

Wherein X is methyl or phenyl and a is 1, 2 or 3.

A preparation method of a high-impact-resistance remodelable flame-retardant epoxy resin based on a siloxane Schiff base structure comprises the following steps:

step 1: adding an aromatic aldehyde compound and a phase transfer catalyst into excessive epoxy chloropropane, and fully performing ring opening reaction at the temperature of 60-100 ℃; dropwise adding a sodium hydroxide solution into the mixture obtained in the step 1 under an ice bath condition, fully performing a ring-closing reaction, diluting and washing an organic solvent, taking an organic phase, drying, and performing rotary evaporation to obtain an epoxidized aromatic aldehyde compound;

step 2: adding the epoxidized aromatic aldehyde compound obtained in the step (1), a catalyst and siloxane diamine into a solvent in a protective atmosphere, fully reacting at 100-120 ℃, and performing rotary evaporation to obtain a liquid epoxy monomer;

and step 3: and fully mixing the liquid epoxy monomer and the curing agent, and curing and forming to obtain the required high-impact-resistance remodelable flame-retardant epoxy resin based on the siloxane Schiff base structure.

Further, in the step 1, the molar ratio of the aromatic aldehyde compound to the phase transfer catalyst is 1: 0.05-0.2, and the molar ratio of the aromatic aldehyde compound to the sodium hydroxide is 1: 2-5; the molar ratio of the epoxidized aromatic aldehyde compound to the siloxane diamine in the step 2 is 2.0-2.1: 1; the molar ratio of the liquid epoxy monomer to the curing agent in the step 3 is 1: 0.5-1.

Further, the ring-opening reaction time of the step 1 is 2-6 hours, and the ring-closing reaction time is 2-6 hours; the reaction time of the step 2 is 6-12 h.

Further, the curing process in step 3 is as follows:

precuring for 1-2 h at 80 ℃, hot pressing for 0-2 h at 110 ℃, hot pressing for 0-18 h at 120 ℃, hot pressing for 0-18 h at 140 ℃, hot pressing for 0-4 h at 160 ℃ and hot pressing for 0-4 h at 180 ℃.

Further, the aromatic aldehyde compound in the step 1 is

Any one, two or more of them are constituted at an arbitrary ratio.

Further, the phase transfer catalyst in step 1 is any one, two or more of tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, benzyltriethylammonium chloride, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride and tetradecyltrimethylammonium chloride in any proportion.

Further, the siloxane diamine in the step 2 is

Wherein X is methyl or phenyl and a is 1, 2 or 3.

Further, the catalyst in the step 2 is glacial acetic acid or hydrochloric acid; wherein the molar ratio of the aromatic aldehyde compound to the glacial acetic acid is 1: 0.06-0.10, and the molar ratio of the aromatic aldehyde compound to the hydrochloric acid is 1: 0.04-0.08.

The curing agent in step 3 is one or two or more of an amine curing agent, a phenol curing agent, a carboxylic acid curing agent, an acid anhydride curing agent, a thiol curing agent, a tertiary amine curing agent, and an imidazole curing agent at any ratio.

The invention has the beneficial effects that:

(1) the epoxy resin obtained by the invention has the tensile strength of 47-78 MPa, the bending strength of 98-170 MPa and the unnotched impact strength of 27.1-65.3 kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is reduced by 31-56% compared with bisphenol A epoxy resin, and the total smoke release TSR is reduced by 20-57% compared with bisphenol A epoxy resin; the reprocessing and remodeling efficiency is 60-98%;

(2) according to the invention, a rigid-flexible epoxy network is obtained by combining a flexible chain segment of siloxane diamine and rigidity of aromatic Schiff base; the aromatic Schiff base epoxy resin has higher mechanical property than the existing epoxy resin, does not sacrifice the remoldable capability of a Schiff base epoxy network, still maintains the dynamic reversible property of imine bonds, and solves the inherent contradiction between the high mechanical property and the easy plasticity of the aromatic Schiff base epoxy resin;

(3) due to the molecular structure with good combination of rigidity and flexibility, the flexibility of a network topological structure is increased, the plastic deformation capacity of a matrix is enhanced, the exceptional impact resistance is shown, the epoxy resin is far higher than that of the existing commercial epoxy resin system, and the epoxy resin has strong competitiveness in practical application;

(4) the epoxy resin obtained by the invention contains an aromatic Schiff base structure capable of being crosslinked into carbon and an inert Si-O-Si chain segment which is easy to enrich on the surface of the carbon layer after decomposition, so that a high-strength and compact carbon layer can be formed more easily, thermal oxygen can be effectively isolated, gas products can be prevented from escaping, the peak heat release rate and total smoke release are reduced, and the fire safety of the epoxy resin is obviously improved;

(5) the strong motion capability of the epoxy resin network obtained by the invention is also embodied in that the epoxy resin network can realize at least three times of high-efficiency remodeling cycles in a reprocessing mode, so that the cyclic utilization of the high-impact-resistance flame-retardant epoxy resin is realized;

(6) in the preparation method, the solvent can be directly removed after the reaction is finished for solidification without complex post-treatment, and the obtained epoxy resin prepolymer monomer is low-viscosity liquid, so that the preparation method has good processability, is simple and is easy to operate; and the epoxy thermosetting material meeting the requirements of different thermal properties and mechanical properties can be obtained by adjusting the type and molecular weight of the flexible siloxane chain segment in the pre-polymerized monomer and the functionality of the aromatic aldehyde compound.

Drawings

FIG. 1 shows the NMR spectrum of a liquid epoxy monomer obtained in example 7 of the present invention.

FIG. 2 is a graph showing the bending strength versus displacement of the epoxy resin obtained in example 24 of the present invention and that of comparative example 1.

FIG. 3 is a bar graph of unnotched impact strengths of the epoxy resin obtained in example 7 of the present invention and comparative example 1.

FIG. 4 is a graph showing the change of heat release rate with time in the cone calorimetry test of the epoxy resin obtained in example 7 of the present invention and comparative example 1.

FIG. 5 is a graph of total smoke release over time for the epoxy resin of example 7 of the present invention and comparative example 1 in a cone calorimetry test.

FIG. 6 is a tensile stress-strain curve of a bar after multiple rework and reshaping cycles of the epoxy resin obtained in example 7 of the present invention.

Detailed Description

The invention is further illustrated by the following examples and figures.

It is worth mentioning that:

the tensile property data obtained for each of the following examples and comparative examples is 75X 4X 2mm³The standard dumbbell type sample of (1) is measured by using an INSTRON 3366 type electronic universal material testing machine according to the standard of ASTM D638;

the bending property is that the thickness of the film is 80X 10X 4mm³The standard strip-shaped sample is measured by an INSTRON 3366 type electronic universal material testing machine according to the standard of ASTM D790;

the unnotched impact strength is 80X 10X 4mm³The standard strip-shaped sample of (2) is measured according to the ASTM D256 standard using a model ZBC 1400-2 cantilever impact tester;

the cone calorimetric test is to measure 100X 3.2mm³According to ISO 5660-1, using an FTT type cone calorimeter at 35kW/m²Measured at the radiation power of (a);

the epoxy resin was reprocessed by cutting standard dumbbell-shaped bars for tensile testing to a size of about 2X 2mm with pliers³And (3) hot-pressing and forming the small blocks again, then measuring the tensile strength of the newly obtained dumbbell-shaped sample bars again, wherein the percentage of the tensile strength of the sample before remolding is the reprocessing and remolding efficiency, the above process is a remolding cycle, and three times of shearing and breaking-reprocessing cycles are carried out.

in the formula, R₁Is composed of

Any one, two or more of them are formed in an arbitrary proportion; n and

the number of the groups is consistent; r₂Is composed of

Wherein X is methyl or phenyl and a is 1, 2 or 3.

step 1: adding an aromatic aldehyde compound and a phase transfer catalyst into excessive epoxy chloropropane, and carrying out ring opening reaction for 2-6 h at the temperature of 60-100 ℃; and (2) dropwise adding a sodium hydroxide solution into the mixture obtained in the step (1) under an ice bath condition, carrying out ring-closing reaction for 2-6 h, diluting with an organic solvent, fully washing with deionized water and saturated saline solution, collecting an organic phase, drying over night with anhydrous magnesium sulfate, and removing the solvent by rotary evaporation to obtain the epoxidized aromatic aldehyde compound.

The molar ratio of the aromatic aldehyde compound to the phase transfer catalyst is 1: 0.05-0.2, and the preferred molar ratio of the aromatic aldehyde compound to the epichlorohydrin is 1: 10; the concentration of the dropwise added sodium hydroxide solution is 16.7-40 wt%; the organic solvent is one of dichloromethane, chloroform, ethyl acetate and acetone.

The aromatic aldehyde compound is

Any one, two or more of them are constituted at an arbitrary ratio.

The phase transfer catalyst is one or more of tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, benzyltriethylammonium chloride, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride and tetradecyltrimethylammonium chloride in any proportion.

Step 2: adding the epoxidized aromatic aldehyde compound obtained in the step (1), a catalyst and siloxane diamine into dioxane in a protective atmosphere (nitrogen or argon is used as the protective atmosphere), carrying out condensation reaction for 6-12 h at the temperature of 100-120 ℃, and removing the solvent by rotary evaporation to obtain a liquid epoxy monomer;

siloxane diamines are

Wherein X represents a methyl group or a phenyl group; a is 1, 2 or 3.

The catalyst is glacial acetic acid or hydrochloric acid, wherein the molar ratio of the aromatic aldehyde compound to the glacial acetic acid is 1: 0.06-0.10, and the molar ratio of the aromatic aldehyde compound to the hydrochloric acid is 1: 0.04-0.08. The molar ratio of the epoxy aromatic aldehyde compound to the siloxane diamine is 2.0-2.1: 1.

And step 3: and fully mixing the liquid epoxy monomer and the curing agent, removing bubbles in vacuum, pouring into a mould for forming and curing, and obtaining the high-impact-resistance remodelable flame-retardant epoxy resin based on the siloxane Schiff base structure.

The curing agent is one or more of an amine curing agent, a phenol curing agent, a carboxylic acid curing agent, an acid anhydride curing agent, a thiol curing agent, a tertiary amine curing agent and an imidazole curing agent in any proportion. The molar ratio of the liquid epoxy monomer to the curing agent is 1: 0.5-1.

The curing process is as follows:

precuring for 1-2 h at 80 ℃, hot pressing for 0-2 h at 110 ℃ by using a flat vulcanizing machine, hot pressing for 0-18 h at 120 ℃, hot pressing for 0-18 h at 140 ℃, hot pressing for 0-4 h at 160 ℃ and hot pressing for 0-4 h at 180 ℃.

Example 1

step 1: 24.4g of p-hydroxybenzaldehyde and 3.3g of tetrabutylammonium bromide are added to 185g of epichlorohydrin; the ring-opening reaction is carried out for 2h at the temperature of 60 ℃ and cooled. Dropwise adding 16.7 wt% of sodium hydroxide solution into the reaction system under the condition of ice water bath, and carrying out ring-closing reaction for 2 h; diluting the two-phase mixed solution by dichloromethane, washing by deionized water and saturated saline, drying the organic phase by anhydrous magnesium sulfate overnight, and removing the solvent by rotary evaporation to obtain the 4- (2-epoxy methoxyl) benzaldehyde.

Step 2: 17.8g of 4- (2-epoxymethoxy) benzaldehyde, 12.4g of 1, 3-bis (3-aminopropyl) tetramethyldisiloxane and the appropriate amount of the catalyst glacial acetic acid were added to 100mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 6h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: uniformly mixing 87g of liquid epoxy monomer and 13g of liquid isophorone diamine (IPDA), removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

precuring for 1h at the temperature of 80 ℃, and hot pressing for 18h at the temperature of 120 ℃ by a flat vulcanizing machine.

The tensile strength of the obtained epoxy resin is 52MPa, the bending strength is 108MPa, and the unnotched impact strength is 58.7kJ/m²(ii) a The peak value heat release rate PHRR in the cone calorimetric test is 595kW/m²Total smoke release TSR of 23m²(ii) a The rework remodeling efficiency was 98%.

Example 2

Step 2: 17.8g of 4- (2-epoxymethoxy) benzaldehyde, 18.6g of 1, 3-bis (3-aminopropyl) -1, 3-dimethyl-1, 3-diphenyldisiloxane and a suitable amount of catalytic hydrochloric acid were added to 100mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 87g of liquid epoxy monomer and 13g of completely molten 4,4' -diaminodiphenylmethane (DDM) uniformly, removing bubbles in vacuum, pouring into a mould for forming and curing, wherein the curing process is as follows:

precuring for 1h at the temperature of 80 ℃, hot pressing for 1h at the temperature of 120 ℃ in a flat vulcanizing machine, and hot pressing for 18h at the temperature of 140 ℃.

The tensile strength of the obtained epoxy resin is 60MPa, the bending strength is 120MPa, and the unnotched impact strength is 45.2kJ/m²(ii) a The peak value heat release rate PHRR in the cone calorimetric test is 575kW/m²Total smoke release TSR of 19m²(ii) a The rework remodeling efficiency was 95%.

Example 3

Step 2: 17.8g of 4- (2-epoxymethoxy) benzaldehyde, 14.7g of 1, 5-bis (2-aminoethyl) hexamethyltrisiloxane and the appropriate amount of catalyst glacial acetic acid were added to 100mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 83g of liquid epoxy monomer and 17g of 4,4' -Diamino Diphenyl Sulfone (DDS) uniformly until the mixture is uniform and transparent, removing bubbles in vacuum, pouring the mixture into a mould for forming and curing, wherein the curing process is as follows:

precuring for 1h at the temperature of 80 ℃, hot pressing for 1h at the temperature of 110 ℃ in a flat vulcanizing machine, hot pressing for 16h at the temperature of 140 ℃ and hot pressing for 2h at the temperature of 160 ℃.

The tensile strength of the obtained epoxy resin is 56MPa, the bending strength is 113MPa, and the unnotched impact strength is 62.5kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetric test is 541kW/m²Total smoke release TSR of 16m²(ii) a The rework remodeling efficiency was 98%.

Example 4

Step 2: 17.8g of 4- (2-epoxymethoxy) benzaldehyde, 16.1g of 1, 5-bis (3-aminopropyl) hexamethyltrisiloxane and the appropriate amount of catalyst glacial acetic acid were added to 100mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: uniformly mixing 88g of liquid epoxy monomer and 12g of liquid IPDA, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin is 53MPa, the bending strength is 110MPa, and the unnotched impact strength is 60.7kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 550kW/m²Total smoke release TSR of 19m²(ii) a The rework remodeling efficiency was 96%.

Example 5

Step 2: 17.8g of 4- (2-epoxymethoxy) benzaldehyde, 28.5g of 1, 5-bis (3-aminopropyl) -1, 5-dimethyl-1, 3,3', 5-tetraphenyltrisiloxane and the appropriate amount of catalytic hydrochloric acid were added to 120mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 12h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: uniformly mixing 54g of liquid epoxy monomer and 46g of liquid methylhexahydrophthalic anhydride (MHHPA), removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

precuring for 1h at the temperature of 80 ℃, and hot pressing for 6h at the temperature of 120 ℃ by a flat vulcanizing machine.

The tensile strength of the obtained epoxy resin is 59MPa, the bending strength is 116MPa, and the unnotched impact strength is 58.3kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 540kW/m²Total smoke release TSR of 16m²(ii) a The rework remodeling efficiency was 95%.

Example 6

step 1: 30.4g of vanillin and 6.5g of tetrabutylammonium bromide are added to 185g of epichlorohydrin; the ring-opening reaction is carried out for 2h at the temperature of 80 ℃ and cooled. Dropwise adding 16.7 wt% of sodium hydroxide solution into the reaction system under the ice-water bath condition, and carrying out ring-closing reaction for 3 h; diluting the two-phase mixed solution by dichloromethane, washing by deionized water and saturated saline solution, drying the organic phase by anhydrous magnesium sulfate overnight, and removing the solvent by rotary evaporation to obtain the epoxidized vanillin.

Step 2: 20.8g of epoxidized vanillin, 11.0g of 1, 3-bis (2-aminoethyl) tetramethyldisiloxane and the appropriate amount of the catalyst glacial acetic acid were added to 100mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 8h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 86g of liquid epoxy monomer and 14g of completely molten DDM uniformly, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

precuring for 1h at the temperature of 80 ℃, hot pressing for 1h at the temperature of 110 ℃ in a flat vulcanizing machine, and hot pressing for 18h at the temperature of 140 ℃.

The tensile strength of the obtained epoxy resin is 50MPa, the bending strength is 103MPa, and the unnotched impact strength is 40.7kJ/m²(ii) a The peak value heat release rate PHRR in the cone calorimetric test is 575kW/m²Total smoke release TSR of 20m²(ii) a The rework remodeling efficiency was 98%.

Example 7

Step 2: 20.8g of epoxidized vanillin, 12.4g of 1, 3-bis (3-aminopropyl) tetramethyldisiloxane and a suitable amount of catalytic hydrochloric acid were added to 100mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

The nuclear magnetic resonance hydrogen spectrum of the liquid epoxy monomer obtained in the embodiment is shown in fig. 1, and it can be seen from the graph that the aldehyde peak at 9.88ppm almost completely disappears, the peak of hydrogen on carbon of schiff base newly appears at 8.17ppm, which indicates the formation of imine bond, the five groups of peaks at 4.32-2.76ppm belong to hydrogen on epoxy group, and the chemical shift and the integral area of the other peaks are respectively consistent with the theoretical peak position and atomic number of hydrogen on the target compound, which indicates the successful synthesis of the schiff base epoxy monomer.

The tensile strength of the obtained epoxy resin is 55MPa, the bending strength is 111MPa, and the unnotched impact strength is 61.8kJ/m²(ii) a The peak value heat release rate PHRR in the cone calorimetric test is 586kW/m²Total smoke release TSR of 21m²(ii) a The rework remodeling efficiency was 98%.

FIG. 3 is a graph showing the relationship between the bending strength and the displacement between the epoxy resin obtained in the present example and the epoxy resin obtained in comparative example 1. It can be seen from the figure that the flexural strength at break and the displacement of the epoxy resin are much greater than those of the comparative examples, and the epoxy resin obtained in this example exhibits excellent flexural properties.

FIG. 4 is a graph showing the change of heat release rate with time in the cone calorimetry test of the epoxy resin obtained in this example and comparative example 1. It can be seen from the graph that the peak heat release rate PHRR of the obtained epoxy resin is reduced by 51% as compared with bisphenol A type epoxy resin.

FIG. 5 is a graph showing the total smoke release over time in the cone calorimetry test for the epoxy resin obtained in this example and comparative example 1. It can be seen from the figure that the total smoke release TSR of the resulting epoxy resin is reduced by 40% compared to bisphenol A type epoxy resin.

FIG. 6 is a tensile stress-strain curve of a sample strip after multiple reworking and reshaping cycles of the epoxy resin obtained in this example. The drawing shows that the tensile strength of the epoxy resin reworked sample strip can be well maintained after 1-3 times of shearing-reworking cycles, and the reworking and remolding efficiency is 98%.

Example 8

Step 2: 20.8g of epoxidized vanillin, 18.6g of 1, 3-bis (3-aminopropyl) -1, 3-dimethyl-1, 3-diphenyldisiloxane and a suitable amount of catalytic hydrochloric acid were added to 100mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 86g of liquid epoxy monomer and 14g of DDS until the mixture is uniform and transparent, removing bubbles in vacuum, pouring the mixture into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin is 62MPa, the bending strength is 120MPa, and the unnotched impact strength is 47.9kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 560kW/m²Total smoke release TSR of 18m²(ii) a The rework remodeling efficiency was 94%.

Example 9

Step 2: 20.8g of epoxidized vanillin, 14.7g of 1, 5-bis (2-aminoethyl) hexamethyltrisiloxane and the appropriate amount of catalyst glacial acetic acid were added to 100mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: uniformly mixing 87g of liquid epoxy monomer and 13g of completely molten DDM, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin is 57MPa, the bending strength is 115MPa, and the unnotched impact strength is 65.3kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 539kW/m²Total smoke release TSR of 15m²(ii) a The rework remodeling efficiency was 98%.

Example 10

Step 2: 20.8g of epoxidized vanillin, 16.1g of 1, 5-bis (3-aminopropyl) hexamethyltrisiloxane and the appropriate amount of catalyst glacial acetic acid were added to 100mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: uniformly mixing 54g of liquid epoxy monomer and 46g of liquid MHHPA, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin is 58MPa, the bending strength is 116MPa, and the unnotched impact strength is 64.4kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 545kW/m²Total smoke release TSR of 16m²(ii) a The rework remodeling efficiency was 97%.

Example 11

Step 2: 20.8g of epoxidized vanillin, 28.5g of 1, 5-bis (3-aminopropyl) -1, 5-dimethyl-1, 3,3', 5-tetraphenyltrisiloxane and the appropriate amount of catalytic hydrochloric acid were added to 120mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 12h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 88g of liquid epoxy monomer and 12g of DDS until the mixture is uniform and transparent, removing bubbles in vacuum, pouring the mixture into a mold for forming and curing, wherein the curing process is as follows:

precuring for 1h at the temperature of 80 ℃, hot pressing for 1h at the temperature of 110 ℃ in a flat vulcanizing machine, hot pressing for 14h at the temperature of 140 ℃ and hot pressing for 4h at the temperature of 160 ℃.

The tensile strength of the obtained epoxy resin is 60MPa, the bending strength is 117MPa, and the unnotched impact strength is 57.8kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 535kW/m²Total smoke release TSR of 16m²(ii) a The rework remodeling efficiency was 94%.

Example 12

step 1: 33.2g of ethyl vanillin and 6.5g of tetrabutylammonium bromide are added to 185g of epichlorohydrin; the ring-opening reaction is carried out for 3h at the temperature of 80 ℃ and cooled. Dropwise adding 20 wt% of sodium hydroxide solution into the reaction system under the ice-water bath condition, and carrying out ring-closure reaction for 3 h; diluting the two-phase mixed solution by dichloromethane, washing by deionized water and saturated saline solution, drying the organic phase by anhydrous magnesium sulfate overnight, and removing the solvent by rotary evaporation to obtain the epoxidized ethyl vanillin.

Step 2: 22.2g of epoxidized ethyl vanillin, 12.4g of 1, 3-bis (3-aminopropyl) tetramethyldisiloxane and a suitable amount of catalytic hydrochloric acid were added to 100mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 12h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

The tensile strength of the obtained epoxy resin is 58MPa, the bending strength is 115MPa, and the unnotched impact strength is 57.5kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 602kW/m²Total smoke release TSR of 25m²(ii) a The rework remodeling efficiency was 95%.

Example 13

Step 2: 22.2g of epoxidized ethyl vanillin, 18.6g of 1, 3-bis (3-aminopropyl) -1, 3-dimethyl-1, 3-diphenyldisiloxane and a suitable amount of catalytic hydrochloric acid were added to 100mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 12h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: uniformly mixing 90g of liquid epoxy monomer and 10g of liquid IPDA, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin was 58MPa, the bending strength was 117MPa, and the unnotched impact strength was 43.6kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 587kW/m²Total smoke release TSR of 22m²(ii) a The rework remodeling efficiency was 94%.

Example 14

Step 2: 22.2g of epoxidized ethyl vanillin, 13.3g of 1, 5-bis (aminomethyl) hexamethyltrisiloxane and the appropriate amount of catalyst glacial acetic acid were added to 100mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 8h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 84g of liquid epoxy monomer and 16g of DDS until the mixture is uniform and transparent, removing bubbles in vacuum, pouring the mixture into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin was 52MPa, the bending strength was 105MPa, and the unnotched impact strength was 42.6kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 559kW/m²Total smoke release TSR of 18m²(ii) a The rework remodeling efficiency was 96%.

Example 15

Step 2: 22.2g of epoxidized ethyl vanillin, 14.7g of 1, 5-bis (2-aminoethyl) hexamethyltrisiloxane and the appropriate amount of catalyst glacial acetic acid were added to 100mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: 89g of liquid epoxy monomer and 11g of liquid IPDA are uniformly mixed, and the mixture is poured into a mould for forming and curing after vacuum defoaming, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin is 54MPa, the bending strength is 112MPa, and the unnotched impact strength is 60.9kJ/m²(ii) a The peak value heat release rate PHRR in the cone calorimetry test is 548kW/m²Total smoke release TSR of 18m²(ii) a The rework remodeling efficiency was 96%.

Example 16

Step 2: 22.2g of epoxidized ethyl vanillin, 16.1g of 1, 5-bis (3-aminopropyl) hexamethyltrisiloxane and the appropriate amount of catalyst glacial acetic acid were added to 100mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: uniformly mixing 88g of liquid epoxy monomer and 12g of completely molten DDM, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin is 56MPa, the bending strength is 115MPa, and the unnotched impact strength is 63.4kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 544kW/m²Total smoke release TSR of 17m²(ii) a The rework remodeling efficiency was 97%.

Example 17

Step 2: 22.2g of epoxidized ethyl vanillin, 28.5g of 1, 5-bis (3-aminopropyl) -1, 5-dimethyl-1, 3,3', 5-tetraphenyltrisiloxane and the appropriate amount of catalytic hydrochloric acid were added to 120mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 12h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: uniformly mixing 92g of liquid epoxy monomer and 8g of liquid IPDA, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin is 56MPa, the bending strength is 114MPa, and the unnotched impact strength is 57.5kJ/m²(ii) a The peak value heat release rate PHRR in the cone calorimetry test is 547kW/m²Total smoke release TSR of 18m²(ii) a The rework remolding efficiency was 93%.

Example 18

step 1: adding 36.4g syringaldehyde and 13.0g tetrabutylammonium bromide to 185g epichlorohydrin; the ring-opening reaction is carried out for 3h at the temperature of 100 ℃ and cooled. Dropwise adding 30 wt% sodium hydroxide solution into the reaction system under the condition of ice water bath, and carrying out ring-closure reaction for 4 h; diluting the two-phase mixed solution by dichloromethane, washing by deionized water and saturated saline solution, drying the organic phase by anhydrous magnesium sulfate overnight, and removing the solvent by rotary evaporation to obtain the epoxidized syringaldehyde.

Step 2: 23.8g of epoxidized syringaldehyde, 9.6g of 1, 3-bis (aminomethyl) tetramethyldisiloxane and the appropriate amount of catalyst glacial acetic acid were added to 80mL of dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 8 hours at the temperature of 100 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

The tensile strength of the obtained epoxy resin is 47MPa, the bending strength is 98MPa, and the unnotched impact strength is 36.8kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 560kW/m²Total smoke release TSR of 19m²(ii) a The rework remodeling efficiency was 98%.

Example 19

Step 2: epoxidized syringaldehyde 23.8g, 1, 3-bis (3-aminopropyl) tetramethyldisiloxane 12.4g and the appropriate amount of catalytic hydrochloric acid were added to 100mL dioxane under a nitrogen atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 85g of liquid epoxy monomer and 15g of DDS until the mixture is uniform and transparent, removing bubbles in vacuum, pouring the mixture into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin is 58MPa, the bending strength is 113MPa, and the unnotched impact strength is 55.1kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 590kW/m²Total smoke release TSR of 21m²(ii) a The rework remodeling efficiency was 97%.

Example 20

Step 2: 23.8g of epoxidized syringaldehyde, 18.6g of 1, 3-bis (3-aminopropyl) -1, 3-dimethyl-1, 3-diphenyldisiloxane and an appropriate amount of catalytic hydrochloric acid were added to 100mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

The tensile strength of the obtained epoxy resin is 59MPa, the bending strength is 119MPa, and the unnotched impact strength is 48.4kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 580kW/m²Total smoke release TSR of 21m²(ii) a The rework remodeling efficiency was 95%.

Example 21

Step 2: 23.8g of epoxidized syringaldehyde, 14.7g of 1, 5-bis (2-aminoethyl) hexamethyltrisiloxane and the appropriate amount of catalyst glacial acetic acid were added to 100mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

The tensile strength of the obtained epoxy resin is 59MPa, the bending strength is 119MPa, and the unnotched impact strength is 62.5kJ/m²(ii) a The peak value heat release rate PHRR in the cone calorimetry test is 547kW/m²Total smoke release TSR of 18m²(ii) a The rework remodeling efficiency was 97%.

Example 22

Step 2: epoxy syringaldehyde 25.0g, 1, 5-bis (3-aminopropyl) hexamethyltrisiloxane 16.1g and glacial acetic acid as a catalyst in an appropriate amount were added to dioxane 100mL under argon atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

The tensile strength of the obtained epoxy resin was 57MPa, the bending strength was 117MPa, and the unnotched impact strength was 62.9kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 542kW/m²Total smoke release TSR of 17m²(ii) a The rework remodeling efficiency was 97%.

Example 23

Step 2: epoxidized syringaldehyde 25.0g, 1, 5-bis (3-aminopropyl) -1, 5-dimethyl-1, 3,3', 5-tetraphenyltrisiloxane 28.5g and the appropriate amount of catalytic hydrochloric acid were added to 120mL dioxane under an argon atmosphere. Condensation reaction is carried out for 12h at the temperature of 120 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: uniformly mixing 91g of liquid epoxy monomer and 9g of completely molten DDM, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin is 59MPa, the bending strength is 116MPa, and the unnotched impact strength is 58.9kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 539kW/m²Total smoke release TSR of 17m²(ii) a The rework remolding efficiency was 93%.

Example 24

step 1: adding 27.6g of protocatechuic aldehyde and 4.6g of benzyltriethylammonium chloride to 185g of epichlorohydrin; the ring-opening reaction is carried out for 3h at the temperature of 80 ℃ and cooled. Dropwise adding 40 wt% sodium hydroxide solution into the reaction system under the condition of ice water bath, and carrying out ring-closing reaction for 6 h; diluting the two-phase mixed solution by dichloromethane, washing by deionized water and saturated saline solution, drying the organic phase by anhydrous magnesium sulfate overnight, and removing the solvent by rotary evaporation to obtain the epoxidized protocatechuic aldehyde.

Step 2: 25.0g of epoxidized protocatechualdehyde, 12.4g of 1, 3-bis (3-aminopropyl) tetramethyldisiloxane and an appropriate amount of catalytic hydrochloric acid were added to 100mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 78g of liquid epoxy monomer and 22g of completely molten DDM uniformly, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

precuring for 2h at the temperature of 80 ℃, hot pressing for 2h at the temperature of 110 ℃ in a flat vulcanizing machine, hot pressing for 4h at the temperature of 140 ℃ and hot pressing for 2h at the temperature of 180 ℃.

The tensile strength of the obtained epoxy resin was 69MPa, the bending strength was 163MPa, and the unnotched impact strength was 28.6kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 825kW/m²Total smoke release TSR of 28m²(ii) a The rework remodeling efficiency was 62%.

FIG. 2 is a graph showing the relationship between flexural strength and displacement of the epoxy resin obtained in the present example and that of comparative example 1. It can be seen from the figure that the epoxy resin obtained in this example has a bending strength at break and a displacement much larger than those of the comparative examples, and it can be seen that the epoxy resin obtained in this example exhibits excellent bending properties.

Example 25

Step 2: 25.0g of epoxidized protocatechualdehyde, 18.6g of 1, 3-bis (3-aminopropyl) -1, 3-dimethyl-1, 3-diphenyldisiloxane and an appropriate amount of catalytic hydrochloric acid were added to 100mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 83g of liquid epoxy monomer and 17g of liquid IPDA uniformly, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

precuring for 2h at the temperature of 80 ℃, hot pressing for 4h at the temperature of 120 ℃ in a flat vulcanizing machine, and hot pressing for 2h at the temperature of 140 ℃.

The tensile strength of the obtained epoxy resin was 66MPa, the bending strength was 159MPa, and the unnotched impact strength was 27.1kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 810kW/m²Total smoke release TSR of 27m²(ii) a The rework remodeling efficiency was 60%.

Example 26

Step 2: 25.0g of epoxidized protocatechuic aldehyde, 14.7g of 1, 5-bis (2-aminopropyl) hexamethyltrisiloxane and an appropriate amount of catalyst glacial acetic acid were added to 100mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 10h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 79g of liquid epoxy monomer and 21g of completely molten DDM uniformly, removing bubbles in vacuum, pouring into a mold for forming and curing, wherein the curing process is as follows:

The tensile strength of the obtained epoxy resin is 74MPa, the bending strength is 168MPa, and the unnotched impact strength is 30.5kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 797kW/m²Total smoke release TSR of 24m²(ii) a The rework remodeling efficiency was 64%.

Example 27

Step 2: 25.0g of epoxidized protocatechuic aldehyde, 16.1g of 1, 5-bis (3-aminopropyl) hexamethyltrisiloxane and an appropriate amount of catalyst glacial acetic acid were added to 100mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 12h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

And step 3: mixing 76g of liquid epoxy monomer and 24g of DDS until the mixture is uniform and transparent, removing bubbles in vacuum, pouring the mixture into a mold for forming and curing, wherein the curing process is as follows:

precuring for 2h at the temperature of 80 ℃, hot pressing for 2h at the temperature of 110 ℃ in a flat vulcanizing machine, hot pressing for 2h at the temperature of 140 ℃ and hot pressing for 4h at the temperature of 180 ℃.

The tensile strength of the obtained epoxy resin is 73MPa, the bending strength is 165MPa, and the unnotched impact strength is 35.9kJ/m²(ii) a The peak value heat release rate PHRR in the cone calorimetric test is 802kW/m²Total smoke release TSR of 25m²(ii) a The rework remodeling efficiency was 67%.

Example 28

Step 2: epoxidized protocatechualdehyde 25.0g, 1, 5-bis (3-aminopropyl) -1, 5-dimethyl-1, 3,3', 5-tetraphenyltrisiloxane 28.5g and the appropriate amount of catalytic hydrochloric acid were added to 120mL of dioxane under an argon atmosphere. Condensation reaction is carried out for 12h at the temperature of 110 ℃, and the solvent is removed by rotary evaporation, thus obtaining the liquid epoxy monomer.

precuring for 2h at the temperature of 80 ℃, hot pressing for 2h at the temperature of 120 ℃ in a flat vulcanizing machine, and hot pressing for 4h at the temperature of 140 ℃.

The tensile strength of the obtained epoxy resin is 78MPa, the bending strength is 170MPa, and the unnotched impact strength is 27.4kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 786kW/m²Total smoke release TSR of 23m²(ii) a The rework remodeling efficiency was 60%.

Comparative example 1

80g of bisphenol A epoxy resin E51 and 20g of completely molten DDM were mixed uniformly, and the obtained homogeneous liquid epoxy prepolymer was defoamed in vacuum and immediately transferred to a preheated polytetrafluoroethylene mold. Curing was carried out using a press at 80 ℃ for 2h, 160 ℃ for 2h, and then 180 ℃ for 2 h.

The tensile strength of the obtained epoxy resin is 68MPa, the bending strength is 113MPa, and the unnotched impact strength is 12.0kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 1203kW/m²Total smoke release TSR of 35m²(ii) a Epoxy resins do not have remolding capabilities.

Comparative example 2

76g of bisphenol A epoxy resin E51 and 24g of DDS were mixed until uniform and transparent, and the resulting liquid epoxy prepolymer was defoamed under vacuum and then rapidly transferred to a preheated polytetrafluoroethylene mold. Curing was carried out using a press at 80 ℃ for 2h, 160 ℃ for 2h, and then at 200 ℃ for 2 h.

The tensile strength of the obtained epoxy resin is 70MPa, the bending strength is 115MPa, and the unnotched impact strength is 11.0kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 1123kW/m²Total smoke release TSR of 36m²(ii) a Epoxy resins do not have remolding capabilities.

Comparative example 3

82g of bisphenol A epoxy resin E51 and 18g of liquid IPDA were mixed uniformly, and the obtained liquid epoxy prepolymer was defoamed in vacuum and then rapidly transferred to a preheated polytetrafluoroethylene mold. Curing was carried out using a press at 80 ℃ for 2h, 120 ℃ for 2h, and then at 140 ℃ for 2 h.

The tensile strength of the obtained epoxy resin is 65MPa, the bending strength is 110MPa,the unnotched impact strength is 10.0kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 1250kW/m²Total smoke release TSR of 38m²(ii) a Epoxy resins do not have remolding capabilities.

Comparative example 4

54g of bisphenol A epoxy resin E51 and 46g of liquid MHHPA were mixed uniformly, and the obtained liquid epoxy prepolymer was defoamed in vacuum and then rapidly transferred to a preheated polytetrafluoroethylene mold. Curing was carried out using a press at 80 ℃ for 2h, 100 ℃ for 2h, and then at 120 ℃ for 2 h.

The tensile strength of the obtained epoxy resin was 62MPa, the bending strength was 105MPa, and the unnotched impact strength was 13.0kJ/m²(ii) a The peak heat release rate PHRR in the cone calorimetry test is 1180kW/m²Total smoke release TSR of 38m²(ii) a Epoxy resins do not have remolding capabilities.

The epoxy resin prepared by the invention is designed by a method of rigidly combining a flexible chain segment of siloxane diamine and an aromatic Schiff base. The resulting rigid-flexible epoxy network not only has mechanical properties comparable to or higher than existing commercial epoxy resins, but also does not sacrifice the removability of the schiff base epoxy network. The dynamic reversible property of the imine bond is still maintained, and the inherent contradiction between the high mechanical property and the easy plasticity of the aromatic Schiff base epoxy resin is solved. Due to the molecular structure with good combination of rigidity and flexibility, the flexibility of the network topological structure is increased, the plastic deformation capacity of the matrix is enhanced, the exceptional impact resistance is shown, the impact resistance is far higher than that of the existing commercial epoxy resin system, and the competitive power is strong in practical application. Because the epoxy resin contains an aromatic Schiff base structure capable of being crosslinked into carbon and an inert Si-O-Si chain segment which is easy to be enriched on the surface of the carbon layer after decomposition, a high-strength and compact carbon layer is easier to form, the thermal oxygen can be effectively isolated and the escape of gas products can be prevented, so that the peak heat release rate and the total smoke release are reduced, and the fire safety of the epoxy resin is obviously improved. The epoxy resin network has strong movement capacity, can realize at least three times of high-efficiency remodeling cycles through a reprocessing mode, and realizes the recycling of the high-impact-resistance flame-retardant epoxy resin.

The method can be used for curing after the reaction is finished and the solvent is directly removed without complex post-treatment, and meanwhile, the obtained epoxy resin prepolymer monomer is low-viscosity liquid and has good processability. The preparation process has low cost, simple operation, easy molding and processing and is beneficial to mass production. And the epoxy thermosetting material meeting the requirements of different thermal properties and mechanical properties can be obtained by adjusting the type and molecular weight of the flexible siloxane chain segment in the pre-polymerized monomer and the functionality of the aromatic aldehyde compound.

Claims

1. A preparation method of high impact resistance remodelable flame-retardant epoxy resin based on siloxane Schiff base structure,

the method is characterized by comprising the following steps:

step 2: adding the epoxidized aromatic aldehyde compound obtained in the step (1), a catalyst and siloxane diamine into a solvent in a protective atmosphere, fully reacting at 100-120 ℃, and performing rotary evaporation to obtain a liquid epoxy monomer; the molar ratio of the epoxy aromatic aldehyde compound to the siloxane diamine is 2.0-2.1: 1;

and step 3: fully mixing the liquid epoxy monomer and the curing agent, and curing and forming to obtain the required high-impact-resistance remodelable flame-retardant epoxy resin based on the siloxane Schiff base structure;

the aromatic aldehyde compound is

Any one, two or more of them are formed in an arbitrary proportion;

siloxane diamines are

Wherein X is methyl or phenyl, a is 1, 2 or 3;

the structure of the liquid epoxy monomer is as follows:

in the formula, R₁Is composed of

Any one, two or more of them are formed in an arbitrary proportion; n and

the number of the groups is consistent; r₂Is composed of

Wherein X is methyl or phenyl and a is 1, 2 or 3.

2. A high impact resistant remodelable flame retardant epoxy resin based on a siloxane Schiff base structure obtained by the preparation method of claim 1.

3. The preparation method according to claim 1, wherein the molar ratio of the aromatic aldehyde compound to the phase transfer catalyst in step 1 is 1:0.05 to 0.2, and the molar ratio of the aromatic aldehyde compound to sodium hydroxide is 1:2 to 5; the molar ratio of the liquid epoxy monomer to the curing agent in the step 3 is 1: 0.5-1.

4. The preparation method according to claim 1, wherein the ring-opening reaction time of the step 1 is 2-6 h, and the ring-closing reaction time is 2-6 h; the reaction time of the step 2 is 6-12 h.

5. The method according to claim 1, wherein the curing process in step 3 is as follows:

6. The method according to claim 1, wherein the phase transfer catalyst in step 1 is one, two or more selected from tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, benzyltriethylammonium chloride, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride and tetradecyltrimethylammonium chloride in any ratio.

7. The method according to claim 1, wherein the catalyst in step 2 is glacial acetic acid or hydrochloric acid, wherein the molar ratio of the aromatic aldehyde compound to the glacial acetic acid is 1: 0.06-0.10, and the molar ratio of the aromatic aldehyde compound to the hydrochloric acid is 1: 0.04-0.08.

8. The method according to claim 1, wherein the curing agent in step 3 is one or more of an amine curing agent, a phenol curing agent, a carboxylic acid curing agent, an acid anhydride curing agent, a thiol curing agent, a tertiary amine curing agent, and an imidazole curing agent, and is formed in any ratio.