CN113861680A

CN113861680A - Preparation method of degradable and toughened polybenzoxazine

Info

Publication number: CN113861680A
Application number: CN202111301745.8A
Authority: CN
Inventors: 王智; 乔子贺; 王美晨; 范晓天; 刘辉辉; 姜瑾
Original assignee: North University of China
Current assignee: North University of China
Priority date: 2021-11-04
Filing date: 2021-11-04
Publication date: 2021-12-31
Anticipated expiration: 2041-11-04
Also published as: CN113861680B

Abstract

The invention relates to the field of toughening and degradation of thermosetting resin, in particular to a preparation method of degradable and toughened polybenzoxazine; the method comprises the following steps: dissolving a Vitrimer prepolymer and a prepolymer of a crosslinking agent in a solvent, ultrasonically mixing the Vitrimer prepolymer and benzoxazine dissolved in a proper amount of the solvent to prepare a uniform solution, removing the solvent in a vacuum oven to obtain a polymer prepolymer, then preparing a resin casting body by adopting a heating and curing process for the prepolymer, or coating the prepolymer on carbon fiber cloth to obtain a prepreg, and preparing a fiber composite material by adopting a hot-pressing and curing process; according to the invention, a flexible network is introduced into benzoxazine, so that the toughness of the resin is improved, and the flexible network can be decomposed into small molecules by adding a chemical reagent capable of participating in dynamic exchange of the flexible network, so that a cross-linked network structure of a blending system is damaged, and the degradation of the resin is realized. The method is expected to be applied to the field of degradation and recovery of thermosetting resin and composite materials thereof, and has certain practical significance.

Description

Preparation method of degradable and toughened polybenzoxazine

Technical Field

The invention relates to the field of toughening and degradation of thermosetting resin, in particular to a preparation method of degradable and toughened polybenzoxazine.

Background

The benzoxazine resin has wide raw material source and flexible molecular design, and a condensate thereof has excellent heat resistance and excellent mechanical property and is widely applied to the fields of electronics, aerospace and the like. However, as a high-performance resin, the further application and popularization of benzoxazine are greatly limited due to the problems of high curing temperature of benzoxazine, high brittleness of a cured product, difficulty in processing a waste product and the like. Through structural design, the toughness of the benzoxazine resin can be effectively improved by modification by a molecular design method, but the synthesis period of the method is long, and the method is not beneficial to industrial popularization. Therefore, blending copolymerization with a second component resin system is a very efficient and rapid modification method which is a priority for benzoxazine industrialization.

Vitrimer is a new type of polymer material with a three-dimensional network structure that can activate dynamic exchange reactions within the polymer network at certain temperatures, including but not limited to transesterification, transamination, transalkylation, olefin metathesis, imine exchange, disulfide exchange, silyl ether exchange, etc., which makes Vitrimer networks malleable at high temperatures. The Vivitrimer network swells in a conventional organic solvent but does not dissolve, the network can be rearranged in an association type dynamic exchange mode at a certain temperature, and an old covalent bond can be broken after a new covalent bond is formed, so that the crosslinking density of the network cannot be reduced in the dynamic exchange process, the structure can be kept complete in the rearrangement process and cannot be depolymerized, and the performance of the material cannot be obviously changed. In addition, the flexible network can be decomposed into small molecules by adding a chemical reagent capable of participating in dynamic exchange of the flexible network, so that a cross-linked network structure of a blending system is damaged, and the degradation of the resin can be realized. Therefore, the Virimer material with the associated dynamic exchange characteristic is used as a toughening component, and a new solution is provided for the toughening of benzoxazine and the treatment of resin and composite material waste thereof.

Disclosure of Invention

The invention overcomes the defects of the prior art and provides a preparation method of degradable and toughened polybenzoxazine. The idea of the invention is derived from the recovery and reprocessing of a dynamic exchange network, and the three-dimensional cross-linked network can be depolymerized by participating in the dynamic exchange reaction by a chemical reagent to generate a small molecular substance and degrade a cured substance of the small molecular substance. The Vitrimer with the flexible chain segment is introduced into the benzoxazine, so that a large amount of energy is dissipated due to the effects of deflection disproportionation of cracks, ductile stretching of the flexible chain and the like when the material is impacted, and the toughness is improved; the Vitrimer network in the blended system can be depolymerized by chemical agents, thereby decomposing the resin into low molecular weight polymers.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a preparation method of degradable and toughened polybenzoxazine comprises the following steps: dissolving a Vitrimer prepolymer and a prepolymer of a crosslinking agent in a solvent, ultrasonically mixing the Vitrimer prepolymer and benzoxazine dissolved in a proper amount of the solvent to prepare a uniform solution, removing the solvent in a vacuum oven to obtain a polymer prepolymer, then preparing a resin casting body by adopting a heating curing process for the prepolymer, or coating the prepolymer on carbon fiber cloth to obtain a prepreg, and preparing the fiber composite material by adopting a hot-pressing curing process.

The Vitrimer prepolymer used was prepared according to the method disclosed in Vinylogous Urethane Vitrimers.

Further, the benzoxazine is one or a combination of bisphenol A type benzoxazine, naphthol type benzoxazine and diamine type benzoxazine.

Further, the dynamic bond exchange type of the Vitrimer is one or a combination of ester exchange, amino exchange, alkyl exchange, olefin double decomposition exchange, imine exchange, borate exchange, disulfide bond exchange and silyl ether exchange.

Further, the cross-linking agent is a mixture of m-xylylenediamine and tri (2-aminoethyl) amine in a molar ratio of 1: 1.

Preferably, the mass ratio of the prepolymer of the vitrier prepolymer and the cross-linking agent to the benzoxazine is 1: 100-5: 100, and the mass ratio of the prepolymer of the vitrier prepolymer and the cross-linking agent is 1.15: 1.

Furthermore, the dosage ratio of the prepolymer of the Vitrimer prepolymer and the cross-linking agent to the solvent is 1 g/mL, and the dosage ratio of the benzoxazine to the solvent is 0.5-0.75 g/mL.

Preferably, the content of the prepreg glue is controlled within the range of 35-40%.

Further, the heating and curing process of the resin casting body is heating and curing at 180 ℃ for 60 min, and then heating and curing at 200 ℃ for 90 min; the hot-pressing curing process of the fiber composite material comprises 5 MPa hot-pressing curing at 160 ℃ for 60 min, 10 MPa hot-pressing curing at 180 ℃ for 60 min, and 10 MPa hot-pressing curing at 200 ℃ for 90 min.

Compared with the prior art, the invention has the following beneficial effects:

the toughening method is simple to operate and has low requirement on equipment, the benzoxazine resin prepared by the method has good mechanical property, the impact property is improved by 71.85% at most compared with pure benzoxazine resin, and the strength of the fiber monofilament recovered after the prepared fiber composite material is subjected to degradation treatment can be maintained to be 88.43% of that of the original fiber monofilament. The method has simple steps, and the prepared material is degradable, has good mechanical property, is easy to realize industrial production, and is beneficial to solving the problem of waste treatment of thermosetting resin and composite materials thereof.

Drawings

Fig. 1 is a pictorial representation of a polybenzoxazine-Vitrimer resin casting (left) and its carbon fiber composite (right) prepared in examples 3 and 4. The resin casting body is a sample bar with the thickness of 80 multiplied by 10 multiplied by 4 mm prepared according to GB/T2567-2008, and the carbon fiber composite material is a composite plate cut into the thickness of 20 multiplied by 20 mm.

FIG. 2 is a graph of impact strength for examples 1 to 3 and comparative example 1.

FIG. 3 shows the cross-sectional morphology of the carbon fiber composite material prepared in example 4 and the morphology of the recycled fiber after the degradation cleaning treatment.

FIG. 4 is a graph showing the monofilament tensile strength of the virgin carbon fiber used in example 4 and the recycled fiber of the prepared carbon fiber composite.

Detailed Description

The present invention is further illustrated by the following specific examples.

Example 1

Dissolving a certain amount of Vitrimer prepolymer, crosslinking agents of m-xylylenediamine and tri (2-aminoethyl) amine in a proper amount of chloroform, and ultrasonically mixing for 10 min to prepare a solution; dissolving bisphenol A benzoxazine in appropriate amount of chloroform, and performing ultrasonic treatment for 10 min to obtain a solution. And ultrasonically mixing the two solutions for 10 min to obtain a uniform mixed solution. The mass ratio of the Vitrimer prepolymer and the prepolymer of the cross-linking agent to the bisphenol A benzoxazine is 1: 100. The dosage ratio of the Vitrimer prepolymer to the prepolymer of the cross-linking agent to the solvent is 1 g/mL. The dosage ratio of the benzoxazine to the solvent is 0.5-0.75 g/mL, and the mass ratio of the vitrier prepolymer to the cross-linking agent is 1.15: 1.

The above solution was poured into a teflon mold and the solvent was removed in a vacuum oven at 100 ℃.

The solvent-removed prepolymer was cured using the following procedure: heating and curing at 180 deg.C/60 min and 200 deg.C/90 min.

The impact strength of the finally obtained polybenzoxazine-Vitrimer resin casting (recorded as B-PVUv 1) reaches 13.24 KJ/m²The yield is improved by 34.55 percent compared with pure resin.

Example 2

This example differs from example 1 in that: the mass ratio of the Vitrimer prepolymer and the crosslinking agent prepolymer to the bisphenol A benzoxazine is 3: 100. The other steps and parameters were the same as in example 1. The impact strength of the finally obtained polybenzoxazine-Vitrimer resin casting (recorded as B-PVUv 3) reaches 16.91 KJ/m²The improvement is 71.85% compared with the pure resin.

Example 3

This example differs from example 1 in that: the mass ratio of the Vitrimer prepolymer and the crosslinking agent prepolymer to the bisphenol A benzoxazine is 5: 100. The other steps and parameters were the same as in example 1. Obtained finallyThe polybenzoxazine-Vitrimer resin casting (designated as B-PVUv 5) has an impact strength of 14.12 KJ/m²The yield is improved by 43.5 percent compared with pure resin.

Example 4

The preparation steps and parameters of the resin prepolymer in the embodiment are the same as those in the embodiment 3, and then the prepolymer is coated on the carbon fiber cloth to prepare the prepreg, and the content of the glue is controlled to be 35-40%.

The prepreg was cured using the following steps: hot-pressing and curing at 5 MPa/160 ℃/60 min, 10 MPa/180 ℃/60 min, 10 MPa/200 ℃/90 min.

And finally obtaining the polybenzoxazine-Vitrimer/carbon fiber composite material.

The composite material is degraded by a chemical agent to recover carbon fibers, and the monofilament strength of the obtained fibers is 88.43 percent of that of the original fibers.

Comparative example 1

This example differs from examples 1 to 3 in that: only the bisphenol a benzoxazine solution was prepared to obtain a prepolymer, and the other steps and parameters were the same as in example 1. The impact strength of the finally obtained polybenzoxazine resin (recorded as BOZ) is 9.84 KJ/m²。

Claims

1. A preparation method of degradable and toughened polybenzoxazine is characterized by comprising the following steps: dissolving a Vitrimer prepolymer and a prepolymer of a crosslinking agent in a solvent, ultrasonically mixing the Vitrimer prepolymer and benzoxazine dissolved in a proper amount of the solvent to prepare a uniform solution, removing the solvent in a vacuum oven to obtain a polymer prepolymer, then preparing a resin casting body by adopting a heating curing process for the prepolymer, or coating the prepolymer on carbon fiber cloth to obtain a prepreg, and preparing the fiber composite material by adopting a hot-pressing curing process.

2. The method for preparing degradable and toughened polybenzoxazine according to claim 1, wherein the benzoxazine is one or a combination of bisphenol A type benzoxazine, naphthol type benzoxazine and diamine type benzoxazine.

3. The method for preparing degradable and toughened polybenzoxazine according to claim 1, wherein the dynamic bond exchange type of Vitrimer is one or more of ester exchange, amino exchange, alkyl exchange, olefin metathesis exchange, imine exchange, borate exchange, disulfide exchange and silyl ether exchange.

4. The method for preparing degradable and toughened polybenzoxazine according to claim 1, wherein the cross-linking agent is a mixture of m-xylylenediamine and tris (2-aminoethyl) amine in a molar ratio of 1: 1.

5. The preparation method of the degradable and toughened polybenzoxazine as claimed in claim 1, wherein the mass ratio of the prepolymer of the vitrimer prepolymer and the cross-linking agent to the benzoxazine is 1:100 to 5:100, and the mass ratio of the prepolymer of the vitrimer to the cross-linking agent is 1.15: 1.

6. The preparation method of degradable and toughened polybenzoxazine according to claim 1, wherein the prepolymer-solvent dosage ratio of the Vitrimer prepolymer and the crosslinking agent is 1 g/mL, and the dosage ratio of the benzoxazine to the solvent is 0.5-0.75 g/mL.

7. The method for preparing degradable and toughened polybenzoxazine according to claim 1, wherein the prepreg glue content is controlled to be in a range of 35-40%.

8. The preparation method of degradable and toughened polybenzoxazine according to claim 1, wherein the heating and curing process of the resin casting body is 180 ℃ heating and curing for 60 min, and then 200 ℃ heating and curing for 90 min; the hot-pressing curing process of the fiber composite material comprises 5 MPa hot-pressing curing at 160 ℃ for 60 min, 10 MPa hot-pressing curing at 180 ℃ for 60 min, and 10 MPa hot-pressing curing at 200 ℃ for 90 min.