阅读说明：本技术 一种高硬度热固性自修复聚氨酯及其制备方法 (High-hardness thermosetting self-repairing polyurethane and preparation method thereof ) 是由 钟江 柳茂陈 荣金闯 申亮 于 2019-10-17 设计创作，主要内容包括：本发明提供了一种高硬度热固性自修复聚氨酯及其制备方法。该技术方案以含2-羟乙基二硫化物为功能性基团的异氰酸酯封端的聚氨酯与聚乙烯醇接枝聚己内酯交联固化,合成具有高自修复效率及高硬度透明的热固性自修复聚氨酯。本发明基于二硫键交换反应实现材料的自修复,通过聚乙烯醇接枝聚己内酯作为交联剂提供交联网络,所得材料具有优异的力学性能,较高的杨氏模量,同时该材料具有良好的透明性,较高的自修复效率,还具备形状记忆、再加工等性能。此外,本发明还公开了聚乙烯醇接枝聚己内酯的一种合成方法,该方法所制备的聚乙烯醇接枝聚己内酯具有多个羟基位点,增加分子链间氢键相互作用,可提供较高的化学及物理交联度。(The invention provides high-hardness thermosetting self-repairing polyurethane and a preparation method thereof. According to the technical scheme, isocyanate-terminated polyurethane containing 2-hydroxyethyl disulfide as a functional group and polyvinyl alcohol grafted polycaprolactone are crosslinked and cured to synthesize the thermosetting self-repairing polyurethane with high self-repairing efficiency, high hardness and transparency. The self-repairing material is realized based on the disulfide bond exchange reaction, the polyvinyl alcohol grafted polycaprolactone is used as a cross-linking agent to provide a cross-linked network, and the obtained material has excellent mechanical properties and higher Young modulus, and meanwhile, the material has good transparency and higher self-repairing efficiency, and also has the properties of shape memory, reprocessing and the like. In addition, the invention also discloses a synthesis method of the polyvinyl alcohol grafted polycaprolactone, and the polyvinyl alcohol grafted polycaprolactone prepared by the method has a plurality of hydroxyl sites, increases the hydrogen bond interaction between molecular chains, and can provide higher chemical and physical crosslinking degrees.)

1. The high-hardness thermosetting self-repairing polyurethane is characterized in that the molecular structure of the polyurethane comprises a hard segment, a soft segment and a cross-linked structure; wherein, the hard segment is the copolymer of dicyclohexylmethane 4,4 '-diisocyanate and 2, 2' -dithiodiethanol, the soft segment is polytetrahydrofuran, and the crosslinking structure is polyvinyl alcohol graft polycaprolactone.

2. The high-hardness thermosetting self-repairing polyurethane as claimed in claim 1, wherein the molar ratio of the hard segment to the soft segment to the cross-linked structure is 1: 0.09-0.2: 0.05-0.25.

3. The high-hardness thermosetting self-repairing polyurethane according to claim 2, wherein the molecular weight of the polytetrahydrofuran is 900-1100 g/mol.

4. A preparation method of the high-hardness thermosetting self-repairing polyurethane disclosed by claim 3 is characterized by comprising the following steps of:

1) under the protection of inert gas, polytetrahydrofuran and dicyclohexylmethane 4, 4' -diisocyanate are mixed and react, and a catalyst dibutyltin dilaurate and a solvent N, N-dimethylformamide are added to obtain an isocyanate-terminated prepolymer;

2) adding 2,2 '-dithiodiethanol and dicyclohexylmethane 4, 4' -diisocyanate into the system reacted in the step 1), and reacting under the protection of inert gas to obtain a linear isocyanate-terminated polymer;

3) adding a polyvinyl alcohol grafted polycaprolactone crosslinking agent into the system reacted in the step 2), uniformly mixing, and curing and drying to obtain the high-hardness thermosetting self-repairing polyurethane material.

5. The method of claim 4, wherein step 1) comprises: heating polytetrahydrofuran at the temperature of 100-140 ℃ for 1-3 h under a vacuum condition, then adding dicyclohexylmethane 4, 4' -diisocyanate, N-dimethylformamide and dibutyltin dilaurate into the polytetrahydrofuran under the protection of nitrogen, and stirring and reacting at the temperature of 60-80 ℃ for 0.5-2 h to obtain the isocyanate-terminated prepolymer.

6. The method according to claim 4 or 5, wherein the molar ratio of polytetrahydrofuran to dicyclohexylmethane 4, 4' -diisocyanate in step 1) is 1:2.

7. The method of claim 4, wherein step 2) comprises: adding 2,2 '-dithiodiethanol and dicyclohexylmethane 4, 4' -diisocyanate into the system reacted in the step 1), and stirring and reacting for 1-2 hours at the temperature of 60-80 ℃ under the protection of inert gas to obtain the linear isocyanate terminated polymer.

8. The method according to claim 4 or 7, wherein the molar ratio of the isocyanate terminated prepolymer, 2 '-dithiodiethanol, and dicyclohexylmethane 4, 4' -diisocyanate in step 2) is 1:1 to 4:2 to 6.

9. The method of claim 4, wherein step 3) comprises: adding polyvinyl alcohol grafted polycaprolactone serving as a cross-linking agent into the system reacted in the step 2), stirring for 10-30 min at the temperature of 60-70 ℃ under the protection of nitrogen, pouring the obtained solution into a mold, curing for 12-16 h at the temperature of 60 ℃, and then drying for 12-24 h at the temperature of 90 ℃ to obtain the high-hardness thermosetting self-repairing polyurethane.

10. The method of claim 4 or 9, wherein the polyvinyl alcohol-grafted polycaprolactone is prepared by: dissolving polyvinyl alcohol in dimethyl sulfoxide, adding epsilon-caprolactone and a catalyst under the protection of nitrogen, mixing at room temperature for 3-4 h, reacting at 130-140 ℃ for 5-6 h, extracting, washing and drying a reaction product.

Technical Field

The invention relates to the technical field of self-repairing polyurethane materials, in particular to high-hardness thermosetting self-repairing polyurethane and a preparation method thereof.

Background

The self-repairing material is a novel material capable of realizing self-healing effect from a molecular level when the material is damaged, and is widely researched in recent years, and the self-repairing material can prolong the service life of the material, so that the durability of the material is improved.

Self-repairing materials can be divided into two types according to healing mechanisms: extrinsic self-repair and intrinsic self-repair. The external aid type self-repairing system depends on a cross-linking agent, an initiator and functional molecules which are wrapped by structures such as micro-capsules, micro-spheres, micro-blood vessels and the like as a therapeutic agent, and when the material is damaged, the micro-structures release the internal therapeutic agent so as to achieve the effect of repairing cracks. However, the repair mechanism is difficult to repair for many times due to the limited number of microstructures, and the service life of the material is limited. The intrinsic self-repairing material achieves the self-repairing effect by means of the function of a non-covalent bond or the exchange reaction of reversible dynamic chemical bonds, and the material prepared by the mechanism has the advantages of good repairing effect, capability of being repaired for multiple times and the like, so that the intrinsic self-repairing material is widely concerned. The non-covalent bond self-repairing method comprises the modes of hydrogen bonds, coordination bonds and the like, and the reversible dynamic chemical bonds comprise the methods of dynamic ester exchange, Diels-Alder (DA) reaction, dynamic enamine bonds, dynamic diene ether bonds, dynamic disulfide bonds and the like. Through the addition of the dynamic chemical bond, after the material is damaged, the damaged material can realize self-repairing or reprocessing under external stimulation of certain temperature or illumination and the like.

Polyurethane materials are widely used in various industries because of their advantages such as excellent transparency, easy processing, and excellent properties. Polyurethane materials can be divided into two main categories of thermoplastic polyurethane and thermosetting polyurethane, wherein thermosetting polyurethane has more excellent mechanical properties, but compared with thermoplastic polyurethane, the thermoplastic polyurethane has no performances such as reprocessing, dissolving and the like due to higher crosslinking density. The self-repairing thermosetting polyurethane is expected to solve the problem, however, how to prepare the thermosetting polyurethane with the self-repairing capability is exact, and the prior art which can be used for reference is unavailable at present; moreover, how to ensure that the self-repairing thermosetting polyurethane has good performances in the aspects of hardness, toughness, transparency, repairing efficiency and the like also becomes a technical problem to be solved urgently.

Disclosure of Invention

The invention aims to solve the technical problem of how to provide thermosetting self-repairing polyurethane with a brand new structure.

The invention also provides a novel preparation method of the thermosetting self-repairing polyurethane.

The invention also aims to solve the technical problem of how to improve the mechanical properties of the thermosetting self-repairing polyurethane material, such as hardness, toughness and the like.

The invention also aims to solve the technical problem of how to reduce the repair condition of the thermosetting self-repairing polyurethane material and improve the repair efficiency.

The invention also aims to solve the technical problem of how to keep the thermosetting self-repairing polyurethane material with good transparency and endow the thermosetting self-repairing polyurethane material with certain shape memory and reprocessing performance.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

a high-hardness thermosetting self-repairing polyurethane, the molecular structure of which comprises a hard segment, a soft segment and a cross-linking structure; wherein, the hard segment is the copolymer of dicyclohexylmethane 4,4 '-diisocyanate and 2, 2' -dithiodiethanol, the soft segment is polytetrahydrofuran, and the crosslinking structure is polyvinyl alcohol graft polycaprolactone.

Preferably, the molar ratio of the hard segment to the soft segment to the cross-linked structure is 1: 0.09-0.2: 0.05-0.25.

Preferably, the molecular weight of the polytetrahydrofuran is 900-1100 g/mol.

On the basis of the technical scheme, the invention further provides a preparation method of the high-hardness thermosetting self-repairing polyurethane, which comprises the following steps:

1) under the protection of inert gas, polytetrahydrofuran and dicyclohexylmethane 4, 4' -diisocyanate are mixed and react, and a catalyst dibutyltin dilaurate and a solvent N, N-dimethylformamide are added to obtain an isocyanate-terminated prepolymer;

2) adding 2,2 '-dithiodiethanol and dicyclohexylmethane 4, 4' -diisocyanate into the system reacted in the step 1), and reacting under the protection of inert gas to obtain a linear isocyanate-terminated polymer;

3) adding a polyvinyl alcohol grafted polycaprolactone crosslinking agent into the system reacted in the step 2), uniformly mixing, and curing and drying to obtain the high-hardness thermosetting self-repairing polyurethane material.

Preferably, step 1) comprises: heating polytetrahydrofuran at the temperature of 100-140 ℃ for 1-3 h under the vacuum condition (for removing water in a system; the process can be carried out in a conventional container such as a three-necked bottle or a reaction kettle and the like), then adding dicyclohexylmethane 4, 4' -diisocyanate, N-dimethylformamide and dibutyltin dilaurate under the protection of nitrogen (by being matched with an oil bath and magnetic stirring at the same time), and stirring and reacting at the temperature of 60-80 ℃ for 0.5-2 h to obtain the isocyanate-terminated prepolymer. Further preferably, the reaction is carried out under stirring at 70 ℃ for 1 hour.

Preferably, the molar ratio of polytetrahydrofuran to dicyclohexylmethane 4, 4' -diisocyanate in step 1) is 1:2.

Preferably, step 2) comprises: adding 2,2 '-dithiodiethanol and dicyclohexylmethane 4, 4' -diisocyanate into the system obtained after the reaction in the step 1), and stirring and reacting for 1-2 hours at the temperature of 60-80 ℃ under the protection of inert gas to obtain a linear isocyanate-terminated polymer (also called disulfide chain-extended isocyanate-terminated linear polymer). Further preferably, the reaction is carried out under stirring at 70 ℃ for 1.5 hours.

Preferably, the molar ratio of the isocyanate-terminated prepolymer, 2 '-dithiodiethanol and dicyclohexylmethane 4, 4' -diisocyanate in the step 2) is 1:1 to 4:2 to 6. Further preferably, the molar ratio of the isocyanate terminated prepolymer, 2 '-dithiodiethanol and dicyclohexylmethane 4, 4' -diisocyanate in step 2) is 1:2.75: 4.

Preferably, step 3) comprises: adding polyvinyl alcohol grafted polycaprolactone into the system reacted in the step 2) as a cross-linking agent, stirring at the temperature of 60-70 ℃ for 10-30 min (for fully and uniformly mixing) under the protection of nitrogen, pouring the obtained solution into a mold, curing at the temperature of 60 ℃ for 12-16 h, and drying at the temperature of 90 ℃ for 12-24 h to obtain the high-hardness thermosetting self-repairing polyurethane. Preferably, the high-hardness thermosetting self-repairing polyurethane is obtained by fully mixing the components at the temperature of 60 ℃ for 30min, pouring the obtained solution into a mold, curing the solution at the temperature of 60 ℃ for 12h, and drying the solution at the temperature of 90 ℃ for 12 h.

Preferably, the molar ratio of the linear isocyanate-terminated polymer to the crosslinking agent in step 3) is 1:1 to 4. It is further preferred that the molar ratio of linear isocyanate-terminated polymer to crosslinker in step 3) is 1: 3.

Preferably, the polyvinyl alcohol-grafted polycaprolactone is prepared by the following method: dissolving polyvinyl alcohol in dimethyl sulfoxide, adding epsilon-caprolactone and a catalyst (the catalyst can be preferably zinc chloride) under the protection of nitrogen, mixing for 3-4 h at room temperature, reacting for 5-6 h at 130-140 ℃, and extracting, washing and drying a reaction product. It is further preferred that the mixing is carried out at 25 ℃ for 4 hours, followed by heating to 140 ℃ for 5 hours.

Preferably, the molar ratio of the polyvinyl alcohol to the epsilon-caprolactone is 1: 1.

Preferably, the extraction is performed with dichloromethane as the extractant.

Preferably, the washing is done with methane as a washing agent.

Preferably, in the above preparation method of the polyvinyl alcohol-grafted polycaprolactone, the amount of the catalyst is 1% of the total mass of the reactants of the system in which the catalyst is arranged.

Preferably, the molar ratio of-NCO to-OH in the system after the completion of step 3) is 1.1: 1.

The invention provides high-hardness thermosetting self-repairing polyurethane and a preparation method thereof. According to the technical scheme, isocyanate-terminated polyurethane containing 2-hydroxyethyl disulfide as a functional group and polyvinyl alcohol grafted polycaprolactone are crosslinked and cured to synthesize the thermosetting self-repairing polyurethane with high self-repairing efficiency, high hardness and transparency. The invention also discloses a synthesis method of the polyhydroxy graft polymer polyvinyl alcohol graft polycaprolactone.

The high-hardness thermosetting self-repairing polyurethane material disclosed by the invention realizes self-repairing through a disulfide bond exchange reaction, and provides a cross-linked network by using polyvinyl alcohol grafted polycaprolactone as a cross-linking agent, and the high-hardness thermosetting self-repairing polyurethane material comprises the following characteristics: the thermosetting polyurethane material with the high self-repairing effect is screened by regulating the proportion of the cross-linking agent, the preparation method is novel, the obtained material has excellent mechanical property and higher Young modulus, and meanwhile, the material has good transparency and higher self-repairing efficiency and also has the properties of shape memory, reprocessing and the like. The polyhydroxy graft polymer polyvinyl alcohol graft polycaprolactone disclosed by the invention has a plurality of hydroxyl sites, increases the interaction of hydrogen bonds among molecular chains, and can provide high chemical and physical crosslinking degrees.

Compared with the prior art, the beneficial effects of the invention are concentrated in the following aspects:

(1) the thermosetting self-repairing polyurethane obtained by the optimized steps has high Young modulus value of 111.6MPa, tensile strength of 20.5MPa and elongation at break of 538%, and has excellent performances of high hardness, high toughness and the like, and the repairing efficiency of the thermosetting self-repairing polyurethane is as high as 94%.

(2) The invention achieves self-repairing effect based on the combination of disulfide bonds and hydrogen bonds, has moderate required conditions, and can achieve higher repairing efficiency at moderate temperature.

(3) The obtained polyurethane material has high transparency, is a colorless transparent material, has certain shape memory and reprocessing performance, can reprocess and mold thermosetting polyurethane, and reduces environmental pollution and resource waste.

Drawings

FIG. 1 is a reaction schematic diagram of a synthetic self-healing polyurethane sample according to the present invention;

FIG. 2 is an IR spectrum of the cross-linking agent, polyvinyl alcohol grafted polycaprolactone in example 1 of the present invention after synthesis;

FIG. 3 is an IR spectrum of a self-healing polyurethane synthesized according to example 2 of the present invention;

FIG. 4 is a thermal weight loss curve (nitrogen atmosphere, heating rate of 10 ℃/min) of a self-repairing polyurethane sample according to the present invention;

FIG. 5 is an optical photograph of a self-healing polyurethane sample according to the present invention;

FIG. 6 is a stress-strain curve before and after self-repair of self-repair polyurethane in example 2 of the present invention;

FIG. 7 is a photomicrograph of the healing process of a self-healing polyurethane sample of example 2 of the present invention;

FIG. 8 is a photograph of a rework process of a self-healing polyurethane sample of example 2 of the present invention;

FIG. 9 is a photograph of a shape memory of a sample of self-healing polyurethane according to example 2 of the present invention.

Detailed Description

Hereinafter, specific embodiments of the present invention will be described in detail. Well-known structures or functions may not be described in detail in the following embodiments in order to avoid unnecessarily obscuring the details. Approximating language, as used herein in the following examples, may be applied to identify quantitative representations that could permissibly vary in number without resulting in a change in the basic function. Unless defined otherwise, technical and scientific terms used in the following examples have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.