CN112898528A - Liquid crystal polyurethane for modified epoxy resin and preparation method and application thereof - Google Patents
Liquid crystal polyurethane for modified epoxy resin and preparation method and application thereof Download PDFInfo
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/65—Low-molecular-weight compounds having active hydrogen with high-molecular-weight compounds having active hydrogen
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- C08G18/00—Polymeric products of isocyanates or isothiocyanates
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- C08G18/3872—Low-molecular-weight compounds having heteroatoms other than oxygen having sulfur containing groups having sulfur atoms between two carbon atoms, the sulfur atoms being directly linked to carbon atoms or other sulfur atoms containing groups having one sulfur atom between two carbon atoms the sulfur atom belonging to a sulfoxide or sulfone group
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Abstract
The invention is suitable for the technical field of chemical industry and high polymer materials, and provides liquid crystal polyurethane for modifying epoxy resin, a preparation method and application thereof, wherein the liquid crystal polyurethane is a polycondensate of a liquid crystal element, polyethylene glycol and diisocyanate, or a polycondensate of the liquid crystal element and the diisocyanate; the liquid crystal element is a Schiff base structure liquid crystal element synthesized by the reaction of 4, 4' -diaminodiphenyl sulfone and p-hydroxybenzaldehyde. The liquid crystal polyurethane provided by the embodiment of the invention has the advantages of lower melting point, wide liquid crystal interval and fluidity, and good compatibility with epoxy resin, and can effectively improve the toughness of the epoxy resin and achieve the effect of toughening modification. The epoxy resin modified by the liquid crystal polyurethane can be applied to the fields of microelectronic packaging materials, automobile parts, aerospace, building materials, coatings, adhesives and the like.
Description
Technical Field
The invention belongs to the technical field of chemical engineering and high polymer materials, and particularly relates to liquid crystal polyurethane for modifying epoxy resin, and a preparation method and application thereof.
Background
Epoxy resin is an important thermosetting resin, and because epoxy groups, active groups such as hydroxyl groups, ether bonds and the like and polar groups exist in the epoxy resin, the epoxy resin has many excellent properties including high mechanical properties, excellent bonding properties, low curing shrinkage, good molding manufacturability, excellent dielectric properties, high thermal stability, chemical corrosion resistance and the like, so that the epoxy resin is widely applied to various fields. Meanwhile, the epoxy resin has the defects of high crosslinking density of a cured product, large internal stress, crisp texture, poor toughness, easy cracking and weak impact resistance, and the application of the epoxy resin is limited. In recent years, attention has been paid to the modification of epoxy resins.
The mechanism of toughening the epoxy resin by the liquid crystal polymer is mainly a silver-grain shear yield mechanism and a crack nail anchoring mechanism. As liquid crystal molecules contain a large number of rigid liquid crystal units, rigid mesomorphic units in the liquid crystal polymer are oriented and phase-separated in the forming process to form a two-phase structure, the epoxy matrix is subjected to yield deformation under the action of stress, and the stress concentration is generated on the two-phase interface to cause the crazing and the shear band to absorb energy, thereby improving the toughness of the system. In addition, the anisotropic mesogenic domains formed during the molding process, the regions of oriented liquid crystals are surrounded by an isotropic network, which structure resembles a fiber-reinforced structure. The liquid crystal domain transverse frame is arranged on the fracture surface, two sides of the crack are connected like a bridge, and the bridging force plays a role of nail anchoring on the crack, so that the crack is prevented from further expanding, and the toughening purpose is achieved.
The liquid crystal polyurethane is used as a novel high-performance high polymer material, has high strength, high modulus, electric insulation, corrosion resistance, weather aging resistance, microwave permeability and excellent molding processability, shows excellent comprehensive performances such as unique easy flowability, excellent thermal stability and dimensional stability, lower linear expansion coefficient and density and the like in a liquid crystal state, and has better effect on toughening and modifying various epoxy resins. Therefore, research and development of liquid crystal polyurethane is currently crucial.
Disclosure of Invention
An object of an embodiment of the present invention is to provide a liquid crystal polyurethane for modifying epoxy resin, which aims to solve the problems set forth in the background art.
The embodiment of the invention is realized by that the liquid crystal polyurethane for modifying the epoxy resin is a polycondensate of a liquid crystal element, polyethylene glycol and diisocyanate or a polycondensate of a liquid crystal element and diisocyanate; the liquid crystal element is a Schiff base structure liquid crystal element synthesized by the reaction of 4, 4' -diaminodiphenyl sulfone and p-hydroxybenzaldehyde.
Specifically, the liquid crystal polyurethane is a condensation polymer which is linearly and randomly arranged and has the weight-average molecular weight of 1000-50000.
As a preferable scheme of the embodiment of the invention, the molar ratio of the liquid crystal element, the polyethylene glycol and the diisocyanate is (10-50): 40-0): 50.
As another preferable scheme of the embodiment of the invention, the structural formula of the liquid crystal polyurethane is as follows:
wherein n is the degree of polymerization.
In another preferred embodiment of the present invention, the diisocyanate is diphenylmethane diisocyanate.
Another object of an embodiment of the present invention is to provide a method for preparing the above liquid crystal polyurethane for modifying epoxy resin, which includes the following steps:
dissolving 4, 4' -diamino diphenyl sulfone and p-hydroxybenzaldehyde in absolute ethyl alcohol, and then adding a first catalyst for reaction to obtain a liquid crystal element;
dissolving a liquid crystal element in a solvent, or dissolving the liquid crystal element and polyethylene glycol in the solvent to obtain a mixed solution A;
adding a second catalyst into the mixed solution A for mixing to obtain a mixed solution B;
dissolving diisocyanate in a solvent, and then slowly dropwise adding the diisocyanate into the mixed solution B for reaction to obtain a mixed solution C;
and adding the mixed solution C into water to separate out solids to obtain the liquid crystal polyurethane.
Since the reaction for synthesizing the liquid crystal polyurethane of the present invention is a polycondensation reaction, in the above preparation method, the sum of the molar numbers of the alcoholic hydroxyl group and the phenolic hydroxyl group in the reaction should be the same as the molar number of the isocyanate group to achieve a higher weight average molecular weight.
As another preferable scheme of the embodiment of the invention, the first catalyst is p-toluenesulfonic acid, and the dosage of the p-toluenesulfonic acid is 1-5% of the mass of 4, 4' -diaminodiphenyl sulfone.
As another preferable mode of the embodiment of the present invention, the second catalyst is dibutyltin dilaurate.
As another preferable mode of the embodiment of the present invention, the solvent is any one of N, N-Dimethylformamide (DMF), Tetrahydrofuran (THF), acetonitrile, ethyl acetate, and dimethyl sulfoxide (DMSO).
The embodiment of the invention also aims to provide the liquid crystal polyurethane prepared by the preparation method.
Another object of the embodiments of the present invention is to provide an application of the liquid crystal polyurethane in reinforcing and/or toughening modified epoxy resin.
The invention can adopt a gel permeation chromatograph to test the weight average molecular weight of the liquid crystal polymer with the ionic group; the texture and liquid crystal domain of the liquid crystal polymer were observed using a polarizing microscope with a hot stage.
The liquid crystal polyurethane for modifying the epoxy resin provided by the embodiment of the invention has a rigid rod-shaped structure, and a liquid crystal polymer can be oriented to form microfibers, so that the liquid crystal polyurethane has a higher modulus, has good vibration absorption characteristics and flame retardant performance, and is an excellent engineering structure material. The liquid crystal polyurethane prepared by the invention has a wider liquid crystal interval, so that the liquid crystal polyurethane has a wide application range in processing. The liquid crystal polyurethane is used for toughening or reinforcing modified epoxy resin, the using amount is low, and good toughening and reinforcing effects can be achieved. The epoxy resin modified by the liquid crystal polyurethane can be applied to the fields of automobile parts, precise electronic instruments, optical fibers, medical instruments, waterproof materials, textile fields, insulating materials, energy storage materials, body armor or parachutes and the like.
Drawings
FIG. 1 is a polarization microscope photograph of a liquid crystal polyurethane prepared in example 1 of the present invention, which is a liquid crystal weave pattern at a magnification of 200 times, specifically at a temperature between the melting point and the clearing point.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
This embodiment provides a method for preparing a liquid crystal polyurethane for a modified epoxy resin, which includes the steps of:
s1, adding 1mol of 4,4 '-diamino diphenyl sulfone, 2mol of p-hydroxybenzaldehyde and 500mL of absolute ethyl alcohol into a reaction bottle provided with a thermometer, a condenser tube and a stirrer, stirring and dissolving, adding p-toluenesulfonic acid with the mass of 2 wt% of 4, 4' -diamino diphenyl sulfone, carrying out reflux reaction for 5 hours, cooling to room temperature, precipitating light yellow crystals, and filtering under reduced pressure to obtain the mesogen.
S2, adding 0.2mol of the above mesogen, 0.8mol of polyethylene glycol (600) and 500mL of DMF into another reaction flask equipped with a thermometer, a condenser and a stirrer, and stirring to dissolve to obtain a mixed solution A.
S3, adding 1 wt% of dibutyltin dilaurate serving as a catalyst into the mixed solution A, and mixing to obtain a mixed solution B.
S4, dissolving 1mol of diphenylmethane diisocyanate in 500mL of DMF, slowly dropwise adding the solution into the mixed solution B, uniformly stirring, and then heating to 70 ℃ for reaction for 10 hours to obtain a mixed solution C.
And S5, pouring the mixed solution C into a large amount of water to precipitate solids, and washing, filtering and drying the obtained solid crude product by using ethanol to obtain the liquid crystal polyurethane. The liquid crystal polyurethane has the yield of 90 percent, the melting point of 135 ℃, the clearing point of 204 ℃, and the test result of a polarizing microscope of the liquid crystal texture is shown in figure 1.
In addition, the liquid crystal polyurethane (the dosage is only 7 wt% of the epoxy resin) is added into the epoxy resin for modification, and the impact strength of the obtained modified epoxy resin composite material is 5.6kJ/m2Increased to 13.3kJ/m2The tensile strength and the bending strength are respectively improved by 36 percent and 14 percent, and meanwhile, the thermal decomposition starting temperature is improved by 21 ℃.
Example 2
This embodiment provides a method for preparing a liquid crystal polyurethane for a modified epoxy resin, which includes the steps of:
s1, adding 0.5mol of 4,4 '-diamino diphenyl sulfone, 1mol of p-hydroxybenzaldehyde and 200mL of absolute ethyl alcohol into a reaction bottle provided with a thermometer, a condenser tube and a stirrer, stirring and dissolving, adding 1 wt% of p-toluenesulfonic acid of 4, 4' -diamino diphenyl sulfone, carrying out reflux reaction for 6h, cooling to room temperature, precipitating light yellow crystals, and filtering under reduced pressure to obtain the mesogen.
S2, adding 0.3mol of the above mesogen, 0.7mol of polyethylene glycol (600) and 500mL of DMF into another reaction flask equipped with a thermometer, a condenser and a stirrer, and stirring to dissolve to obtain a mixed solution A.
S3, adding 1 wt% of dibutyltin dilaurate serving as a catalyst into the mixed solution A, and mixing to obtain a mixed solution B.
S4, dissolving 1mol of diphenylmethane diisocyanate in 500mL of DMF, slowly dropwise adding the solution into the mixed solution B, uniformly stirring, and then heating to 60 ℃ to react for 8 hours to obtain a mixed solution C.
And S5, pouring the mixed solution C into a large amount of water to precipitate solids, and washing, filtering and drying the obtained solid crude product by using ethanol to obtain the liquid crystal polyurethane. The liquid crystal polyurethane has the yield of 92 percent, the melting point of 141 ℃ and the clearing point of 206 ℃.
In addition, the liquid crystal polyurethane (the dosage is only 9 wt% of the epoxy resin) is added into the epoxy resin for modification, and the impact strength of the obtained modified epoxy resin composite material is 5.6kJ/m2Increased to 17.5kJ/m2The tensile strength and the bending strength are respectively improved by 45 percent and 21 percent, and simultaneously, the thermal decomposition starting temperature is improved by 19 ℃.
Example 3
This embodiment provides a method for preparing a liquid crystal polyurethane for a modified epoxy resin, which includes the steps of:
s1, adding 2mol of 4,4 '-diamino diphenyl sulfone, 4mol of p-hydroxybenzaldehyde and 1000mL of absolute ethyl alcohol into a reaction bottle provided with a thermometer, a condenser tube and a stirrer, stirring and dissolving, adding p-toluenesulfonic acid with the mass of 5 wt% of 4, 4' -diamino diphenyl sulfone, carrying out reflux reaction for 8 hours, cooling to room temperature, precipitating light yellow crystals, and filtering under reduced pressure to obtain the mesogen.
S2, adding 0.5mol of the above mesogen, 0.5mol of polyethylene glycol (600) and 500mL of DMF into another reaction flask equipped with a thermometer, a condenser and a stirrer, and stirring to dissolve to obtain a mixed solution A.
S3, adding 1 wt% of dibutyltin dilaurate serving as a catalyst into the mixed solution A, and mixing to obtain a mixed solution B.
S4, dissolving 1mol of diphenylmethane diisocyanate in 500mL of DMF, slowly dropwise adding the solution into the mixed solution B, uniformly stirring, and then heating to 80 ℃ to react for 12 hours to obtain a mixed solution C.
And S5, pouring the mixed solution C into a large amount of water to precipitate solids, and washing, filtering and drying the obtained solid crude product by using ethanol to obtain the liquid crystal polyurethane. The liquid crystal polyurethane has the yield of 92 percent, the melting point of 150 ℃ and the clearing point of 198 ℃.
In addition, the liquid crystal polyurethane (the dosage is only 9 wt% of the epoxy resin) is added into the epoxy resin for modification, and the impact strength of the obtained modified epoxy resin composite material is 5.6kJ/m2Increased to 19.7kJ/m2The tensile strength and the bending strength are respectively improved by 50 percent and 26 percent, and meanwhile, the thermal decomposition starting temperature is improved by 18 ℃.
Example 4
This embodiment provides a method for preparing a liquid crystal polyurethane for a modified epoxy resin, which includes the steps of:
s1, adding 1mol of 4,4 '-diamino diphenyl sulfone, 2mol of p-hydroxybenzaldehyde and 500mL of absolute ethyl alcohol into a reaction bottle provided with a thermometer, a condenser tube and a stirrer, stirring and dissolving, adding p-toluenesulfonic acid with the mass of 2 wt% of 4, 4' -diamino diphenyl sulfone, carrying out reflux reaction for 5 hours, cooling to room temperature, precipitating light yellow crystals, and filtering under reduced pressure to obtain the mesogen.
S2, adding 1mol of the above mesogen and 500mL of acetonitrile into another reaction flask equipped with a thermometer, a condenser and a stirrer, and stirring and dissolving to obtain a mixed solution A.
S3, adding 1 wt% of dibutyltin dilaurate serving as a catalyst into the mixed solution A, and mixing to obtain a mixed solution B.
S4, dissolving 1mol of diphenylmethane diisocyanate in 500mL of acetonitrile, slowly dropwise adding the solution into the mixed solution B, uniformly stirring, and then heating to 70 ℃ to react for 10 hours to obtain a mixed solution C.
And S5, pouring the mixed solution C into a large amount of water to precipitate solids, and washing, filtering and drying the obtained solid crude product by using ethanol to obtain the liquid crystal polyurethane.
Example 5
This embodiment provides a method for preparing a liquid crystal polyurethane for a modified epoxy resin, which includes the steps of:
s1, adding 1mol of 4,4 '-diamino diphenyl sulfone, 2mol of p-hydroxybenzaldehyde and 500mL of absolute ethyl alcohol into a reaction bottle provided with a thermometer, a condenser tube and a stirrer, stirring and dissolving, adding p-toluenesulfonic acid with the mass of 2 wt% of 4, 4' -diamino diphenyl sulfone, carrying out reflux reaction for 5 hours, cooling to room temperature, precipitating light yellow crystals, and filtering under reduced pressure to obtain the mesogen.
S2, adding 0.2mol of the above mesogen, 0.8mol of polyethylene glycol (600) and 500mL of tetrahydrofuran into another reaction flask equipped with a thermometer, a condenser and a stirrer, and stirring to dissolve to obtain a mixed solution A.
S3, adding 1 wt% of dibutyltin dilaurate serving as a catalyst into the mixed solution A, and mixing to obtain a mixed solution B.
S4, dissolving 1mol of diphenylmethane diisocyanate in 500mL of tetrahydrofuran, slowly dropwise adding the solution into the mixed solution B, uniformly stirring, and then heating to 70 ℃ for reaction for 10 hours to obtain a mixed solution C.
And S5, pouring the mixed solution C into a large amount of water to precipitate solids, and washing, filtering and drying the obtained solid crude product by using ethanol to obtain the liquid crystal polyurethane.
Example 6
This embodiment provides a method for preparing a liquid crystal polyurethane for a modified epoxy resin, which includes the steps of:
s1, adding 1mol of 4,4 '-diamino diphenyl sulfone, 2mol of p-hydroxybenzaldehyde and 500mL of absolute ethyl alcohol into a reaction bottle provided with a thermometer, a condenser tube and a stirrer, stirring and dissolving, adding p-toluenesulfonic acid with the mass of 3 wt% of 4, 4' -diamino diphenyl sulfone, carrying out reflux reaction for 5 hours, cooling to room temperature, precipitating light yellow crystals, and filtering under reduced pressure to obtain the mesogen.
S2, adding 0.5mol of the above mesogen, 0.5mol of polyethylene glycol (600) and 400mL of ethyl acetate into another reaction flask equipped with a thermometer, a condenser and a stirrer, and stirring to dissolve them to obtain a mixed solution A.
S3, adding 0.5 wt% of dibutyltin dilaurate serving as a catalyst into the mixed solution A, and mixing to obtain a mixed solution B.
S4, dissolving 1mol of diphenylmethane diisocyanate in 600mL of ethyl acetate, slowly dropwise adding the solution into the mixed solution B, uniformly stirring, and then heating to 70 ℃ for reaction for 10 hours to obtain a mixed solution C.
And S5, pouring the mixed solution C into a large amount of water to precipitate solids, and washing, filtering and drying the obtained solid crude product by using ethanol to obtain the liquid crystal polyurethane.
Example 6
This embodiment provides a method for preparing a liquid crystal polyurethane for a modified epoxy resin, which includes the steps of:
s1, adding 1mol of 4,4 '-diamino diphenyl sulfone, 2mol of p-hydroxybenzaldehyde and 500mL of absolute ethyl alcohol into a reaction bottle provided with a thermometer, a condenser tube and a stirrer, stirring and dissolving, adding 4 wt% of p-toluenesulfonic acid based on 4, 4' -diamino diphenyl sulfone, carrying out reflux reaction for 5 hours, cooling to room temperature, precipitating light yellow crystals, and filtering under reduced pressure to obtain the mesogen.
S2, adding 0.6mol of the above mesogen, 0.4mol of polyethylene glycol (600) and 600mL of dimethyl sulfoxide into another reaction flask equipped with a thermometer, a condenser and a stirrer, and stirring to dissolve to obtain a mixed solution A.
S3, adding 1.5 wt% of dibutyltin dilaurate serving as a catalyst into the mixed solution A, and mixing to obtain a mixed solution B.
S4, dissolving 1mol of diphenylmethane diisocyanate in 400mL of dimethyl sulfoxide, slowly dropwise adding the dissolved diphenylmethane diisocyanate into the mixed solution B, uniformly stirring, and heating to 70 ℃ for reacting for 10 hours to obtain a mixed solution C.
And S5, pouring the mixed solution C into a large amount of water to precipitate solids, and washing, filtering and drying the obtained solid crude product by using ethanol to obtain the liquid crystal polyurethane.
The polarizing microscope used in the present invention is a LEICA DMRX type polarizing microscope with a hot stage, which is THMSE600 from Linkam, uk. The materials in the examples of the present invention are all commercially available products.
In summary, the liquid crystal polyurethane provided by the embodiment of the invention has a rigid rod-like structure, and the liquid crystal polymer can be oriented to form microfibers, so that the liquid crystal polyurethane has a higher modulus, and meanwhile, the liquid crystal polyurethane has good vibration absorption characteristics and flame retardant properties, and is an excellent engineering structure material. The liquid crystal polyurethane prepared by the invention has a wider liquid crystal interval, so that the liquid crystal polyurethane has a wide application range in processing. In addition, the liquid crystal polyurethane is used for toughening modified epoxy resin, the using amount of the liquid crystal polyurethane is only 1-15 wt% of the epoxy resin, and a good effect can be achieved, compared with unmodified epoxy resin, the impact strength is 1-4 times of that of the liquid crystal polyurethane, the tensile strength is improved by about 57%, and the bending strength is increased by about 29%.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (10)
1. A liquid-crystalline polyurethane for modifying an epoxy resin, characterized in that the liquid-crystalline polyurethane is a polycondensate of a mesogen, a polyethylene glycol and a diisocyanate, or a polycondensate of a mesogen and a diisocyanate; the liquid crystal element is a Schiff base structure liquid crystal element synthesized by the reaction of 4, 4' -diaminodiphenyl sulfone and p-hydroxybenzaldehyde.
2. The liquid crystal polyurethane for modifying epoxy resin of claim 1, wherein the molar ratio of the mesogen, the polyethylene glycol and the diisocyanate is (10-50): (40-0): 50.
3. The liquid crystal polyurethane for modifying epoxy resin according to claim 1 or 2, wherein the structural formula of the liquid crystal polyurethane is:
wherein n is the degree of polymerization.
4. The liquid-crystalline polyurethane for modifying an epoxy resin according to claim 1 or 2, wherein the diisocyanate is diphenylmethane diisocyanate.
5. A method for preparing the liquid crystal polyurethane for modifying epoxy resin according to any one of claims 1 to 4, comprising the steps of:
dissolving 4, 4' -diamino diphenyl sulfone and p-hydroxybenzaldehyde in absolute ethyl alcohol, and then adding a first catalyst for reaction to obtain a liquid crystal element;
dissolving a liquid crystal element in a solvent, or dissolving the liquid crystal element and polyethylene glycol in the solvent to obtain a mixed solution A;
adding a second catalyst into the mixed solution A for mixing to obtain a mixed solution B;
dissolving diisocyanate in a solvent, and then slowly dropwise adding the diisocyanate into the mixed solution B for reaction to obtain a mixed solution C;
and adding the mixed solution C into water to separate out solids to obtain the liquid crystal polyurethane.
6. The method of claim 5, wherein the first catalyst is p-toluenesulfonic acid in an amount of 1-5% by mass of 4, 4' -diaminodiphenyl sulfone.
7. The method of claim 5, wherein the second catalyst is dibutyltin dilaurate.
8. The method of claim 5, wherein the solvent is any one of N, N-dimethylformamide, tetrahydrofuran, acetonitrile, ethyl acetate and dimethylsulfoxide.
9. A liquid-crystalline polyurethane obtained by the production method as claimed in any one of claims 5 to 8.
10. Use of a liquid crystalline polyurethane according to any one of claims 1 to 4 and 9 for reinforcing and/or toughening modified epoxy resins.
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| CN113881006A (en) * | 2021-11-12 | 2022-01-04 | 中国科学院长春应用化学研究所 | Liquid crystal type polyurethane prepolymer for toughening epoxy resin adhesive and preparation method and application thereof |
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