CN113248741B - Preparation method of cross-linked shape memory polyurethane - Google Patents
Preparation method of cross-linked shape memory polyurethane Download PDFInfo
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- C08J2375/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
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Abstract
The invention discloses a preparation method of cross-linked shape memory polyurethane, and relates to the technical field of shape memory polymers. The preparation method of the cross-linked shape memory polyurethane comprises the following steps: s10, dissolving polyester polyurethane in a first organic solvent to obtain a polyester polyurethane solution; s20, adding an initiator into the polyester type polyurethane solution, uniformly mixing, drying to remove the first organic solvent, and then reacting for 0.5-2 h at 80-120 ℃ to obtain the cross-linked shape memory polyurethane. The initiator is heated to generate free radicals, and the free radicals can capture hydrogen on a polyester polyurethane molecular chain to generate new free radicals on the polyester polyurethane molecular chain, so that the free radicals on different molecular chains of the polyester polyurethane are mutually combined to form chemical cross-linking bonds, and the cross-linked shape memory polyurethane with the shape fixing rate of more than 95% and the shape recovery rate of more than 97% is prepared.
Description
Technical Field
The invention relates to the technical field of shape memory polymers, in particular to a preparation method of cross-linked shape memory polyurethane.
Background
Shape Memory Polymers (SMPs) are polymers that can be induced by an external environment (e.g., light, magnetism, electricity, solvent, temperature, etc.) to adjust their state parameters (e.g., shape, strain, etc.) back to their original state. Compared with shape memory ceramics or shape memory alloys, the shape memory polymer has the characteristics of light weight, various stimulation modes, adjustable performance, easiness in processing and the like, is a research hotspot of intelligent high polymer materials, and is widely applied to the fields of biomedical materials, self-repairing materials, intelligent textile materials, drug controlled release, aerospace and the like. At present, the polymers with Shape Memory Effect (SME) mainly include polyurethane, polynorbornene, polyisoprene, styrene butadiene rubber, polyethylene, etc., wherein Shape Memory Polyurethane (SMPU) is a block copolymer copolymerized by a hard segment with a higher glass transition temperature and a soft segment with a lower glass transition temperature, and different glass transition temperatures can be obtained by adjusting the structure and the amount of each component of polyurethane. SMPU also has the advantages of excellent low-temperature impact resistance, good biocompatibility, large deformation, wide shape memory temperature design range and the like, so that the SMPU is increasingly favored by researchers.
Carbamate in the SMPU hard segment has high polarity, and a strong hydrogen bond effect can be formed between the hard segment and the hard segment, so that the carbamate can be used as a stationary phase for memorizing the initial shape of the SMPU. The soft segment is in a high elastic state at normal temperature due to low glass transition temperature, is used as a reversible phase, and can realize reversible solidification and softening in the process of temperature reduction and temperature rise. Compared with other shape memory polymers taking chemical crosslinking as a stationary phase, the SMPU has weaker binding capacity of binding a hydrogen bond into the stationary phase, so the SMPU still has the defects of low shape recovery speed, low recovery rate, poor repeated memory effect, low mechanical property and the like.
At present, in order to improve the shape recovery speed, the recovery rate, the repeated memory effect, the mechanical property and the like of the shape memory polyurethane, a great deal of research work is carried out by researchers at home and abroad, part of the work is to add a cross-linking agent in the polyurethane synthesis process to provide chemical cross-linking points, so that the recovery speed and the shape memory effect of the polyurethane can be improved to a certain extent, but the challenge is provided for the synthesis process (the cross-linking agent is generally a silane coupling agent with three silane oxygen groups, which easily causes unstable polymerization), and the thermosetting polyurethane has certain difficulty in later-stage molding preparation, so that the application of the thermosetting polyurethane is limited.
Disclosure of Invention
The invention mainly aims to provide a preparation method of cross-linked shape memory polyurethane, and aims to provide shape memory polyurethane with high shape recovery speed, good repeated memory effect and wide application range.
In order to achieve the purpose, the invention provides a preparation method of cross-linking type shape memory polyurethane, which comprises the following steps:
s10, dissolving polyester polyurethane in a first organic solvent to obtain a polyester polyurethane solution;
s20, adding an initiator into the polyester type polyurethane solution, uniformly mixing, drying to remove the first organic solvent, and then reacting for 0.5-2 h at 80-120 ℃ to obtain the cross-linked shape memory polyurethane.
Optionally, before step S10, the method further includes:
a1, mixing dried polyester dihydric alcohol with isocyanate to form a first reaction system, and reacting the first reaction system for 2-4 hours at 70-90 ℃ under the action of an organic tin catalyst to obtain a polyester type polyurethane prepolymer;
a2, adding a chain extender into the polyurethane prepolymer at the temperature of 30-45 ℃ to form a second reaction system, and completely reacting the second reaction system at the temperature of 45-65 ℃ to obtain a mixed solution containing polyester type polyurethane;
and A3, separating the polyester polyurethane in the mixed solution, and drying to obtain the polyester polyurethane.
Optionally, a second organic solvent is included in the first system; and/or the presence of a gas in the gas,
a third organic solvent is included in the second system.
Optionally, the second organic solvent comprises any one of acetone, tetrahydrofuran, N-dimethylformamide; and/or the presence of a gas in the atmosphere,
the third organic solvent comprises any one of acetone, tetrahydrofuran and N, N-dimethylformamide.
Optionally, in step A1:
the molar ratio between the polyester diol and the isocyanate is 1: (2-6);
the mass of the organic tin catalyst is 0.5-2% of the sum of the mass of the polyester dihydric alcohol and the mass of the isocyanate.
Optionally, the molar ratio between the polyester diol and the chain extender is 1: (1-5).
Optionally, the polyester diol comprises at least one of polycaprolactone diol with molecular weight of 500-5000; and/or the presence of a gas in the atmosphere,
the isocyanate comprises at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate and lysine diisocyanate; and/or the presence of a gas in the atmosphere,
the chain extender comprises at least one of ethylene glycol, propylene glycol, 1, 4-butanediol, diethylene glycol, 1, 4-cyclohexanediol and hydrogenated bisphenol A.
Optionally, step A3 specifically includes:
and adding the mixed solution into excessive water, washing the obtained precipitate for multiple times, and drying under vacuum to obtain white floccule, namely the polyester polyurethane.
Optionally, the first organic solvent comprises any one of acetone, tetrahydrofuran, and N, N-dimethylformamide; and/or the presence of a gas in the gas,
the initiator comprises at least one of di (4-methylbenzoyl) peroxide, dibenzoyl peroxide, 1-di (tert-butylperoxy) cyclohexane, tert-butylperoxy-2-ethylhexyl carbonate, n-butyl-4, 4-di (tert-butylperoxy) valerate and dicumyl peroxide.
Optionally, the mass of the initiator is 0.5-10% of the mass of the polyester polyurethane
According to the technical scheme provided by the invention, polyester polyurethane is dissolved in a first organic solvent, then an initiator is added into the first organic solvent, the first organic solvent is removed by drying after uniform mixing, and finally, thermal crosslinking reaction is carried out to obtain the crosslinking type shape memory polyurethane. The initiator is heated to generate free radicals, and the free radicals can capture hydrogen on a polyester polyurethane molecular chain to generate new free radicals on the polyester polyurethane molecular chain, so that the free radicals on different molecular chains of the polyester polyurethane are mutually combined to form chemical cross-linking bonds, and the cross-linked shape memory polyurethane with the shape fixing rate of more than 95% and the shape recovery rate of more than 97% is prepared.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other relevant drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a graph showing a shape recovery test of a cross-linked shape memory polyurethane prepared in example 1 of the present invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between the various embodiments may be combined with each other, but must be based on the realization of the capability of a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
At present, in order to improve the shape recovery speed, recovery rate, repeated memory effect, mechanical property and the like of the shape memory polyurethane, a great deal of research work is carried out by researchers at home and abroad, part of the work is to add a cross-linking agent in the polyurethane synthesis process to provide chemical cross-linking points, so that the recovery speed and the shape memory effect of the polyurethane can be improved to a certain extent, but the challenge is provided for the synthesis process (the cross-linking agent is generally a silane coupling agent with three silane oxygen groups, so that the polymerization is easy to cause instability), and the thermosetting polyurethane has certain difficulty in later-stage molding preparation, so that the application of the thermosetting polyurethane is limited.
In view of the above, the present invention provides a method for preparing a cross-linked shape memory polyurethane, which in one embodiment comprises the following steps:
and S10, dissolving the polyester polyurethane in a first organic solvent to obtain a polyester polyurethane solution.
The polyurethane includes polyester polyurethane and polyether polyurethane, and in this embodiment, the polyester polyurethane is selected to obtain the cross-linked shape memory polyurethane. The polyester polyurethane may be commercially available or may be prepared by itself. In order to adjust the contents of the soft segment and the hard segment in the polyester polyurethane so as to obtain different glass transition temperatures according to the requirement, in the present embodiment, the step S10 is preceded by the following steps:
step A1, mixing dried polyester dihydric alcohol with isocyanate to form a first reaction system, and reacting the first reaction system for 2-4 hours at 70-90 ℃ under the action of an organic tin catalyst to obtain the polyester type polyurethane prepolymer.
In this example, the molar ratio between the polyester diol and the isocyanate was 1: (2-6); the mass of the organic tin catalyst is 0.5-2% of the sum of the mass of the polyester dihydric alcohol and the mass of the isocyanate.
In order to reduce the viscosity of the polyester diol and the isocyanate, and thus control the reaction rate thereof, in one embodiment, a second organic solvent is included in the first reaction system to dilute the polyester diol and the isocyanate. Wherein the second organic solvent comprises any one of acetone, tetrahydrofuran, and N, N-Dimethylformamide (DMF). In addition, the present invention does not limit the specific addition amount of the second organic solvent, and in this example, 5 to 20mL of the second organic solvent is added per 1mol of the polyester diol.
The present invention does not limit the specific adding sequence of the second organic solvent, and in this embodiment, the step A1 includes:
and A11, after the polyester diol is dried in vacuum, dissolving the polyester diol in a second organic solvent at 50-85 ℃ under the protection of nitrogen to obtain the polyester diol solution.
It should be noted that the polyester diol is vacuum dried to remove moisture in the polyester diol, so as to avoid the influence of the moisture on the subsequent reaction. Furthermore, under the protection of nitrogen, the water vapor entering in the process of dissolving the polyester glycol in the second organic solvent is avoided. In one embodiment, the stirring is carried out at a speed of 400-600 r/min and at a temperature of 50-85 ℃ so that the polyester diol can be dissolved in the second organic solvent more quickly and sufficiently.
The polyester diol comprises at least one of polycaprolactone diol with the molecular weight of 500-5000, namely the polyester diol can be polycaprolactone diol with the molecular weight of 500, a mixture of polycaprolactone diol with the molecular weight of 1000 and polycaprolactone diol with the molecular weight of 2000, polycaprolactone diol with the molecular weight of 5000 and the like.
And A12, mixing isocyanate and a second organic solvent to obtain an isocyanate solution, and adding the isocyanate solution into the polyester diol solution to form a first reaction system.
The isocyanate includes at least one of Toluene Diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene Diisocyanate (HDI), and Lysine Diisocyanate (LDI).
And A2, adding a chain extender into the polyurethane prepolymer at the temperature of 30-45 ℃ to form a second reaction system, and completely reacting the second reaction system at the temperature of 45-65 ℃ to obtain a mixed solution containing the polyester polyurethane.
In order to reduce the viscosity of the chain extender and thereby control the reaction rate thereof, in this embodiment, a third organic solvent is included in the second reaction system. The invention does not limit the specific adding sequence of the third solvent, and in an embodiment, the chain extender and the third solvent are mixed to obtain a chain extender solution; and slowly adding the chain extender solution into the polyurethane prepolymer to form a second reaction system.
To control the reaction rate of the polyurethane prepolymer, in one embodiment, the molar ratio between the polyester diol and the chain extender is 1: (1-5).
In one embodiment, the third organic solvent includes any one of acetone, tetrahydrofuran, and N, N-dimethylformamide. In addition, the present invention does not limit the specific addition amount of the third organic solvent, and in this example, 5 to 20mL of the third organic solvent is added per 1mol of the polyester diol.
The chain extender comprises at least one of ethylene glycol, propylene glycol, 1, 4-butanediol, diethylene glycol, 1, 4-cyclohexanediol and hydrogenated bisphenol A, namely the chain extender can be ethylene glycol, propylene glycol, a mixed solution of propylene glycol and hydrogenated bisphenol A, a mixed solution of ethylene glycol and propylene glycol and the like.
And A3, separating the polyester polyurethane in the mixed solution, and drying to obtain the polyester polyurethane.
In an embodiment, step A3 specifically includes: and adding the mixed solution into excessive water to separate out a precipitate, washing the obtained precipitate for multiple times, and drying under vacuum to obtain white floccule, namely the polyester polyurethane.
And S20, adding an initiator into the polyester polyurethane solution, uniformly mixing, drying to remove the first organic solvent, and reacting at 80-120 ℃ for 0.5-2 h to obtain the cross-linked shape memory polyurethane.
Wherein the initiator comprises at least one of bis (4-methylbenzoyl) Peroxide (PMB), dibenzoyl peroxide (BPO), 1-bis (t-butylperoxy) cyclohexane (PHC), t-butylperoxy-2-ethylhexyl carbonate (BE), n-butyl-4, 4-bis (t-butylperoxy) valerate (PHV) and dicumyl peroxide (DCP). In order to control the degree of crosslinking of the polyester urethane, in the present embodiment, the mass of the initiator is 0.5 to 10% of the mass of the polyester urethane.
In an embodiment, step S20 specifically includes: adding an initiator into the polyester type polyurethane solution at room temperature, continuously stirring for 30-60 min after the initiator is dissolved, then pouring the mixture into a tetrafluoroethylene mold to prepare a film, drying the film at 20-35 ℃ for 20-48 h in a vacuum environment to remove the first organic solvent, then heating to 80-120 ℃ and reacting for 0.5-2 h to obtain a cross-linked type polyurethane film, namely cross-linked type shape memory polyurethane.
Further, after the thermal crosslinking reaction is completed to obtain the crosslinked shape memory polyurethane, the initiator can be removed by a solvent so as to leave no residue in the prepared crosslinked shape memory polyurethane system.
Wherein, the first solvent comprises any one of acetone, tetrahydrofuran and N, N-dimethylformamide. In the present invention, the relationship among the first organic solvent, the second organic solvent, and the third organic solvent is not limited, and they may be the same organic solvent or different organic solvents, and preferably the same organic solvent.
According to the technical scheme provided by the invention, polyester polyurethane is dissolved in a first organic solvent, then an initiator is added into the first organic solvent, the first organic solvent is removed by drying after uniform mixing, and finally, thermal crosslinking reaction is carried out to obtain the crosslinking type shape memory polyurethane. The initiator is heated to generate free radicals, and the free radicals can capture hydrogen on a polyester polyurethane molecular chain to generate new free radicals on the polyester polyurethane molecular chain, so that the free radicals on different molecular chains of the polyester polyurethane are mutually combined to form chemical cross-linking bonds, and the cross-linked shape memory polyurethane with the shape fixing rate of more than 95% and the shape recovery rate of more than 97% is prepared.
Compared with the prior method for adding the cross-linking agent in the polyester polyurethane synthesis process, the method adopts a post-crosslinking mode and introduces chemical crosslinking points into the synthesized polyester polyurethane material, so that the prepared cross-linking type shape memory polyurethane has the advantages of high recovery speed, high recovery rate, good repeated memory effect, excellent mechanical property, simple and easy cross-linking process, controllable degree of crosslinking and convenience for later-stage forming preparation, and is a method for efficiently introducing the chemical crosslinking points.
The technical solutions of the present invention are further described in detail below with reference to specific examples and drawings, it should be understood that the following examples are merely illustrative of the present invention and are not intended to limit the present invention.
Example 1
(1) Vacuum drying 1mol of polyester diol (polycaprolactone diol with molecular weight of 2000), heating to 60 ℃ under the protection of nitrogen and at the rotating speed of 500r/min to completely dissolve the polyester diol into 15mLDMF to obtain a polyester diol solution, mixing 3mol of isocyanate (toluene diisocyanate) with 10mLDMF to obtain an isocyanate solution, adding the isocyanate solution into the polyester diol solution to form a first reaction system, and reacting the first reaction system for 3 hours at 80 ℃ under the action of an organic tin catalyst (wherein the mass of the organic tin catalyst is 1.5% of the mass sum of the polyester diol and the isocyanate) to obtain a polyester polyurethane prepolymer;
(2) Adding 2mol of chain extender (ethylene glycol) and 20ml of DMF into the polyurethane prepolymer at 40 ℃ to form a second reaction system, and completely reacting the second reaction system at 50 ℃ to obtain a mixed solution containing polyester polyurethane;
(3) Adding the mixed solution into excessive water to separate out precipitate, washing the obtained precipitate for multiple times, and drying under vacuum to obtain white floccule, namely the polyester type polyurethane;
(4) Dissolving polyester polyurethane in 15mL of DMF to obtain a polyester polyurethane solution;
(5) Adding an initiator (PMB) accounting for 5% of the mass of the polyester polyurethane into the polyester polyurethane solution at room temperature, continuously stirring for 40min after the initiator is completely dissolved, then pouring the mixture into a tetrafluoroethylene mold to prepare a film, drying the film at 25 ℃ for 40h in a vacuum environment, and then heating to 100 ℃ to react for 1h to obtain a cross-linked polyurethane film, namely the cross-linked shape memory polyurethane.
Example 2
(1) Vacuum drying 1mol of polyester diol (comprising a mixture of polycaprolactone diol with molecular weight of 500 and polycaprolactone diol with molecular weight of 2000), heating to 65 ℃ under the protection of nitrogen and at the rotating speed of 500r/min, completely dissolving the polyester diol in 10mL of acetone to obtain a polyester diol solution, mixing 4mol of isocyanate (dicyclohexylmethane diisocyanate) with 10mL of acetone to obtain an isocyanate solution, adding the isocyanate solution into the polyester diol solution to form a first reaction system, and reacting the first reaction system for 2.5 hours at 75 ℃ under the action of an organic tin catalyst (wherein the mass of the organic tin catalyst is 1% of the mass sum of the polyester diol and the isocyanate) to obtain a polyester polyurethane prepolymer;
(2) Dissolving 3mol of a chain extender (propylene glycol) in 15mL of acetone at 45 ℃ to obtain a chain extender solution, adding the chain extender solution into a polyester type polyurethane prepolymer to form a second reaction system, and completely reacting the second reaction system at 60 ℃ to obtain a mixed solution containing polyester type polyurethane;
(3) Adding the mixed solution into excessive water to separate out a precipitate, washing the obtained precipitate for multiple times, and drying under vacuum to obtain white floccule, namely the polyester polyurethane;
(4) Dissolving polyester polyurethane in 20mL of acetone to obtain a polyester polyurethane solution;
(5) Adding an initiator (BPO) with the mass being 7% of that of the polyester polyurethane into the polyester polyurethane solution at room temperature, continuously stirring for 50min after the initiator is completely dissolved, then pouring the mixture into a tetrafluoroethylene mold to prepare a film, drying the film at 30 ℃ for 36h in a vacuum environment, and then heating to 90 ℃ to react for 1.5h to obtain a cross-linked polyurethane film, namely the cross-linked shape memory polyurethane.
Example 3
(1) Vacuum drying 1mol of polyester diol (polycaprolactone diol with the molecular weight of 5000), heating to 50 ℃ under the protection of nitrogen and at the rotating speed of 600r/min to completely dissolve the polyester diol into 15mL of tetrahydrofuran to obtain a polyester diol solution, mixing 2mol of isocyanate (lysine diisocyanate) with 5mL of tetrahydrofuran to obtain an isocyanate solution, adding the isocyanate solution into the polyester diol solution to form a first reaction system, and reacting the first reaction system at 70 ℃ for 4 hours under the action of an organic tin catalyst (wherein the mass of the organic tin catalyst is 2% of the mass sum of the polyester diol and the isocyanate) to obtain a polyester polyurethane prepolymer;
(2) Dissolving 5mol of a chain extender (a mixed solution of 1, 4-butanediol and diethylene glycol) in 15mL of tetrahydrofuran at 40 ℃ to obtain a chain extender solution, adding the chain extender solution into a polyester type polyurethane prepolymer to form a second reaction system, and completely reacting the second reaction system at 65 ℃ to obtain a mixed solution containing polyester type polyurethane;
(3) Adding the mixed solution into excessive water to separate out a precipitate, washing the obtained precipitate for multiple times, and drying under vacuum to obtain white floccule, namely the polyester polyurethane;
(4) Dissolving polyester polyurethane in 10mL of tetrahydrofuran to obtain a polyester polyurethane solution;
(5) Adding an initiator (a mixture of DCP and BE) with the mass being 10% of the mass of the polyester polyurethane into the polyester polyurethane solution at room temperature, continuously stirring for 30min after the initiator is completely dissolved, then pouring the mixture into a tetrafluoroethylene mold to prepare a film, drying the film at 20 ℃ for 48h in a vacuum environment, and then heating to 80 ℃ to react for 2h to obtain a cross-linked polyurethane film, namely the cross-linked shape memory polyurethane.
Example 4
(1) Vacuum drying 1mol of polyester diol (including a mixture of polycaprolactone diol with molecular weights of 1000, 2000 and 5000 respectively), heating to 85 ℃ under the protection of nitrogen and at a rotating speed of 400r/min, completely dissolving the polyester diol in 5ml of DMF to obtain a polyester diol solution, mixing 6mol of isocyanate (including a mixture of toluene diisocyanate and hexamethylene diisocyanate) with 20ml of DMF to obtain an isocyanate solution, adding the isocyanate solution into the polyester diol solution to form a first reaction system, and reacting the first reaction system at 90 ℃ for 2 hours under the action of an organic tin catalyst (wherein the mass of the organic tin catalyst is 0.5 percent of the sum of the mass of the polyester diol and the mass of the isocyanate) to obtain a polyester polyurethane prepolymer;
(2) Dissolving 1mol of chain extender (a mixed solution of diethylene glycol, 1, 4-cyclohexanediol and hydrogenated bisphenol A) in 15ml DMF at 30 ℃ to obtain a chain extender solution, adding the chain extender solution into a polyester type polyurethane prepolymer to form a second reaction system, and completely reacting the second reaction system at 45 ℃ to obtain a mixed solution containing polyester type polyurethane;
(3) Adding the mixed solution into excessive water to separate out a precipitate, washing the obtained precipitate for multiple times, and drying under vacuum to obtain white floccule, namely the polyester polyurethane;
(4) Dissolving polyester polyurethane in 5mL of tetrahydrofuran to obtain a polyester polyurethane solution;
(5) Adding an initiator (a mixture of PHC and PHV) with the mass being 0.5 percent of the mass of the polyester polyurethane into the polyester polyurethane solution at room temperature, continuously stirring for 60min after the initiator is completely dissolved, then pouring the mixture into a tetrafluoroethylene mold to prepare a film, drying the film at 35 ℃ for 20h in a vacuum environment, and then heating to 120 ℃ to react for 0.5h to obtain a cross-linked polyurethane film, namely the cross-linked shape memory polyurethane.
When the shape recovery test was performed on the cross-linked shape memory polyurethane prepared in the example of the present invention, since the cross-linked shape memory polyurethanes prepared in the examples 1 to 4 of the present invention were successfully prepared in the same manner, the test results were analyzed using the cross-linked shape memory polyurethane prepared in the example 1 as an example.
Fig. 1 is a schematic diagram of a shape recovery test performed on a cross-linked shape memory polyurethane prepared according to an embodiment of the present invention, wherein the initial state, the stretched state, and the recovery state after stimulation of the cross-linked shape memory polyurethane are shown from left to right. As can be seen from figure 1, the shape recovery rate of the cross-linked shape memory polyurethane is high, and the shape fixation rate is more than 95% and the shape recovery rate is more than 97% after multiple experiments.
The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.
Claims (3)
1. A preparation method of cross-linked shape memory polyurethane is characterized by comprising the following steps:
s10, dissolving polyester polyurethane in a first organic solvent to obtain a polyester polyurethane solution;
s20, adding an initiator into the polyester type polyurethane solution, uniformly mixing, drying to remove the first organic solvent, and then reacting at 80-120 ℃ for 0.5-2h to obtain cross-linked shape memory polyurethane; the initiator comprises at least one of di (4-methylbenzoyl) peroxide, dibenzoyl peroxide, 1-di (tert-butylperoxy) cyclohexane, tert-butylperoxy-2-ethylhexyl carbonate, n-butyl-4, 4-di (tert-butylperoxy) valerate and dicumyl peroxide; the mass of the initiator is 0.5 to 10 percent of that of the polyester polyurethane;
before step S10, the method further includes:
a1, mixing dried polyester diol with isocyanate to form a first reaction system, and reacting the first reaction system under the action of an organic tin catalyst at 70-90 ℃ for 2-4 h to obtain a polyester polyurethane prepolymer;
a2, adding a chain extender into the polyurethane prepolymer at the temperature of 30-45 ℃ to form a second reaction system, and heating the second reaction system to the temperature of 45-65 ℃ to completely react to obtain a mixed solution containing polyester polyurethane;
a3, separating out the polyester polyurethane in the mixed solution, and drying to obtain the polyester polyurethane;
wherein the first reaction system comprises a second organic solvent; the second reaction system comprises a third organic solvent; the second organic solvent comprises any one of acetone, tetrahydrofuran and N, N-dimethylformamide; the third organic solvent comprises any one of acetone, tetrahydrofuran and N, N-dimethylformamide;
in step A1:
the molar ratio between the polyester diol and the isocyanate is 1: (2 to 6);
the mass of the organotin catalyst is 0.5 to 2 percent of the sum of the mass of the polyester diol and the mass of the isocyanate;
the molar ratio of the polyester diol to the chain extender is 1: (1 to 5);
the polyester dihydric alcohol comprises at least one of polycaprolactone dihydric alcohol with the molecular weight of 500-5000; the isocyanate comprises at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate and lysine diisocyanate; the chain extender comprises at least one of ethylene glycol, propylene glycol, 1, 4-butanediol, diethylene glycol, 1, 4-cyclohexanediol and hydrogenated bisphenol A.
2. The method of preparing a cross-linked shape memory polyurethane according to claim 1, wherein the step A3 specifically comprises:
and adding the mixed solution into excessive water, washing the obtained precipitate for multiple times, and drying under vacuum to obtain white floccule, namely the polyester polyurethane.
3. The method of preparing the cross-linked shape memory polyurethane according to claim 1, wherein the first organic solvent comprises any one of acetone, tetrahydrofuran, and N, N-dimethylformamide.
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