A cross-linked liquid crystal poly (aminourea) ester elastomer material and its preparation method and application

Abstract

The present invention provides a cross-linked liquid crystal poly (amino urea) ester elastomer material and its preparation method and application, relating to the field of functional materials technology. The preparation method of the cross-linked liquid crystal poly (amino urea) ester elastomer material provided by the present invention comprises the following steps: 4,4'-methylene bis (phenyl isocyanate), biphenyl liquid crystal monomer, polyhydroxy polyether, catalyst and polar solvent are mixed, and polymerization reaction is carried out to obtain a cross-linked polymer product system; the cross-linked polymer product system is cured and formed to obtain a cross-linked liquid crystal poly (amino urea) ester elastomer material. The cross-linked liquid crystal poly (amino urea) ester elastomer material prepared by the present invention has high mechanical strength, excellent tear resistance and fatigue resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials, and in particular to a cross-linked liquid crystal poly (aminourea) ester elastomer material, a preparation method thereof, and applications thereof. Background Art

[0002] Sealing materials prevent fluids or solid particles from leaking between adjacent interfaces and prevent external impurities such as dust, sand, and moisture from invading equipment. They are essential components in major industries such as chemical, petroleum, coal, transportation, and machinery manufacturing, and play a crucial role in economic development. With the development of various new materials, polyurethane elastomers have taken a dominant position in the sealing field. Compared to rubber materials, polyurethane sealing materials offer advantages such as wear resistance, aging resistance, a wide temperature range, media resistance, and excellent dynamic performance. They are suitable for use in seals for hydraulic seals, oil seals, automotive, water-lubricated bearings, aerospace, civil industry, and large-scale special equipment such as shield machines. In the hydraulic seal field, polyurethane seals can have a service life several times that of nitrile rubber under the same operating conditions.

[0003] Typically, the key parameters for evaluating the performance of polyurethane elastomer sealing materials include mechanical strength, resilience, heat resistance, wear resistance, and media resistance. Resilience and tear resistance are particularly critical factors affecting their service life. This is especially true for large equipment like tunnel boring machines, where seals are exposed to the lubricating medium on one end and to the external environment (such as sediment, aqueous solutions, etc.) on the other. Therefore, it is particularly important to develop polyurethane elastomer sealing materials with high mechanical strength, excellent tear resistance, and fatigue resistance. Summary of the Invention

[0004] The object of the present invention is to provide a cross-linked liquid crystal poly (aminourea) ester elastomer material and its preparation method and application. The cross-linked liquid crystal poly (aminourea) ester elastomer material prepared by the present invention has high mechanical strength, excellent tear resistance and fatigue resistance.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a cross-linked liquid crystal poly (aminourea) ester elastomer material, comprising the following steps:

[0007] 4,4'-methylenebis(phenyl isocyanate), a biphenyl liquid crystal monomer, a polyhydroxy polyether, a catalyst, and a polar solvent are mixed to carry out a polymerization reaction to obtain a cross-linked polymer product system; the total molar amount of -OH groups of the biphenyl liquid crystal monomer and the polyhydroxy polyether is less than the molar amount of -NCO groups of 4,4'-methylenebis(phenyl isocyanate);

[0008] The cross-linked polymer product system is cured and formed to obtain a cross-linked liquid crystal poly (aminourea) ester elastomer material.

[0009] Preferably, the molar ratio of the 4,4'-methylenebis(phenyl isocyanate), biphenyl liquid crystal monomer and polyhydroxy polyether is 4.1:1 to 2:1.

[0010] Preferably, the biphenyl liquid crystal monomer is a hydroxyl-terminated biphenyl liquid crystal monomer.

[0011] Preferably, the hydroxyl-terminated biphenyl liquid crystal monomer has a structure shown in Formula I:

[0012]

[0013] Preferably, the number average molecular weight of the polyhydroxy polyether is 500-3000.

[0014] Preferably, the polymerization reaction temperature is 60-90° C., and the polymerization reaction time is 4-8 hours.

[0015] Preferably, the curing temperature is 70-100° C., and the curing time is 6-24 hours.

[0016] Preferably, the curing and molding further includes drying; the drying temperature is 70 to 90° C., and the drying time is 18 to 36 hours.

[0017] The present invention provides a cross-linked liquid crystal poly (aminourea) ester elastomer material prepared by the preparation method described in the above technical solution.

[0018] The present invention provides the use of the cross-linked liquid crystal poly (aminourea) ester elastomer material described in the above technical solution as an intelligent sealing material.

[0019] The present invention provides a method for preparing a cross-linked liquid crystal poly (aminourea) ester elastomer material. In the present invention, during the polymerization reaction process, a biphenyl liquid crystal monomer and a polyhydroxy polyether react with -OH and -NCO of 4,4'-methylenebis(phenyl isocyanate) to generate carbamate. The present invention limits the molar amount of the total -OH of the biphenyl liquid crystal monomer and the polyhydroxy polyether to be less than the molar amount of -NCO of 4,4'-methylenebis(phenyl isocyanate). The excess -NCO reacts with the carbamate in the system to generate urea groups, forming a cross-linked structure, and then obtaining a cross-linked liquid crystal poly (aminourea) ester elastomer material. In the present invention, the biphenyl liquid crystal monomer has good mechanical properties and shape memory properties. The biphenyl liquid crystal monomer is introduced into a polyurethane material. By utilizing the rigid rod-like structure of the biphenyl liquid crystal monomer, the mechanical properties of the obtained cross-linked liquid crystal poly (aminourea) ester elastomer material can be regulated. At the same time, the cross-linked liquid crystal poly (aminourea) ester elastomer material has good mechanical properties, fatigue resistance and tear resistance, and also helps to improve the service life of mechanical parts and long-term sealing reliability. In addition, during the stretching process, the biphenyl liquid crystal unit forms an orientation due to the π-π interaction, and the dynamic dissociation of the high-density hydrogen bonds in the polymer network and the interlocking of the orientation structure are interlocked, so the mechanical properties of the material can be improved by mechanical training. In addition, the polyurethane material has good molecular design characteristics and shape memory properties. By utilizing the shape memory properties of the polyurethane material, the cross-linked liquid crystal poly (amino-urea) ester elastomer material is used as a sealing material. When endogenous heat is generated in an adverse working condition, the wear and deformation can be self-compensated or self-repaired according to the rising change of the response temperature, which is conducive to further improving the life and reliability of mechanical parts. The results of the embodiment show that the tensile strength of the cross-linked liquid crystal poly (amino-urea) ester elastomer material prepared by the present invention is ≥30.0MPa, and the elongation at break is ≥300%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the chemical structure of a cross-linked liquid crystal poly (aminourea) ester elastomer material prepared in an embodiment;

[0021] Figure 2 The infrared spectrum of the cross-linked liquid crystal poly (aminourea) ester elastomer material prepared in Example;

[0022] Figure 3 This is the shape memory cycle curve of the cross-linked liquid crystal poly (aminourea) ester elastomer material prepared in Example 3;

[0023] Figure 4 A comparison diagram of the original stress-strain curve and the stress-strain curve after mechanical training of the cross-linked liquid crystal poly (aminourea) ester elastomer material prepared in Example 3;

[0024] Figure 5 This is a graph showing the change in tensile strength versus cycle number in a 100-cycle loading-unloading cycle test of the cross-linked liquid crystal poly(aminourea) ester elastomer material prepared in Example 3;

[0025] Figure 6 This is a tear energy histogram of the cross-linked liquid crystal poly (aminourea) ester elastomer material prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a cross-linked liquid crystal poly (aminourea) ester elastomer material, comprising the following steps:

[0027] 4,4'-methylenebis(phenyl isocyanate), a biphenyl liquid crystal monomer, a polyhydroxy polyether, a catalyst, and a polar solvent are mixed to carry out a polymerization reaction to obtain a cross-linked polymer product system; the total molar amount of -OH groups of the biphenyl liquid crystal monomer and the polyhydroxy polyether is less than the molar amount of -NCO groups of 4,4'-methylenebis(phenyl isocyanate);

[0028] The cross-linked polymer product system is cured and formed to obtain a cross-linked liquid crystal poly (aminourea) ester elastomer material.

[0029] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known to those skilled in the art or are prepared using methods well known to those skilled in the art.

[0030] The present invention mixes 4,4'-methylenebis(phenyl isocyanate), a biphenyl liquid crystal monomer, a polyol polyether, a catalyst, and a polar solvent, and conducts a polymerization reaction to obtain a cross-linked polymer product system. In the present invention, the molar ratio of the 4,4'-methylenebis(phenyl isocyanate), biphenyl liquid crystal monomer, and polyol polyether is preferably 4.1:1 to 2:1, and more preferably 4.1:1:1, 4.1:1.5:1, or 4.1:2:1. In the present invention, the amount of the biphenyl liquid crystal monomer is preferably 10-40% of the total amount of the 4,4'-methylenebis(phenyl isocyanate), biphenyl liquid crystal monomer, and polyol polyether, and more preferably 15-30%. By controlling the amount of each raw material within the aforementioned range, the present invention obtains a cross-linked liquid crystal poly(aminourea) ester elastomer material. Simultaneously, by controlling the amount of the biphenyl liquid crystal monomer within the aforementioned range, the cross-linked liquid crystal poly(aminourea) ester elastomer material exhibits excellent shape memory properties in addition to good mechanical properties.

[0031] In the present invention, the 4,4'-methylenebis(phenyl isocyanate) is used as a rigid structure and crosslinking agent for synthesizing a crosslinked liquid crystal poly(aminourea) ester elastomer material. In an embodiment of the present invention, the 4,4'-methylenebis(phenyl isocyanate) is purchased from Anaiji Company.

[0032] In the present invention, the biphenyl liquid crystal monomer is preferably a hydroxyl-terminated biphenyl liquid crystal monomer; the hydroxyl-terminated biphenyl liquid crystal monomer preferably has a structure shown in Formula I:

[0033]

[0034] In the present invention, the hydroxyl-terminated biphenyl liquid crystal monomer having the structure shown in Formula I is preferably prepared by a method well known to those skilled in the art (Document DOI: 10.1080 / 02678292.2020.1766587).

[0035] The present invention introduces biphenyl liquid crystal monomer into polyurethane material, can realize the regulation and control of gained cross-linked liquid crystal poly (amino urea) ester elastomer material mechanical property, simultaneously make described cross-linked liquid crystal poly (amino urea) ester elastomer material have good mechanical property, fatigue resistance and tear resistance, can improve the service life and long-term sealing reliability of mechanical parts. In addition, due to biphenyl liquid crystal unit in stretching process, due to π-π interaction formation orientation, the dynamic dissociation of high-density hydrogen bond in polymer network and pedicled combination interlock the orientation structure, therefore can improve the mechanical property of material by mechanical training. In addition, polyurethane material has good molecular design characteristic and shape memory performance, utilizes the shape memory performance of polyurethane material, cross-linked liquid crystal poly (amino urea) ester elastomer material is used as sealing material, when bad working condition produces endogenous heat, can make self-compensation or self-repairing behavior to wear deformation situation according to the rising change of response temperature, be conducive to making the service life and reliability of mechanical parts be further improved.

[0036] In the present invention, the number average molecular weight of the polyhydroxy polyether is preferably 500 to 3000, more preferably 1000 to 2000. In the present invention, the polyhydroxy polyether is preferably a dihydroxy polyether. In the present invention, the dihydroxy polyether functions to synthesize the soft segment of the cross-linked liquid crystal poly(aminourea) ester elastomer material. In an embodiment of the present invention, the dihydroxy polyether is specifically purchased from BASF.

[0037] In the present invention, the catalyst is preferably dibutyltin dilaurate (DBTDL). In the present invention, the mass ratio of the biphenyl liquid crystal monomer to the catalyst is preferably 2-9:0.263, more preferably 3.86-7.72:0.263.

[0038] In the present invention, the polar solvent preferably includes N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, toluene, or tetrahydrofuran, and more preferably N,N-dimethylformamide (DMF). The use of a polar solvent in the present invention enables the biphenyl liquid crystal monomer to be fully dissolved. In the present invention, the mass ratio of the biphenyl liquid crystal monomer to the polar solvent is preferably 2 to 9:47.2, and more preferably 3.86 to 7.72:47.2.

[0039] In the present invention, the mixing of 4,4'-methylenebis(phenyl isocyanate), a biphenyl liquid crystal monomer, a polyhydroxy polyether, a catalyst, and a polar solvent preferably includes: mixing the polyhydroxy polyether, the biphenyl liquid crystal monomer, and a portion of the polar solvent to obtain a biphenyl liquid crystal monomer solution; mixing 4,4'-methylenebis(phenyl isocyanate), the catalyst, and the remaining polar solvent to obtain a 4,4'-methylenebis(phenyl isocyanate) solution; and dropwise adding the 4,4'-methylenebis(phenyl isocyanate) solution to the biphenyl liquid crystal monomer solution. In the present invention, the volume ratio of the portion of the polar solvent to the remaining polar solvent is preferably 2 to 8:3, more preferably 5:3. In the present invention, the dropwise addition is preferably completed within 30 minutes.

[0040] In the present invention, the polymerization reaction temperature is preferably 60-90° C., more preferably 70-80° C.; the polymerization reaction time is preferably 4-8 hours, more preferably 5-6 hours. In the present invention, the polymerization reaction is preferably carried out in a nitrogen atmosphere.

[0041] After obtaining the cross-linked polymer product system, the present invention cures the cross-linked polymer product system to obtain a cross-linked liquid crystal poly(aminourea) ester elastomer material. In the present invention, the curing temperature is preferably 70 to 100° C., more preferably 75 to 85° C.; the curing time is preferably 6 to 24 hours, preferably 18 to 22 hours. In the present invention, the curing is preferably performed in a forced air oven.

[0042] In the present invention, the curing process is preferably performed in a mold; the mold is preferably a polytetrafluoroethylene mold. In the present invention, the mold is preferably preheated before adding the cross-linked polymer system. In the present invention, the preheating temperature is preferably 90-110°C, more preferably 100°C.

[0043] Prior to the curing process, the cross-linked polymer product system in the mold is preferably degassed. In the present invention, the degassing is preferably performed in a vacuum oven; the vacuum level is preferably 0.5 to 0.6 bar; the degassing temperature is preferably 75 to 85°C, more preferably 80°C; and the degassing time is preferably 3 to 7 minutes, more preferably 3 minutes.

[0044] In the present invention, the curing and molding process preferably includes drying. The drying temperature is preferably 70-90°C, more preferably 75-85°C, and the drying time is preferably 18-36 hours, more preferably 22-26 hours. In the present invention, the drying is preferably performed in a vacuum oven. During the curing and drying process, the cross-linked polymer product system transforms from a liquid with a certain viscosity to a solid state until its mass no longer changes.

[0045] The present invention provides a cross-linked liquid crystal poly (aminourea) ester elastomer material prepared by the preparation method described in the above technical solution.

[0046] The present invention provides the use of the cross-linked liquid crystal poly(aminourea) ester elastomer material described in the above technical solution as an intelligent sealing material. In the present invention, the use preferably includes: subjecting the cross-linked liquid crystal poly(aminourea) ester elastomer material to mechanical training. In the present invention, the mechanical training preferably includes: subjecting the cross-linked liquid crystal poly(aminourea) ester elastomer material to cyclic loading and unloading at a strain of 150%. The present invention can further improve the mechanical properties of the cross-linked liquid crystal poly(aminourea) ester elastomer material through mechanical training.

[0047] The cross-linked liquid crystal poly (aminourea) ester elastomer material provided by the present invention has good shape memory properties, mechanical properties and fatigue resistance, and is suitable for use in the main drive sealing field of large-scale tunnel boring machines.

[0048] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0049] Some of the raw materials in the following examples and comparative examples are from:

[0050] Dihydroxy polyether was purchased from BASF with a number average molecular weight of 1000;

[0051] The biphenyl liquid crystal monomer is a hydroxyl-terminated biphenyl liquid crystal monomer having a structure shown in Formula I, and was prepared according to the literature method (DOI number: 10.1080 / 02678292.2020.1766587);

[0052] 4,4'-Methylenebis(phenyl isocyanate) was purchased from Anaiji Company.

[0053] Example 1

[0054] Weigh 10 g of dihydroxy polyether into a three-necked flask with mechanical stirring, add 3.86 g of hydroxyl-terminated biphenyl liquid crystal monomer and 50 mL of DMF as solvent, stir evenly and keep for 2 hours under N2 atmosphere to obtain a biphenyl liquid crystal monomer solution; weigh 10.25 g of 4,4'-methylenebis(phenyl isocyanate), dissolve it in 30 mL of DMF, and after 4,4'-methylenebis(phenyl isocyanate) is fully dissolved, add 0.25 mL of catalyst DBTDL and stir evenly to obtain a 4,4'-methylenebis(phenyl isocyanate) solution; the 4,4'-methylenebis(phenyl isocyanate) The solution was added dropwise to the biphenyl liquid crystal monomer solution within 30 minutes, the reaction system was controlled at 80° C., and the reaction was stopped after 6 hours under a nitrogen atmosphere. The mixture was poured into a polytetrafluoroethylene mold preheated to 100° C. and degassed in an 80° C. vacuum oven for 3 minutes, cured in an 80° C. forced air oven for 22 hours, and dried in an 80° C. vacuum oven for 24 hours. The mixture was cooled to room temperature and demolded to obtain a cross-linked liquid crystal poly (amino-urea) ester elastomer material.

[0055] Example 2

[0056] Weigh 10 g of dihydroxy polyether into a three-necked flask with mechanical stirring, add 5.79 g of hydroxyl-terminated biphenyl liquid crystal monomer and 50 mL of DMF as solvent, stir evenly and keep for 2 hours under N2 atmosphere to obtain a biphenyl liquid crystal monomer solution; weigh 10.25 g of 4,4'-methylenebis(phenyl isocyanate), dissolve it in 30 mL of DMF, and after 4,4'-methylenebis(phenyl isocyanate) is fully dissolved, add 0.25 mL of catalyst DBTDL and stir evenly to obtain a 4,4'-methylenebis(phenyl isocyanate) solution; the 4,4'-methylenebis(phenyl isocyanate) The solution was added dropwise to the biphenyl liquid crystal monomer solution within 30 minutes, the reaction system was controlled at 80° C., and the reaction was stopped after 6 hours under a nitrogen atmosphere. The mixture was poured into a polytetrafluoroethylene mold preheated to 100° C. and degassed in an 80° C. vacuum oven for 3 minutes, cured in an 80° C. forced air oven for 22 hours, and dried in an 80° C. vacuum oven for 24 hours. The mixture was cooled to room temperature and demolded to obtain a cross-linked liquid crystal poly (amino-urea) ester elastomer material.

[0057] Example 3

[0058] Weigh 10 g of dihydroxy polyether in a three-necked flask with mechanical stirring, add 7.72 g of hydroxyl-terminated biphenyl liquid crystal monomer and 50 mL of DMF as solvent, stir evenly and keep for 2 hours under N2 atmosphere to obtain a biphenyl liquid crystal monomer solution; then weigh 10.25 g of 4,4'-methylenebis(phenyl isocyanate) and dissolve it in 30 mL of In DMF, after 4,4'-methylenebis(phenyl isocyanate) is fully dissolved, 0.25 mL of catalyst DBTDL is added and stirred evenly to obtain a 4,4'-methylenebis(phenyl isocyanate) solution; the 4,4'-methylenebis(phenyl isocyanate) solution is added dropwise to the biphenyl liquid crystal monomer solution, and the addition is completed within 30 minutes. The reaction system is controlled at 80°C, and the reaction is stopped after 6 hours under a nitrogen atmosphere; the mixture is poured into a polytetrafluoroethylene mold preheated to 100°C, degassed in an 80°C vacuum oven for 3 minutes, cured in an 80°C blast oven for 22 hours, and dried in an 80°C vacuum oven for 24 hours. The mixture is cooled to room temperature and demolded to obtain a cross-linked liquid crystal poly(amino-urea) ester elastomer material.

[0059] Comparative Example 1

[0060] Weigh 10 g of dihydroxy polyether in a three-necked flask with mechanical stirring, add 1.93 g of hydroxyl-terminated biphenyl liquid crystal monomer and 50 mL of DMF as solvent, stir evenly and keep for 2 h under N2 atmosphere to obtain a biphenyl liquid crystal monomer solution; then weigh 10.25 g of 4,4'-methylenebis(phenyl isocyanate) and dissolve it in 30 mL of In DMF, after 4,4'-methylenebis(phenyl isocyanate) is fully dissolved, 0.25 mL of catalyst DBTDL is added and stirred evenly to obtain a 4,4'-methylenebis(phenyl isocyanate) solution; the 4,4'-methylenebis(phenyl isocyanate) solution is added dropwise to the biphenyl liquid crystal monomer solution, and the addition is completed within 30 minutes. The reaction system is controlled at 80°C, and the reaction is stopped after 6 hours under a nitrogen atmosphere; the mixture is poured into a polytetrafluoroethylene mold preheated to 100°C, degassed in an 80°C vacuum oven for 3 minutes, cured in an 80°C blast oven for 22 hours, and dried in an 80°C vacuum oven for 24 hours. The mixture is cooled to room temperature and demolded to obtain a cross-linked liquid crystal poly(amino-urea) ester elastomer material.

[0061] Comparative Example 2

[0062] Weigh 10 g of dihydroxy polyether in a three-necked flask with mechanical stirring, add 11.58 g of hydroxyl-terminated biphenyl liquid crystal monomer and 50 mL of DMF as solvent, stir evenly and keep for 2 hours under N2 atmosphere to obtain a biphenyl liquid crystal monomer solution; then weigh 10.25 g of 4,4'-methylenebis(phenyl isocyanate) and dissolve it in 30 mL of In DMF, after 4,4'-methylenebis(phenyl isocyanate) is fully dissolved, 0.25 mL of catalyst DBTDL is added and stirred evenly to obtain a 4,4'-methylenebis(phenyl isocyanate) solution; the 4,4'-methylenebis(phenyl isocyanate) solution is added dropwise to the biphenyl liquid crystal monomer solution, and the addition is completed within 30 minutes. The reaction system is controlled at 80°C, and the reaction is stopped after 6 hours under a nitrogen atmosphere; the mixture is poured into a polytetrafluoroethylene mold preheated to 100°C, degassed in an 80°C vacuum oven for 3 minutes, cured in an 80°C blast oven for 22 hours, and dried in an 80°C vacuum oven for 24 hours. The mixture is cooled to room temperature and demolded to obtain a cross-linked liquid crystal poly(amino-urea) ester elastomer material.

[0063] Comparative Example 3

[0064] Weigh 10 g of dihydroxy polyether in a three-necked flask with mechanical stirring, add 50 mL of DMF as solvent, stir evenly and keep for 2 h under N2 atmosphere to obtain a dihydroxy polyether solution; then weigh 10.25 g of 4,4'-methylenebis(phenyl isocyanate) and dissolve it in 30 mL of After 4,4'-methylenebis(phenyl isocyanate) was fully dissolved in DMF, 0.25 mL of the catalyst DBTDL was added and stirred evenly to obtain a 4,4'-methylenebis(phenyl isocyanate) solution. The 4,4'-methylenebis(phenyl isocyanate) solution was then added dropwise to the dihydroxy polyether solution over 30 minutes. The reaction system was controlled at 80°C and reacted under a nitrogen atmosphere for 6 hours before stopping the reaction. The resulting mixture was poured into a polytetrafluoroethylene mold preheated to 100°C and degassed in an 80°C vacuum oven for 3 minutes. The mixture was then cured in an 80°C forced air oven for 22 hours and dried in an 80°C vacuum oven for 24 hours. The mixture was cooled to room temperature and demolded to obtain a cross-linked poly(aminourea) ester elastomer. Due to the low degree of crosslinking, no film was formed, and performance testing could not be performed.

[0065] Test Case

[0066] (1) The mechanical properties of the cross-linked liquid crystal poly (amino-urea) ester elastomer materials prepared in the examples and comparative examples were tested at room temperature (25°C) using a Shimadzu AG-X (5000N) electronic universal testing machine. The tensile speed was 10 mm / min, and the sample shape was cut into a dumbbell shape according to the standard GB / T528-2009.

[0067] (2) The shape memory properties of Example 3 were tested using a TA850. Samples were cut into 20 mm × 3 mm × 0.2 mm dimensions before testing. The test procedure was as follows: 1) The sample was heated to 80°C and stretched to 50% at a rate of 5% / min; 2) The sample was maintained at 50% deformation and cooled to 0°C at a rate of 5°C / min; 3) The external force was removed, and the temperature was raised to 80°C and maintained for 20 minutes; 4) The above thermodynamic process was repeated four times.

[0068] (3) The samples of Example 3 were subjected to mechanical training and reinforcement testing using a universal tensile testing machine, and mechanical properties were tested at a tensile rate of 10 mm / min. The testing process was as follows: the rectangular specimens of Example 3 were subjected to cyclic loading and unloading at a strain of 150%. After three loading and unloading cycles, the rectangular specimens were cut into dumbbell shapes according to GB / T528-2009, and the mechanical properties of the specimens were tested at a tensile rate of 10 mm / min at room temperature.

[0069] (4) A tensile test was conducted on a single-edge notched specimen (notch length 1 mm) at room temperature using a universal testing machine to test the fracture energy of the specimen. Under the conditions of a tensile speed of 3 mm / min, a distance of 10 mm, and a width of 5 mm, the notched and unnotched specimens were tested, and the tear energy of the embodiment and comparative example was calculated using formula (1);

[0070]

[0071] In formula (1), c = 1 mm represents the notch length, λ represents the elongation at break of the notched specimen, and w represents the area of ​​the stress-strain curve of the unnotched specimen integrated to λ.

[0072] The test results are shown in Table 1 and Figures 3 to 6 shown.

[0073] Table 1 Comparison of mechanical properties of the embodiment and the comparative example

[0074] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Elongation at break (%) 365.2 327.4 350.7 44.9 111.1 Tensile strength (MPa) 59.9 40.5 38.2 11.2 15.11

[0075] As can be seen from Table 1, the cross-linked liquid crystal poly (aminourea) ester elastomer material prepared in the present invention has high mechanical properties, and the mechanical properties of the cross-linked liquid crystal poly (aminourea) ester elastomer material can be controlled by adjusting the content of the biphenyl liquid crystal monomer.

[0076] Figure 1 The chemical structure diagram of the cross-linked liquid crystal poly (amino-urea) ester elastomer prepared in the embodiment is shown in FIG. Figure 1 It can be seen that the cross-linked liquid crystal poly (aminourea) ester elastomer prepared in the present invention has a cross-linked structure.

[0077] Figure 2This is the infrared spectrum of the cross-linked liquid crystal poly (aminourea) ester elastomer material prepared in Example 1, wherein 2262 cm -1 The -NCO characteristic peak at 770 cm disappeared, confirming the complete reaction between -NCO and -OH. -1 The benzene ring bending vibration peaks around 1730cm are characteristic peaks of biphenyl liquid crystal monomers. -1 The peaks at 1640 cm-1 correspond to the free carbonyl peaks of carbamate. -1 The hydrogen bonded hydroxyl peak corresponding to the urea group indicates the successful preparation of the cross-linked liquid crystal poly (aminourea) ester elastomer

[0078] Figure 3 The shape memory cycle curve of the cross-linked liquid crystal poly (aminourea) ester elastomer material prepared in Example 3 is shown in FIG. Figure 3 It can be seen that the cross-linked liquid crystal poly (aminourea) ester elastomer material prepared in the present invention has a shape fixation rate and a shape recovery rate greater than 80%, and has good shape memory properties.

[0079] Figure 4 The figure is a comparison of the original stress-strain curve of the cross-linked liquid crystal poly (amino-urea) ester elastomer material prepared in Example 3 and the stress-strain curve after mechanical training. Figure 4 It can be seen that the cross-linked liquid crystal poly (amino-urea) ester elastomer material prepared by the present invention has significantly improved mechanical strength after three loading-unloading cycle tests under a strain of 150%. This is a property discovered for the first time in polyurethane elastomers. This excellent performance is mainly due to the fact that during the stretching process, the biphenyl liquid crystal units form an orientation due to π-π interactions, and the dynamic dissociation and combination of high-density hydrogen bonds in the polymer network interlock the orientation structure, thereby improving the mechanical strength of the sample in the subsequent stretching process.

[0080] Figure 5 This is a graph showing the change in tensile strength with the number of cycles in a 100-cycle loading-unloading cycle test of the cross-linked liquid crystal poly(aminourea) ester elastomer material prepared in Example 3. Figure 5 It can be seen that the cross-linked liquid crystal poly (amino-urea) ester elastomer material prepared by the present invention has good fatigue resistance. After 100 loading-unloading cycle tests, its mechanical strength has not been significantly reduced. This excellent performance helps to improve the sealing performance of the material.

[0081] Figure 6 This is a histogram of the tearing energy of the cross-linked liquid crystal poly (aminourea) ester elastomer material prepared in an embodiment of the present invention. Figure 6 It can be seen that the cross-linked liquid crystal poly (aminourea) ester elastomer material prepared by the present invention has good tear resistance, and its tear energy is greater than 40kJ / m 2The rigid rod-like structure of the liquid crystal helps reduce material wear and tear to extend the service life of the seal.

[0082] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a cross-linked liquid crystal poly (aminourea) ester elastomer material, comprising the following steps: 4,4'-methylenebis(phenyl isocyanate), a biphenyl liquid crystal monomer, a polyhydroxy polyether, a catalyst, and a polar solvent are mixed to carry out a polymerization reaction to obtain a cross-linked polymer product system; the total molar amount of -OH groups of the biphenyl liquid crystal monomer and the polyhydroxy polyether is less than the molar amount of -NCO groups of 4,4'-methylenebis(phenyl isocyanate); curing the cross-linked polymer product system to obtain a cross-linked liquid crystal poly (aminourea) ester elastomer material; The polyhydroxy polyether is a dihydroxy polyether; The molar ratio of the 4,4'-methylenebis(phenyl isocyanate), biphenyl liquid crystal monomer and polyhydroxy polyether is 4.1:1 to 2:1; The biphenyl liquid crystal monomer is a hydroxyl-terminated biphenyl liquid crystal monomer, and the hydroxyl-terminated biphenyl liquid crystal monomer has a structure shown in Formula I:

2. The preparation method according to claim 1, characterized in that The number average molecular weight of the polyhydroxy polyether is 500 to 3000.

3. The preparation method according to claim 1, characterized in that The polymerization reaction temperature is 60-90° C., and the polymerization reaction time is 4-8 hours.

4. The preparation method according to claim 1, characterized in that The curing temperature is 70-100° C., and the curing time is 6-24 hours.

5. The preparation method according to claim 1, characterized in that The curing and molding process further includes drying; the drying temperature is 70 to 90° C., and the drying time is 18 to 36 hours.

6. A cross-linked liquid crystal poly (aminourea) ester elastomer material prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the cross-linked liquid crystal poly (aminourea) ester elastomer material according to claim 6 as an intelligent sealing material.

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