Damping polyurethane material for bridge track and preparation method thereof

Abstract

The present invention belongs to the technical field of polyurethane, and specifically relates to a damping polyurethane material for bridge tracks and a preparation method thereof. The material comprises the following raw materials: PEG derivatives, TDI-80, carbon nanotube-modified MDI, trimethylpentanediol, dibutyltin dilaurate, bismuth isooctanoate and DBU; wherein the PEG derivative is an ABA-type block copolymer, block A is a PPG segment, and block B is a PEG segment. By adjusting the flexible chain structure and hard segment composition in the polyurethane, the microscopic phase separation structure of the material is effectively improved, thereby enhancing the damping effect. Among them, the structures of PEG and PPG have hydrolysis resistance due to the presence of ether bonds, thereby enhancing the weather resistance of the material. The introduction of carbon nanotubes disrupts the arrangement structure of the original molecules, improves the strength of the material, and also enhances the surface bonding between the material and the substrate. The damping polyurethane material for bridge tracks obtained exhibits good performance stability during long-term use.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane, and in particular relates to a damping polyurethane material for bridge tracks and a preparation method thereof. Background Art

[0002] In the field of rail transit systems and bridge engineering, factors such as vehicle operating loads, aerodynamic loads (such as wind-induced vibrations), and wheel-rail dynamic excitations can cause structural vibration and noise pollution. This pollution not only significantly affects passenger comfort and environmental quality along the line, but also causes fatigue accumulation damage to key load-bearing components, threatening the long-term service safety of engineering structures. Therefore, the development of damping materials with both high-efficiency shock absorption performance and long-term durability has become a difficult problem that needs to be solved in this field.

[0003] Polyurethane materials are recognized as a highly promising damping material system due to their unique microphase separation structure (formed by block copolymerization of thermodynamically incompatible soft segments and hard segments) that can effectively dissipate vibration energy in a wide frequency range. Their damping performance is usually characterized by the loss factor tanδ (i.e., the ratio of loss modulus to storage modulus E'). The tanδ peak value and effective damping temperature range can be precisely controlled by the molecular chain structure design of polyurethane, thereby optimizing the dynamic mechanical response.

[0004] However, existing technical solutions mostly focus on laboratory optimization of the intrinsic damping properties of materials, and often ignore the stability and durability of materials in actual application environments. For example, in rail transit scenarios, polyurethane damping materials need to withstand the coupling effects of multiple factors such as high-frequency alternating stress, temperature and humidity cyclic changes, ultraviolet radiation, and chemical medium erosion for a long time. They are prone to problems such as molecular chain breakage, microphase structure destruction, and interface bonding failure, resulting in reduced damping efficiency or even loss of function. Therefore, how to simultaneously improve the broadband damping performance, anti-fatigue characteristics, and environmental tolerance of polyurethane materials through molecular structure design has become a technical bottleneck restricting its engineering application. Summary of the invention

[0005] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a damping polyurethane material for bridge tracks. By adjusting the flexible chain structure and hard segment composition in the polyurethane, the microscopic phase separation structure of the material is effectively improved, thereby enhancing the damping effect. Among them, the structures of PEG and PPG have hydrolysis resistance due to the ether bonds, thereby enhancing the weather resistance of the material. In addition, the introduction of carbon nanotubes disrupts the original molecular arrangement structure, which not only improves the strength of the material, but also enhances the surface bonding between the material and the substrate. The obtained damping polyurethane material for bridge tracks shows good performance stability during long-term use, ensuring that its shock absorption and noise reduction performance will not degrade due to material fatigue under long-term repeated loads.

[0006] Another object of the present invention is to provide a method for preparing a damping polyurethane material for bridge tracks, which has a simple process and is easy to control.

[0007] The damping polyurethane material for bridge track of the present invention comprises the following raw materials in parts by weight:

[0008] PEG derivatives: 100 parts;

[0009] TDI-80: 25-35 parts;

[0010] Carbon nanotube modified MDI: 15-25 parts;

[0011] Trimethylpentanediol: 8-12 parts;

[0012] Dibutyltin dilaurate: 0.15-0.25 parts;

[0013] Bismuth isooctanoate: 0.3-0.4 parts;

[0014] DBU: 0.06-0.08 parts;

[0015] The PEG derivative is an ABA type block copolymer, wherein block A is a PPG segment and block B is a PEG segment, and its structural formula is as follows:

[0016] ;

[0017] Where, 2≤x≤19, 2≤y≤36, 1≤z≤17;

[0018] The preparation method of the carbon nanotube modified MDI is:

[0019] (1) Under nitrogen protection, the dried multi-walled carbon nanotubes and a mixture of sulfuric acid and nitric acid were subjected to an acidification treatment under ultrasonic conditions, then heated to reflux, cooled and filtered, washed with deionized water to a pH of 5-6, and then vacuum dried at 80°C for 12 h to obtain carboxylated carbon nanotubes;

[0020] (2) Under nitrogen protection, the carboxylated carbon nanotubes and MDI are mixed and reacted, and after the reaction is completed, carbon nanotube-modified MDI is obtained.

[0021] In the step (1), the mixed solution of sulfuric acid and nitric acid is prepared by mixing 98wt.% sulfuric acid and 65wt.% nitric acid in a volume ratio of 5:1, and the mass volume ratio of the multi-walled carbon nanotubes to the mixed solution of sulfuric acid and nitric acid is (5-10) g: 200 mL.

[0022] In the step (1), the frequency of ultrasound is 35-45kHz and the time is 2-3h.

[0023] In the step (1), the heating reflux conditions are: heating to 115-130° C. and reflux for 2-4 hours.

[0024] In the step (2), the mass ratio of carboxylated carbon nanotubes to MDI is (1-4):15.

[0025] In the step (2), the reaction temperature is 60-80°C and the reaction time is 7-9h.

[0026] The preparation method of the damping polyurethane material for bridge track comprises the following steps:

[0027] S1: Mixing PEG derivatives with TDI-80 for prepolymerization;

[0028] S2: adding carbon nanotube-modified MDI, dibutyltin dilaurate, bismuth isooctanoate and DBU to step S1, and continuing the reaction;

[0029] S3: After adding trimethylpentanediol to step S2, the material is poured into a mold, and after curing, a damping polyurethane material for bridge tracks is obtained.

[0030] In the step S1, the prepolymerization temperature is 65-95° C. and the time is 2-3 hours.

[0031] In the step S2, the reaction temperature is 65-95° C. and the reaction time is 3-6 hours.

[0032] In the step S3, the curing temperature is 90-115° C. and the curing time is 1-2 hours.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention optimizes the microscopic phase separation structure by adjusting the ratio of polyurethane soft and hard segments and chemically grafting carbon nanotubes. At the same time, the synergistic effect of carbon nanotube-modified MDI composite hard segment and soft segment is utilized to stimulate the triple energy dissipation mechanism of interface slip, segment motion and hydrogen bond dissociation under dynamic load. The loss factor (tanδ) is greater than 0.35 in the range of -50°C to 80°C, which significantly improves the damping effect of the material.

[0035] (2) The present invention uses PEG derivatives containing PPG and PEG structures, which significantly improves the tensile strength of the material to more than 30 MPa compared with a simple mixed polyol system;

[0036] (3) The damping polyurethane material for bridge tracks of the present invention has both a hydrolysis-resistant ether bond structure and surface bonding enhanced by carbon nanotubes, and can maintain stable damping properties over a wide temperature range; its molecular structure contains a large number of side methyl groups, which can ensure that the material's shock-absorbing and noise-reducing performance does not decay under long-term repeated loads, and is suitable for long-term use in harsh environments such as bridge tracks;

[0037] (4) The preparation method of the damping polyurethane material for bridge tracks described in the present invention precisely controls the raw material ratio and reaction parameters, and combines the staged reaction path and the compound catalyst to coordinately control the reaction rate. The method adopts the grafting reaction method, effectively solves the dispersion problem of carbon nanotubes and avoids the risk of gelation, ensures the uniformity of the material microstructure, and finally achieves the high stability and repeatability of product performance. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the embodiments.

[0039] The raw materials used in the examples and comparative examples are conventional commercially available raw materials unless otherwise specified, and the process methods used in the examples and comparative examples are conventional methods in the art unless otherwise specified.

[0040] Some of the raw materials used in the examples and comparative examples are described as follows:

[0041] PEG derivatives were purchased from Xi'an Qiyue Biotechnology Co., Ltd.;

[0042] PPG-4000, purchased from Shandong Bluestar Dongda Chemical Co., Ltd.;

[0043] PEG-1000, purchased from Changhua Chemical Technology Co., Ltd.;

[0044] TDI-80, purchased from Wanhua Chemical Group Co., Ltd.;

[0045] MDI-100 was purchased from Wanhua Chemical Group Co., Ltd.

[0046] Example 1

[0047] The damping polyurethane material for bridge track comprises the following raw materials in parts by weight:

[0048] PEG derivative (x=2, y=18, z=1, number average molecular weight 985): 100 parts;

[0049] TDI-80: 25 parts;

[0050] Carbon nanotube modified MDI: 20 parts;

[0051] Trimethylpentanediol: 8 parts;

[0052] Dibutyltin dilaurate: 0.25 parts;

[0053] Bismuth isooctanoate: 0.35 parts;

[0054] DBU: 0.06 parts;

[0055] The preparation method of the carbon nanotube modified MDI is:

[0056] (1) Under nitrogen protection, a mixture of multi-walled carbon nanotubes and sulfuric acid and nitric acid in a mass volume ratio of 8 g:200 mL was ultrasonically treated at 40 kHz for 2.5 h, then heated to 125°C, heated under reflux for 3 h, cooled and filtered, washed with deionized water to a pH of 5.5±0.5, and then vacuum dried at 80°C for 12 h to obtain carboxylated carbon nanotubes; wherein the mixture of sulfuric acid and nitric acid was prepared by mixing 98 wt.% sulfuric acid and 65 wt.% nitric acid in a volume ratio of 5:1;

[0057] (2) Under nitrogen protection, carboxylated carbon nanotubes and MDI-100 in a mass ratio of 4:15 were mixed and reacted at 80°C for 9 hours. After the reaction was completed, carbon nanotube-modified MDI was obtained.

[0058] The preparation method of the damping polyurethane material for bridge track comprises the following steps:

[0059] S1: Mix the PEG derivative with TDI-80 and prepolymerize at 80±15℃ for 2h;

[0060] S2: Add carbon nanotube-modified MDI, dibutyltin dilaurate, bismuth isooctanoate and DBU to step S1, and continue the reaction at 80±15°C for 4.5h;

[0061] S3: After adding trimethylpentanediol to step S2, the material is poured into a mold, and after curing at 102.5±12.5°C for 1.5 hours, a damping polyurethane material for bridge tracks is obtained.

[0062] Example 2

[0063] The damping polyurethane material for bridge track comprises the following raw materials in parts by weight:

[0064] PEG derivative (x=10, y=6, z=9, number average molecular weight 1529): 100 parts;

[0065] TDI-80: 35 parts;

[0066] Carbon nanotube modified MDI: 15 parts;

[0067] Trimethylpentanediol: 10 parts;

[0068] Dibutyltin dilaurate: 0.15 parts;

[0069] Bismuth isooctanoate: 0.3 parts;

[0070] DBU: 0.08 parts;

[0071] The preparation method of the carbon nanotube modified MDI is:

[0072] (1) Under nitrogen protection, a mixture of multi-walled carbon nanotubes and sulfuric acid and nitric acid in a mass volume ratio of 5 g:200 mL was ultrasonically treated at 35 kHz for 2 h, then heated to 115°C, heated under reflux for 2 h, cooled and filtered, washed with deionized water to a pH of 5.5±0.5, and then vacuum dried at 80°C for 12 h to obtain carboxylated carbon nanotubes; wherein the mixture of sulfuric acid and nitric acid was prepared by mixing 98 wt.% sulfuric acid and 65 wt.% nitric acid in a volume ratio of 5:1;

[0073] (2) Under nitrogen protection, carboxylated carbon nanotubes and MDI-100 in a mass ratio of 2.5:15 were mixed and reacted at 70°C for 8 hours. After the reaction was completed, carbon nanotube-modified MDI was obtained.

[0074] The preparation method of the damping polyurethane material for bridge track comprises the following steps:

[0075] S1: Mix the PEG derivative with TDI-80 and prepolymerize at 80±15℃ for 2.5h;

[0076] S2: Add carbon nanotube-modified MDI, dibutyltin dilaurate, bismuth isooctanoate and DBU to step S1, and continue the reaction at 80±15°C for 3h;

[0077] S3: After adding trimethylpentanediol to step S2, the material is poured into a mold, and after curing at 102.5±12.5°C for 2 hours, a damping polyurethane material for bridge tracks is obtained.

[0078] Example 3

[0079] The damping polyurethane material for bridge track comprises the following raw materials in parts by weight:

[0080] PEG derivative (x=19, y=36, z=17, number average molecular weight 3980): 100 parts;

[0081] TDI-80: 30 parts;

[0082] Carbon nanotube modified MDI: 25 parts;

[0083] Trimethylpentanediol: 12 parts;

[0084] Dibutyltin dilaurate: 0.2 parts;

[0085] Bismuth isooctanoate: 0.4 parts;

[0086] DBU: 0.07 parts;

[0087] The preparation method of the carbon nanotube modified MDI is:

[0088] (1) Under nitrogen protection, a mixture of multi-walled carbon nanotubes and sulfuric acid and nitric acid in a mass volume ratio of 10 g:200 mL was ultrasonically treated at 45 kHz for 3 h, then heated to 130°C, heated under reflux for 4 h, cooled and filtered, washed with deionized water to a pH of 5.5±0.5, and then vacuum dried at 80°C for 12 h to obtain carboxylated carbon nanotubes; wherein the mixture of sulfuric acid and nitric acid was prepared by mixing 98 wt.% sulfuric acid and 65 wt.% nitric acid in a volume ratio of 5:1;

[0089] (2) Under nitrogen protection, carboxylated carbon nanotubes and MDI-100 in a mass ratio of 1:15 were mixed and reacted at 60°C for 7 hours. After the reaction was completed, carbon nanotube-modified MDI was obtained.

[0090] The preparation method of the damping polyurethane material for bridge track comprises the following steps:

[0091] S1: Mix the PEG derivative with TDI-80 and prepolymerize at 80±15℃ for 3h;

[0092] S2: Add carbon nanotube-modified MDI, dibutyltin dilaurate, bismuth isooctanoate and DBU to step S1, and continue the reaction at 80±15°C for 6h;

[0093] S3: After adding trimethylpentanediol to step S2, the material is poured into a mold, and after curing at 102.5±12.5°C for 1 hour, a damping polyurethane material for bridge tracks is obtained.

[0094] Comparative Example 1

[0095] The difference from Example 3 is that an equal amount of PEG derivative is replaced by PPG-4000, and the rest is the same as Example 3.

[0096] Comparative Example 2

[0097] The difference from Example 1 is that the PEG derivative is replaced by PEG-1000 in equal amounts, and the rest is the same as Example 1.

[0098] Comparative Example 3

[0099] The difference from Example 2 is that the carbon nanotube-modified MDI is replaced by 12.9 parts of MDI-100 and 2.1 parts of carbon nanotubes, and the rest is the same as Example 2.

[0100] Comparative Example 4

[0101] The difference from Example 2 is that the PEG derivative is replaced by a blend of 18 parts of PPG-4000 and 82 parts of PEG-1000 (number average molecular weight is 1540), and the rest is the same as Example 2.

[0102] Comparative Example 5

[0103] The difference from Example 1 is that an equal amount of trimethylpentanediol is replaced by 3-methyl-1,5-pentanediol, and the rest is the same as Example 1.

[0104] The polyurethane materials prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests, and the test methods were as follows:

[0105] Dynamic Mechanical Analysis (DMA): Tested according to ASTM D4065-20, with a frequency of 1 Hz and a heating rate of 3 °C / min;

[0106] Tensile strength (MPa): Tested in accordance with ASTM D412-16 (2021);

[0107] Elongation at break (%): Tested in accordance with ASTM D412-16 (2021);

[0108] Akron wear loss (mm 3 ): Tested according to ASTM D5963-22;

[0109] The test results are shown in Table 1-2.

[0110] Table 1 DMA test results

[0111]

[0112] It can be seen from Table 1 that the polyurethane materials prepared in Examples 1-3 have wide temperature range damping characteristics, that is, the tanδ value is greater than 0.3 in the range of -50 to 80°C, which is significantly better than the comparative example.

[0113] In Comparative Example 1, after the PEG derivative is replaced with PPG-4000 in equal amounts, the flexible PEG segment is missing in its molecular structure, resulting in a significant decrease in the flexibility of the molecular chain and a smaller free volume, and the molecular motion and rotation are hindered. Therefore, the loss factor (tanδ) is lower than that in Example 3 in the range of -50°C to 80°C.

[0114] In Comparative Example 2, an equal amount of PEG derivatives was replaced with linear PEG-1000. Since the PEG molecular structure does not contain side methyl groups, the molecular chain has high regularity and strong polarity, which further reduces the free volume and significantly reduces the loss factor.

[0115] In Comparative Example 3, physical blending of carbon nanotubes and MDI is adopted. Due to the lack of chemical bonding, the interfacial bonding between the carbon nanotubes and the polyurethane matrix is ​​weak, and interfacial debonding is easily caused under the action of external force. Energy cannot be effectively dissipated through nanoslippage, resulting in a decrease in the loss factor.

[0116] In Comparative Example 4, the PEG derivative was replaced with a physical mixed alcohol of PPG and PEG. Since PPG and PEG are thermodynamically incompatible, microphase separation was induced after mixing, forming areas with uneven soft and hard segments, destroying the continuity of the hydrogen bond network, resulting in the loss of phase region synergy and a decrease in the loss factor.

[0117] In Comparative Example 5, trimethylpentanediol is replaced by 3-methyl-1,5-pentanediol. Since the number of methyl groups on the side of the chain extender is reduced, the steric hindrance of the molecular chain is reduced, the free volume is reduced and the movement of the chain segments is restricted, the rigidity of the material is enhanced, and the loss factor is also reduced.

[0118] Table 2 Mechanical properties test results

[0119]

[0120] It can be seen from Table 2 that the polyurethane materials prepared in Examples 1-3 have high tensile strength, excellent elongation at break, and low Akron abrasion loss.

[0121] In Comparative Example 1, due to the dense side methyl groups in the PPG-4000 molecular chain, the hydrogen bonding effect is weak, and the hard segment phase area is small and dispersed, resulting in a significant decrease in tensile strength; while the improved flexibility of the soft segment increases the elongation at break, but the insufficient interfacial bonding force leads to an increase in wear.

[0122] In Comparative Example 2, since the PEG-1000 molecular chain has high polarity and regular arrangement, a dense hydrogen bond network is formed, and the tensile strength is equivalent to that of the embodiment; however, due to the lack of ABA block structure to inhibit segment slippage, the interface is easily destroyed during the wear process, and the wear amount is greatly increased.

[0123] In Comparative Example 3, the physically blended carbon nanotubes cannot effectively transfer stress due to weak interfacial bonding, resulting in a decrease in tensile strength; at the same time, the poor dispersion of carbon nanotubes causes stress concentration, the elongation at break increases, but the wear performance deteriorates.

[0124] In Comparative Example 4, due to phase separation caused by the blending of PPG and PEG, the interfacial bonding force of the soft and hard segments was weakened, and the tensile strength decreased; and the uneven size of the phase domains aggravated the local failure during the wear process, and the wear amount increased significantly.

[0125] In Comparative Example 5, due to the reduction of the side methyl groups of 3-methyl-1,5-pentanediol, the molecular chains are arranged more closely, and the hydrogen bond density is increased, which increases the tensile strength; however, the limited mobility of the chain segments leads to a decrease in the elongation at break, while the dense structure slightly improves the wear amount.

[0126] The present invention breaks through the performance bottleneck of traditional polyurethane materials through the organic combination of material design and process innovation. The difference in experimental data is essentially due to the performance leap brought about by molecular-level structural regulation. The damping polyurethane material for bridge tracks of the present invention not only meets the high standard requirements of rail transit for shock absorption and noise reduction, but also has leading technological innovation in the field of materials science, which is of great significance to promoting technological progress and application expansion in related fields.

Claims

1. A damping polyurethane material for bridge track, characterized in that: The invention comprises the following raw materials in parts by weight: PEG derivatives: 100 parts; TDI-80: 25-35 parts; Carbon nanotube modified MDI: 15-25 parts; Trimethylpentanediol: 8-12 parts; Dibutyltin dilaurate: 0.15-0.25 parts; Bismuth isooctanoate: 0.3-0.4 parts; DBU: 0.06-0.08 parts; The PEG derivative is an ABA type block copolymer, wherein block A is a PPG segment and block B is a PEG segment, and its structural formula is as follows: ； Where, 2≤x≤19, 2≤y≤36, 1≤z≤17; The preparation method of the carbon nanotube modified MDI is: (1) subjecting multi-walled carbon nanotubes to an acidification treatment with a mixture of sulfuric acid and nitric acid under ultrasonic conditions, followed by heating under reflux, washing, and drying to obtain carboxylated carbon nanotubes; (2) Carboxylated carbon nanotubes and MDI in a mass ratio of (1-4):15 are mixed and reacted to obtain carbon nanotube-modified MDI.

2. The damping polyurethane material for bridge track according to claim 1, characterized in that: In the step (1), the mixed solution of sulfuric acid and nitric acid is prepared by mixing 98wt.% sulfuric acid and 65wt.% nitric acid in a volume ratio of 5:1, and the mass volume ratio of the multi-walled carbon nanotubes to the mixed solution of sulfuric acid and nitric acid is (5-10)g:200mL.

3. The damping polyurethane material for bridge track according to claim 1, characterized in that: In the step (1), the frequency of ultrasound is 35-45kHz and the time is 2-3h.

4. The damping polyurethane material for bridge track according to claim 1, characterized in that: In the step (1), the heating reflux conditions are: heating to 115-130° C. and reflux for 2-4 hours.

5. The damping polyurethane material for bridge track according to claim 1, characterized in that: In the step (2), the reaction temperature is 60-80°C and the reaction time is 7-9h.

6. A method for preparing a damping polyurethane material for bridge track according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Mixing PEG derivatives with TDI-80 for prepolymerization; S2: adding carbon nanotube-modified MDI, dibutyltin dilaurate, bismuth isooctanoate and DBU to step S1, and continuing the reaction; S3: After adding trimethylpentanediol to step S2, the material is poured into a mold, and after curing, a damping polyurethane material for bridge tracks is obtained.

7. The method for preparing the damping polyurethane material for bridge track according to claim 6, characterized in that: In the step S1, the prepolymerization temperature is 65-95° C. and the time is 2-3 hours.

8. The method for preparing the damping polyurethane material for bridge track according to claim 6, characterized in that: In the step S2, the reaction temperature is 65-95° C. and the reaction time is 3-6 hours.

9. The method for preparing the damping polyurethane material for bridge track according to claim 6, characterized in that: In the step S3, the curing temperature is 90-115° C. and the curing time is 1-2 hours.

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