Impact-resistant temperature-sensitive flexible polyurethane material as well as preparation method and application thereof

Abstract

The invention discloses an impact-resistant temperature-sensitive flexible polyurethane material as well as a preparation method and application thereof. The preparation method comprises the following steps: weighing thermoplastic polyurethane and polyvinylidene fluoride, putting the thermoplastic polyurethane and the polyvinylidene fluoride into a solvent, and heating and stirring at 70-80 DEG C and 800 rpm to obtain a TPU / PVDF solution; carbon black is taken and placed in the synthesized TPU / PVDF solution, then a 1-ethyl-3-methylimidazole bis (trifluoromethanesulfonyl) imide salt solution is dropwise added, heating and stirring are conducted at the temperature of 70-80 DEG C and the speed of 800 rpm, and a TPU / PVDF / C / TFSI solution is obtained; and scraping the TPU / PVDF / C / TFSI solution on a glass slide to obtain a film, drying at 60 DEG C, and stripping to obtain the impact-resistant temperature-sensitive flexible polyurethane material. The material disclosed by the invention is wide in response temperature range, high in flexibility, high in tensile strength, high in strain, not easy to damage, low in manufacturing cost and easy to synthesize, and has a good application prospect, and resistance signal response with high sensitivity and stable circulation can be realized under high-temperature impact of non-physiological temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of temperature sensing, and in particular relates to an impact-resistant temperature-sensitive flexible polyurethane material and a preparation method and application thereof. Background Art

[0002] With the development of science and technology, flexible materials with excellent temperature sensing performance, self-healing and stretchability have attracted much attention in electronic skin, wearable electronic devices and artificial muscles. These application areas can cover all physiological temperatures, but there is a lack of materials that need to be resistant to high temperature shock.

[0003] Compared with traditional heavy materials such as metals and their alloys, soft polymer materials including elastomers and gels have excellent mechanical compliance, high elongation, good compliance and light weight. Based on the physical properties of soft polymer materials, it provides technical support for replacing traditional materials, extending the service life of materials and reducing costs while stabilizing output signals.

[0005] At present, the commonly used goaf coal spontaneous combustion monitoring and early warning systems mainly include bundle tube monitoring and distributed optical fiber monitoring. Although these two systems can effectively realize monitoring and early warning of goafs, their layout is relatively complicated and they are easily damaged and broken. Even if they are armored, they are easily broken by large pieces of gangue falling from the goaf, making them difficult to protect. However, both of these existing methods use two lanes to arrange measuring points. The goaf between the two lanes is a monitoring blind spot, and the monitoring range is limited, making it difficult to form effective real-time monitoring of the entire goaf. Therefore, it is necessary to develop a temperature sensor that is not easy to be damaged and can respond sensitively to high-temperature impact, so as to solve the problem of coal spontaneous combustion in goafs. Summary of the invention

[0006] In view of the deficiencies in the prior art, the purpose of the present invention is to provide an impact-resistant temperature-sensitive flexible polyurethane material and a preparation method and application thereof. The material not only has good flexibility, high tensile strength, high strain, light weight, thin shape, and is not easily damaged, but also has a wide response temperature range and can perform sensitive and stable resistance signal response under high temperature shock of non-physiological temperature. In addition, the preparation method of the present invention is simple, low cost, easy to synthesize, and has good application prospects.

[0007] In order to solve the problems of the prior art, the technical solution adopted by the present invention is:

[0008] A method for preparing an impact-resistant temperature-sensitive flexible polyurethane material comprises the following steps:

[0009] Step 1: Synthesis of TPU / PVDF solution

[0010] Weigh thermoplastic polyurethane and polyvinylidene fluoride in a solvent, heat and stir at 70-80° C. and 800 rpm to obtain a TPU / PVDF solution with a mass concentration of 16%-20%;

[0011] Step 2: Synthesis of TPU / PVDF / C / TFSI solution

[0012] Weigh carbon black and add it to the TPU / PVDF solution, then drop 1-ethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt solution into it, and heat and stir at 70-80°C and 800rpm to obtain a TPU / PVDF / C / TFSI solution;

[0013] Step 3: Synthesis of thin films

[0014] The TPU / PVDF / C / TFSI solution was scraped onto a glass slide to obtain a 500-1000 μm thin film, which was dried in a vacuum drying oven and peeled off to obtain an impact-resistant temperature-sensitive flexible polyurethane material.

[0015] As an improvement, the solvent in step 1 is a DMF solution or a DMSO solution.

[0016] As an improvement, the mass ratio of the thermoplastic polyurethane to polyvinylidene fluoride in step 1 is 1-3:1.

[0017] As an improvement, the amount of carbon black added in step 2 is 1.15%-3.05% of the total amount of the TPU / PVDF / C / TFSI solution.

[0018] As an improvement, the amount of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt solution added in step 2 is 0.55%-0.74% of the total amount of the TPU / PVDF / C / TFSI solution.

[0019] As an improvement, the vacuum drying temperature in step 3 is 50-60° C., and the drying time does not exceed 2 hours.

[0020] The impact-resistant temperature-sensitive flexible polyurethane material prepared by the preparation method responds at 24-85° C., has a tensile strength of 2.6 MPa, and a high strain of 415%.

[0021] As an improvement, the impact-resistant temperature-sensitive flexible polyurethane material has a fast temperature-sensitive response, a response time of less than 88 ms, and a stable reversible cycle of more than 10,000 times, and has robust stability.

[0022] The above-mentioned impact-resistant temperature-sensitive flexible polyurethane material is used in the preparation of sensors for monitoring spontaneous combustion of coal in goaf areas.

[0023] Beneficial effects:

[0024] Compared with the prior art, the impact-resistant temperature-sensitive flexible polyurethane material of the present invention and its preparation method and application have the following advantages:

[0025] 1. The preparation method of the present invention is simple and low in cost. The obtained impact-resistant temperature-sensitive flexible polyurethane material has excellent structural performance, strong impact resistance and sufficient flexibility;

[0026] 2. The present invention uses PVDF as the main body of temperature sensing performance and adds TPU, which not only improves the stretchability of the composite material, but also improves the temperature sensing performance; the resulting material breaks through the physiological temperature and is suitable for temperature monitoring of 24-85°C, with excellent sensitivity and robust stability;

[0027] 3. The impact-resistant temperature-sensitive flexible polyurethane material of the present invention can be used in the field of spontaneous combustion monitoring of coal in goaf areas and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a physical model diagram of the impact-resistant temperature-sensitive flexible polyurethane material prepared in Example 3 of the present invention;

[0029] Figure 2 This is a SEM image of the impact-resistant temperature-sensitive flexible polyurethane material prepared in Example 3 of the present invention;

[0030] Figure 3 The resistance signal response of the impact-resistant temperature-sensitive flexible polyurethane material prepared in Example 3 of the present invention when subjected to temperature shock;

[0031] Figure 4 The sensitivity test of the resistance signal response of the materials prepared under different parameters at 40°C, (a) to (e) correspond to Examples 1 to 5 respectively;

[0032] Figure 5 The resistance change curves of the material prepared in Example 3 when subjected to high temperature impact at 60°C (a), 80°C (b), and 85°C (c);

[0033] Figure 6 This is the SEM image of the material prepared in Comparative Example 1.

[0034] Figure 7 The stress-strain curves of the materials prepared under different parameters.

[0035] Figure 8 (a) A goaf model constructed according to an embodiment of the present invention;

[0036] Figure 8 (b) is the application of the material prepared in Example 3 under the background of spontaneous combustion of coal in goaf;

[0037] Figure 8(c) is a morphology comparison diagram of the PVDF material prepared in Comparative Example 4 before and after being subjected to 80°C thermal shock, with the left side being before thermal shock and the right side being after shock;

[0038] Figure 8 (d) is a morphology comparison diagram of the TPU / PVDF stretchable, flexible, and highly thermal shock resistant temperature sensing material prepared in Example 3 before and after being subjected to a thermal shock at 80°C, with the left side being before the thermal shock and the right side being after the shock;

[0039] Figure 8 (e) is the temperature response of the PVDF material prepared in Comparative Example 4 when the temperature of the goaf slowly rises from 70°C to 80°C;

[0040] Figure 8 (f) is the temperature response of the TPU / PVDF stretchable, flexible, and highly thermal shock resistant temperature sensing material prepared in Example 3 when the temperature of the goaf slowly rises from 70°C to 80°C;

[0041] Figure 8 (g) is the temperature response of the material in Example 3 to the cyclic impact of temperature and pressure in the goaf, simulating the process of temperature rise and temperature drop due to heat accumulation and the scene of being hit by random falling rocks;

[0042] Figure 8 (h) Figure 8 (g) Zoomed-in view of the pressure response. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0044] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0045] Example 1

[0046] The preparation of a stretchable, flexible, and highly thermal shock-resistant temperature sensing material based on TPU / PVDF includes the following steps:

[0047] Step 1: Synthesis of TPU / PVDF solution

[0048] Weigh 0.4 g of thermoplastic polyurethane (TPU) and 0.4 g of polyvinylidene fluoride (PVDF) and place them in 4 ml of DMF solution, heat and stir at 70°C and 800 rpm for 1 hour to obtain a TPU / PVDF solution with a mass concentration of 20% (when the solution is a DMSO solution, the stirring time is 4 hours);

[0049] Step 2: Synthesis of TPU / PVDF / C / TFSI solution

[0050] Weigh 2.1% of carbon black in the TPU / PVDF / C / TFSI solution and add it to the TPU / PVDF solution, then drop 0.6% of 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide (TFSI) solution in the TPU / PVDF / C / TFSI solution, heat and stir at 70°C and 800 rpm for 1 hour (when the solution is a DMSO solution, the stirring time is 4 hours);

[0051] Step 3: Synthesis of thin films

[0052] Take the TPU / PVDF / C / TFSI solution and use a film scraper to scrape a 750 μm film on a glass slide, then put it into a vacuum drying oven and dry it at 60°C for 1 hour. Finally, peel off the clean and dry film to obtain an impact-resistant temperature-sensitive flexible polyurethane material.

[0053] Example 2

[0054] The mass ratio of TPU and PVDF in Example 1 was adjusted to TPU:PVDF=2:1, and the rest was the same as Example 1.

[0055] Example 3

[0056] The mass ratio of TPU and PVDF in Example 1 was adjusted to TPU:PVDF=3:1, and the rest was the same as Example 1.

[0057] The microstructure of the film was characterized by environmental scanning electron microscopy (ESEM, Quanta250), and the surface was analyzed by energy spectrum analysis in surface analysis mode.

[0058] The crystal structures of the pure TPU film, the pure PVDF film and the mixed film of Example 3 were analyzed by X-ray diffraction (XRD).

[0059] The surface functional groups of the film materials were measured by Fourier transform infrared spectroscopy (FTIR). The water contact angle (WCA) of the film materials was measured by optical contact angle measurement device (OCA).

[0060] The resistance change curve of the sample at different temperatures was detected by using Keithley 2400 digital source meter and Keithley 2400 software on the computer.

[0061] The mechanical tensile test was carried out using a tensile testing machine to obtain the stress-strain curves of the material under different parameters. Figure 7 It can be obtained that the tensile strength of this temperature-sensitive sensor can reach 2.6MPa and the maximum strain can reach 415%.

[0062] Figure 1 This is a physical picture of the material prepared in Example 3. It can be seen from the figure that the material of the present invention has good flexibility.

[0063] Figure 2 This is a SEM characterization image of the stretchable, flexible, and highly thermal shock resistant temperature sensing material prepared in Example 3, which shows a good porous morphology, and the proportion of pores with a diameter of 200nm to 600nm is 30% to 55%.

[0064] Example 4

[0065] The mass ratio of TPU and PVDF in Example 1 was adjusted to TPU:PVDF=4:1, and the rest was the same as Example 1.

[0066] Example 5

[0067] The mass ratio of TPU and PVDF in Example 1 was adjusted to TPU:PVDF=5:1, and the rest was the same as Example 1.

[0068] Example 6

[0069] Use a 2400 digital source meter to measure the stable value of the material resistance at 24°C, then quickly place the material in a 55°C environment, record the resistance signal change until it stabilizes, then take it out of the high temperature environment, place it back at room temperature, and record the resistance signal recovery until it stabilizes. The material in Example 3 was tested according to this detection method, and the results are as follows: Figure 3 shown.

[0070] Figure 3 The curve shows that when the temperature of the TPU / PVDF stretchable, flexible, and highly temperature-shock-resistant temperature sensor material increases, the resistance response changes and the resistance signal gradually becomes stable, which intuitively proves that the composite material of the present invention exhibits corresponding capabilities to temperature changes.

[0071] Specifically, through a 16°C temperature difference shock, we compared the ratio of TPU and PVDF in which the sensitivity response is optimal. The results are as follows: Figure 4As shown in the figure, when the mass ratio of TPU and PVDF is 3:1 for compounding, the material has the greatest sensitivity to temperature response and the fastest reaction time, specifically 88ms.

[0072] The material prepared in Example 3 was subjected to a high temperature shock test. Taking 24°C as a reference, when the material was subjected to a temperature shock of 60°C, it showed good sensitivity, and after multiple shock cycles, it still maintained a stable response, and the average sensitivity was 44%. Figure 5 (a) shown. Figure 3 In fact Figure 5 One cycle in the middle cycle fully demonstrates the curve change process of the material.

[0073] The temperature was raised to 80℃, and the room temperature was used as a reference. The high temperature shock test and multiple cycle tests were repeated. The obtained sensitivity was high, and the average sensitivity was 53%, which proved that the material had excellent and robust stability to 80℃ high temperature shock. Figure 5 (b) shows the specific change curve.

[0074] When the shock temperature is further increased to 85°C, the sensitivity increases again and remains stable. The average sensitivity after multiple cycles of shock is 58%. Figure 5 (c) as shown.

[0075] Figure 5 This shows that within a certain temperature range, the higher the impact temperature to which the material of the present invention is subjected, the better its temperature measurement sensitivity, which further indicates its advantage in being applicable to the field of high temperature detection.

[0076] Combined with the above experiments, it can be seen that the present invention establishes a one-to-one correspondence between the resistance response of the TPU / PVDF flexible film material and different temperature changes, which is convenient for obtaining the detection temperature through the spectrum. Combined with the soft characteristics of the material, it has good application prospects.

[0077] Comparative Example 1

[0078] The same procedures as in Example 3 were followed except that the 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide (TFSI) solution was not added.

[0079] Comparative Example 2

[0080] Except that the addition amount of carbon black is changed to 8%, the rest is the same as Example 3.

[0081] Comparative Example 3

[0082] Except that the addition amount of carbon black is changed to 0.8%, the rest is the same as Example 3.

[0083] Comparative Example 4

[0084] The mass of polyvinylidene fluoride (PVDF) increased by 0.8 g, and the rest was the same as in Example 3 except that thermoplastic polyurethane (TPU) was not added.

[0085] When the 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (TFSI) solution is not added in Comparative Example 1, the film-forming effect of the obtained material is poor; the resistance is too large and the conductivity is extremely poor; and the response to temperature is unstable and insensitive, and the temperature change cannot be monitored by the resistance signal.

[0086] Comparing Comparative Example 2 and Comparative Example 3, the film obtained by increasing and decreasing the carbon content respectively has poor effect, that is, the carbon content of the present invention is preferably 1.15%-3.05% of the total amount of the solution. Although the carbon content is too low, it can respond to the temperature, but it will lead to poor film formation and uneven large holes, such as Figure 6 Too high a carbon content will result in no response to temperature or an unstable response.

[0087] Example 7

[0088] A goaf model is now constructed to test the effect of the impact-resistant temperature-sensitive flexible polyurethane material of the present invention on the spontaneous combustion monitoring of coal in goaf. According to the similarity theory, the filling materials and layout of the goaf experimental model should be highly consistent with the actual site of the goaf. In order to achieve a high degree of similarity with the actual conditions, the internal structure should be based on the void law of the coal and rock mass that actually falls in the goaf, that is, the "O" ring theory. The "O" ring theory divides the goaf into three parts, namely the natural accumulation area, the pressure expansion area, and the compaction stability area. The coal and rock void ratio in the deep compaction area of ​​the goaf is small and is in a stable state. The void ratio of the rock and coal blocks in the boundary area of ​​the goaf gradually increases from the compaction area to the boundary area of ​​the goaf. The rock blocks in the boundary area are in a natural accumulation state with large voids. According to the literature, the void ratio of the goaf is generally between 10% and 40%, so the void ratios of these three areas are designed to be 35%, 25%, and 10%, respectively. . In the construction of the similar model of the goaf, the internal filling materials are consistent with the actual goaf, that is, rocks and coal blocks are selected. Screen out rocks and coal blocks with particle sizes of <1cm, 1-2cm and 2-3cm as fillers inside the model; lay them in different areas from outside to inside according to the set porosity of the coal and rock blocks. First, lay a layer of rock blocks about 5cm thick at the bottom of the box as bedrock, and then fill coal blocks on top of the bedrock as the accumulated coal in the goaf according to the above principles. Set the total accumulation height to about 7cm. The coal and rock blocks are laid as follows: Figure 8 (a) shown.

[0089] The material in Example 3 was laid on the surface of the coal seam to conduct a simulation experiment of spontaneous combustion of coal in the goaf. Figure 8(b). First, set the temperature of the goaf area to 40℃, which is achieved by the heating stage. When the temperature rises from room temperature 24.6℃ to 40℃, the resistance signal drops sharply until it stabilizes. Stop heating and start ventilation and heat dissipation through the simulation device shell equipment to restore the temperature to room temperature. At this time, the resistance signal rises back to a level close to the initial electrical signal and stabilizes again. Perform multiple cycles and record data. The resistance signal curve is as follows Figure 8 Then, random rock fall was introduced into the goaf, with a rock pressure range of 0.01-40 MPa, and the resistance signal was recorded. The curve is shown in the right half of 8(g), and the enlarged detail is shown in Figure 8 (h) As shown in this intuitive comparison, it can be determined that according to the large-scale laying of this material in the goaf, the early warning of spontaneous combustion of coal in the goaf can be achieved through temperature detection, and it is easy to distinguish it from the resistance signal caused by falling rocks.

[0090] Since traditional optical fiber or cable signal monitoring systems are easily damaged by falling rocks and have high maintenance costs, and most of them are arranged in tunnels, the monitoring sites are limited. The material of the present invention can fill the gap in the field of flexible materials for monitoring and early warning of spontaneous combustion of coal in goaf areas.

[0091] pass Figure 8 (c) and Figure 8 From the thermal shock comparison of the experimental temperature (d), it can be found that for the pure PVDF material membrane, the morphology has been destroyed after being impacted by high temperature and the inertial force of rock, and it is difficult to put it into secondary use. However, the morphological structure of the material of the present invention does not change significantly under the impact of temperature and the inertial force of rock, indicating that it has good impact resistance and also provides a new research direction in the field of self-healing.

[0092] Figure 8 (e) and Figure 8 (f) is the resistance response of the material prepared in Comparative Example 4 and the material prepared in Example 3 when the temperature of the goaf rises from 70°C to 80°C. It can be seen that the material of the present invention has better resistance response performance and monitoring stability in the field of inertial impact caused by high temperature and rock, and the sensitivity is also greater.

Claims

1. A method for preparing an impact-resistant temperature-sensitive flexible polyurethane material, characterized in that: The following steps are involved: Step 1: Synthesis of TPU / PVDF solution Weigh thermoplastic polyurethane and polyvinylidene fluoride in a solvent, heat and stir at 70-80° C. and 800 rpm to obtain a TPU / PVDF solution with a mass concentration of 16%-20%; Step 2: Synthesis of TPU / PVDF / C / TFSI solution Weigh carbon black and add it to the TPU / PVDF solution, then drop 1-ethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt solution into it, and heat and stir at 70-80°C and 800rpm to obtain a TPU / PVDF / C / TFSI solution; Step 3: Synthesis of thin films The TPU / PVDF / C / TFSI solution was scraped onto a glass slide to obtain a 500-1000 μm thin film, which was dried in a vacuum drying oven and peeled off to obtain an impact-resistant temperature-sensitive flexible polyurethane material.

2. The method for preparing an impact-resistant temperature-sensitive flexible polyurethane material according to claim 1, characterized in that: The solvent described in step 1 is a DMF solution or a DMSO solution.

3. The method for preparing an impact-resistant temperature-sensitive flexible polyurethane material according to claim 1, characterized in that: The mass ratio of the thermoplastic polyurethane to polyvinylidene fluoride is 1-3:

1.

4. The method for preparing an impact-resistant temperature-sensitive flexible polyurethane material according to claim 1, characterized in that: The amount of carbon black added in step 2 is 1.15%-3.05% of the total amount of the TPU / PVDF / C / TFSI solution.

5. The method for preparing an impact-resistant temperature-sensitive flexible polyurethane material according to claim 1, characterized in that: In step 2, the amount of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt solution added is 0.55%-0.74% of the total amount of the TPU / PVDF / C / TFSI solution.

6. The method for preparing an impact-resistant temperature-sensitive flexible polyurethane material according to claim 1, characterized in that: The vacuum drying temperature in step 3 is 50-60° C., and the drying time does not exceed 2 hours.

7. An impact-resistant temperature-sensitive flexible polyurethane material obtained by the preparation method according to claim 1, characterized in that: The impact-resistant temperature-sensitive flexible polyurethane material responds at 24-85° C., has a tensile strength of 2.6 MPa, and a high strain of 415%.

8. The impact-resistant temperature-sensitive flexible polyurethane material according to claim 7, characterized in that: The impact-resistant temperature-sensitive flexible polyurethane material has a fast temperature-sensitive response, a response time of less than 88 ms, and a stable reversible cycle of more than 10,000 times, and has robust stability.

9. Application of an impact-resistant temperature-sensitive flexible polyurethane material obtained by the preparation method described in claim 1 in preparing sensors for monitoring spontaneous combustion of coal in goaf areas.

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