Temperature driven piezoresistive sensor and method of manufacturing the same

Abstract

The application provides a temperature-driven piezoresistive sensor and a preparation method thereof, and belongs to the field of foamed materials. The application provides a preparation method of a temperature-driven piezoresistive sensor, which comprises the following steps: melt blending a thermoplastic elastomer and / or degradable polyester with polycaprolactone to obtain a to-be-foamed body; and sequentially performing saturated adsorption and pressure relief foaming on the to-be-foamed body in an environment containing a gas foaming agent to obtain the temperature-driven piezoresistive sensor; the temperature of the saturated adsorption is (T m -60℃)~T m , T m is the melting point of the to-be-foamed body; the pressure of the saturated adsorption is 10-30 MPa, the time of the saturated adsorption is d x (30-180) min, d is the thickness or particle size of the to-be-foamed body, and the unit is mm; and the pressure relief speed of the pressure relief foaming is 10-300 MPa / s.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of foamed materials, in particular to a temperature-driven piezoresistive sensor and a preparation method thereof. BACKGROUND

[0002] With the development of smart materials, traditional single-function materials gradually cannot meet the needs of modern high-performance multifunctional systems. Temperature-driven materials can cause physical deformation through temperature changes and are widely used in self-adaptive drivers. Piezoresistive sensors are based on the characteristics of material resistance changing with external pressure or strain and are widely used in pressure, strain detection, health monitoring and other fields. Traditional temperature-driven devices and piezoresistive sensors are mostly separate functional units, which have unique advantages in their respective fields, but have certain limitations in integrated applications. SUMMARY

[0003] The present application provides a temperature-driven piezoresistive sensor and a preparation method thereof. The temperature-driven piezoresistive sensor prepared by the present application has both temperature-driven and piezoresistive sensing functions.

[0004] The present application provides a preparation method of a temperature-driven piezoresistive sensor, comprising the following steps:

[0005] The thermoplastic elastomer and / or degradable polyester are melt-blended with polycaprolactone to obtain a foaming body;

[0006] The foaming body is placed in an environment containing a gas blowing agent to sequentially perform saturation adsorption and pressure relief foaming to obtain the temperature-driven piezoresistive sensor;

[0007] The saturation adsorption temperature is (T m -60℃)~T m , and Tm is the melting point of the foaming body; the saturation adsorption pressure is 10-30 MPa, and the saturation adsorption time is d x (30-180) min, d is the thickness or particle size of the foaming body, unit: mm;

[0008] The pressure relief speed of the pressure relief foaming is 10-300 MPa / s.

[0009] Preferably, the thermoplastic elastomer includes one or more of thermoplastic polyurethane, thermoplastic polyester elastomer and thermoplastic nylon elastomer.

[0010] Preferably, the degradable polyester includes polybutylene terephthalate-adipate and / or polybutylene succinate-terephthalate.

[0011] Preferably, the relative molecular weight of the polycaprolactone is 65000.

[0012] Preferably, the total mass of the thermoplastic elastomer and / or the degradable polyester and the mass of the polycaprolactone The ratio is 1.5-6:1.

[0013] Preferably, after the melt blending, the obtained blend is subjected to ball milling and granulation to obtain the to-be-foamed body.

[0014] Preferably, the gas foaming agent comprises supercritical fluid CO2 and / or supercritical fluid N2.

[0015] Preferably, after the pressure relief foaming, the obtained foamed body is placed in ice water for cell structure setting.

[0016] The application also provides a temperature-driven piezoresistive sensor prepared by the preparation method.

[0017] The application also provides an application of the temperature-driven piezoresistive sensor in intelligent robots, health monitoring or automatic control.

[0018] The application adds polycaprolactone and obtains a temperature-driven piezoresistive sensor at a suitable saturation adsorption temperature, a suitable saturation adsorption pressure, a suitable saturation adsorption time and a suitable pressure relief speed. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A temperature-driven performance comparison chart of the foamed material of Example 1 and the foamed material of Comparative Example 1;

[0020] Figure 2 A sensing performance comparison chart of the foamed material of Example 1 and the foamed material of Comparative Example 1. DETAILED DESCRIPTION

[0021] The application provides a preparation method of a temperature-driven piezoresistive sensor, comprising the following steps:

[0022] Melt blending a thermoplastic elastomer and / or a degradable polyester with polycaprolactone to obtain a to-be-foamed body;

[0023] Placing the to-be-foamed body in an environment containing a gas foaming agent to sequentially perform saturation adsorption and pressure relief foaming, to obtain the temperature-driven piezoresistive sensor;

[0024] The saturation adsorption temperature is (T m -60℃) to T m , and T m is the melting point of the to-be-foamed body; the saturation adsorption pressure is 10-30 MPa, and the saturation adsorption time is d x (30-180) min, where d is the thickness or particle size of the to-be-foamed body, in mm;

[0025] The pressure relief foaming speed is 10-300 MPa / s.

[0026] In the present application, the raw materials used are all commercially available products well known in the art, unless otherwise specified.

[0027] In the present application, the thermoplastic elastomer and / or the degradable polyester are preferably dried before being melt-blended with polycaprolactone.

[0028] In the present application, the thermoplastic elastomer and / or the degradable polyester are preferably dried before being melt-blended with polycaprolactone.

[0029] In the present invention, the total mass of the thermoplastic elastomer and / or the degradable polyester and the mass of the polycaprolactone The mass ratio is preferably 1.5-6:1, and in specific embodiments of the present application, the mass ratio of the total mass of the thermoplastic elastomer and / or the degradable polyester to the mass of polycaprolactone can be 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4.5:1, 5:1, 5.5:1, or 6:1; the thermoplastic elastomer preferably includes one or more of thermoplastic polyurethane, thermoplastic polyester elastomer, and thermoplastic nylon elastomer; and the degradable polyester includes polybutylene terephthalate-adipate and / or polybutylene succinate-terephthalate.

[0030] In the present application, the relative molecular weight of the polycaprolactone is preferably 65,000.

[0031] In the present application, the obtained blend is preferably subjected to ball milling and granulation after the melt-blending to obtain the to-be-foamed body.

[0032] In the present application, the rotation speed of the ball milling is preferably 200 rpm, and the time is preferably 8 h.

[0033] In the present application, the to-be-foamed body is sequentially subjected to saturation adsorption and pressure relief foaming in an environment containing a gas foaming agent to obtain the temperature-driven-pressure resistance sensor.

[0034] In the present application, the gas foaming agent preferably includes supercritical fluid CO2 and / or supercritical fluid N2.

[0035] In the present application, the temperature of the saturation adsorption is (T m -60℃) to T m , and T m is the melting point of the to-be-foamed body, and in specific embodiments of the present application, the temperature of the saturation adsorption can be T m -50℃, T m -40℃, T m -30℃, T m -20℃, or T m-10℃; the pressure of the saturated adsorption is 10-30 MPa, and the time of the saturated adsorption is d x (30-180) min, in the specific embodiments of the present application, the pressure of the saturated adsorption can be 15 MPa, 20 MPa or 25 MPa, and the time of the saturated adsorption can be d x 60 min, d x 80 min, d x 100 min, d x 120 min or d x 150 min, d is the thickness or particle size of the to-be-foamed body, and the unit is mm;

[0036] In the present application, the pressure relief speed of the pressure relief foaming is 10-300 MPa / s, and in the specific embodiments of the present application, the pressure relief speed of the pressure relief foaming can be 50 MPa / s, 100 MPa / s, 150 MPa / s, 200 MPa / s or 250 MPa / s.

[0037] In the present application, after the pressure relief foaming, the present application preferably further comprises: placing the obtained foamed body in ice water for cell setting.

[0038] The present application also provides a temperature-driven piezoresistive sensor prepared by the preparation method in the above technical solution.

[0039] The present application also provides an application of the temperature-driven piezoresistive sensor in the above technical solution in intelligent robots, health monitoring or automatic control.

[0040] The temperature-driven piezoresistive sensor and the preparation method thereof provided by the present application will be described in detail below in combination with embodiments, but they should not be understood as limitations to the protection scope of the present application.

[0041] Example 1

[0042] After commercially available polybutylene adipate terephthalate (TH801T, melting point 120.7℃) and polycaprolactone (600C, melting point 58.1℃) were dried in a vacuum oven at 40℃ for 12h, the polybutylene adipate terephthalate and the polycaprolactone were taken in a mass ratio of 4, and were blended in a torque rheometer at a temperature of 190℃ and a rotation speed of 50rpm for 10min, and the obtained blend was granulated and subjected to CNTs ball milling (the rotation speed of the ball milling was 200rpm, and the time was 8h) to obtain a to-be-foamed body with a particle size of 1mm.

[0043] The to-be-foamed body was placed in a high-pressure foaming device, and the air in the high-pressure foaming device was replaced by CO2 purging. And CO2 was injected into the high-pressure foaming device to a pressure of 15MPa, and the polymer sample was saturated in CO2 at a temperature of 115℃ for 120min, and then the obtained foamed product was rapidly cooled in ice water until the cell setting.

[0044] Examples 2-7

[0045] The parameters different from Example 1 are shown in Table 1, and the rest are the same as Example 1.

[0046] Table 1 Parameters different from Example 1 for Examples 2-7

[0047]

[0048]

[0049] Comparative Example 1

[0050] A commercially available polybutylene adipate terephthalate (TH801T, melting temperature 120.7°C) was dried in a vacuum oven at 40°C for 12h, and then blended in a torque rheometer at a temperature of 190°C and a rotation speed of 50rpm for 10min. The obtained blend was granulated and subjected to CNTs ball milling (ball milling rotation speed 200rpm, time 8h) to obtain a foaming body with a particle size of 1mm.

[0051] The foaming body was placed in a high-pressure foaming device, and the air in the high-pressure foaming device was replaced by CO2purging. CO2was injected into the foaming body to a pressure of 15MPa, and the polymer sample was saturated in CO2at a temperature of 115°C for 120min. The obtained foaming product was rapidly cooled in ice water until the cells were set by rapidly depressurizing at a speed of 200MPa / s.

[0052] The foaming products of Example 1 and Comparative Example 1 were subjected to temperature-driven testing and pressure resistance sensing testing at different shape recovery temperatures, and the results are shown in Figures 1-2 . Figure 1 The temperature-driven performance comparison chart of the foaming material of Example 1 and the foaming material of Comparative Example 1 is Figure 2 , and the sensing performance comparison chart of the foaming material of Example 1 and the foaming material of Comparative Example 1 is

[0053] It can be seen from Figures 1-2 that Example 1 has excellent temperature-driven and sensing performance.

[0054] Comparative Examples 2-5

[0055] The parameters different from Example 1 are shown in Table 2, and the rest are the same as Example 1.

[0056] Table 2 Parameters different from Example 1 for Comparative Examples 2-5

[0057]

[0058] The foamed products obtained in Examples 1-7 and Comparative Examples 1-5 were immersed in a water bath, the temperature of which was 20°C, and the water absorption was measured.80℃, under the action of external force, the compression fixed strain is 7%, and keeps 30s, and cools to 20℃, after removing the external force, the shape fixed strain of the foamed product is the initial strain, the sample is placed in the oven, the oven temperature is the shape recovery temperature, and the strain is recorded, the above strain is based on the initial length of the foamed sample. The change rate of resistance of the foamed sample under different shape recovery temperatures is recorded, and the change rate of resistance of the foamed sample under different shape recovery temperatures is recorded.

[0059] Table 3 test results of foamed products of examples 1-7 and comparative examples 1-5

[0060]

[0061] As can be seen from table 3, the temperature-driven piezoresistive sensor can be easily prepared by the method of examples 1-7.

[0062] In comparative example 1, because polycaprolactone is not added, the driving performance of the prepared foamed material is too poor.

[0063] In comparative example 2, because the saturation adsorption temperature is too low, the melt strength is too high, which is not conducive to cell growth, the foaming ratio of the foamed sample is too low, and the prepared foamed material beads cannot be bonded, so there is no driving and sensing performance.

[0064] In comparative example 3, because the saturation adsorption pressure is too low, the dissolved CO2 in the sample is too little, the foaming ratio of the foamed sample is too low, and the prepared foamed material beads cannot be bonded, so there is no driving and sensing performance.

[0065] In comparative example 4, because the saturation adsorption time is too short, the dissolved CO2 in the sample does not reach unsaturation, and the gas used for cell nucleation and growth is too little, resulting in too low foaming ratio of the foamed sample, and the prepared foamed material beads cannot be bonded, so there is no driving and sensing performance.

[0066] In comparative example 5, because the pressure relief speed is too slow, the driving force for cell growth is too low, resulting in too low foaming ratio of the foamed sample, and the prepared foamed material beads cannot be bonded, so there is no driving and sensing performance.

[0067] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method of fabricating a temperature driven piezoresistive sensor, characterized by, The method comprises the following steps: melting blending thermoplastic elastomer and / or degradable polyester with polycaprolactone to obtain a to-be-foamed body; the ratio of the total mass of the thermoplastic elastomer and / or degradable polyester to the mass of polycaprolactone is 1.5-6:1 placing the to-be-foamed body in an environment containing a gas blowing agent to sequentially perform saturation adsorption and pressure relief foaming to obtain the temperature-driven pressure resistance sensor; The temperature of the saturated adsorption is (T m -60℃)~T m , T m is the melting point of the to-be-foamed body; the pressure of the saturated adsorption is 10~30MPa, and the time of the saturated adsorption is d×(30~180)min, d is the thickness or particle size of the to-be-foamed body, in mm; the pressure relief speed of the pressure relief foaming is 10-300 MPa / s.

2. The production method according to claim 1, characterized by, The thermoplastic elastomer comprises one or more of thermoplastic polyurethane, thermoplastic polyester elastomer and thermoplastic nylon elastomer.

3. The preparation method according to claim 1, characterized in that, The degradable polyester comprises polybutylene terephthalate-adipate and / or polybutylene succinate-terephthalate.

4. The method of claim 1, wherein, The relative molecular weight of the polycaprolactone is 65,000.

5. The preparation method according to claim 1, characterized in that, After the melting blending, the obtained blend is further subjected to ball milling and granulation to obtain the to-be-foamed body.

6. The method of claim 1, wherein, The gas blowing agent comprises supercritical fluid CO2 and / or supercritical fluid N2.

7. The preparation method according to claim 1, characterized in that, After the pressure relief foaming, the obtained foamed body is further placed in ice water to perform cell shaping.

8. The temperature-driven pressure resistance sensor prepared by the preparation method in any one of claims 1-7.

9. The temperature-driven pressure resistance sensor in claim 8 in the application of intelligent robots, health monitoring or automatic control.

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