CN112011160A - High-toughness polymer-based temperature-sensitive composite material and preparation method and application thereof - Google Patents

High-toughness polymer-based temperature-sensitive composite material and preparation method and application thereof Download PDF

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CN112011160A
CN112011160A CN202010915188.8A CN202010915188A CN112011160A CN 112011160 A CN112011160 A CN 112011160A CN 202010915188 A CN202010915188 A CN 202010915188A CN 112011160 A CN112011160 A CN 112011160A
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赵中国
艾桃桃
张鑫
陈立贵
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Shaanxi University of Technology
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Abstract

The invention belongs to the technical field of polymer conductive composite materials, and particularly relates to a high-toughness high-sensitivity polymer-based temperature-sensitive composite material and a preparation method and application thereof. The invention provides a high-toughness polymer-based temperature-sensitive composite material, which comprises a polymer matrix and a conductive filler, wherein the conductive filler forms a conductive network in the polymer matrix, and the conductive network is a three-dimensional conductive network formed by a one-dimensional conductive filler and a two-dimensional conductive filler; the conductive filler accounts for 0.1-5 w% of the high-toughness temperature-sensitive composite material, and the mass ratio of the one-dimensional conductive filler to the two-dimensional conductive filler in the conductive filler is 1: 1. The flexible strain sensor prepared by the method has high strength, high toughness and high sensitivity; the experimental method is simple and different, can obviously improve the effective utilization rate of the monomer, is convenient for industrial production, and expands the application field of the monomer.

Description

High-toughness polymer-based temperature-sensitive composite material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of polymer conductive composite materials, and particularly relates to a high-toughness high-sensitivity polymer-based temperature-sensitive composite material and a preparation method and application thereof.
Background
The temperature-sensitive sensor is mainly prepared from metal or metal oxide semiconductor, has high sensitivity to temperature change, but has poor stability and complex processing, cannot bear large strain, and is easy to damage under external force impact.
The prior art reports that high-molecular-base Conductive Polymers (CPCs) can be used as a temperature-sensitive sensor, and the high-molecular-base Conductive Polymers (CPCs) are prepared by doping conductive particles such as metal powder, graphite, CB and carbon nanotubes into an organic polymer serving as a matrix, so that the heat-sensitive performance of the polymer can be improved to a certain extent; the CPCs exhibit positive temperature coefficient characteristics (PTC) and negative temperature coefficient characteristics (NTC) under the action of a temperature field, the PTC effect means that the conductivity of the polymer conductive composite decreases with increasing temperature, and the NTC effect means that the conductivity of the polymer conductive composite increases with increasing temperature. In the current research on the polymer-based conductive composite material, the PTC effect is often shown by adding graphene, multi-walled carbon nanotubes or metal powder and the like, and the temperature response time is slow, so that the application prospect of the conductive polymer composite material is greatly limited.
Disclosure of Invention
Aiming at the defects, the invention provides a flexible strain sensor with high toughness and high sensitivity and a preparation method thereof, and the flexible strain sensor such as a polylactic acid product prepared by the method has high strength, high toughness and high sensitivity; the experimental method is simple and different, can obviously improve the effective utilization rate of the monomer, is convenient for industrial production, and expands the application field of the monomer.
The technical scheme of the invention is as follows:
the first technical problem to be solved by the invention is to provide a high-toughness polymer-based temperature-sensitive composite material, which comprises a polymer matrix and a conductive filler, wherein the conductive filler forms a conductive network in the polymer matrix, and the conductive network is a three-dimensional conductive network formed by a one-dimensional conductive filler and a two-dimensional conductive filler; the conductive filler accounts for 0.1-5 w% of the high-toughness temperature-sensitive composite material, and the mass ratio of the one-dimensional conductive filler to the two-dimensional conductive filler in the conductive filler is 1: 1.
Further, the polymer matrix is at least one of polylactic acid (PLA), polybutylene succinate (PBS) or polybutylene terephthalate-adipate (PBAT); preferably polylactic acid.
Further, when the polymer matrix is polylactic acid, the polylactic acid is modified polylactic acid, and the modified polylactic acid is prepared by adopting the following method: carrying out a branching reaction on polylactic acid by carrying out melt processing on dicumyl peroxide (DCP) and polyethylene glycol diacrylate (PEGDA) at 180-200 ℃ for 5-10 min; wherein the proportion of each raw material is as follows: 100 parts of polylactic acid, 0.25 part of dicumyl peroxide (DCP) and 0.05-0.5 part of polyethylene glycol diacrylate (PEGDA).
Further, the one-dimensional conductive filler is at least one of a multi-walled carbon nanotube, a single-walled carbon nanotube or a carbon fiber.
Further, the two-dimensional conductive filler is at least one of graphene nanoplatelets, graphene or graphite.
The second technical problem to be solved by the present invention is to provide a preparation method of the high-toughness polymer-based temperature-sensitive composite material, wherein the preparation method comprises: the one-dimensional conductive filler and the two-dimensional conductive filler are used as composite conductive fillers and are melted and blended with the polymer matrix at the temperature higher than the melting point of the polymer matrix and lower than the thermal decomposition temperature of the polymer matrix.
Further, the melt blending temperature is 180-200 ℃, and the blending time is 5-8 min.
The third technical problem to be solved by the invention is to provide a flexible temperature-sensitive sensor, which is prepared by adopting the polymer-based temperature-sensitive composite material.
The fourth technical problem to be solved by the present invention is to provide a method for reducing the conductive percolation value of a polymer material, wherein the method comprises: simultaneously introducing a one-dimensional conductive filler and a two-dimensional conductive filler into a high polymer material, namely melting and blending the high polymer material, the one-dimensional conductive filler and the two-dimensional conductive filler; the mass ratio of the conductive filler to the high polymer material is as follows: 0.5 wt% to 3 wt%: 99.5 wt% -97 wt%, wherein the mass ratio of the one-dimensional conductive filler to the two-dimensional conductive filler in the conductive filler is 1: 1.
Further, the high polymer material is at least one of polylactic acid (PLA), polybutylene succinate (PBS) or polybutylene terephthalate-adipate (PBAT); preferably polylactic acid.
Further, when the polymer matrix is polylactic acid, the polylactic acid is modified polylactic acid, and the modified polylactic acid is prepared by adopting the following method: carrying out a branching reaction on polylactic acid by carrying out melt processing on dicumyl peroxide (DCP) and polyethylene glycol diacrylate (PEGDA) at 180-200 ℃ for 5-10 min; wherein the proportion of each raw material is as follows: 100 parts of polylactic acid, 0.25 part of dicumyl peroxide (DCP) and 0.05-0.5 part of polyethylene glycol diacrylate (PEGDA).
Further, the one-dimensional conductive filler is at least one of a multi-walled carbon nanotube, a single-walled carbon nanotube or a carbon fiber.
Further, the two-dimensional conductive filler is at least one of graphene nanoplatelets, graphene or graphite.
The fifth technical problem to be solved by the present invention is to provide a composite material having both NTC effect and PTC effect (i.e. a composite material integrating NTC and PTC effect), wherein the composite material comprises a polymer matrix and a conductive filler, the conductive filler forms a conductive network in the polymer matrix, and the conductive network is a three-dimensional conductive network formed by a one-dimensional conductive filler and a two-dimensional conductive filler; the conductive filler accounts for 0.1-5 w% of the high-toughness temperature-sensitive composite material, and the mass ratio of the one-dimensional conductive filler to the two-dimensional conductive filler in the conductive filler is 1: 1.
The sixth technical problem to be solved by the present invention is to provide a preparation method of the above composite material having both NTC effect and PTC effect, wherein the preparation method comprises: the one-dimensional conductive filler, the two-dimensional conductive filler and the polymer matrix are melted and blended at a temperature higher than the melting point of the polymer matrix and lower than the thermal decomposition temperature.
The invention has the beneficial effects that:
1) the polymer-based temperature-sensitive material prepared by the method overcomes the defects of low toughness and strength of polymer substrates such as polylactic acid, and greatly expands the application field of bio-based polymer materials; through the construction of the three-dimensional conductive network, the temperature response speed, the repeatability and the flexibility of the polymer-based temperature-sensitive material can be remarkably improved, and the problems of poor biocompatibility, low mechanical strength, low sensitivity and repeatability and the like of the traditional sensor are solved.
2) When the modified polylactic acid is selected as a matrix, the DCP can promote the linear polylactic acid to be decomposed to generate unstable tertiary carbon free radicals, and the unstable tertiary carbon free radicals can generate a branching reaction with the polyethylene glycol diacrylate under the action of the DCP, so that the strength can be improved, and the toughness of the material can be improved; the solution-melting method is adopted, the dispersion of conductive ions in a matrix can be obviously improved, and the polymer-based temperature-sensitive material prepared by the method has a low percolation value of the conductive filler; and the method is simple to operate, the conductive filler is low in price, and the method is suitable for large-scale production.
3) The polymer-based temperature-sensitive material prepared by the invention has degradability, can be self-decomposed under natural conditions, and plays a role in environmental friendliness and acid and alkali corrosion resistance.
4) Compared with other polymer-based temperature-sensitive materials, the polymer-based temperature-sensitive material prepared by the invention has better toughness, temperature sensitivity and repeatability, so that the polymer-based temperature-sensitive material prepared by the invention can be widely applied to the fields of medicine, human health monitoring, wearable equipment and the like.
Drawings
FIGS. 1(a) and 1(b) are graphs showing the change with time of the extensional viscosity of the materials obtained in examples 1 and 2, respectively.
FIG. 2 is a TEM image of the material obtained in example 7.
FIG. 3 is a graph showing the change in conductivity of the composite materials obtained in examples 5 to 12 and comparative examples 1 to 13.
FIG. 4 is a graph of the change in conductivity of the composite materials obtained in example 7, comparative example 1, and comparative example 11 during a single ramping.
The specific implementation mode is as follows:
in the invention, the response principle of the polymer matrix/conductive filler temperature-sensitive sensor to the temperature is as follows: firstly, the conductive fillers interact with each other, and the resistance of a single conductive filler per se is reduced along with the increase of the temperature, and secondly, as the conductive network structure formed in the invention is a three-dimensional conductive network structure formed by one-dimensional conductive fillers and two-dimensional conductive fillers, the surface of the conductive filler can fluctuate in the temperature increase process, so that the contact rate between the conductive fillers is increased, and the resistance is changed.
The following examples are provided to further illustrate the embodiments of the present invention and are not intended to limit the scope of the present invention.
Example 1
1) Drying PLA granules at 70 ℃ in vacuum for 24 hours; placing 100 parts by weight of PLA into an internal mixer for blending, wherein the blending time is 5min, the rotating speed is 50rpm, and the processing temperature is 180 ℃;
2) to verify that polylactic acid was injection molded after processing modification using a HAAKE MiniJet Pro mini injection molding machine: the injection pressure is 450bar, the melt temperature is 180 ℃, and the mold temperature is 100 ℃; the samples were subjected to mechanical property tests, and the results are shown in table 1.
Example 2
1) Drying PLA granules at 70 ℃ in vacuum for 24 hours; according to 100 parts by weight of PLA, 0.3 part by weight of DCP and 0.2 part by weight of PEGDA are put into an internal mixer for blending, the blending time is 5min, the rotating speed is 50rpm, and the processing temperature is 180 ℃;
2) to verify that polylactic acid was injection molded after processing modification using a HAAKE MiniJet Pro mini injection molding machine: the injection pressure is 450bar, the melt temperature is 180 ℃, and the mold temperature is 100 ℃; the samples were subjected to mechanical property tests, and the results are shown in table 1.
Example 3
1) Drying PLA granules at 70 ℃ in vacuum for 24 hours; blending 100 parts by weight of PLA, 0.3 part by weight of DCP and 0.4 part by weight of PEGDA in an internal mixer for 5min at the rotation speed of 50rpm and the processing temperature of 180 ℃;
2) to verify that polylactic acid was injection molded after processing modification using a HAAKE MiniJet Pro mini injection molding machine: the injection pressure is 450bar, the melt temperature is 180 ℃, and the mold temperature is 100 ℃; the samples were subjected to mechanical property tests, and the results are shown in table 1.
Example 4
1) Drying PLA granules at 70 ℃ in vacuum for 24 hours; according to 100 parts by weight of PLA, 0.3 part by weight of DCP and 0.5 part by weight of PEGDA are put into an internal mixer for blending, the blending time is 5min, the rotating speed is 50rpm, and the processing temperature is 180 ℃;
2) to verify that polylactic acid was injection molded after processing modification using a HAAKE MiniJet Pro mini injection molding machine: the injection pressure is 450bar, the melt temperature is 180 ℃, and the mold temperature is 100 ℃; the samples were subjected to mechanical property tests, and the results are shown in table 1.
TABLE 1 comparison of mechanical Properties of samples obtained in examples 1 to 4
Tensile Strength (MPa) Elongation at Break (%)
Example 1 64.8 20.5
Example 2 66.4 17.5
Example 3 72.5 31.4
Example 4 75.4 34.6
Through the data analysis in table 2, the modified polylactic acid with the preferred PEGDA content of 0.4 weight part is used for preparing the polymer-based temperature-sensitive material: dispersing conductive filler in an organic solvent at room temperature, performing ultrasonic treatment for 60-90 min to obtain a dispersion liquid of the conductive filler, adding PLA into the conductive dispersion liquid, stirring for 60-80 min to obtain a polymer/conductive filler dispersion liquid, performing ultrasonic dispersion at 70-90 ℃ until the organic solvent is volatilized, transferring the organic solvent into a vacuum oven at 60-80 ℃ for drying treatment, and finally performing melt blending, pressing, cooling and demolding on the pre-blended material to obtain the polymer-based temperature-sensitive material.
Example 5
1) The proportions of the raw materials are shown in Table 2;
2) firstly, drying LCBPLA granules at 70 ℃ in vacuum for 24h, and preparing the LCBPLA/MWCNTs-GnPs temperature-sensitive material: according to the proportion in the table 2, firstly, MWCNTs-GnPs are dispersed in acetone, and ultrasonic dispersion is carried out for 60-90 min, so that MWCNTs-GnPs dispersion liquid is obtained. And then adding LCBPLA into the dispersion liquid, mechanically stirring for 60min, then performing ultrasonic dispersion at the temperature of 70-90 ℃ until the solvent is completely volatilized, transferring the mixture into a vacuum oven at the temperature of 60-80 ℃ for drying treatment, and finally putting the pre-blend into a torque rheometer for processing, wherein the processing temperature is 180 ℃, the rotation speed is 50rpm, and the processing time is 5 min.
3) Hot-press molding: preheating the blend obtained in the step 2) at 180 ℃ for 5min, then maintaining the pressure at 10MPa for 5min, and then cooling to room temperature at 5MPa to obtain the required polymer temperature-sensitive material.
It is to be noted that the weight ratio of MWCNTs/GnPs in the above-mentioned composition is 1: 1.
The formulations of examples 6-10 are shown in Table 2 and were prepared in the same manner as in example 5.
Table 2 raw materials formulation table for examples 6-10
Examples LCBPLA MWCNTs-GnPs MWCNTs-GnPs mass fraction (wt%)
6 99.5 0.5 0.5%
7 99.4 0.6 0.6%
8 99.2 0.8 0.8%
9 99 1 1%
10 98 2 2%
11 97.5 2.5 2.5%
12 97 3 3%
Comparative example 1
1) The proportions of the raw materials are shown in Table 3;
2) firstly, drying LCBPLA granules at 70 ℃ in vacuum for 24h, and preparing the LCBPLA/MWCNTs temperature-sensitive material: firstly, dispersing MWCNTs in acetone according to the proportion in the table 2, and performing ultrasonic dispersion for 60-90 min to obtain MWCNTs dispersion liquid. And then adding LCBPLA into the dispersion liquid, mechanically stirring for 60min, then performing ultrasonic dispersion at the temperature of 70-90 ℃ until the solvent is completely volatilized, transferring the mixture into a vacuum oven at the temperature of 60-80 ℃ for drying treatment, and finally putting the pre-blend into a torque rheometer for processing, wherein the processing temperature is 180 ℃, the rotation speed is 50rpm, and the processing time is 5 min.
3) Hot-press molding: preheating the blend obtained in the step 2) at 180 ℃ for 5min, then maintaining the pressure at 10MPa for 5min, and then cooling to room temperature at 5MPa to obtain the required polymer temperature-sensitive material.
The formulations of comparative examples 2 to 6 are shown in Table 3, and the preparation methods are the same as in comparative example 1.
TABLE 3 formulation tables for comparative examples 2-6
Comparative example LCBPLA MWCNTs MWCNTs mass fraction (wt%)
1 99.5 0.5 0.5%
2 99.3 0.7 0.7%
3 99.2 0.8 0.8%
4 99 1 1%
5 98 2 2%
6 97.5 2.5 2.5%
Comparative example 7
1) The proportions of the raw materials are shown in Table 4;
2) firstly, drying LCBPLA granules at 70 ℃ in vacuum for 24h, and preparing the LCBPLA/GnPs temperature-sensitive material: firstly, MWCNTs are dispersed in acetone according to the proportion in the table 2, and are subjected to ultrasonic dispersion for 60-90 min to obtain GnPs dispersion liquid. And then adding LCBPLA into the dispersion liquid, mechanically stirring for 60min, then performing ultrasonic dispersion at the temperature of 70-90 ℃ until the solvent is completely volatilized, transferring the mixture into a vacuum oven at the temperature of 60-80 ℃ for drying treatment, and finally putting the pre-blend into a torque rheometer for processing, wherein the processing temperature is 180 ℃, the rotation speed is 50rpm, and the processing time is 5 min.
3) Hot-press molding: preheating the blend obtained in the step 2) at 180 ℃ for 5min, then maintaining the pressure at 10MPa for 5min, and then cooling to room temperature at 5MPa to obtain the required polymer temperature-sensitive material.
The formulations of comparative examples 7 to 10 are shown in Table 4, and the preparation methods are the same as in comparative example 1.
TABLE 4 raw material formulation tables for comparative examples 7 to 10
Comparative example LCBPLA(g) GnPs(g) Mass fraction (wt%) of GnPs
7 99 1 1%
8 98 2 2%
9 97.5 2.5 2.5%
10 97 3 3%
11 96.5 3.5 3.5%
12 96 4 4%
13 95 5 5%
And (3) performance testing:
to investigate the formation of long chain branches, examples 1 and 2 were subjected to dynamic rheology testing using an ARES rheometer mounted on an extensional viscosity jig (EVF) to investigate the extensional flow behavior of modified polylactic acid when stretched in the molten state, where extensional viscosity is more sensitive to the formation of long chain branches than to shear rheology. In particular, at a certain strain, with an increase in transient viscosity, a strain hardening behaviour can be observed, which can be used to characterize the formation of long branched chain structures. FIG. 1a shows the shear rate at various shear rates from 0.02 to 0.5s-1Lower extensional viscosity curve, it can be seen that the strain softening behavior is such that the extensional viscosity increases and then decreases at the beginning of the extension. This phenomenon is due to the lack of long-branched structure in these samples. Whereas in FIG. 1b a certain degree of strain hardening is shown, the occurrence of this phenomenon requires more than 2 branching points on the branched chain, indicating the formation of a long branched chain structure.
FIG. 2 is a transmission electron micrograph of example 7 of the present invention, in which white regions are a polylactic acid matrix and black regions are a conductive filler. As can be seen from the figure, the one-dimensional MWCNTs are distributed on the surface of the two-dimensional GnPs, so that a three-dimensional conductive network structure is formed.
And (3) testing electrical properties: in order to examine the conductivity of the composite material of the present invention, a conductivity test was performed on 10mm × 30mm × 0.5mm samples prepared in examples and comparative examples using a homoeographic resistance meter TH2684A (yokoku corporation, yokoku), and the results are shown in fig. 2. From the figure, the percolation values of the MWCNTs and the GnPs which are respectively added into the long-chain branched polylactic acid matrix are respectively 0.63 and 3.2, and after the MWCNTs and the GnPs are compounded, the percolation value of the composite material is obviously reduced to about 0.52, which fully embodies that the percolation value of the composite material can be obviously reduced by the method adopted by the invention.
Temperature-resistance test: in order to examine the temperature-sensitive characteristic of the composite material, a Teck DMM4050 is adopted to carry out temperature-resistance test on the examples and the comparative examples, and the change of resistance is recorded in real time, wherein the heating rate is 2 ℃/min, and the temperature interval is 40 ℃ to 180 ℃. The data were processed to obtain a conductivity change (conductivity/initial conductivity) curve, as shown in fig. 4. It can be clearly found from the figure that when the MWCNTs and the GnPs are added separately, the composite material shows a phenomenon that the conductivity is reduced along with the increase of the temperature, the phenomenon is called PTC effect, while after the MWCNTs and the GnPs are added simultaneously, a certain PTC effect and NTC effect are shown, and the change value of the conductivity shows that 0.6 percent of the MWCNTs-GnPs/LCBPLA has larger change, which indicates that the composite material is more sensitive to the temperature.
Mechanical property analysis: the examples and comparative examples were subjected to mechanical property tests as shown in table 5. The data in the table are compared to find that the tensile strength and the elongation at break of the composite material can be improved by the formation of the long branched chain structure, and the toughness and the strength of the composite material can be further improved after the MWCNTs-GnPs are introduced into the composite material.
TABLE 5 structural comparison of tensile Properties and elongations at break of the samples obtained in examples 1-11
Tensile Strength (MPa) Elongation at Break (%)
Example 1 64.8 20.5
Example 4 75.4 34.6
Example 6 78.6 32.5
Example 7 82.4 34.6
Example 8 83.3 42.1
Example 9 79.1 33.2
Example 10 68.6 26.8
Example 11 62.1 22.4
Example 11 54.9 12.8
The experiment shows that the preparation method of the conductive composite material provided by the invention is simple, and the conductive composite material has higher strength and toughness, higher response speed to temperature and higher stability, so that the conductive composite material can be used as a temperature sensor with excellent performance. The MWCNTs, GnPs and the polymer composite material can endow the bio-based polymer material with good toughness and biodegradability, and can resist corrosion in the environment. The preparation method is simple and quick, and saves cost.

Claims (10)

1. The high-toughness polymer-based temperature-sensitive composite material is characterized by comprising a polymer matrix and conductive fillers, wherein the conductive fillers form a conductive network in the polymer matrix, and the conductive network is a three-dimensional conductive network formed by one-dimensional conductive fillers and two-dimensional conductive fillers; the conductive filler accounts for 0.1-5 w% of the high-toughness temperature-sensitive composite material, and the mass ratio of the one-dimensional conductive filler to the two-dimensional conductive filler in the conductive filler is 1: 1.
2. The high-toughness polymer-based temperature-sensitive composite material according to claim 1, wherein the polymer matrix is at least one of polylactic acid, polybutylene succinate or polybutylene terephthalate-adipate; preferably polylactic acid.
3. The high-toughness polymer-based temperature-sensitive composite material according to claim 2, wherein when the polymer matrix is polylactic acid, the polylactic acid is modified polylactic acid, and the modified polylactic acid is prepared by the following method: carrying out a branching reaction on polylactic acid by carrying out melt processing on dicumyl peroxide and polyethylene glycol diacrylate at 180-200 ℃ for 5-10 min; wherein the proportion of each raw material is as follows: 100 parts of polylactic acid, 0.25 part of dicumyl peroxide and 0.05-0.5 part of polyethylene glycol diacrylate.
4. A high-toughness polymer-based temperature-sensitive composite material according to any one of claims 1 to 3, wherein the one-dimensional conductive filler is at least one of a multi-walled carbon nanotube, a single-walled carbon nanotube or a carbon fiber;
further, the two-dimensional conductive filler is at least one of graphene nanoplatelets, graphene or graphite.
5. The preparation method of the high-toughness polymer-based temperature-sensitive composite material according to any one of claims 1 to 4, wherein the preparation method comprises the following steps: the one-dimensional conductive filler and the two-dimensional conductive filler are used as composite conductive fillers and are melted and blended with the polymer matrix at a temperature higher than the melting point of the polymer matrix and lower than the thermal decomposition temperature of the polymer matrix;
further, the melt blending temperature is 180-200 ℃, and the blending time is 5-8 min.
6. A flexible temperature-sensitive sensor is characterized in that the flexible temperature-sensitive sensor is made of a polymer-based temperature-sensitive composite material; the polymer-based temperature-sensitive composite material is prepared by the method of any one of claims 1 to 4; or the high-toughness polymer-based temperature-sensitive composite material according to claim 5.
7. A method for reducing the conductive percolation value of a high polymer material is characterized by comprising the following steps: simultaneously introducing a one-dimensional conductive filler and a two-dimensional conductive filler into a high polymer material, namely melting and blending the high polymer material, the one-dimensional conductive filler and the two-dimensional conductive filler; the mass ratio of the conductive filler to the high polymer material is as follows: 0.5 wt% to 3 wt%: 99.5 wt% -97 wt%, wherein the mass ratio of the one-dimensional conductive filler to the two-dimensional conductive filler in the conductive filler is 1: 1.
8. the method for reducing the conductive percolation value of a high polymer material according to claim 7, wherein the high polymer material is at least one of polylactic acid, polybutylene succinate or polybutylene terephthalate-adipate; preferably polylactic acid;
further, when the polymer matrix is polylactic acid, the polylactic acid is modified polylactic acid, and the modified polylactic acid is prepared by adopting the following method: carrying out a branching reaction on polylactic acid by carrying out melt processing on dicumyl peroxide and polyethylene glycol diacrylate at 180-200 ℃ for 5-10 min; wherein the proportion of each raw material is as follows: 100 parts of polylactic acid, 0.25 part of dicumyl peroxide and 0.05-0.5 part of polyethylene glycol diacrylate;
further, the one-dimensional conductive filler is at least one of a multi-wall carbon nanotube, a single-wall carbon nanotube or a carbon fiber;
further, the two-dimensional conductive filler is at least one of graphene nanoplatelets, graphene or graphite.
9. The composite material with the NTC effect and the PTC effect is characterized by comprising a high polymer matrix and conductive filler, wherein the conductive filler forms a conductive network in the high polymer matrix, and the conductive network is a three-dimensional conductive network formed by one-dimensional conductive filler and two-dimensional conductive filler; the conductive filler accounts for 0.1-5 w% of the high-toughness temperature-sensitive composite material, and the mass ratio of the one-dimensional conductive filler to the two-dimensional conductive filler in the conductive filler is 1: 1.
10. The method for preparing the composite material having both the NTC effect and the PTC effect according to claim 9, wherein the method comprises: the one-dimensional conductive filler, the two-dimensional conductive filler and the polymer matrix are melted and blended at a temperature higher than the melting point of the polymer matrix and lower than the thermal decomposition temperature.
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